Donor Fat-Based Stem Cells May Provide Augmented Healing of Rectovaginal Fistulas of Crohn’s Disease Patients

Fistulas are openings in organ systems that connect with another system. They usually result from wounds or erosions in the lining of a tube or duct that gets deeper and deeper and eventually opens into another tube or duct. Physical injuries can cause fistulas, but so can diseases such as Crohn’s disease. Anal fistulas result from erosions of the rectum that open to the outside and are typically very painful and do not readily heal.

Damián García-Olmo and his colleagues at the Universidad Autónoma de Madrid have conducted several clinical trials that have examined the ability of adipose-derived stem cells (ASCs) to facilitate the healing of fistulas in Crohn’s disease patients. A phase I study, which primarily examines safety, was published in 2005 (see García-Olmo D., et al., Dis Colon Rectum 2005; 48:1416-1423). According to this study, “No adverse effects were observed in any patient at the end of the follow-up period (minimum follow-up, 12 months; maximum follow-up, 30 months; follow-up average, 22 months).” The Phase II study was published in 2009 (García-Olmo, D., et al., Dis Colon Rectum 2009; 52:79-86). According to the results of this study, fistula healing was observed in 71 percent of patients who were treated with ASCs in combination with fibrin glue compared with 16 percent of patients who received fibrin glue alone. Quality of life scores were also higher in patients who received ASCs than in those who received fibrin glue alone. Once again, the stem cell treatments were well tolerated. The third study was a multicenter, randomized, single-blind clinical trial that enrolled 200 adult patients from 19 centers that were randomly assigned to three groups. The first group received 20 million stem cells (group A, 64 patients). The second group received 20 million adipose-derived stem cells plus fibrin glue (group B, 60 patients). The third group received only fibrin glue (group C, 59 patients). In treatment of anal fistulas in Crohn’s disease patients, a dose of 20 or 60 million adipose-derived stem cells alone or in combination with fibrin glue were demonstrably safe and did promote healing. However, there were no statistically significant differences between the three groups once the 3 groups were compared.

These studies suggest that stem cells from fat might have a place in the treatment of fistulas in Crohn’s disease patients. The application of the stem cells is feasible and safe, and requires no new equipment or skill. The stem cells also might augment the healing of these fistulas.

Unfortunately, anal fistulas are not the only type of fistulas that Crohn’s disease patients can experience. Female Crohn’s disease patients can have fistulas that open from their rectum into their birth canal. These rectovaginal fistula can deposit the contents of the gastrointestinal tract into the lower reproductive tract. While Crohn’s disease is not the only cause rectovaginal fistulas, Crohn’s disease patients are at higher risks for complications, which include: loss of control over stool deposition (fecal incontinence), hygiene problems combined with recurrent vaginal or urinary tract infections, inflammation of the birth canal and skin around the anus (perineum), abscess formation, which can become life-threatening if not treated, and recurrence of the fistula. Surgical treatment of rectovaginal fistulas requires that the tissue be free of inflammation before surgery, which can take time and cause extensive amounts of patient suffering.

Garcia-Olmo and his colleagues have conducted a small phase I-IIa clinical trial to evaluate the possibility of banked fat-based stem cells to treat recto-vaginal fistulas in female Crohn’s patients. This study has several limitations because it is so small and they have to exclude at least half of the participants because of complications beyond their control. Therefore, this study is not statistically significant. However, it does show what might be the beginnings of a stem-based treatment for this horrid condition.

The design of the study included 11 subjects who were initially enrolled in the study, but one of those recruited patients did not meet the criteria for the study. Therefore, ten subjects, all of whom suffered from Crohn’s disease and had rectovaginal fistulas were treated with 20 million fat-based stem cells that had been donated by a healthy volunteer in addition to surgical repair of their fistulas. These donated fat-based stem cells were provided by a Spanish biotechnology company called Cellerix S.L. Three months after this stem cell treatment, two patients were healed and the other either were given an additional treatment of 40 million fat-based stem cells. Of this group, four were healed. However, five of these patients experienced severe flare-ups of their Crohn’s disease that required treatment with biological agents, which disqualified these patients from further consideration from this study. The biological agents used to treat the Crohn’s disease flare-ups are very powerful medicines and can significantly influence the outcome of this study. Thus half of the subjects in this study had to be excluded. Of the five subjects that remained, 3 showed healing of their fistulas, and 2 did not.

The authors present the data as a “final efficacy rate of 60%.” However, given the high rate of exclusion and the very low numbers of subjects in this study, all we can say with any confidence is that based on the previous successes of this treatment in other studies, there is precedent for such a technique to be safe and somewhat effective, and that the data in this study are in a favorable direction. However, that’s about it.

One feature of this study that differs from the other clinical trials done by this same group is that the previous studies utilized the patient’s own fat-based stem cells, whereas this study used stem cells from a healthy donor. The authors stress that this modification greatly simplifies the procedure and decreases its expense. Because of the ease of the treatments, it reduces postoperative hospitalization and is minimally invasive. This new trial suggests that further work is warranted and the results or even minimally hopeful.

This work was published in the journal Stem Cells Translational Medicine 2016; 5(11): 1441-1446.

ASTIC Clinical Trial Fails to Show Clear Advantage to Hematopoietic Stem Cell Transplantation as a Treatment for Crohn’s Disease

Patients with Crohn’s disease (CD) sometimes suffer from daily bouts of stomach pain and diarrhea. These constant gastrointestinal episodes can prevent them from absorbing enough nutrition to meet their needs, and, consequently, they can suffer from weakness, fatigue, and a general failure to flourish.

To treat Crohn’s disease, physicians use several different types of drugs. First there are the anti-inflammatory drugs, which include oral 5-aminosalicylates such as sulfasalazine (Azulfidine), which contains sulfur, and mesalamine (Asacol, Delzicol, Pentasa, Lialda, Apriso). These drugs, have several side effects, but on the whole are rather well tolerated. If these don’t work, then corticosteroids such as prednisone are used. These have a large number of side effects, including a puffy face, excessive facial hair, night sweats, insomnia and hyperactivity. More-serious side effects include high blood pressure, diabetes, osteoporosis, bone fractures, cataracts, glaucoma and increased chance of infection.

If these don’t work, then the stronger immune system suppressors are brought out. These drugs have some very serious side effects. Azathioprine (Imuran) and mercaptopurine (Purinethol) are two of the most widely used of this group. If used long-term, these drugs can make the patient more susceptible to certain infections and cancers including lymphoma and skin cancer. They may also cause nausea and vomiting. Infliximab (Remicade), adalimumab (Humira) and certolizumab pegol (Cimzia) are the next line of immune system suppressors. These drugs are TNF inhibitors that neutralize an immune system protein known as tumor necrosis factor (TNF). These drugs are also associated with certain cancers, including lymphoma and skin cancers. The next line of drugs include Methotrexate (Rheumatrex), which is usually used to treat cancer, psoriasis and rheumatoid arthritis, but methotrexate also quells the symptoms of Crohn’s disease in patients who don’t respond well to other medications. Short-term side effects include nausea, fatigue and diarrhea, and rarely, it can cause potentially life-threatening pneumonia. Long-term use can lead to bone marrow suppression, scarring of the liver and sometimes to cancer. You will need to be followed closely for side effects.

Then there are specialty medicines for patients who do not respond to other medicines or who suffer from openings in their lower large intestines to the outside world (fistulae). These include cyclosporine (Gengraf, Neoral, Sandimmune) and tacrolimus (Astagraf XL, Hecoria). These have the potential for serious side effects, such as kidney and liver damage, seizures, and fatal infections. These medications are definitely cannot be used for long period of time as their side effects are too dangerous.

If the patient still does not experience any relief, then two humanized mouse monoclonal antibodies natalizumab (Tysabri) and vedolizumab (Entyvio). Both of these drugs bind to and inhibit particular cell adhesion molecules called integrins, and in doing so prevent particular immune cells from binding to the cells in the intestinal lining. Natalizumab is associated with a rare but serious risk of a brain disease that usually leads to death or severe disability called progressive multifocal leukoencephalopathy. In fact, so serious are the side effects of this medicine that patients who take this drug must be enrolled in a special restricted distribution program. The other drug, vedolizumab, works in the same way as natalizumab but does not seem to cause this brain disease. Finally, a drug called Ustekinumab (Stelara) is usually used to treat psoriasis. Studies have shown it’s useful in treating Crohn’s disease and might useful when other medical treatments fail. Ustekinumab can increase the risk of contracting tuberculosis and an increased risk of certain types of cancer. Also there is a risk of posterior reversible encephalopathy syndrome. More common side effects include upper respiratory infection, headache, and tiredness.

If this litany of side effects sounds undesirable, then maybe a cell-based treatment can help Crohn’s patients. To that end, a clinical trial called the Autologous Stem Cell Transplantation International Crohn’s Disease or ASTIC trial was conducted and its results were published in the December 15th, 2015 edition of the Journal of the American Medical Association.

The ASTIC trial enrolled 45 Crohn’s disease patients, all of whom underwent stem cell mobilization with cyclophosphamide and filgrastim, and were then randomly assigned to immediate stem cell transplantation (at 1 month) or delayed transplantation (at 13 months; control group).  Blood samples were drawn and mobilized stem cells were isolated from the blood.  In twenty-three of these patients, their bone marrow was partially wiped out and reconstituted by means of transplantations with their own bone marrow stem cells. The other 22 patients were given standard Crohn disease treatment (corticosteroids and so on) as needed.

The bad news is that hematopoietic stem cell transplantations (HSCT) were not significantly better than conventional therapy at inducing sustained disease remission, if we define remission as the patient not needing any medical therapies (i.e. drugs) for at least 3 months and no clear evidence of active disease on endoscopy and GI imaging at one year after the start of the trial. All patients in this study had moderately to severely active Crohn’s disease that was resistant to treatment, had failed at least 3 immunosuppressive drugs, and whose disease that was not amenable to surgery.  All participants in this study had impaired function and quality of life.  Also, the stem cell transplantation procedure, because it involved partially wiping out the bone marrow, cause considerable toxicities.

Two patients who underwent HSCT (8.7%) experienced sustained disease remission compared to one control patient (4.5%). Fourteen patients undergoing HSCT (61%) compared to five control patients (23%) had discontinued immunosuppressive or biologic agents or corticosteroids for at least 3 months. Eight patients (34.8%) who had HSCTs compared to two (9.1%) patients treated with standard care regimens were free of the signs of active disease on endoscopy and radiology at final assessment.

However, there were 76 serious adverse events in patients undergoing HSCT compared to 38 in controls, and one patient undergoing HSCT died.

So increased toxicities and not really a clear benefit to it; those are the downsides of the ASCTIC study.  An earlier report of the ASTIC trial in 2013, while data was still being collected and analyzed was much more sanguine.  Christopher Hawkey, MD, from the University of Nottingham in the United Kingdom said this: “Some of the case reports are so dramatic that it’s reasonable to talk about this being a cure in those patients.”  These words came from a presentation given by Dr. Hawkey at Digestive Disease Week 2013.  Further analysis, however, apparently, failed to show a clear benefit to HSCT for the patients in this study.  It is entirely possible that some patients in this study did experience significant healing, but statistically, there was no clear difference between HSCT and conventional treatment for the patients in this study.

The silver lining in this study, however, is that compared to the control group, significantly more HSCT patients were able to stop taking all their immunosuppressive therapies for the three months prior to the primary endpoint. That is a potential upside to this study, but it is unlikely for most patients that this upside is worth the heightened risk of severe side effects. An additional potential upside to this trial is that patients who underwent HSCT showed greater absolute reduction of clinical and endoscopic disease activity. Again, it is doubtful if these potential benefits are worth the higher risks for most patients although it might be worth it for some patients.

Therefore, when HSCT was compared with conventional therapy, there was no statistically significant improvement in sustained disease remission at 1 year. Furthermore, HSCT was associated with significant toxicity. Overall, despite some potential upside to HSCT observed in this study, the authors, I think rightly, conclude that their data do not support the widespread use of HSCT for patients with refractory Crohn’s disease.

Could HSCT help some Crohn’s patients more than others? That is a very good question that will need far more work with defined patient populations to answer.  Perhaps further work will ferret out the benefits HSCT has for some Crohn’s disease patients relative to others.

The ASTIC trial was a collaborative project between the European Society for Blood and Marrow Transplantation (EBMT) and the European Crohn’s and Colitis Organization (ECCO) and was funded by the Broad Medical Foundation and the Nottingham Digestive Diseases Centers.

Pre-treatment of MSCs Can Reduce Their Regenerative Properties

Mesenchymal stem cells (MSCs) are excellent suppressors of unwanted inflammation.  This anti-inflammatory activity has been established for systemic inflammatory diseases in animal experiments (Klinker MW, Wei CH. World J Stem Cells. 2015 Apr 26;7(3):556-67), and in clinical trials with human patients (Dulamea A. J Med Life. 2015 Jan-Mar;8(1):24-7; Simonson OE et al., Stem Cells Transl Med. 2015 Oct;4(10):1199-213. doi: 10.5966/sctm.2015-0021).  Stem cell researchers have also shown that MSCs can suppress inflammation in the bowel (see Swenson E and Theise N. Clinical and Experimental Gastroenterology 2010;3:1-10; Chen Z, et al., Biochem Biophys Res Commun. 2014 Aug 8;450(4):1402-8).

After being introduced into the body of a patient, MSCs to move to the site where they are needed (a phenomenon known as “homing”) and promote tissue repair and healing.  Sometime MSC homing works quite well, but other times, it is so-so.  Therefore, several inventive scientists have devised ways to beef up homing to specific sites in order to improve MSC-based tissue healing.  Also, investigators are equally interested in increasing the ability of MSCs to stick to tissues once they arrive there to ensure that the homed MSCs stay where they are needed (see Kavanagh DP, Robinson J, and Kalia N. Stem Cell Rev 2014;10:587-599).  Unfortunately, at the moment, the whole homing process is a bit of a black box and while artificially increasing homing might help in the laboratory, whether or not it increases the therapeutic benefit of MSCs is even less well understood.

A new report from the laboratory of Neena Kalia, who works at the University of Birmingham, UK, has examined the effect of artificial enhancement on the therapeutic capacity of MSCs to treat inflammation in the bowel.  This is an important study because pre-treatment strategies have been suggested as ways to boost MSC homing and retention to various tissues.  The Kalia study suggests such pre-treatment strategies should be viewed with a degree of skepticism.

In this study, Kalia her coworkers induced inflammation in the gastrointestinal tracts of mice by clamping off the blood supply to the this tissue for a time and then releasing the clamps and letting the blood flow anew.  This type of damage, known as ischemia/reperfusion (IR) injury deprives cells of vital oxygen and nutrients for a short period of time, which causes some cells to die.  When the blood is allowed to flow into the tissue, inflammation is induced in the damaged tissue.  Therefore, this technique can efficiently induce  inflammation in tissues in the gastrointestinal tract.

Two groups of mice were treated with bone marrow-derived MSCs.  One group had experiences IR injury to their gastrointestinal tracts, and the other group did not.  In these experiments, administered MSCs showed similar levels of and cell adhesion in both injured and non-injured guts.  In general, cell adhesion levels were nothing to write home about:  as reported in the paper, “limited cell adhesion observed.”  Despite these initial observations, those MSCs that found their way to the gut were able to help heal the tissues to some degree.  There were fewer white blood cells in the middle part of the small intestine (jejunum), and the degree of blood flow seemed to have improved.  Unfortunately, the lower part of the small intestine (ileum) was not helped to the same degree, and the paper reports that a fair number of MSCs got stuck in small blood vessels, which suggests that these vessels got stuck on their way to the intestine.

If these results seem underwhelming, it might be because they are.  Undaunted, Kalia and her crew tried to boost the regenerative abilities of their isolated MSCs by pretreating them.  Kalia’s laboratory and other laboratories as well have used a variety of chemical agents to augment the healing abilities of MSCs.  These agents include things like tumor necrosis factor (TNF)-α, CXCL12 (also known as stromal cell-derived factor 1 or SDF1, which strongly activates white blood cells), interferon (IFN)-γ, or hydrogen peroxide.  When these pre-treated MSCs were administered to mice whose guts were damaged by means of IR injury, the pretreatment not only did not enhance their intestinal recruitment, but actually decreased the healing capacities of MSCs.  Pretreatment of MSCs with tumor necrosis factor (TNF)-α, CXCL12, interferon (IFN)-γ, or hydrogen peroxide did not enhance their intestinal recruitment.  Pretreatment with TNFα and IFNγ abrogated ability of transplanted MSCs to reduce white blood cells infiltration and improve blood flow in the jejunum.

Kalia and her colleagues utilized a technique called “intravital” microscopy for this study.  Intravital microscopy can track individual cells in a living animals (Kavanagh DP, Yemm AI, Zhao Y, et al. PLoS One 2013;8:e59150). With this technique, they were able to efficiently monitor adhesion in the tinyu blood vessels in the injured intestinal tissue.  They documented poor MSC adhesion to the gut lining and that pre-treatment with various factors hopes failed to enhance adhesion of MSCs to the gut.

This study successfully demonstrated that MSCs can rapidly limit white blood cells recruitment to the inflamed gut, and improve tissue perfusion if they are administered after intestinal IR injury. However, Kalia’s study also shows that strategies to improve MSC therapeutic efficacy by means of pretreatment of MSCs may not be all it’s cracked up to be.  They suggest that in the future, cytokine or chemical pretreatments designed to enhance MSC recruitment and function will require more than just successful experiments in a cell culture system.  Instead, pretreatment strategies will need to be carefully validated in living organisms in order the confirm that such protocols help rather than hinder the therapeutic function of implanted stem cells.

This paper was published in the journal Stem Cells – Kavanagh DP, Suresh S, Newsome PN, et al. Stem Cells 2015;33:2785-2797

Laboratory-Grown Intestine Shows Promise in Mice and Dogs

David Hackam is a pediatric surgeon at the Johns Hopkins Children’s Center. Unfortunately, Dr. Hackam spends a good deal of his time removing dead sections of intestine from sick babies, but he would deeply love to be able to do more than just take out intestines but actually replace the dead or dying intestinal tissue. It is that desire that has driven Hackam and his colleagues to grow intestines in the laboratory.

They begin with stem cells taken from the small intestines of human infants and mice and apply them to intestine-shaped scaffolds. The stem cells dig in, grow and form mini-intestines that just might be able to treat disorders like necrotizing enterocolitis and Crohn’s disease someday. Transplantation experiments in laboratory animals have shown that this laboratory-grown tissue and scaffolding are not rejected, but integrate into the tissues of the animals. Experiments in dogs have shown that the scaffold allowed dogs to heal from damage to the colon lining, essentially restoring healthy bowel function.

The study is a “great breakthrough,” says Hans Clevers, a stem cell biologist at the Hubrecht Institute in Utrecht, the Netherlands, who was not involved in the new research. Clevers and his colleagues were the first to identify stem cells in the intestine, and his lab developed the technique Hackam’s team used to grow intestinal tissue.

Making replacement organs by growing cells on scaffolds molded into the shape of the organ is not a new idea, since other researchers have used exactly this technique to make bladders and blood vessels. However, the laboratory-grown intestines made by Hackam and his group come closer to the shape and structure of a natural intestine than anything created in the laboratory before. In previous experiments carried out in other laboratories, the gut lining has been grown on flat scaffolds or in culture flasks. Under these conditions, the tissue tends to roll up into little balls that have the absorptive surface on the inside. Hackam and his coworkers, however, overcame this problem by using a scaffold fabricated from materials similar to surgical sutures. This material can be molded into any desired intestinal size and shape, and in Hackam’s hands, the scaffolds formed a true tube-shaped (like a real gut), with tiny projections on the inner surface that can help the tissue form functional small intestinal villi (the small fingers of tissue that increase the surface area of the intestine to increase nutrient absorption. “They can now make sheets of cells that can be clinically managed,” Clevers says. “Surgeons can handle these things and just stick them in.”

To grow the gut lining in the lab, the researchers painted the scaffold with a sticky collagen-rich substance and then dripped onto it a solution of stem cells from the small intestine. This concoction was grown in a culture system for a week. Interestingly, Hackam and his team found that if they added connective tissue cells, immune cells, and probiotics (bacteria that help maintain a healthy gut), all of these things helped the stem cells mature and differentiate.

Hackam’s group also sutured intestines grown from mouse stem cells into the tissue surrounding the abdominal organs of the mouse. The lab-grown intestines developed their own blood supply and normal gut structures despite the fact that they were not connected to the animals’ digestive tract. “Using the mouse’s own stem cells, we can actually create something that looks just like the native intestine,” Hackam says. The next step, he says, is “to hook it up.”

Before “hooking it up,” Hackam needed to be sure that the scaffold could be tolerated in living animals. Therefore he tested the new scaffold in dogs. He removed sections of large intestinal lining and replaced it with pieces of scaffolding. The dogs made a complete recovery: their gut lining regrew onto the scaffold and functioned normally to absorb water from the colon. After a few weeks, the scaffolding had completely dissolved and was replaced with normal connective tissue. “The scaffold was well tolerated and promoted healing by recruiting stem cells,” Hackam says. “[The dogs] had a perfectly normal lining after 8 weeks.”

This technique could help more than just dogs and mice, but could aid human patients. According to Hackam, scaffolds could be custom-designed for individual human patients to replace a portion of an intestine or the entire organ. This could be a revolutionary treatment for patients with necrotizing enterocolitis, a condition that destroys intestinal tissue in about 12% of premature babies in the United States. It could also potentially repair the intestines of patients with Crohn’s disease, an inflammatory bowel disorder that can have life-threatening complications and that affects more than 500,000 people in the United States. However, these lab-grown intestines must pass several other tests before they are ready for human clinical trials, Hackam cautions.

The first test that these laboratory-grown intestines must pass is the absorption test. Laboratory-grown small intestines must be transplanted into live animals and they must properly absorb food. Also, the technology that is used will also require some adjustments. For example, Mari Sogayar, a molecular biologist at the University of São Paulo in Brazil, points out that the collagen product that helps the stem cells stick to the scaffold is not meant for use in people. In the next experiments, Hackam says, the researchers plan to use a surgical-grade alternative.

“I take care of children who have intestinal deficiencies, eating deficiencies, and they are very much at wits’ end,” Hackam says. “I think what we can offer in the scientific community is a path toward something that one day will help a child.”

Mesenchymal Stem Cells Heal Gastrointestinal Ulcers

Stomach ulcers are a complication of routine use of aspirin, Advil, or other non-steroidal anti-inflammatory drugs. Additionally, radiation therapy, or inflammatory bowel disease can also cause stomach ulcers, and these are painful and potentially dangerous for patients. Trying to get our heads around ulcers is not easy, but a new study by Manieri and colleagues have provided some understanding of ulcer formation and ways that mesenchymal stem cells (MSCs) might help heal these painful lesions.

Manieri and others used prostaglandin-deficient mice as a model system for ulcer formation. In these mice, their stomachs do not produce the prostaglandins that protect the layers of the stomach from being digested by its own acid and enzymes. Consequently, these mice are subject to so-called “penetrating ulcer formation,” or ulcers that penetrate the underlying muscular layer (muscularis propria). When Manieri and his colleagues took biopsies of the colon of these prostaglandin-deficient mice, they observed extensive necrosis of the upper and lower layers of the colon.

When these mice were treated with stable prostaglandin-I2 (PGI2) analogs, Manieri and others showed that they could ameliorate the damage to the colon. However, when this research group analyzed the ulcer beds in these mutant mice, they noticed that CD31+ endothelial cells, which form blood vessels, were found in very low numbers. This suggested that reduced blood vessel formation could be a key driver of penetrating ulcer formation. To confirm their hypothesis, the authors stained the wound sites for vascular endothelial growth factor (VEGF). They saw fewer VEGF+ cells in the mutant mice compared with wild-type animals, which suggests that impaired blood vessel production contributes to ulceration. To further test this hypothesis, Manieri and others treated wild-type mice with tivozanib (a VEGF receptor antagonist), which also caused smooth muscle necrosis in the colon.

Next Manieri and others injected MSCs from the colons of mice that showed increased expression of VEGF into the ulcerated colon of mutant mice. The MSCs dutifully migrated to the ulcer beds, and rescued the muscle necrosis phenotype. These results show that MSC administration can provide a soothing treatment prospect for patients who are dealing with gastrointestinal ulceration.

See N. A. Manieri et al., Mucosally transplanted mesenchymal stem cells stimulate intestinal healing by promoting angiogenesis. J. Clin. Invest. 10.1172/JCI81423 (2015).

Nusse Laboratory at Sanford Identifies Elusive Mouse Liver Stem Cell

Stanford University life science researchers have managed to successfully identify a stem cell population that has eluded many laboratories for some time. Essentially, the Stanford team has discovered a previously unknown population of liver cells in mice that function as liver stem cells. Such a find could aid drug testing and increase our present understanding of liver biology and disease.

Researchers in the laboratory of Roel Nusse at the Stanford University School of Medicine have identified a cell type in the liver of laboratory mice that can both self-renew and make new liver cells. This discovery by Nusse and others settles a long-standing conundrum of how the liver maintains itself when liver cells grow old and die.

“There’s always been a question as to how the liver replaces dying hepatocytes,” said professor of developmental biology Roel Nusse, PhD. “Most other tissues have a dedicated population of cells that can divide to make a copy of themselves, which we call self-renewal, and can also give rise to the more-specialized cells that make up that tissue. But there never was any evidence for a stem cell in the liver.”

It was assumed for some time that mature hepatocytes (liver cells) would themselves divide to replace a dying neighbor. However, hepatocytes have an abnormal amount of DNA, which would make cell division extremely difficult.

Nusse and his team published this research in the Aug. 5 edition of the journal Nature. The first author of this paper, Bruce Wang, MD, an assistant professor of gastroenterology and hepatology at the University of California-San Francisco, led the research while serving as a visiting scholar in Nusse’s lab.

The liver is a large, multi-lobed organ that filters toxins from the blood, synthesizes blood proteins, and makes digestive enzymes and bile. It is involved in many important metabolic processes. The liver contains a central vein that carries blood through it. The stem cells identified by Wang and Nusse are found adjacent to this vein.

Classically, hepatocytes were largely thought to be all alike. Most mature hepatocytes are “polyploid,” which means that they have more than the normal two copies of each chromosome. With all this extra DNA, it makes it difficult or even impossible, for these cells to divide normally, but this extra DNA might confer other benefits.

“If it’s not necessary for a cell to maintain the capacity to divide, it can do whatever it wants with its genome,” said Nusse. “Red blood cells, for instance, have no DNA. Muscle cells have many copies of each chromosome.” Having extra copies of chromosomes might allow these cells to make large amounts of particular proteins quickly, for example.

However, the cell population identified by Wang and Nusse in the livers of laboratory mice is diploid, and have only two copies of each chromosome. These cells can divide to make carbon copies of themselves, or to make cells that begin their lives as diploid but then acquire additional copies of their chromosomes as they move away from the central vein into the main body of the liver.

“People in the field have always thought of hepatocytes as a single cell type,” said Wang. “And yet the cell we identified is clearly different from others in the liver. Maybe we should accept that there may be several subtypes of hepatocytes, potentially with different functions.”

To identify liver-specific stem cells, Wang and Nusse identified cells that express the protein Axin2. They found these axin2-expressing cells surrounding the central vein. Axin2 is produced by cells in response to the presence of members of the Wnt signaling protein family, and decades of research by Nusse and other laboratories have shown that the Wnt proteins play a critical role in embryonic development, and in the growth and maintenance of stem cells throughout the body.

Interestingly, Wang and Nusse, and others showed that the endothelial cells that line the interior surface of the central vein in the liver produce Wnt2 and Wnt9b. These secreted Wnt proteins confer stem cell properties on the neighboring hepatocytes that surround the central vein.

Finally, Nusse’s team discovered that a portion of the descendants of the Axin2-expressing cells move outward from the central vein over time, become polyploid and begin to express other, hepatocyte-specific genes. About one year after being born, these descendant cells had effectively replaced about 30 percent of the entire mouse liver, and made up about 40 percent of all hepatocytes in the liver.

These newly identified liver stem cells also express genes associated with very early embryonic development, which may give a clue as to when and where they arise.

“Perhaps these stem cells in the adult liver actually arise very early in development,” said Nusse, “when the embryo sets aside a certain population of cells to maintain the organ during adult life.”

Although the current research was conducted in mice, it is possible that there are more than just one kind of hepatocyte in humans as well, and this realization could transform the study of liver biology. For example, hepatocytes have proven notoriously difficult to grow in laboratory culture for study or for use in drug testing.

“The most common reason that promising new drugs for any type of condition fail is that they are found to be toxic to liver,” said Wang. “Researchers have been trying for decades to find a way to maintain hepatocytes in the laboratory on which to test the effects of potential medications before trying them in humans. Perhaps we haven’t been culturing the right subtype. These stem cells might be more likely to fare well in culture.”

There’s also an opportunity to better understand human disease.

“Does liver cancer arise from a specific subtype of cells?” said Wang. “This model also gives us a way to understand how chromosome number is controlled. Does the presence of the Wnt proteins keep the stem cells in a diploid state? These are fundamental biological questions we can now begin to address.”

Pregnancy and Delivery Unaffected in Women Patients With Crohn’s Disease Who Were Treated With Fat-Based Stem Cells

Fat is a readily accessible source of mesenchymal stem cells (MSCs). When fat is extracted by liposuction, the result is a so-called stromal vascular fraction (SVF) that contains a mishmash of mast cells (important in allergies), blood vessel-making cells, blood vessel-associated cells, fibroblasts, and MSCs. These adipose-derived stem cells (ASCs) as they are called, can be relatively easily prepared once the SVF is digested by enzymes, and centrifuges. The living adult MSCs are then rather easily identified because they adhere to plastic tissue culture plates.

Fat-based MSCs have been used in clinical studies to help heal patients with Crohn’s disease who have “fistulas.”  For a picture of a fistula, see here.  Crohn’s disease (CD) is one of a group of gastrointestinal diseases known as IBDs or inflammatory bowel diseases. CD features inflammation of any part of the GI tract, and this inflammation can affect multiple layers of the GI tract. Fistulas form when a hole is eroded through the GI tract and into another organ system. For example, in women, the rectum and erode and form an opening in the vagina. Alternatively, an opening can appear in some place other than the anus. Because of the repeated irritation and extensive inflammation of these lesions, they tend to not heal.

Beginning in 2003, Damián García-Olmo and his team at the Jiménez Diaz Foundation University Hospital in Madrid, Spain have tested the efficacy of fat-based stem cells in treating patients with CD-based fistulas.  The results have been encouraging and highly positive, since ASCs promote healing of the fistulas and decrease recovery time (see de la Portilla F, et al. (2013) Int J Colorectal Dis 28:313–323; García-Olmo D, et al. (2003) Int J Colorectal Dis 18:451–454; García-Olmo D, et al. (2005) Dis Colon Rectum 48:1416–1423; Garcia-Olmo D, et al. (2009) Dis Colon Rectum 52:79–86).

Recently, Garcia-Olmo and his colleagues examined data from several their patients who went on to become pregnant after their treatment with fat-based stem cells and even given birth. This study, which was published in the June 2015 edition of Stem Cells Translational Medicine, examined six patients from these previous clinical trials who were successfully treated with fat-based stem cells, had satisfactory resolution and healing of their lesions, and then went on to become pregnant and give birth.

Of the five women examined in this study, one was treated for rectovaginal and perinatal fistulas, two for rectovaginal fistulas only, and two others for perianal fistulas only. All women received 2 doses of 20 million and 40 million stem cells at three-four-month intervals. One patient, however, received 2 doses of 6.6 million and 20 million stem cells nine months apart.

The fertility of these women and their pregnancies were unaffected by their previous cell therapies. There were no signs of treatment-related malformations in the babies they delivered, and their bodies did not show any identifiable signs of structural abnormalities as a result of the stem cell treatments. It must be said, that all four women who delivered healthy babies (one of them even had twins) elected for Caesarian sections. The fifth woman, unfortunately, miscarried twice, both times during the first trimester.

However, even though this represents a small data set, this study does strongly suggest that injection of a patient’s own fat-based stem cells does not negatively affect a woman’s ability to conceive, the course of her pregnancy, or the health of her baby.

A Patient’s Own Stem Cells Treats Their Crohn’s Disease

Stem cells isolated from the fat of patients with Crohn’s disease, an inflammatory disease of the bowel, relieved them from fistulas, which are a common, and potentially dangerous side effect of the disease. This is according to the results of a phase 2 clinical trial published in the latest issue of STEM CELLS Translational Medicine (SCTM).

Patients with Crohn’s disease suffer from a painful, chronic disease in which the body’s immune system attacks its own gastrointestinal tract. In Crohn’s patients, inflammation within the bowel can sometimes extend completely through the intestinal wall and create a what is known as a “fistula.”. Fistulas are abnormal connections between the intestine and another organ or even the skin. If left untreated, a fistula can become infected and form an abscess that can be life threatening.

Chang Sik Yu, M.D., Ph.D., of the Asan Medical Center in Seoul, Korea, who is a senior author of the SCTM paper, describes the results of a clinical trial that was conducted in collaboration with four other hospitals in South Korea. According to Dr. Yu: “Crohn’s fistula is one of the most distressing diseases as it decreases patient’s quality of life and frequently recurs. It has been reported to occur in up to 38 percent of Crohn’s patients and over the course of the disease, 10 to 18 percent of them must undergo a proctectomy, which is a surgical procedure to remove the rectum.”

Overall, the treatments currently available for Crohn’s fistula remain unsatisfactory because they fail to achieve complete closure, lower recurrence of the fistulas and do not limit adverse effects, Dr. Yu said. Given the challenges and unmet medical needs in Crohn’s fistula, attention has turned to stem cell therapy as a possible treatment.

Several studies, including those undertaken by Dr. Yu’s team, have shown that mesenchymal stem cells (MSCs) do indeed improve Crohn’s disease and Crohn’s fistula. Their phase II trial enrolled 43 patients for a term of one year, over the period from January 2010 to August 2012. These patients received injections of their own fat-based MSCs, and 82 percent of them experienced complete closure of fistula eight weeks after the final ASC injection. 75 percent of the trial participants remained fistula-free two years later.

“It strongly demonstrated MSCs derived from ASCs are a safe and useful therapeutic tool for the treatment of Crohn’s fistula,” Dr. Yu said.

The latest study was intended to evaluate the long-term outcome by following 41 of the original 43 patients for yet another year. Dr. Yu reported, “Our long-term follow-up found that one or two doses of autologous ASC therapy achieved complete closure of the fistulas in 75 percent of the patients at 24 months, and sustainable safety and efficacy of initial response in 83 percent. No adverse events related to ASC administration were observed. Furthermore, complete closure after initial treatment was well sustained.”

“These results strongly suggest that autologous ASCs may be a novel treatment option for Crohn’s fistulae,” he said.

“Stem cells derived from fat tissue are known to regulate the immune response, which may explain these successful long-term results treating Crohn’s fistulae with a high risk of recurrence,” said Anthony Atala, M.D., Editor-in-Chief of STEM CELLS Translational Medicine and director of the Wake Forest Institute for Regenerative Medicine.

REALISTIC Trial to Test Efficacy of Bone Marrow Stem Cells on Liver Disease

Chronic liver disease is the fifth leading cause of death in the United Kingdom. With the long-standing shortage of donated, transplantable livers, the prognosis of such patients seems grim.

Several preclinical studies in animals have established that mobilization of bone marrow stem cells or direct injection of bone marrow stems into a damaged liver can augment healing and improve survival (Sukaida I, and others, Hepatology 2004;40:1304–11; and Yannaki E, and others, Exp Hematol 2005;33:108–19). Some small clinical trials have examined the use of a patient’s own bone marrow stem cells to prime the liver and stimulate its own internal healing mechanisms. These studies were small and varied in the manner in which the stem cells were delivered, but they di show that the stem cell treatments were safe and even improved the health of the liver significantly (Gordon MY, and others, Stem Cells 2006;24:1822–30; Terai S, and others, Stem Cells 2006;24:2292–8). Also, in patients with liver cancer who had to have portions of their livers removed, bone marrow stem cell treatments accelerated liver healing (am Esch JS, and others, Ann Surg 2012;255:79–85; am Esch JS, and others, Stem Cells 2005;23:463–70; and Furst G, and others, Radiology 2007;243:171–9).

Clearly there is a need for a larger, more systematic study of the efficacy of bone marrow stem cells as a therapeutic agent in patients with liver failure. To that end, Philip Newsome and his colleagues at the University of Birmingham, in collaboration with colleagues from Scotland, Newcastle, and Nottingham have initiated the REALISTIC trial, which stands for REpeated AutoLogous Infusions of STem cells In Cirrhosis.

This is a multi-center clinical trial and it will examine patients with Cirrhosis (fatty liver disease), regardless of the cause of that liver disease. Patients whose livers were damaged by excessive alcohol use, hepatitis B or C infections, or genetic conditions are all eligible for this study, but anyone who liver is too far-gone to be helped by a treatment like this or has had a liver transplant is not eligible.

Patients will receive injections of a drug called lenograstim (G-CSF) to mobilize bone marrow stem cells into the blood. These blood-based stem cells will then be collected and concentrated, and then implanted into the liver. Patients will be assessed at 3 months after the treatment and then followed-up for 1 year. Liver health will be assessed by means of medical imaging of the liver and various blood tests.

Patients will be evaluated using the Model for End-Liver Disease or MELD scoring system. Secondary tests will measure the degree of liver scarring, the degree of liver stiffness, blood tests, survival, and liver function.

Patients will also be placed into three groups. One group will only have the bone marrow stem cells mobilized from bone marrow without being collected. Another group will have the cells collected and implanted into the liver. The third group will receive standard care with not stem cells treatments.

There is a need for a study like this. I only hope that Newsome and his group can recruit the patients and get started collecting data as soon as they can.

Induced Pluripotent Stem Cells Differentiated into Intestinal Cells

Even the liver is the main organize when it comes to the metabolization of drugs, the small intestine also plays an important role in all aspects of drug metabolism. Unfortunately, no laboratory system exists at present that serves as a standardized system for evaluating the way drugs interact with the small intestine.

A new study by Tamihide Matsubara and his colleagues from Nagoya City University in Japan has sought to alleviate this problem. Matsubara and his coworkers used human induced pluripotent stem (iPS) cells to produce functional human intestinal enterocytes and showed that they faithfully recapitulated the drug metabolism of normal, human intestinal enterocytes.

To make intestinal enterocytes from iPS cells, Matsubara and others treated these cells with chemicals called activin A and fibroblast growth factor 2 to drive the cells to become intestinal-like stem cells. These cultured intestinal-like stem cells them differentiated into enterocytes when grown in a culture medium that contained epidermal growth factor and other small-molecule compounds.

The differentiated cells expressed intestinal marker genes and drug transporters. For example, they expressed sucrase-isomaltase, an intestine-specific marker, and enterocyte drug-metabolizing enzymes such as CYP1/2, CYP2C9, CYP2C19, CYP2D6, CYP3A4/5, UGT, and SULT. Inhibitor studies showed that the intestinal oligopeptide transporter SLC15A1/PEPT1 was inhibited by the pain reliever ibuprofen, just like in naturally-occurring enterocytes. Also, active forms of vitamin D increased the expression of the enzymes CYP3A4 and CYP3A4/5, which is also observed in naturally-occurring human enterocytes.

These results show that Matsubara and his colleagues have successfully generated enterocyte-like cells that have the same drug metabolizing capacities as naturally-occurring enterocytes. These cells would be very useful for developing novel evaluation systems to predict individual human intestinal drug metabolism.

Children’s Hospital Los Angeles Researchers Grow Functional Tissue-Engineered Intestine from Human Cells

Children’s Hospital Los Angeles is the home of a remarkable new study that has succeeded in growing tissue-engineered small intestine from human cells. This tissue engineered intestine recapitulates several key functional characteristics of human intestine such as the ability to absorb sugars. It also has structural features of human small intestine, such as a mucosal lining, support structures tiny and ultra-structural components like cellular connections.

This work was published in the American Journal of Physiology; GI and Liver and brings surgeons one step closer to using tissue engineered intestines in human patients.

Tissue-engineered small intestines are grown from stem cells isolated from the intestine. These laboratory-grown tissues offer a promising treatment for clinical conditions such as short-bowel syndrome (SBS), which is a major cause of intestinal failure, particularly in premature babies and newborns with congenital intestinal anomalies. Tissue engineered small intestines may also, perhaps in the future, offer a therapeutic alternative to intestinal transplantations, which is fraught with the problems of donor shortage and the need for lifelong immunosuppression.

Senior author Dr. Tracy Grikscheit, who is a principal investigator at the Saban Research Institute, which is housed at the Children’s Hospital of Los Angeles (CHLA), and the Developmental Biology and Regenerative Medicine program at the Children’s Hospital of Los Angeles. Dr. Grikscheit is also a pediatric surgeon at CHLA and assistant professor of surgery at the Keck School of Medicine of the University of Southern California.

Grikscheit main interest, as a clinician, is to find strategies to treat the most vulnerable young patients. For example, babies who are born prematurely can sometimes develop a devastating disease called necrotizing enterocolitis (NEC), in which life-threatening intestinal damage demands that large portions of the small intestine be surgically removed. Without a long enough intestine, NEC babies are dependent on intravenous feeding. This intravenous feeding is costly and may cause liver damage. NEC and other contributors to intestinal failure occur in 24.5 out of 100,000 live births, and the incidence of SBS is increasing and nearly a third of patients die within five years.

CHLA scientists had previously shown that tissue-engineered small intestine could be generated from human small intestine donor tissue implanted into immunocompromised mice. These initial studies were published in July 2011 in the biomedical journal Tissue Engineering, Part A, and while it was a hopeful study, only basic components of the intestine were identified in the implanted intestine. To be clinically relevant, it is necessary to make tissue engineered intestines that form a healthy barrier that can still absorb nutrition and regulate the exchange of electrolytes.

This new study, however, showed that mouse tissue engineered small intestines are quite similar to the tissue-engineered small intestines made from human intestinal stem cells. Both contain important building blocks such as the stem and progenitor cells that continue to regenerate the intestine throughout the lie of the organism. These cells are found within the engineered tissue in specific locations and are close to other specialized cells that are known to be necessary for the intestine to function as a fully functioning organ.

“We have shown that we can grow tissue-engineered small intestine that is more complex than other stem cell or progenitor cell models that are currently used to study intestinal regeneration and disease, and proven it to be fully functional as it develops from human cells,” said Grikscheit. “Demonstrating the functional capacity of this tissue-engineered intestine is a necessary milestone on our path toward one day helping patients with intestinal failure.”

Growing Human Esophagus Tissue from Human Cells

Tracy Grikscheit of the Saban Research Institute of Children’s Hospital Los Angeles and her colleagues have successfully grown a tissue engineered esophagus on a relatively simple biodegradable scaffold after seeding it with the appropriate stem and progenitor cells.

Progenitor cells have the ability to differentiate into specific cell types and can migrate to a particular target tissue. Their differentiation potential depends on the parent cell type from which they descended and their “niche” or local surroundings. The scaffold upon which these cells were seeded is composed of a simple polymer, but interestingly, several different combinations of cell types were able to generate a replacement organ that worked well when transplanted into laboratory mice.

“We found that multiple combinations of cell populations allowed subsequent formation of engineered tissue. Different progressive cells can find the right “partner” cell in order to grow into specific esophageal cell types; such as epithelium, muscle or nerve cells, and without the need for exogenous growth factors. This means that successful tissue engineering of the esophagus is simpler than we previously thought,” said Grikscheit.

Videos published the paper show a network of muscle cells properly wired with nerves that properly self-organizes whose muscles spontaneously contract.  Such structures are called an esophageal organoid unit (EOU) in culture. Spontaneous contraction is observed within these EOUs.

This study could be the impetus for clinical procedures that can treat children born with portions of their esophagus missing. Since the esophagus carries liquids and food to the stomach from the mouth, it is a vitally important part of the body.

This protocol, could also be applied to patients who have suffered from esophageal cancer and had to have their esophagus removed. Esophageal cancer is one of the fastest growing types of cancer in the United States to date. Alternatively, people who have accidentally swallowed caustic liquids may also benefit from this type of esophageal repair.

This simple scaffold made of a polyglycolic acid/poly-L-lactic acid and coated with the protein collagen is inexpensive and versatile and completely sufficient for the growth of tissue-engineered esophagi from human cells, according to this study. When established in culture, this system can also serve as a model system to study the cell dynamics and physiology of the esophagus.

A deeper understanding of how esophageal cells behave in response to injury and how various donor cells could potentially expand the pool of potential donor cells for engineered tissue.

Even though this technique has only been tested in animals to date, fine-tuning of this technique might very well ready it for clinical trials in the future.

Small Human Stomach Organoids Made From Induced Pluripotent Stem Cells

A new study published in the international journal Nature describes, for the first time, the use of human pluripotent stem cells to create a three-dimensional stomach-like mini-organ. This is the beginning of what might become an unprecedented tool for examining the genesis of diseases such as stomach cancer to diabetes.

Jim Wells and his colleagues at Cincinnati Children’s Hospital Medical Center used human pluripotent stem cells, which are made from mature human cells through a combination of genetic engineering and cell culture techniques, to grow a their miniature stomachs. Wells’ group then used their mini-stomachs also known as gastric organoids, in collaboration with scientists from University of Cincinnati College of Medicine, to study the infection of stomach tissue by the bacterium Helicobacter pylori, which causes peptic ulcer disease and stomach cancer.

According to Wells, a scientist in the divisions of Developmental Biology and Endocrinology at Cincinnati Children’s, this is the first time anyone has succeeded in making three-dimensional human gastric organoids (hGOs). This achievement may present new opportunities for drug discovery, modeling early stages of stomach cancer and studying some of the factors that give rise to obesity related diabetes. This work also represents the first time researchers have produced three-dimensional human embryonic foregut, which is a good starting point for generating other foregut organ tissues such as the lungs and pancreas. “Until this study, no one had generated gastric cells from human pluripotent stem cells (hPSCs),” Wells said. “In addition, we discovered how to promote formation of three-dimensional gastric tissue with complex architecture and cellular composition.”

a, Schematic representation of a typical antral gland showing normal cell types and associated molecular markers. b–g, Immunofluorescent staining demonstrated that day-34 hGOs consisted of normal cell types found in the antrum, but not the fundus. The hGO epithelium contained surface mucous cells that express MUC5AC (b, left), similar to the P12 mouse antrum (b, right), but not ATP4B-expressing parietal cells (c, left) that characterize the fundus (c, right). SOX9+ cells were found at the base of the hGO epithelium (d, left), similar to the progenitor cells found in the P12 antrum (d, right). Furthermore, hGOs contained MUC6+ antral gland cells (e) and LGR5-expressing cells (yellow arrow) (f). Boxed regions in b–f are shown as high magnification images below (b, c, d) or to the right (e, f) of the original. g, Day-34 hGOs also contained endocrine cells (SYP) that expressed the gastric hormones GAST, SST, GHRL and serotonin (5-HT). Scale bars, 100 μm (original images in b–f) and 20 μm (magnified images in b–f and g). Marker expression data are representative from a minimum of 10 independent experiments, except LGR5-eGFP data, which is a representative example from two separate experiments. DAPI, 4′,6-diamidine-2-phenylindole.
a, Schematic representation of a typical antral gland showing normal cell types and associated molecular markers. b–g, Immunofluorescent staining demonstrated that day-34 hGOs consisted of normal cell types found in the antrum, but not the fundus. The hGO epithelium contained surface mucous cells that express MUC5AC (b, left), similar to the P12 mouse antrum (b, right), but not ATP4B-expressing parietal cells (c, left) that characterize the fundus (c, right). SOX9+ cells were found at the base of the hGO epithelium (d, left), similar to the progenitor cells found in the P12 antrum (d, right). Furthermore, hGOs contained MUC6+ antral gland cells (e) and LGR5-expressing cells (yellow arrow) (f). Boxed regions in b–f are shown as high magnification images below (b, c, d) or to the right (e, f) of the original. g, Day-34 hGOs also contained endocrine cells (SYP) that expressed the gastric hormones GAST, SST, GHRL and serotonin (5-HT). Scale bars, 100 μm (original images in b–f) and 20 μm (magnified images in b–f and g). Marker expression data are representative from a minimum of 10 independent experiments, except LGR5-eGFP data, which is a representative example from two separate experiments. DAPI, 4′,6-diamidine-2-phenylindole.

Wells’ gastric organoids are a significant advance in gastroenterological research because distinct differences in development and architecture of the adult stomach limit the reliability of mouse models for studying human stomach development and disease.

As a research tool, human gastric organoids may help clarify other unknown features of the stomach, such as identifying those biochemical processes in the gut that allow gastric-bypass patients to become diabetes-free soon after surgery before losing significant weight. Medical conditions such as obesity-fueled diabetes and the metabolic syndrome are of great interest to public health workers, given the explosion of global cases in the last few decades. A major challenge to addressing these and other medical conditions that involve the stomach has been a relative lack of reliable laboratory model systems to accurately recapitulate human biology.

The key to growing human gastric organoids was to identify the developmental steps involved in normal stomach formation. Manipulation of these processes in a cell culture system drove human pluripotent stem cells to form immature stomach tissue. In culture and over the course of a month, these steps resulted in the formation of 3D human gastric organoids that were around 3mm (1/10th of an inch) in diameter. Wells and his colleagues also used this approach to identify steps that go awry when the stomach does not form correctly.

In collaboration with his colleagues, Kyle McCracken, an MD/PhD graduate student in Wells’ laboratory, and Yana Zavros, PhD, a researcher at UC’s Department of Molecular and Cellular Physiology, Wells showed that his gastric organoids were rapidly infected by H. pylori bacteria. Within 24 hours of inoculation, the bacteria had triggered significant biochemical changes to the organ, and the human gastric organoids faithfully mimicked the early stages of H. pylori-induced gastric disease. McCracken also noticed activation of a cancer gene called c-Met, which is one of the first stages in the induction of stomach cancer, an important long-term sequel to peptic ulcer disease. McCracken was also surprised by the rapid spread of infection in the tissues of his human gastric organoids.

a, Day-34 hGOs contained a zone of MKI67+ proliferative cells similar to the embryonic (E18.5) and postnatal (P12) mouse antrum. b, Using hGOs to model human-specific disease processes of H. pylori infection. Pathogenic (G27) and attenuated (ΔCagA) bacteria were microinjected into the lumen of hGOs and after 24 h, bacteria (both G27 and ΔCagA strains) were tightly associated with the apical surface of the hGO epithelium. c, Immunoprecipitation (IP) for the oncogene c-Met demonstrates that H. pylori induced a robust activation (tyrosine phosphorylation (pTyr)) of c-Met, and this is a CagA-dependent process. Furthermore, CagA immunoprecipitated with c-Met, suggesting that these proteins interact in hGO epithelial cells. Phosphorylated c-Met (phos. c-MET) and CagA control lysates were not immunoprecipitated but used to confirm molecular masses. The molecular mass markers are indicated (130 and 170 kilodaltons (kDa)) and shown in Extended Data Fig. 9c. IB, immunoblotting. d, Within 24 h, H. pylori infection caused a CagA-dependent twofold increase in the number of proliferating cells in the hGO epithelium, measured by 5-ethynyl-2′-deoxyuridine (EdU) incorporation. *P < 0.05; two-tailed Student’s t-test; n = 3 biological replicates per condition, data representative of 4 independent experiments. Scale bars, 100 μm (a) and 20 μm (b). Error bars represent s.e.m.
a, Day-34 hGOs contained a zone of MKI67+ proliferative cells similar to the embryonic (E18.5) and postnatal (P12) mouse antrum. b, Using hGOs to model human-specific disease processes of H. pylori infection. Pathogenic (G27) and attenuated (ΔCagA) bacteria were microinjected into the lumen of hGOs and after 24 h, bacteria (both G27 and ΔCagA strains) were tightly associated with the apical surface of the hGO epithelium. c, Immunoprecipitation (IP) for the oncogene c-Met demonstrates that H. pylori induced a robust activation (tyrosine phosphorylation (pTyr)) of c-Met, and this is a CagA-dependent process. Furthermore, CagA immunoprecipitated with c-Met, suggesting that these proteins interact in hGO epithelial cells. Phosphorylated c-Met (phos. c-MET) and CagA control lysates were not immunoprecipitated but used to confirm molecular masses. The molecular mass markers are indicated (130 and 170 kilodaltons (kDa)) and shown in Extended Data Fig. 9c. IB, immunoblotting. d, Within 24 h, H. pylori infection caused a CagA-dependent twofold increase in the number of proliferating cells in the hGO epithelium, measured by 5-ethynyl-2′-deoxyuridine (EdU) incorporation. *P < 0.05; two-tailed Student’s t-test; n = 3 biological replicates per condition, data representative of 4 independent experiments. Scale bars, 100 μm (a) and 20 μm (b). Error bars represent s.e.m.

There is a relative dearth of literature on how the human stomach developments, which was a significant impediment to Wells’ research. Wells and his coworkers had to use a combination of published works and studies from his own lab, to answer a number of basic developmental questions about how the stomach forms. Over the course of two years, by experimenting with different factors to drive the formation of the stomach, Wells and his colleagues came upon a protocol that resulted in the formation of 3D human gastric tissues in culture.

a, Schematic representation of the in vitro culture system used to direct the differentiation of pluripotent stem cells into three-dimensional gastric organoids. b, Defining molecular domains of the posterior foregut in E10.5 mouse embryos with Sox2, Pdx1 and Cdx2; Sox2/Pdx1, antrum (a); Sox2, fundus (f); Pdx1, dorsal and ventral pancreas (dp and vp); Pdx1/Cdx2, duodenum (d). c, Posterior foregut spheroids exposed for three days to retinoic acid (2 μM) exhibited >100-fold induction of PDX1 compared to control spheroids, measured by qPCR at day 9. *P < 0.05; two-tailed Student’s t-test; n = 3 biological replicates per condition, data representative of 4 independent experiments. d, Time course qPCR analysis of antral differentiation (according to protocol detailed in Fig. 2a) demonstrated sequential activation of SOX2 at day 6 (posterior foregut (FG) endoderm), followed by induction of PDX1 at day 9 (presumptive antrum). Day-9 antral spheroids had a 500-fold increase in SOX2 and a 10,000-fold increase in PDX1 relative to day-3 definitive endoderm (DE). *P < 0.05; two-tailed Student’s t-test; n = 3 biological replicates per time point, data representative of 2 independent experiments. The pancreatic marker PTF1A was not significantly increased. e, Stereomicrographs showing morphological changes during growth of gastric organoids. By 4 weeks, the epithelium of hGOs exhibited a complex folded and glandular architecture (arrows). D, day. f, Comparison of mouse stomach at E18.5 and day-34 hGOs. Pdx1 was highly expressed in the mouse antrum but excluded from the fundus. Human gastric organoids expressed PDX1 throughout the epithelium and exhibited morphology similar to the late gestational mouse antrum (arrows). Scale bars, 100 μm (b and f) and 250 µm (e). Error bars represent s.d.
a, Schematic representation of the in vitro culture system used to direct the differentiation of pluripotent stem cells into three-dimensional gastric organoids. b, Defining molecular domains of the posterior foregut in E10.5 mouse embryos with Sox2, Pdx1 and Cdx2; Sox2/Pdx1, antrum (a); Sox2, fundus (f); Pdx1, dorsal and ventral pancreas (dp and vp); Pdx1/Cdx2, duodenum (d). c, Posterior foregut spheroids exposed for three days to retinoic acid (2 μM) exhibited >100-fold induction of PDX1 compared to control spheroids, measured by qPCR at day 9. *P < 0.05; two-tailed Student’s t-test; n = 3 biological replicates per condition, data representative of 4 independent experiments. d, Time course qPCR analysis of antral differentiation (according to protocol detailed in Fig. 2a) demonstrated sequential activation of SOX2 at day 6 (posterior foregut (FG) endoderm), followed by induction of PDX1 at day 9 (presumptive antrum). Day-9 antral spheroids had a 500-fold increase in SOX2 and a 10,000-fold increase in PDX1 relative to day-3 definitive endoderm (DE). *P < 0.05; two-tailed Student’s t-test; n = 3 biological replicates per time point, data representative of 2 independent experiments. The pancreatic marker PTF1A was not significantly increased. e, Stereomicrographs showing morphological changes during growth of gastric organoids. By 4 weeks, the epithelium of hGOs exhibited a complex folded and glandular architecture (arrows). D, day. f, Comparison of mouse stomach at E18.5 and day-34 hGOs. Pdx1 was highly expressed in the mouse antrum but excluded from the fundus. Human gastric organoids expressed PDX1 throughout the epithelium and exhibited morphology similar to the late gestational mouse antrum (arrows). Scale bars, 100 μm (b and f) and 250 µm (e). Error bars represent s.d.

Wells emphasized importance of basic research for the eventual success of this project, adding, “This milestone would not have been possible if it hadn’t been for previous studies from many other basic researchers on understanding embryonic organ development.”

While this does represent a terrific stride toward better model systems for gastric research and pathology, these gastric organoids are very immature and lack several of the cell types found in mature stomach tissue. For example, these organoids lack chief cells, which secrete the stomach enzyme pepsin (in an inactive form called pepsinogen), and parietal cells, which produce stomach acid. This is significant because chronic inflammation of the stomach can cause loss of parietal cells, which decreases chief cell differentiation and induce chief cells to transdifferentiate back into neck cells. This leads to overproduction of mucus cells. This mucus cell metaplasia is known as spasmolytic polypeptide expressing metaplasia (SPEM) that seems to be a precancerous condition for the stomach. Also if parietal cells are lost, mature chief cells do not form. This seems to imply that parietal cells secrete factors that lead to differentiation of chief cells, so if lost. These gastric organoids also do not make ECL cells or enterochromaffin-like cells, which secrete histamine, one of the most important regulators of stomach acid production. A prolonged stimulation of these ECL cells causes increased numbers of them. This is especially important in gastrinomas, which are tumors in which there is an excessive secretion of the stomach hormone gastrin, one of the key factors contributing to Zollinger-Ellison syndrome.  The hallmark of this disease is ulceration of the stomach and upper small intestine (duodenum) as a result of excessive and unregulated secretion of gastric acid.  Most commonly, hypergastrinemia is the result of these gastrin-secreting tumors or gastrinomas that develop in the pancreas or duodenum.  Thus, in only this short discussion, we have noted several diseases of the stomach that cannot be modeled with this particular system because these stomach-specific cells are not present.

Therefore, while this is a fantastic model system for stomach development and H. pylori infection, more work remains in order to make a stomach model that more accurately models the adult stomach.

Stem Cell Transplant from Gut Repairs Damaged Gut in Mice with Inflammatory Bowel Disease

Even though a stem population has been identified and studied in the gastrointestinal tract, Wellcome Trust Researchers have identified a new source of GI-based stem cells that have the ability to repair damage from inflammatory bowel disease when transplanted into mice.  This work comes to us from the Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute at the University of Cambridge and BRIC at the University of Copenhagen, Denmark.  This work could translate into patient-specific regenerative therapies for inflammatory bowel diseases such as ulcerative colitis.

Adult tissues contain specialized stem cells populations that maintain individual tissues and organs.  Adult stem cells tend to be restricted to their tissue of origin and also tend to have the ability to differentiate into a limited subset of adult cell types.  Stem cells found in the gut, for example, typically can typically contribute to the replenishment of the gut whereas stem cells in the skin will only contribute to maintenance of the skin.

When examining the developing intestinal tissue in a mouse embryos, Kim Jensen and her team discovered stem cell population hat were quite different from those adult stem cells that have been described in the gut.  These cells actively divided and also could be grown in the laboratory over long periods of time without undergoing differentiation into mature cells.  Under specific culture conditions, however, these cells could be induced to differentiate into mature intestinal tissue.

When these cells were transplanted into mice that suffered from an inflammatory bowel disease, The implanted stem cell attached to the damaged areas within the intestine, and began to integrate into the existing tissue, within three hours of implantation.

The lead researcher in this study, Dr. Kim Jensen, a Wellcome Trust researcher and Lundbeck foundation fellow, said: “We found that the cells formed a living plaster over the damaged gut. They seemed to respond to the environment they had been placed in and matured accordingly to repair the damage.

“One of the risks of stem cell transplants like this is that the cells will continue to expand and form a tumour, but we didn’t see any evidence of that with this immature stem cell population from the gut.”

Cells with similar characteristics were isolated from both mice and humans.  Jensen’s team also generated similar cells by reprogramming adult human cells to make induced Pluripotent Stem Cells (iPSCs) that were also grown under the appropriate culture conditions.

“We’ve identified a source of gut stem cells that can be easily expanded in the laboratory, which could have huge implications for treating human inflammatory bowel diseases. The next step will be to see whether the human cells behave in the same way in the mouse transplant system and then we can consider investigating their use in patients,” added Dr Jensen.

U of Pitt Team Discovers Stem Cells in the Esophagus

Even though several studies have been unsuccessful at identifying a stem population in the esophagus, a study from the University of Pittsburgh has discovered a stem cell pool that services the esophagus. Researchers from the University of Pittsburgh School of Medicine have published an animal report in the journal Cell Reports that might lead to new insights into the development and treatment of esophageal cancer and a precancerous condition known as Barrett’s esophagus.

In the US, more than 18,000 people will be diagnosed with esophageal cancer in 2014 and almost 15,500 people will die from it, according to numbers generated by the American Cancer Society. The precancerous condition known as Barrett’s esophagus is characterized by tissue changes in the lining of the esophagus in which the esophageal lining begins to resemble the tissue architecture of the intestine. Barrett’s esophagus is usually a long-term consequence of gastro-esophageal reflux disease or GERD.

“The esophageal lining must renew regularly as cells slough off into the gastrointestinal tract,” said senior investigator Eric Lagasse, Pharm.D., Ph.D., associate professor of pathology, Pitt School of Medicine, and director of the Cancer Stem Cell Center at the McGowan Institute for Regenerative Medicine. “To do that, cells in the deeper layers of the esophagus divide about twice a week to produce daughter cells that become the specialized cells of the lining. Until now, we haven’t been able to determine whether all the cells in the deeper layers are the same or if there is a subpopulation of stem cells there.”

Lagasse and his team grew small explants of esophageal tissue in culture. These esophageal “organoids” from mice were then used to conduct experiments that were used to identify and track the different cells in the basal layer of the tissue. In these organoids, Lagasse and others found a small population of cells that divide more slowly, are less mature, can differentiate into several different types of esophageal-specific cell types, and have the ability to self-renew. The ability to self-renew is a defining feature of stem cells.

“It was thought that there were no stem cells in the esophagus because all the cells were dividing rather than resting or quiescent, which is more typical of stem cells,” Dr. Lagasse noted. “Our findings reveal that there indeed are esophageal stem cells, and rather than being quiescent, they divide slowly compared to the rest of the deeper layer cells.”

Lagasse and his team would now like to examine human esophageal tissues from patients with Barrett’s esophagus in order to determine if such patients show evidence of esophageal stem cell dysfunction.

“Some scientists have speculated that abnormalities of esophageal stem cells could be the origin of the tissue changes that occur in Barrett’s disease,” Dr. Lagasse said. “Our current and future studies could make it possible to test this long-standing hypothesis.”

Tonsil-Based Stem Cells To Repair the Liver

Byeongmoon Jeong and colleagues report in the journal ACS Applied Materials & Interfaces that injections of stem cells from tonsils, a body part we don’t need, can repair damaged livers without the need for surgery. The liver rids the body of toxins, makes blood proteins, and metabolizes a goodly number of molecules from our food. Liver failure is a deadly condition and a liver transplant is often the only option to restore the patient to health. Unfortunately there is a need for available organs for transplantation, Also, liver transplantation presents certain risks and also is extremely expensive.

A promising alternative to liver transplantation is the implantation of liver cells. Adult stem cells can be used to make new liver cells, and bone marrow-based stem cells have been used, but they these cells have inherent limitations. Recently, scientists have identified another stem cell source that can be used for this purpose from tonsils. Every year, thousands of tonsillectomies are performed to remove tonsils, and the extirpated tonsils are discarded. Now, however, these throw-away tissues could have a new purpose. Scientists have devised ways to grow tonsil-based stem cells on a three-dimensional scaffold that simulates living liver tissue.

Jeong’s team encapsulated tonsil-derived stem cells in a heat-sensitive liquid that solidifies into a gel at body temperature. To these cells ensconced in this gel, they added protein growth factors to stimulate the stem cells to differentiate into liver cells. The stem cells differentiated into liver cells, degraded the scaffold, and formed functioning liver cells. Jeong and others think that with a little tweaking, this procedure could potentially provide an injectable tissue engineering technique to treat liver disease without surgery.

See Seung-Jin Kim, Min Hee Park, Hyo Jung Moon, Jin Hye Park, Du Young Ko, Byeongmoon Jeong. Polypeptide Thermogels As a 3D Culture Scaffold for Hepatogenic Differentiation of Human Tonsil-derived Mesenchymal Stem Cells. ACS Applied Materials & Interfaces, 2014; 140905122318006 DOI:10.1021/am504652y.

Growing Intestinal Stem Cells

Researchers from MIT and Brigham and Women’s Hospital in Boston, MA have discovered a protocol that allows them to grow unlimited quantities of intestinal stem cells. These intestinal stem cells can then be induced to differentiate into pure populations of various types of mature intestinal cells. Scientists can used these cultured intestinal cells to develop new drugs and treat gastrointestinal diseases, such as Crohn’s disease or ulcerative colitis.,

The small intestine has a small repository of adult stem cells that differentiate into mature adult cells that have specialized functions. Until recently, there was no good way to grow large numbers of these intestinal stem cells in culture. Intestinal stem cells, you see, only retain their immature characteristics when they are in contact with supportive cells known as Paneth cells.

paneth cells

In order to grow intestinal stem cells in culture, researchers from the laboratories of Robert Langer at the MIT Koch Institute for Integrative Cancer Research and Jeffrey Karp from the Harvard Medical School and Brigham and Women’s Hospital, determined the specific molecules that Paneth cells make that keep the intestinal stem cells in their immature state. Then they designed small molecules that mimic the Paneth cell-specific molecules. When Langer and Karp’s groups grew the intestinal stem cells in culture with those small molecules, the cells remained immature and grew robustly in culture.

Langer said, “This opens the door to doing all kinds of thing, ranging from someday engineering a new gut for patients with intestinal diseases to doing drug screening for safety and efficacy. It’s really the first time this has been done.”

The inner mucosal layer of the intestine has several vital functions: the absorption of nutrients, the secretion of mucus of create a barrier between our own cells and the bacteria and viruses and habitually inhabit our bowels, and alerting the immune system to the presence of potential disease-causing agents in the bowel.

The intestinal mucosa is organized into a collection of folds with small indentations called “intestinal crypts.”  At the bottom of each crypt is a small pool of intestinal stem cells that divide to routinely replace the specialized cells of the intestinal epithelium.  Because the cells of the intestinal epithelium show a high rate of turnover (they only last for about five days), these stem cells must constantly divide to replenish the intestine.


Once these intestinal stem cells divide, they can differentiate into any type of mature intestinal cell type.  Therefore, these intestinal stem cells provide a marvelous example of a “multipotent stem cell.”

Obtaining large quantities of intestinal stem cells could certainly help gastroenterologists  treat gastrointestinal diseases that damage the epithelial layer of the gut.  Fortunately, recent studies in laboratory animals have demonstrated that the delivery of intestinal stem cells can promote the healing of ulcers and regeneration of new tissue, which offers a new way to treat inflammatory bowel diseases like ulcerative colitis.

This, however, is only one of the many uses for cultured intestinal stem cells.  Researchers are literally salivating over the potential of studying things like goblet cells, which control the immune response to proteins in foods to which many people are allergic.  Alternatively, scientists would like to investigate the properties of enteroendocrine cells, which secrete hunger hormones and play a role in obesity.  I think you can see, that large numbers of intestinal stem cells could be a boon to gastrointestinal research.

Karp said, “If we had ways of performing high-throughput screens of large numbers of these very specific cell types, we could potentially identify new targets and develop completely new drugs for diseases ranging from inflammatory bowel disease to diabetes.”

The laboratory of Hans Clevers in 2007 identified a molecule that is specifically made by intestinal stem cells called Lgr5.  Clevers is a professor at the Hubrecht Institute in the Netherlands and he and his co-workers have just identified particular molecules that enable intestinal stem cells to grow in synthetic culture.  In culture, these small clusters of intestinal stem cells differentiate and form small sphere-like structures called “organoids,” because they consist of a ball of intestinal cells that have many of the same organizational properties of our own intestines, but are made in culture.

Clevers and his colleagues tried to properly define the molecules that bind Paneth cells and intestinal stem cell together.  The purpose of this was to mimic the Paneth cells in culture so that the intestinal stem cells would grow robustly in culture.  Clevers’ team discovered that Paneth cells use two signal transduction pathways (biochemical pathways that cells use to talk to each other) to coordinate their “conversations” with the adjacent stem cells.  These two signal transduction pathways are the Notch and Wnt pathways.

Fortunately, two molecules could be used to induce intestinal stem cell proliferation and prevent their differentiation: valproic acid and CHIR-99021.  When Clevers and others grew mouse intestinal stem cells in the presence of these two compounds, they found that large clusters of cells grew that consisted of 70-90 percent pure stem cells.  When they used inhibitors of the Notch and Wnt pathway, they could drive the cells to form particular types of mature intestinal cells.

“We used different combinations of inhibitors and activators to drive stem cells to differentiate into specific populations of mature cells,” said Xiaolei Yin, first author of this paper.  Yin and others were able to get this strategy to work with mouse stomach and colon cells, and that these small molecules also drove the proliferation of human intestinal stem cells.

Presently, Clevers’ laboratory is trying to engineering intestinal tissues for potential transplantation in human patients and for rapidly testing the effects of drugs on intestinal cells.

Ramesh Shivdasani from Harvard Medical School and Dana-Farber Cancer Institute would like to use these cells to investigate what gives stem cells their ability to self-renew and differentiate into other cell types.  “There are a lot of things we don’t know about stem cells,” said Shivdasani.  “Without access to large quantities of these cells, it’s very difficult to do any experiments.  This opens the door to a systematic, incisive, reliable way of interrogating intestinal stem cell biology.”

X. Yi, et al. “Niche-independent high-purity cultures of Lgr5 intestinal stem cells and their progeny.” Nature Methods 2013; DOI:10.1038/nmeth.2737.

Stem Cell Transplant Repairs the Damage that Results from Inflammatory Bowel Disease

A source of stem cells from the digestive tract can repair a type of inflammatory bowel disease when transplanted into mice has been identified by British and Danish scientists.

This work resulted from a collaboration between stem cell scientists at the Wellcome Trust-Medical Research Council/Cambridge Stem Cell Institute at Cambridge University, and the Biotech Research and Innovation Centre (BRIC) at the University of Copenhagen, Denmark. This research paves the way for patient-specific regenerative therapies for inflammatory bowel diseases such as ulcerative colitis.

All tissues in out body probably contain a stem cell population of some sort, and these tissue-specific stem cells are responsible for the lifelong maintenance of these tissues, and, ultimately, organs. Organ-specific stem cells tend to be restricted in their differentiation abilities to the cell types within that organ. Therefore, stem cells from the digestive tract will tend to differentiate into cell types typically found in the digestive tract, and skin-based stem cells will usually form cell types found in the skin.

When this research team examined developing intestinal tissue in mouse fetuses, they discovered a stem cell population that differed from the adult stem cells that have already been described in the gastrointestinal tract. These new-identified cells actively divided and could be grown in the laboratory over a long period of time without terminally differentiating into adult cell types. When exposed to the right conditions, however, these cells could differentiate into mature intestinal tissue.


Could these cells be used to repair a damaged bowel? To address this question, this team transplanted these cells into mice that suffered from a type of inflammatory bowel disease, and within three hours the stem cells has attached to the damaged areas of the mouse intestine. integrated into the intestine, and contributed to the repair of the damaged tissue.

“We found that the cells formed a living plaster (British English for a bandage) over the damaged gut,” said Jim Jensen, a Wellcome Trust researcher and Lundbeck Foundation fellow, who led the study. “They seemed to response to the environment they had been placed in and matured accordingly to repair the damage. One of the risks of stem cell transplants like this is that the cells will continue to expand and form a tumor, but we didn’t see any evidence of that with this immature stem cell population from the gut.”

Because these cells were derived from fetal intestines, Jensen and his team sought to establish a new source of intestinal progenitor cells.  Therefore, Jensen and others isolated cells with similar characteristics from both mice and humans, and  made similar cells similar cells by reprogramming adult human cells in to induced pluripotent stem cells (iPSCs) and growing them in the appropriate conditions.  Because these cells grew into small spheres that consisted of intestinal tissue, they called these cells Fetal Enterospheres (FEnS).

Established cultures of FEnS expressed lower levels of Lgr5 than mature progenitors and grew in the presence of the Wnt antagonist Dkk1 (Dickkopf).  New cultures can be induced to form mature intestinal organoids by exposure to the signaling molecule Wnt3a. Following transplantation in a model for colon injury, FEnS contributed to regeneration of the epithelial lining of the colon by forming epithelial crypt-like structures that expressed region-specific differentiation markers.

“We’ve identified a source of gut stem cells that can be easily expanded in the laboratory, which could have huge implications for treating human inflammatory bowel diseases. The next step will be to see whether the human cells behave in the same way in the mouse transplant system and then we can consider investigating their use in patients,” Jensen said.

An Efficient Method for Converting Fat Cells to Liver Cells

I have a friend whose wife has systemic lupus erythematosis, and her liver has taken a beating as a result of this disease. She has never had a drop of alcohol for decades and yet she has a liver that looks like the liver of a 70-year-old alcoholic. The scarring of the liver as result of repeated damage and healing has seriously compromised her liver function. She is now a candidate for a liver transplant. Wouldn’t it be nice to simply give her liver cells to heal her liver?

This dream came a little closer to becoming reality in October of this year when scientists at Stanford University developed a fast and efficient way to convert fat cells isolated from routine liposuction into liver cells. Even though these experiments used mice, the stem cells were isolated from human liposuction procedures.

This experiment did not use embryonic stem cells or induced pluripotent stem cells to generate liver cells. Instead it used adult stem cells from fat.

Fat-based stem cells

The liver builds complex molecules, filters and breaks down waste products and toxic substances that might otherwise accumulate to dangerous concentrations.

The liver, unlike other organs, has a capacity to regenerate itself to a significant extent, but the liver’s regenerative abilities cannot overcome the consequences of acute liver poisoning, or chronic damage to the liver, as a result of hepatitis, alcoholism, or drug abuse.

For example, acetaminophen (Tylenol) is a popular pain-reliever, but abusing acetaminophen can badly damage the liver. About 500 people die each year from abuse of acetaminophen, and some 60,000 emergency-room visits and more than 25,000 hospitalizations annually are due to acetaminophen abuse. Other environmental toxins, such as poisonous mushrooms, contribute more cases of liver damage.

Fortunately, the fat-to-liver protocol is readily adaptable to human patients, according to Gary Peltz, professor of anesthesia and senior author of this study. The procedure takes about nine days, which is easily fast enough to treat someone suffering from acute liver poisoning, who might die within a few weeks without a liver transplant.

Some 6,300 liver transplants are performed annually in he United States, and approximately 16,000 patients are on the waiting list for a liver. Every year more than 1,400 people die before a suitable liver can be found for them.

Even though liver transplantations save the lives of patients, the procedure is complicated, not without risks, and even when successful, is fraught with after effects. The largest problem is the immunosuppressant drugs that live patients must take in order to prevent their immune system from rejecting the transplanted liver. Acute rejection is an ongoing risk in any solid organ transplant, and improvements in immunosuppressive therapy have reduced rejection rates and improved graft survival. However, acute rejection still develops in 25% to 50% of liver transplant patients treated with immunosuppressants. Chronic rejection is somewhat less frequent and is declining and occurs in approximately 4% of adult liver transplant patients.

Peltz said, “We believe our method will be transferable to the clinic, and because the new liver tissue is derived from a person’s own cells, we do not expect that immunosuppressants will be needed.”

Peltz also noted that fat-based stem cells do not normally differentiate into liver cells. However, in 2006, a Japanese laboratory developed a technique for converting fat-based stem cells into induced liver cells (called “i-Heps” for short). This method, however, is inefficient, takes 30 days, and relies on chemical stimulation. In short, this technique would not provide enough material to regenerate a liver.

The Stanford University group built upon the Japanese work and improved it. Peltz’s group used a spherical culture and were able to convert fat-bases stem cells into i-Heps in nine days and with 37% efficiency (the Japanese group only saw a 12% rate). Since the publication of their paper, Peltz said that workers in his laboratory have increased the efficiency to 50%.

Dan Xu, a postdoctoral scholar and the lead author of this study, adapted the spherical culture methodology from early embryonic-stem-cell literature. However, instead of growing on flat surfaces in a laboratory dish, the harvested fat cells are cultured in a liquid suspension in which they form spheroids. Peltz noted that the cells were much happier when they were grown in small spheres.

Once they had enough cells, Peltz and his co-workers injected them into immune-deficient laboratory mice that accept human grafts. These mice were bioengineered in 2007 as a result of a collaboration between Peltz and Toshihiko Nishimura from the Tokyo-based Central Institute for Experimental Animals. These mice had a viral thymidine kinase gene inserted into their genomes and when treated with the drug gancyclovir, the mice experienced extensive liver damage.

After gancyclovir treatment, Peltz and his coworkers injected 5 million i-Heps into the livers of these mice, using ultrasound-guided injection procedures, which is typically used for biopsies.

Four weeks later, the mice expressed human blood proteins and 10-20 percent of the mouse livers were repopulated with human liver cells. Blood tests also showed that the mouse livers, which were greatly damaged previous to the transplantation, were processing nitrogenous wastes properly. Structurally, the mouse livers contained human cells that made human bile ducts, and expressed mature human liver cells.

Other tests established that the i-Heps made from fat-based stem cells were more liver-like than i-Heps made from induced pluripotent stem cells.

Two months are injection of the i-Heps, there was no evidence of tumor formation.

Peltz said, “To be successful, we must regenerate about half of the damaged liver’s original cell count.” With the spherical culture, Peltz is able to produce close to one billion injectable i-Heps from 1 liter of liposuction aspirate. The cell replication that occurs after injection expands that number further to over 100 billion i-Heps.

If this is possible, then this procedure could potentially replace liver transplants. Stanford University’s Office of Technology Licensing has filed a patent on the use of spherical culture for hepatocyte (liver cell) induction. Peltz’s group is optimizing this culture and injection techniques,talking to the US Food and Drug Administration, and gearing up for safety tests on large animals. Barring setbacks, the new method could be ready for clinical trials within two to three years, according the estimations by Peltz.

Stomach Cells Naturally Revert to Stem Cells

George Washington University scientists from St. Louis, Missouri have found that the stomach naturally produces more stem cells than previously realized. These stem cells probably repair stomach damage from infections, the foods we eat, and the constant tissue insults from stomach acid.

The reversion of adult cells to a stem cell fate is one of the goals of stem cell research. Shinya Yamanaka’s research group at the Center for iPS Cell Research and Application and the Institute for Frontier Medical Sciences at Kyoto University won the Nobel Prize in 2012 for his work on reprogramming adult cells into embryonic-like stem cells, otherwise known as induced pluripotent stem cells (iPSCs) that was initially published in 2006.

A collaborative research effort between scientists from Washington University School of Medicine in St. Louis and Utrecht Medical Center in the Netherlands have shown that this reversion from adult cells to stem cells occurs naturally in the stomach on a regular basis.

Jason Mills, associate professor of medicine at Washington University, said, “We already knew that these cells, which are called chief cells, can change back into stem cells to make temporary repairs in significant stomach injuries in significant stomach injuries, such as a cut to damage from infection. The fact that they’re making this transition more often, even in the absence of noticeable injuries, suggests that it may be easier than we realized to make some types of mature, specialized adult cells revert to stem cells.”

Chief cells normally produce a protein called pepsinogen. In the presence of stomach acid, pepsinogen activates itself and once active, the new protein product, pepsin, degrades proteins. Pepsin in an enzyme that is most active in the acidic environment of the stomach. Another enzyme released by chief cells is chymosin, which is also known as rennet. Chymosin curdles the proteins in milk and makes them easier to degrade.


Mills and his groups are in the process of studying the transformation of chief cells into stem cells, for injury repair. Mills would also like to investigate the possibility that the potential for growth unleashed by this change may contribute to stomach cancers.

Mills and his collaborator Hans Clevers from the Netherlands have identified stomach stem cell marker proteins that show that chief cells become stem cells even in the absence of serious injury. In the case of serious injury, either in cell culture of in animal models, more chief cells become stem cells, making it possible to repair the damage in the stomach.