Patient-Specific Heart Muscle Cells Before the Baby Is Born

Prenatal ultrasound scans can detect congenital heart defects (CHDs) before birth. Some 1% of all children born per year have some kind of CHD. Most of these children will require some kind of rather invasive, albeit life-saving surgery but an estimated 25% of these children will die before their first birthday. This underscores the need for netter therapies of children with CHDs.

To that end, Shaun Kunisaka from C.S. Mott Children’s Hospital in Ann Arbor, Michigan and his colleagues have used induced pluripotent stem cell (iPSC) technology to make patient-specific heart muscle cells in culture from the baby’s amniotic fluid cells. Because these cells can be generated in less than 16 weeks, and because the amniotic fluid can be harvested at about 20-weeks gestation, this procedure can potentially provide large quantities of heart muscle cells before the baby is born.

In this paper, which was published in Stem Cells Translational Medicine, Kunisaki and others collected 8-10 milliliter samples of amniotic fluid at 20 weeks gestation from two pregnant women who provided written consent for their amniocentesis procedures. The amniotic fluid cells from these small samples were expanded in culture, and between passages 3 and 5, cells were selected for mesenchymal stem cell properties. These amniotic fluid mesenchymal stem cells were then infected with genetically engineered non-integrating Sendai viruses that caused transient expression of the Oct4, Sox2, Klf4, and c-Myc genes in these cells. The transient expression of these four genes drove the cells to dedifferentiate into iPSCs that were then grown and then differentiated into heart muscle cells, using well-worked out protocols that have become rather standard in the field.

Not only were the amniotic fluid mesenchymal stem cells very well reprogrammed into iPSCs, but these iPSCs also could be reliably differentiated into cardiomyocytes (heart muscle cells, that is) that had no detectable signs of the transgenes that were used to reprogram them, and, also, had normal karyotypes. Karyotypes are spreads of a cell’s chromosomes, and the chromosome spreads of these reprogrammed cells were normal.

As to what kinds of heart muscle cells were made, these cells showed the usual types of calcium cycling common to heart muscle cells. These cells also beat faster when they were stimulated with epinephrine-like molecules (isoproterenol in this case). Interestingly, the heart muscle cells were a mixed population of ventricular cells that form the large, lower chambers of the heart, atrial cells, that form the small, upper chambers of the heart, and pacemaker cells that spontaneously form their own signals to beat.

This paper demonstrated that second-trimester human amniotic fluid cells can be reliably reprogrammed into iPSCs that can be reliably differentiated into heart muscle cells that are free of reprogramming factors. This approach does have the potential to produce patient-specific, therapeutic-grade heart muscle cells for treatment before the child is even born.

Some caveats do exist. The use of the Sendai virus means that cells have to be passaged several times to rid them of the viral DNA sequences. Also, to make these clinical-grade cells, all animal produces in their production must be removed. Tremendous advances have been made in this regard to date, but those advancements would have to be applied to this procedure in order to make cells under Good Manufacturing Practices (GMP) standards that are required for clinical-grade materials. Finally, neither of these mothers had children who were diagnosed with a CHD. Deriving heart muscle cells from children diagnosed with a CHD and showing that such cells had the ability to improve the function of the heart of such children is the true test of whether or not this procedure might work in the clinic.

Stem Cell-Derived Smooth Muscle Cells Help Restructure Urethral Sphincter Muscles in Rats

Stress urinary incontinence affects 25%-50% of the female population and is defined as the leakage of the bladder upon exertion. The exertions that can cause the bladder to leak can be as simple as laughing, coughing, sneezing, hiccups, yelling, or even jumping up and down. Stress urinary incontinence costs Americans some $12 billion a year and also causes a good deal of embarrassment and compromises quality of life. Unsurprisingly, stress urinary incontinence also is associated with an increased incidence of anxiety, stress, and depression.

In most cases of stress urinary incontinence, injury to the internal sphincter muscles of the urethra or to the nerves that innervate these muscles (both smooth and voluntary muscles) significantly contribute to the condition. Conservative management of stress urinary incontinence can work at first, but can fail later on. The other option is corrective surgery that reconstructs the urethral sphincter and increases urethral support. However, even though such surgeries can and often do work, recurrence of the incontinence is rather common. Is there a better way?

Yan Wen from Stanford University School of Medicine and colleagues and collaborators from College of Medicine of Case Western Reserve in Cleveland, Ohio, Southern Medical University in Guangzhou, China, and Montana State University have used a novel stem cell-based technique to treat laboratory Rowett nude rats that had a surgically-induced form of stress urinary incontinence. While the results are not overwhelming, they suggest that a stem cell-based approach might be a step in the right direction.

Wen and others used a human embryonic stem cell line called H9 and two different types of induced pluripotent stem cell lines to make, in culture, human smooth muscle progenitor cells (pSMCs). Fortunately, protocols for differentiating pluripotent stem cells into smooth muscle cells is well worked out and rather well understood. These pSMCs were also tagged with a firefly luciferase gene that allowed visualization of the cells after implantation.

Six groups of rats were treated in various ways. The first group had stress urinary incontinence and were only treated with saline solutions. The second group of animals also had stress urinary incontinence and were treated with cultured human pSMCs that were derived from human bladders. The third group of animals also had stress urinary incontinence and were treated with pSMCs made from H9 human embryonic stem cells. The next two groups also had stress urinary incontinence and were treated with two different induced pluripotent stem cell lines; one of which was induced with a retroviral vector and the second of which was made with episomal DNA. Both lines were originally derived from dermal fibroblasts. The final group of rats did not have stress urinary incontinence and were used as a control group.

The cells were introduced into the mice by means of injections into the urethra under anesthesia. Two million cells were introduced in each case, three weeks after the induction of stress urinary incontinence. All animals were examined five weeks after the cells were injected into the animals.

Because the cells were tagged with firefly luciferase, the animals could be given an injection of luciferin, which is the substrate for luciferase. Luciferase catalyzes a reaction with luciferin, and the cells glow. This glow is easily detected by means of a machine called the Xenogen Imaging System. Such experiments showed that the injected cells did not survive terribly well, and by 9 days after the injections, they were usually not detectable. Two rats that had been injected with retrovirally-induced induced pluripotent stem cell-derived pSMCs lasted until 35 days after injection, but these rats were the exception and not the rule.

Did the cells integrate into the urethral sphincter by the signal is too low to be detected using luciferase? The answer to this question was certainly yes, but the amount of integration was nothing to write home about. Small patches of cells showed up in the urethra sphincters that expressed human gene products, and therefore, had to be derived from the injected cells.

In vivo survival of transplanted pSMCs in RNU rats. (A): The RV-iPSC pSMCs were periurethrally injected into the rats and monitored with BLI. (B): At day 12, a small number of the transplanted cells were detected in the proximal rat urethra. The transplanted human cells were determined by positive staining of HuNuclei and smoothelin. (C): Gene expression of human ERV-3 in rat urethras 5 weeks after cell transplantation. Y-axis on left shows the scale for ERV-3 copy numbers from tissue samples. Each human cell contains one copy of ERV-3 transcript; hence, the number of copies is equal to the number of cells. Y-axis on right shows the ERV-3 copy numbers of the standard cell samples. The cell numbers in the standard graph are 0.5 × 103, 1 × 103, 2 × 103, 4 × 103, 8 × 103, and 10 × 103 (red dots). ERV-3 amplifications in all pSMC-treated groups were very low. Abbreviations: BLI, bioluminescent imaging; bSMC, bladder smooth muscle cell; DAPI, 4′,6-diamidino-2-phenylindole; Epi, episomal plasmid; ERV-3, endogenous retrovirus group 3; H&E, hematoxylin and eosin; Hu, human; HuNuclei, human nuclei; iPSC, induced pluripotent stem cell; pSMCs, smooth muscle progenitor cells; RNU, Rowett Nude; RV, retrovirus vector.
In vivo survival of transplanted pSMCs in RNU rats. (A): The RV-iPSC pSMCs were periurethrally injected into the rats and monitored with BLI. (B): At day 12, a small number of the transplanted cells were detected in the proximal rat urethra. The transplanted human cells were determined by positive staining of HuNuclei and smoothelin. (C): Gene expression of human ERV-3 in rat urethras 5 weeks after cell transplantation. Y-axis on left shows the scale for ERV-3 copy numbers from tissue samples. Each human cell contains one copy of ERV-3 transcript; hence, the number of copies is equal to the number of cells. Y-axis on right shows the ERV-3 copy numbers of the standard cell samples. The cell numbers in the standard graph are 0.5 × 103, 1 × 103, 2 × 103, 4 × 103, 8 × 103, and 10 × 103 (red dots). ERV-3 amplifications in all pSMC-treated groups were very low. Abbreviations: BLI, bioluminescent imaging; bSMC, bladder smooth muscle cell; DAPI, 4′,6-diamidino-2-phenylindole; Epi, episomal plasmid; ERV-3, endogenous retrovirus group 3; H&E, hematoxylin and eosin; Hu, human; HuNuclei, human nuclei; iPSC, induced pluripotent stem cell; pSMCs, smooth muscle progenitor cells; RNU, Rowett Nude; RV, retrovirus vector.

The exciting part about these results, however, was that when Wen and others examined the rat urethral sphincters for the presence of things like elastin and other proteins that make for a healthy urethral sphincter, there was a good deal of elastin, but it was not human elastin but rat elastin. Therefore, this elastin synthesis was INDUCED by the implanted cells even though it was not made by the implanted cells. Instead, the implanted cells seemed to signal to the native cells to beef up their own production of sphincter-specific gene products, which made from a better sphincter. This was not the case in animals that received injections of human pSMCs derived from human bladders.

Assessment of elastin fibers in the proximal urethra of the rat. (A): Representative images of cross-section of proximal urethra with Weigert’s Resorcin-Fuchsin’s elastin and van Gieson’s collagen staining. Elastic fiber shown as dark blue, collagen as red pink, and other tissue elements as yellow. Scale bars = 100 µm. (B): Quantification of elastin fibers was assessed using Image-Pro Plus software and expressed as a percentage of the arbitrary ROIs. Each bar represents the mean value ± SEM. Abbreviations: bSMC, human bladder smooth muscle cells; H9-pSMC, surgery plus H9-pSMC injection; Hu-bSMC, surgery plus injection of human bladder smooth muscle cells; pSMCs, smooth muscle progenitor cells; Pure control, no surgery and no treatment; ROIs, regions of interest; Sham saline, surgery plus saline injection.
Assessment of elastin fibers in the proximal urethra of the rat. (A): Representative images of cross-section of proximal urethra with Weigert’s Resorcin-Fuchsin’s elastin and van Gieson’s collagen staining. Elastic fiber shown as dark blue, collagen as red pink, and other tissue elements as yellow. Scale bars = 100 µm. (B): Quantification of elastin fibers was assessed using Image-Pro Plus software and expressed as a percentage of the arbitrary ROIs. Each bar represents the mean value ± SEM. Abbreviations: bSMC, human bladder smooth muscle cells; H9-pSMC, surgery plus H9-pSMC injection; Hu-bSMC, surgery plus injection of human bladder smooth muscle cells; pSMCs, smooth muscle progenitor cells; Pure control, no surgery and no treatment; ROIs, regions of interest; Sham saline, surgery plus saline injection.

Because these mice were sacrificed five weeks after the injections, Wen and others could not assess the urethral function of these animals. Therefore, it is uncertain if the improved tissue architecture of the urethral sphincter properly translated into improved function even though it is reasonable to assume that it would. Having said that, it is possible that the experiments that detected the presence of increased amounts of elastin and collagen in the sphincters of these rats was complicated by the presence of bladder tissue in the preparations. Since bladder tissue was included in all trials of this experiment, it is unlikely that bladder tissue is the sole cause of increase elastin and collagen in the stem cell-treated rats. Secondly, rat regenerative properties may not properly match the regenerative properties in older human patients. Here again, unless such an experiment is attempted in larger animal models and then in human patients, we will never know if this procedure is viable for regenerative treatments in the future.

For now, it is an interesting observation, and perhaps a promising start to might someday become a viable regenerative treatment for human patients.

This paper appeared in Stem Cells Translational Medicine, vol 5, number 12, December 2016, pp. 1719-1729.

Cynata’s MSC Technology Produces Significant Relief of Asthma in Preclinical Study

An Australian stem cell company called Cynata Therapeutics Limited is in the process of developing a therapeutic stem cell platform technology that they called “Cymerus.” The idea for Cymerus originated at the University of Wisconsin-Madison, but Cymerus would generate a protocol by which clinical laboratories could produce very immature mesenchymal stem cells from induced pluripotent stem cells. Such cells would be personalized for patients and their needs, and Cynata’s goal is to produce a platform that is economically feasible and relatively fast so that patients can receive infusions of the cells they so badly need in a timely fashion. These are very ambitious goals to say the least, but Cynata has been hacking away at this problem for some time, and we certainly wish them the best.

Cynata has recently released some very encouraging data in which their personalized mesenchymal stem cells were used to treat laboratory animals with a laboratory-induces form of asthma. Briefly, female mice (BALB/c mice for those who are interested) were injected with a yolk-protein called “ovalbumin.” Ovalbumin is a protein found in egg whites, and because it is an egg-specific protein, mice do not have it and their immune systems have never seen it before. Such an injection causes the mice to mount an immune response to the ovalbumin, and these mice are then administered aerosolized ovalbumin by means of a nebulizer. This causes the animals to develop a rather severe asthmatic attack against ovalbumin.

In this study, Cynata scientists and their collaborators used 48 mice that were divided into six different groups. The first group was untreated animals that did not suffer from ovalbumin asthma. The second group contained eight animals that had no asthma but were treated intravenously with one million mesenchymal stem cells. The third group also had no asthma, but were treated with an intranasal infusions of one million mesenchymal stem cells. The fourth group contain eight asthmatic animals that were untreated during the course of the experiment. The fifth group contain eight asthmatic animals that were treated intravenously with one million mesenchymal stem cells. The final group contained eight asthmatic animals that were treated with intranasal infusions of one million mesenchymal stem cells. As a note, all animals that were treated mesenchymal stem cells were treated three times. So-called airway hyperresponsiveness (AHR) is a measure of the sensitivity and irritability of the bronchial tissues. AHR is an important measure of the tendency of the lungs to undergo constriction during an asthma attack and AHR is usually measured by administering a drug that can cause bronchoconstriction. The greater the degree of bronchoconstriction in such an experiment is indicative of great AHR. The successful treatment of asthma results in reduction in AHR.

The results of this experiment were wonderfully successful. Exposing mice to the ovalbumin caused them to exhibit significantly increased AHR. However, intravenous administration of Cynata’s MSCs in asthmatic animals caused a statistically significant (60-70%) decrease in AHR compared to untreated, sensitized animals. Additionally, intranasal administration of Cynata’s MSCs completely normalized AHR. The AHR in these asthmatic mice was brought down to a level that was largely the same as the non-asthmatic mice. Also, importantly, no adverse side effects were observed during the study.

This study was conducted under the supervision of Associate Professor Chrishan Samuel and Dr. Simon Royce from the Department of Pharmacology at Monash University, Melbourne, Australia. Because the features of this model asthma system closely resemble the clinical manifestations of asthma in humans, these results provide excellent evidence that such a treatment stands a chance of working in human patients.

“We are very excited by these results, which indicate that Cymerus™ MSCs could have a profound effect in the treatment of asthma. This is a debilitating condition, which affects about 10% of the population, resulting in close to 40,000 hospitalizations and several hundred deaths each year, in Australia alone,” said Cynata Vice President of Product Development, Dr. Kilian Kelly. “Although a number of drugs are approved for the treatment of asthma, studies have shown that conventional treatments result in as few as 5% of asthma patients achieving full control of their condition. Consequently, there is a widely recognized need for novel treatments that address – and potentially eliminate – the underlying disease”, added Dr. Kelly.

“This study has clearly demonstrated that Cynata’s MSCs have a dramatic effect on AHR in our model, particularly when directly administered into the allergic lung. We look forward to continuing our analysis of the effects of these unique cells on markers of inflammation and airway remodeling, and we are optimistic of building on the very positive data we have generated so far,” said Associate Professor Samuel.

Asthma is a condition characterized by the inflammation, narrowing, and swelling of the airways, accompanied by excessive mucous production that makes it difficult to breathe. According to the Global Asthma Network, asthma affects over 330 million people globally. Cynata had partnered with Monash University to examine the potential of its Cymerus technology as an alternate treatment for asthma sufferers.

Cymerus™ makes us of induced pluripotent stem cells (iPSCs) that are then differentiated into a specific type of mesenchymal stem cell precursor known as a “mesenchymoangioblast” or MCA. Cymerus potentially provides a source of MSCs that can be made for so-called “off-the-shelf” therapeutic uses.

Induced Pluripotent Stem Cell-Based Model System of Hypertrophic Cardiomyopathy Provides Unique Insights into Disease Pathology

A research team at the Icahn School of Medicine at Mount Sinai led by Bruce Gelb created a model of hypertrophic cardiomyopathy (HCM) by using human induced pluripotent stem cells.

Patients who suffer from an extreme thickening of the walls of the heart exhibit HCM. This excessive heart thickening is associated with a several rare and common illnesses. There is a strong genetic component to the risk for developing HCM. Can stem cell-based model system be used to study the genetics of HCM?

The answer to this question seems to be yes, since laboratory-generated induced pluripotent stem cells lines that have been differentiated into heart cells that, in many cases, closely resemble human heart tissue. Studies with such stem cell-based model systems have reaped useful insights into disease mechanisms (see F Kamdar, et al., J Card Fail. 2015 Sep;21(9):761-70; Lee YK, Ng KM, Tse HF. J Biomed Nanotechnol. 2014 Oct;10(10):2562-85).

In this paper, Bruce Gelb and his colleagues examined a genetic disorder called cardiofaciocutaneous syndrome (CFC). CFC is caused by mutations in a gene called BRAF. It is a rare condition that affects fewer than 300 people worldwide, and causes head, face, skin, and muscular abnormalities, including abnormalities of the heart.

Gelb and his coworkers isolated skin cells from three CFC patients and reprogrammed them into induced pluripotent stem cells, which were then differentiated into heart cells. In this disease model system, the heart muscle cells enlarged, but this seemed to be due to the interaction of the heart muscle cells with heart-specific fibroblasts. Fibroblasts constitute a significant portion of total heart tissue, even though the heart muscle cells are responsible for the actual pumping activity of the heart. In their model system, Gelb and others observed that these fibroblast-like cells produce an excess of a protein growth factor called TGF-beta, which causes the cardiomyocytes to undergo hypertrophy or abnormal enlargement.

This model system has relevance for research on several related and more common genetic disorders, including Noonan syndrome, which is characterized by unusual facial features, short stature, heart defects, and skeletal malformations.

There is no cure for HCM in patients with these related genetic conditions, but if these findings are correct, then scientists might be able to treat HCM by blocking specific cell signals. This is something that scientists already know how to do. Approximately 40 percent of patients with CFC suffer from HCM (two of the three participants in this study had HCM). This suggests a pathogenic connection, though the link has never been adequately researched.

“We believe this is the first time the phenomenon has been observed using a human induced pluripotent stem cell model of the disease,” said Bruce Gelb.

Please see Rebecca Josowitz et al., “Autonomous and Non-Autonomous Defects Underlie Hypertrophic Cardiomyopathy in BRAF-Mutant hiPSC -Derived Cardiomyocytes,” Stem Cell Reports, 2016; DOI: 10.1016/j.stemcr.2016.07.018.

Functional, Though Not Completely Structurally Normal Tissue-Engineered Livers Made from Adult Liver Cells

Tracy C. Grikscheit and her research team from the Saban Research Institute at the Children’s Hospital Los Angeles have produced functional, tissue-engineered human and mouse liver from adult stem and progenitor cells.

The largest organ in our bodies, the liver executes many vital functions. It is located in the upper right portion of the abdomen protected by the rib cage. The liver has two main lobes that are divided into many tiny lobules.

Liver cells are supplied by two different sources of blood. The hepatic artery provides oxygen-rich blood from the heart and the portal vein supplies nutrients from the intestine and the spleen. Normally, veins return blood from the body to the heart, but the portal vein allows chemicals from the digestive tract to enter the liver for “detoxification” and filtering prior to entering the general circulation. The portal vein also delivers the precursors liver cells need to produce the proteins, cholesterol, and glycogen required for normal body activities.

The liver also makes bile. Bile is a mixture of water, bile acids (made from stored cholesterol in the liver), and other sundry chemicals. Bile made by the liver is then stored in the gallbladder. When food enters the duodenum (the uppermost part of the small intestine), the gallbladder contracts and secretes bile is secreted into the duodenum, to aid in the digestion of fats in food.

The liver also stores extra sugar in the form of glycogen, which is converted back into glucose when the body needs it for energy. It also produces blood clotting factors, processes and stores iron for red blood cell production, converts toxic nitrogenous wastes (usually in the form of ammonium) into urea, which is excreted in urine. Finally, the liver also metabolizes foreign substances, like drugs into substances that can effectively excreted by the kidneys.

Both adults and children are affected by various types of liver disease. Liver can be caused by infectious hepatitis, which is caused by a variety of viruses, chronic alcoholism, inherited liver abnormalities (e.g., Wilson’s disease, hemochromatosis, Gilbert’s disease) or various types of liver cancer. One in ten people in the United States suffer from liver cancer and need a liver transplant. Liver transplantation is the only effective treatment for end-stage liver disease, but the scarcity of liver donors and the necessity of life-long immunosuppressive therapy limit treatment options. In some cases (such as inborn errors of metabolism or acute bouts of liver insufficiency), patients may be effectively treated by transplanting small quantities of functional liver tissue.

Alternate approaches that have been investigated, but these protocols have significant limitations. For example, “hepatocyte transplantation” involves the infusion of liver cells from a donated liver. This protocol, however, wastes many cells that do not integrate into the existing liver and such a treatment is usually little more than a stop-gap solution, since most patients require a liver transplant within a year of this treatment.

Human-induced pluripotent stem (iPS) cells are another possibility but, so far, iPS cells differentiate into immature rather than mature, functional, proliferative hepatocytes.

A need remains for a robust treatment that can eliminate the need for immunosuppressive theory. “We hypothesized that by modifying the protocol used to generate intestine, we would be able to develop liver organoid units that could generate functional tissue-engineered liver when transplanted,” said Dr. Grikscheit.

Grikscheit and her co-workers extracted hardy, multicellular clusters of liver cells known as liver organoid units (LOUs) from resected human and mouse livers. These LOUs were loaded onto scaffolds made from nonwoven polyglycolic acid fibers. These scaffolds are completely biodegradable and they provide a structure upon which the LOUs can grow, fuse, and form a structure that resembles a liver.

After transplantation of the LOU/scaffold combinations, they generated tissue-engineered livers or TELis. Tissue-engineered livers developed from the human and mouse LOUs and possessed a variety of key liver-specific cell types that are required for normal hepatic function. However, the cellular organization of these TELis did differ from native liver tissue.

The tissue-engineered livers (TELis) made by Grikscheit’s laboratory contained normal liver components such as hepatocytes that properly expressed the liver-specific protein albumin, CK19-expressing bile ducts, vascular structures surrounded by smooth muscles that expressed smooth muscle-specific actin, desmin-expressing stellate cells, and CD31-expressing endothelial cells. The production of albumin by the TELi hepatocytes indicated that these cells were executing their normal secretory function. In a mouse model of liver failure, their tissue-engineered liver provided some hepatic function. In addition, the hepatocytes proliferated in the tissue-engineered liver.

A cellular therapy for liver disease that utilizes technologies like this would completely change the treatment options for many patients. In particular, children with metabolic disorders and require a new liver to survive might see particular benefits if such a treatment can come to the clinic. By generating functional hepatocytes comparable to those in native liver, establishing that these cells are functional and proliferative, Grikscheit and her colleagues have moved one step closer to that goal.

To access this paper, please see: Nirmala Mavila et al., “Functional Human and Murine Tissue-Engineered Liver Is Generated From Adult Stem/Progenitor Cells,” Stem Cells Translational Medicine, August 2016 DOI: 10.5966/sctm.2016-0205.

Mouse Study Suggests Stem Cells Can Ward Off Glaucoma

Regulating the internal pressure of the eyeball (known as the “intraocular pressure” or IOP) is crucial for the health of the eye.  Failure to maintain a healthy IOP can lead to vision loss in glaucoma.  However, a new set of experiments by Dr. Markus Kuehn and his colleagues at the Iowa City Veterans Affairs Medical Center and the University of Iowa has shown that infusions of stem cells could help restore proper drainage for plugged-up eyes that are at risk for glaucoma.

Kuehn and his coworkers injected stem cells into the eyes of laboratory mice suffering with glaucoma.  These infused cells regenerated the tiny, fragile patch of tissue known as the trabecular meshwork, which functions as a drain for the eyes.  When fluid accumulates in the eye, the increase in IOP can lead to glaucoma.  Glaucoma damages the optic nerve leads to blindness.

“We believe that replacement of damaged or lost trabecular meshwork cells with healthy cells can lead to functional restoration following transplantation into glaucoma eyes,” Kuehn wrote on his lab’s website.  One potential advantage of the approach is that induced pluripotent stem cells (iPSCs) could be created from cells harvested from a patient’s own skin. That gets around the ethical problems with using fetal stem cells.  It also lessens the chance of the patient’s body rejecting the transplanted cells.

In order to differentiate iPSCs into trabecular meshwork (TM) cells, Kuehn’s team cultured the iPSCs in medium that had previously been “conditioned” by actual human trabecular meshwork cells.  Injection of these TM cells into the eyes of laboratory rodents led to a proliferation of new endogenous cells within the trabecular meshwork.  The injected stem cells not only survived in the eyes of the animals, but also induced the eye into producing more of its own TM cells, thus multiplying the therapeutic effect.

Glaucoma has robbed some 120,000 Americans of their sight, according to data provided by the Glaucoma Research Foundation.  African-Americans are at especially high risk, as are people over age 60, those with diabetes, and those with a family history of the disease.  Glaucoma can be treated with medicines, but is not curable.  Management of the disease can delay or even prevent the eventual loss of vision. Among the treatments used are eye drops and laser or traditional surgery.

Kuehn and his team think that their findings show some promise for the most common form of glaucoma, known as primary open angle glaucoma.  It remains unclear if this mouse model is as relevant for other forms of the disease.  Another possible limitation of this research is that the new trabecular meshwork cells generated from the stem cell infusion eventually succumb to the same disease process that caused the breakdown in the first place.  This would require re-treatment and it is unclear whether an approach requiring multiple treatments over time would be viable. Kuehn and others to continue investigate this potentially fruitful approach.

This paper was published in the journal Proceedings of the National Academy of Sciences:  Wei Zhu et al., “Transplantation of iPSC-derived TM cells rescues glaucoma phenotypes in vivo,” Proceedings of the National Academy of Sciences, 2016; 113 (25): E3492 DOI: 10.1073/pnas.1604153113.

Weissman Laboratory Define Roadmap for Pluripotent Human Stem Cell Differentiation into Mesodermal Fates: Cells Rapidly Generate Bone, Heart Muscle

How do we get stem cells to differentiate into the cell types we want? Implanting undifferentiated stem cells into a living organism can sometimes result in cells that differentiate into unwanted cell types. Such a phenomenon is called heterotropic differentiation and it is a genuine concern of regenerative medicine. What is a clinical researcher to do? Answer: make a road map of the events that drive cells to differentiate into specific cell types and their respective precursors.

Researchers in the laboratory of Irving Weissman at Stanford University Researchers at the Stanford University School of Medicine have mapped out the bifurcating lineage choices that lead from pluripotency to 12 human mesodermal lineages, including bone, muscle, and heart. The experiments also defined the sets of biological and chemical signals necessary to quickly and efficiently direct pluripotent stem cells to differentiate into pure populations of any of 12 cell types. This is certainly a remarkable paper in many aspects, since Weissman and his group defined the extrinsic signals that control each binary lineage decision that occur during stem cell differentiation. This knowledge enables any lab to successfully block differentiation toward unwanted cell fates and rapidly steer pluripotent stem cells toward largely pure human mesodermal lineages at most of these differentiation branchpoints.

The ability to make pure populations of these cells within days rather than the weeks or months is one of the Holy Grails of regenerative medicine. Such abilities can, potentially, allow researchers and clinicians to make new beating heart cells to repair damage after a heart attack, or cartilage for osteoarthritic knees or hips, or bone to reinvigorate broken bones or malfunctioning joints, or heal from accidental or surgical trauma.

The Weissman study also highlights those key, but short-lived, patterns of gene expression that occur during human early embryonic segmentation. By mapping stepwise chromatin and single-cell gene expression changes during the somite segmentation stage of mesodermal development, the Weissman group discovered a previously unobservable human embryonic event transiently marked by expression of the HOPX gene. It turns out that these decisions made during human development rely on processes that are evolutionarily conserved among many animals. These insights may also lead to a better understanding of how congenital defects occur.

“Regenerative medicine relies on the ability to turn pluripotent human stem cells into specialized tissue stem cells that can engraft and function in patients,” said Irving Weissman of Stanford. “It took us years to be able to isolate blood-forming and brain-forming stem cells. Here we used our knowledge of the developmental biology of many other animal models to provide the positive and negative signaling factors to guide the developmental choices of these tissue and organ stem cells. Within five to nine days we can generate virtually all the pure cell populations that we need.”

All in all, this roadmap enables scientists to navigate mesodermal development to produce transplantable, human tissue progenitors, and uncover developmental processes.

This paper was published in the journal Cell: Irving L. Weissman et al., “Mapping the Pairwise Choices Leading from Pluripotency to Human Bone, Heart, and Other Mesoderm Cell Types,” Cell, July 2016 DOI: 10.1016/j.cell.2016.06.011.

Patient-Specific Neurons Reveal Vital Clues About Autism

The brains of some people with autism spectrum disorder grow faster than usual early on in life, often before diagnosis. Now new research from scientists at the Salk Institute has used cutting-edge stem cell-based techniques to elucidate those mechanisms that drive excess brain growth, which affects as many as 30 percent of people with autism.

These findings show that it is possible to use stem cell reprogramming technologies to model the earliest stages of complex disorders and to evaluate potential therapeutic drugs. The Salk team, led by Alysson Muotri, discovered that stem cell-derived neurons, derived from stem cells that had been made from cells taken from autism patients, made fewer connections in culture compared to cells from healthy individuals. These same scientists also restored cell-cell communication between these cells by adding a growth factor called IGF-1 (insulin-like growth factor-1). IGF-1 is in the process of being evaluated in clinical trials of autism.

“This technology allows us to generate views of neuron development that have historically been intractable,” said senior investigator Fred H. Gage. “We’re excited by the possibility of using stem cell methods to unravel the biology of autism and to possibly screen for new drug treatments for this debilitating disorder.”

In the United States alone, autism affects approximately one out of every 68 children. Autistic children have problems communicating, show an inhibited ability to interact with others, and usually engage in repetitive behaviors. Mind you, the symptomatic manifestations in autistic children can vary dramatically in type and severity. Autism, to date, has no known, identified cause.

In 2010, Gage and collaborators recreated features of Rett syndrome (a rare disorder that shares features of autism but is caused by mutations in a single gene; MECP2) in a cell culture system. They extracted skin cells from Rett Syndrome patients and converted those cells into induced pluripotent stem cells (iPSCs). Then Gage and others differentiated those Rett-Syndrome-specific iPSCs into neurons, which they grew in culture. These neurons were then studied in detail in a neuron-specific culture system. “In that study, induced pluripotent stem cells gave us a window into the birth of a neuron that we would not otherwise have,” said Marchetto, the study’s first author. “Seeing features of Rett syndrome in a dish gave us the confidence to next study classical autism.”

In this new study, Gage and others created iPSCs from autism patients whose brains had grown up to 23 percent faster than usual during toddlerhood but had subsequently normalized. These iPSCs were then differentiated into neuron precursor cells (NPCs). Examinations of these NPCs revealed that the NPCs made from iPSCs derived from autism patients proliferated faster than those derived from typically developing individuals. This finding supports a theory advanced by some experts that brain enlargement is caused by disruptions to the cell’s normal cycle of division, according to Marchetto.

In addition, the neurons derived from autism-specific iPSCs behaved abnormally in culture. They fired less often compared with those cells derived from healthy people. The activity of these neurons, however, improved if they were treated with IGF-1. IGF-1 enhances the formation of cell-cell connections between neurons, and the establishment and stabilization of these connections seem to normalize neuronal function.

Muotri and Gage and others plan to use these patient-derived cells to elucidate the molecular mechanisms behind IGF-1’s effects. They will examine changes in gene expression and attempt to correlate them with changes in neuronal function. Although the newly derived cells are far from the patients’ brains, a brain cell by itself may, hopefully, reveal important clues about a person and their brain.

This work was published in the journal Molecular Psychiatry: M. C. Marchetto et al., “Altered proliferation and networks in neural cells derived from idiopathic autistic individuals,” Molecular Psychiatry, 2016; DOI: 10.1038/mp.2016.95.

Patient-Specific Heart Cells Made from Amniotic Fluid Cells Before a Baby is Born

The dream of cardiologists is to have stockpiles of cardiac progenitor cells that could be transplanted into a sick heart and regenerate it. Even more remarkable would be a source of heart cells for newborn babies with congenital heart problems. What about making these cells before they are born? Science fiction?

Probably not. Dr. Shaun M. Kunisaki from Mott Children’s Hospital and the University of Michigan School of Medicine and his colleagues made heart progenitor cells from Amniotic Fluid Cells. These cells were acquired from routine amniocentesis procedures, with proper institutional review board approval.

These amniotic fluid specimens (8–10 ml), which were taken from babies at 20 weeks gestation, were expanded in culture and then reprogrammed toward pluripotency using nonintegrating Sendai virus (SeV) vectors that expressed the four commonly-used reprogramming genes; OCT4, SOX2, cMYC, and KLF4. The resulted induced pluripotent stem cell (iPSC) lines were then exposed to cardiogenic differentiation conditions in order to generate spontaneously beating amniotic fluid-derived cardiomyocytes (AF-CMs). AF-CMs were formed with high efficiency.

After 6 weeks, Kunisaki and his team subjected their AF-CMs to a battery of quantitative gene expression experiments. They discovered that their AF-CMs expressed high levels of heart-specific genes (including MYH6, MYL7, TNNT2, TTN, and HCN4). However, Kunisaki and others also found that their AF-CMs consisted of a mixed population of differentiated atrial, ventricular, and nodal cells, as demonstrated by various genes expression profiles.

All AF-CMs were chromosomally normal and had no remnants of the SeV transgenes. Functional characterization of these AF-CMs showed a higher spontaneous beat frequency in comparison with heart cells made from dermal fibroblasts. The AF-CMs also showed normal calcium currents and appropriately responded to neurotransmitters that usually speed up the heart, like norepinephrine.

Collectively, these data suggest that human amniotic fluid-derived cells can be used to produce highly scalable sources of functional, transgene-free, autologous heart cells before child is born. Such an approach may be ideally suited for patients with prenatally diagnosed cardiac anomalies.

The Founder Cell Identity Does Not Affect iPS Cell Differentiation to Hematopoietic Stem Cell Fate

Induced pluripotent stem cells (iPSCs) have many of the characteristics of embryonic stem cells, but are made from mature cells by means of a process called cell reprogramming. To reprogram cells, particular genes are delivered into mature cells, which are then cultured until they h:ave the growth properties of pluripotent cells. Further tests are required to demonstrate that the growing cells actually are iPSCs, but once they pass these tests, these cells can be grown in culture indefinitely and, ideally, differentiated into just about any cell type in our bodies (caveat: some iPSC lines can only differentiate into particular cell lineages). Theoretically, any cell type can be reprogrammed into iPSCs, but work from many laboratories has demonstrated that the identity of the founder cell influences the type of cell into which it can be reprogrammed.

Founder cells can be easily acquired from a donor and come in one of four types: fibroblasts (in skin), keratinocytes (also from skin), peripheral and umbilical cord blood, and dental pulp cells (from baby teeth). A variety of laboratories from around the world have made iPSC lines from a gaggle of different founder cells. Because of the significant influence of founder cells for iPSC characteristics, the use of iPSCs for regenerative medicine and other medical applications requires that the desired iPSC line should be selected based on the founder cell type and the characteristics of the iPSC line.

However, the founder cell identity is not the only factor that affects the characteristics of derived iPSC lines. The methods by which the founder cells are reprogrammed can also profoundly contribute to the differentiation efficiency of iPSC lines. According to Yoshinori Yoshida, Associate Professor at the Center for iPSC Research and Application (CiRA) at Kyoto University, the most commonly used methods of cell reprogramming utilize retroviruses, episomal/plasmids, and Sendai viruses to move genes into cells.

The cells found in blood represent a diverse group of cells that includes red blood cells that carry oxygen, platelets that heal wounds, and white blood cells that fight off infection. All the cells in blood are made by bone marrow-specific stem cells called “hematopoietic stem cells.” The production of clinical grade blood has remained a kind of “holy grail” for cellular reprogramming studies. Some scientists have argued that in order to make good-quality hematopoietic cells, the best founder cells are hematopoietic cells. Is this true? Yoshida and his colleagues examined a very large number of iPSC lines that were made from different founder cells and with differing reprogramming methods.  The results of these experiments were published in the journal Cell Stem Cell (doi:10.1016/j.stem.2016.06.019).

Remarkably, Yoshida and his crew discovered that neither of these factors has a significant effect. What did have a significant effect were the expression of certain genes and the position of particular DNA methylations. These two factors were better indicators of the efficiency at which an iPSC line could differentiate into the hematopoietic stem cells.

“We found the IGF2 (Insulin-like Growth Factor-2) gene marks the beginning of reprogramming to hematopoietic cells”, said Dr. Masatoshi Nishizawa, a hematologist who works in Yoshida’s lab and is the first author of this new study. Higher expression of the IGF2 gene is indicative of iPSCs initiating differentiation into hematopoietic cells. Even though IGF2 itself is not directly related to hematopoiesis, its uptake corresponded to an increase in the expression of those genes involved in directing differentiation into hematopoietic stem cells.

Although IGF2 marked the beginnings of differentiation to hematopoietic lineage, the completion of differentiation was marked by the methylation profiles of the iPS cell DNA. “DNA methylation has an effect on a cell staying pluripotent or differentiating,” explained Yoshida. Completion of the final stages of differentiation was highly correlated with less aberrant methylation during the reprogramming process. Blood founder cells showed a much lesser tendency to display aberrant DNA methylation patterns than did other iPSC lines made from other founder cells. This probably explains why past experiments seemed to indicate that the founder cell contributes to the effectiveness of differentiating iPS cells to the hematopoietic stem cell lineage.

These findings reveal molecular factors that can be used to evaluate the differentiation potential of different iPSC lines, which should, hopefully, expedite the progression of iPSCs to clinical use. Nishizawa expects this work to provide the basis for evaluating iPSC lines for the preparation of other cell types. “I think each cell type will have its own special patterns,” he said.

German Group Uses Induced Pluripotent Stem Cells to Model Nonalcoholic Fatty Liver Disease

A German research group has used pluripotent stem cells to design a new in vitro model system for investigating nonalcoholic fatty liver disease (NAFLD).  NAFLD, or steatosis, is a liver disease whose prevalence is probably much higher than estimated, and the new cases of it are increasing every year throughout the world.  NAFLD is typically associated with obesity and type-2 diabetes.  An estimated one-third of the general population of Western countries is thought to be affected with NAFLD, with or without symptoms.  It usually results from a high caloric diet in combination with a lack of exercise.  The liver begins to accumulate fat as lipid droplets.  Initially, this is a benign state, but it can develop into nonalcoholic steatohepatitis (also known as NASH), an inflammatory disease of the liver.  Then many patients develop fibrosis, cirrhosis or even liver cancer.  However, in many cases patients die of heart failure before they develop severe liver damage.

A major obstacle that dogged NAFLD research was that biopsies of patients and healthy individuals were required.  Researchers from the Institute for Stem Cell Research and Regenerative Medicine at the University Clinic of Düsseldorf, Germany solved this problem by reprogramming skin cells into induced pluripotent stem cells (iPSCs) that they differentiated into hepatocyte-like cells.

“Although our hepatocyte-like cells are not fully mature, they are already an excellent model system for the analysis of such a complex disease”, said Nina Graffmann, first author of the paper that appeared in the journal Stem Cells and Development.

The researchers recapitulated important steps of the disease in cultured cells.  They demonstrated up-regulation of PLIN2, a protein called perilipin that surrounds lipid droplets. Mice without PLIN2 do not become obese, even when overfed with a high fat diet.  Also the key role of PPARα, a transcription factor involved in controlling glucose and lipid metabolism, was reproduced in the tissue culture system.  “In our system, we can efficiently induce lipid storage in hepatocyte-like cells and manipulate associated proteins or microRNAs by adding various factors into the culture.  Thus, our in vitro model offers the opportunity to analyse drugs which might reduce the stored fat in hepatocytes,” Graffmann said.

Senior author James Adjaye and his colleagues hope to expand their model by deriving iPSCs from NAFLD patients.  They hope to discover differences that might explain the course of NAFLD.

“Using as reference the data and biomarkers obtained from our initial analyses on patient liver biopsies and matching serum samples, we hope to better understand the etiology of NAFLD and the development of NASH at the level of the individual, with the ultimate aim of developing targeted therapy options,” said Adjayer.

This paper can be found at Nina Graffmann et al., “Modeling NAFLD with human pluripotent stem cell derived immature hepatocyte like cells reveals activation of PLIN2 and confirms regulatory functions of PPARα,”Stem Cells and Development, 2016; DOI: 10.1089/scd.2015.0383.

Induced Pluripotent Stem Cells from Diabetic Foot Ulcer Fibroblasts

Dr. Jonathan Garlick is professor of Oral Pathology at Tufts University and has achieved some notoriety among stem cell scientists by publishing a stem-cell rap on You Tube to teach people about the importance of stem cells.

Garlick and his colleagues have published a landmark paper in the journal Cellular Reprogramming in which cells from diabetic patients were reprogrammed into induced pluripotent stem cells (iPSCs).

Garlick and his colleagues have established, for the first time, that skin cells from diabetic foot ulcers can be reprogrammed iPSCs. These cells can provide an excellent model system for diabetic wounds and may also used, in the future, to treat chronic wounds.

ESC and iPSCs differentiation to fibroblast fate. ESC and iPSC were differentiated and monitored at various stages of differentiation. Representative images show the morphology of ESC and 2 iPSC lines after days 1, 4, 7, 10, 14, 21 and 28 of differentiation. Early morphologic changes showed differentiation beginning at the periphery of colonies (day 1). At later stages cells acquired fibroblast features of elongated, stellate cells (day 10 at days 21 and 28 of differentiation.
ESC and iPSCs differentiation to fibroblast fate. ESC and iPSC were differentiated and monitored at various stages of differentiation. Representative images show the morphology of ESC and 2 iPSC lines after days 1, 4, 7, 10, 14, 21 and 28 of differentiation. Early morphologic changes showed differentiation beginning at the periphery of colonies (day 1). At later stages cells acquired fibroblast features of elongated, stellate cells (day 10 at days 21 and 28 of differentiation.

Garlick’s team at Tufts University School of Dental Medicine and the Sackler School of Graduate Biomedical Sciences at Tufts, have also used their diabetic-derived iPSCs to show that a protein called fibronectin is linked to a breakdown in the wound-healing process in cells from diabetic foot ulcers.

One of the goals of Garlick’s research is to develop efficient protocols to make functional cell types from iPSCs and to use them to generate 3D tissues that demonstrate a broad range of biological functions. His goal is to use the 3D model system to develop human therapies to replace or regenerate damaged human cells and tissues and restore their normal function.

In this paper, Garlick and his colleagues showed that not only can fibroblasts from diabetic wounds form iPSCs, but they can also participate in 3D skin-like tissues. This model system is more than a disease-in-a-dish system but disease-in-a-tissue system.

Fabrication of three-dimensional tissue construction. (A) A collagen gel embedded with human dermal fibroblasts is layered onto a polycarbonate membrane. (B) After dermal fibroblasts contract and remodel the collagen matrix, keratinocytes are then seeded onto it to create a monolayer that will form the basal layer of the tissue. (C) Tissues are raised to an air-liquid interface to initiate tissue development that mimics in vivo skin.
Fabrication of three-dimensional tissue construction. (A) A collagen gel embedded with human dermal fibroblasts is layered onto a polycarbonate membrane. (B) After dermal fibroblasts contract and remodel the collagen matrix, keratinocytes are then seeded onto it to create a monolayer that will form the basal layer of the tissue. (C) Tissues are raised to an air-liquid interface to initiate tissue development that mimics in vivo skin. From this site.

“The results are encouraging. Unlike cells taken from healthy human skin, cells taken from wounds that don’t heal – like diabetic foot ulcers – are difficult to grow and do not restore normal tissue function,” said Garlick. “By pushing these diabetic wound cells back to this earliest, embryonic stage of development, we have ‘rebooted’ them to a new starting point to hopefully make them into specific cell types that can heal wounds in patients suffering from such wounds.”

Scientists in Garlick’s laboratory used these 3D tissues to test the properties of cells from diabetic foot ulcers and found that cells from the ulcers get are not able to advance beyond synthesizing an immature scaffold made up predominantly of a protein called fibronectin.  Fibronectin, unfortunately, seems to prevent proper closure of wounds.

Fibronectin Sigma

Fibronectin has been shown to be abnormal in other diabetic complications, such as kidney disease, but this is the first study that directly connects it to cells taken from diabetic foot ulcers.

Deriving more effective therapies for foot ulcers has been slow going because of a lack of realistic wound-healing models that mimic the extracellular matrices of human tissues. This scaffolding is critical for wound repair in skin, and other tissue as well.

The work in this paper builds on earlier experiments that showed that cells from diabetic ulcers have fundamental defects that can be simulated using laboratory-grown 3D tissue models. These 3D models will almost certainly be a good model system to test new therapeutics that could improve wound healing and prevent those limb amputations that result when treatments fail.

Garlick’s 3D model will allow him and other researchers to push these studies forward. Can they differentiate their cells into more mature cell types that can be studied in 3D models to see if they will improve healing of chronic wounds?

More than 29 million Americans have diabetes. Diabetic foot ulcers, often resistant to treatment, are a major complication. The National Diabetes Statistics Report of 2014 stated that about 73,000 non-traumatic lower-limb amputations in 2010 were performed in adults aged 20 years or older with diagnosed diabetes, and approximately 60 percent of all non-traumatic lower-limb amputations occur in people with diabetes.

This paper appeared in: Behzad Gerami-Naini, et al., Cellular Reprogramming. June 2016, doi:10.1089/cell.2015.0087.

Large Screening and Analyses of Established Induced Pluripotent Stem Cell Lines Finds Rogue Lines

Induced pluripotent stem cells (iPSCs) have come a long way since the first lines were made by Shinya Yamanaka and his colleagues in 2006. Initial successes of iPSCs in animal models generated a good deal of hope that iPSCs might find a place in the annals of regenerative medicine. However, since that time, further work has created doubts about the safety of these cells, since some, though admittedly not all, iPSC lines show some genetic abnormalities. However, as screening techniques have become better and have increased in sensitivity, the possibility of accurately ascertaining the quality of iPSC lines draws closer and closer.

A new paper that appeared in the June 9 edition of the journal Stem Cell Reports by Carolyn Lutzko and others from a multi-institutional research group known as the Progenitor Cell Biology Consortium, have used these new screening technologies to screen large numbers of established iPSC lines. The results were somewhat sobering; about 30 percent of iPSC lines analyzed from 10 research institutions were genetically unstable and not safe for clinical use.

This work comprehensively characterized of a large collection of iPSC lines. The technology to produce safe and effective iPSCs exists. Nevertheless, this does not mean that all iPSC lines were produced safely and effectively. In this paper, Lutzko and her colleagues discovered that some iPSC lines that were made with inferior protocols. Some iPSC lines were contaminated with bacteria or carried mutations associated with cancer.

“It was very surprising to us the high number of unstable cell lines identified in the study, which highlights the importance of setting safety standards for stem cell therapies,” said Carolyn Lutzko, PhD, senior author and director of translational development in the Translational Core Laboratories at Cincinnati Children’s Hospital Medical Center. “A good number of the cell lines we studied met quality standards, although the unexpected number of lines that did not meet these standards could not be used for clinical therapies.”

In this paper, Lutzko and her collaborators compared 58 different iPSC lines that had been submitted by various research institutions. The cells were generated with a variety of genes, methods and cells of origin that ranged from skin fibroblasts to infant cord blood cells. All iPSC lines were analyzed for genetic stability, degree of pluripotency, and several other scientific criteria.

In order for an iPSC line to be considered for clinical work, they must exhibit a high degree of genetic stability. Genetically unstable iPSC lines run the risk of form derivatives that can become cancerous, show poor survival, or differentiate into unwanted cell types upon transplantation. It also is essential that iPSC lines exhibit the ability to continuously renew and expand without losing pluripotency or introducing new genetic mutations.

All iPSC lines were also compared to human embryonic stem cell lines in order to compare them to an outside standard.

How did these 58 iPSC lines fare in this rather exacting gauntlet of tests? It depended on several factors. First of all the cell of origin was very important. Skin fibroblasts tended to make rather low-quality iPSC lines, on the average, but cord blood stem cells usually made rather high-quality iPSC lines. Additionally, the specific reprogramming method employed also made a difference. Some of the iPSC lines included in the test were reprogrammed by means of viruses that integrate into the genome of the host cell (24%). Others were reprogrammed with plasmids (64%), which do not integrate into the host cell genome and are lost soon after reprogramming and growth occurs. Others were reprogrammed with modified RNAs (7%), and a few others (5%) were reprogrammed with other types of viruses that do not integrate into the genome of the host cell (Sendai virus). In all cases, the iPSC lines were made by introducing genes into a mature cell that drove that cell to de-differentiate and grow. Slightly different cocktails of genes were used, but the results were largely the same – the induction of pluripotency.  On the average, non-integrating methods of introducing reprogramming genes into cells resulted in higher-quality iPSC lines, with a few notable exceptions.

Pluripotency for each iPSC line was tested by means of implanting undifferentiated iPSCs into nude mice and observing the cells form differentiated tumors called “teratomas.” Teratomas contain tissues derived from all three primary germ layers; endoderm (gut region), ectoderm (epidermis, nerve tissue, etc.) and mesoderm (muscles, blood cells, etc.).

Prior to this study, the prevailing view was that low-quality iPSC lines were not pluripotent and could not form proper teratomas. This hypothesis had not been tested because of the expense of implanting all these iPSC lines into nude mice. To test this hypothesis, Lutzko and her colleagues tested if all iPSC lines, both high and low quality lines, could generate teratomas. Their tests showed that both genetically stable and unstable iPSC lines formed teratomas with cells from all three germ layers. Although genetically unstable iPSC lines demonstrated pluripotency, the concern in a clinical context would be that they also could result in cancer – again emphasizing the need for safe reprogramming methods, according to study authors.

The enormous amount of data generated by these experiments required sophisticated computing for high-level computational analyses. First author, Nathan Salomonis, PhD, a researcher in the Division of Biomedical Informatics at Cincinnati Children’s. Salomonis used computational approaches to collate, examine, and analyze the data and produce large data sets that can compare the different methods of cell programming, the differences in gene regulation between lines, and the functional quality of each iPSC line.

According to Salomonis, his robust data sets uncovered those iPSC lines that had lost their ability to differentiate into particular adult cell types. This massive collection of raw processed data is available through the online web database.

Salomonis said that, in the future, members of this research consortium will test the ability of each iPSCs line to differentiate into specific cell types – such as brain, heart, lung and other cells in the human body. After these data are verified and published, this information will be added to the online database as a public resource.

Antiaging Glycoprotein Quadruples Viability of Stem Cells in Retina

When pluripotent stem cells are differentiated into photoreceptor cells, and then implanted into the retina at the back of the eye of a laboratory animal, they do not always survive.  However, pre-treatment of those cells with an antiaging glycoprotein (AAGP), made by ProtoKinetix, causes those transplanted cells to be 300 times more viable than cells not treated with this protein according to a study recently accepted for publication.

AAGP was invented by Dr. Geraldine-Castelot-Deliencourt and developed in partnership with the Institute for Scientific Application (INSA) of France. For her work in this area Dr. Castelot-Deliencourt was honored with France’s highest award for scientific accomplishment, the Francinov Award, in 2006.

ProtoKinetix, Incorporated said that a paper submitted by Kevin Gregory-Evans on the company’s AAGP was accepted for publication by the Journal of Tissue Engineering and Regenerative Medicine for publication.

AAGP significantly improves the viable yield of stem cells transplanted in retinal tissue, according to experiments conducted at the University of British Columbia in the laboratory of Dr. Kevin Gregory-Evans.

AAGP seems to protect cells from inflammation-induced cell death. This is based on experiments in which cultured cells that were treated with AAGP were significantly more resistant to hydrogen peroxide, ultraviolet A (wavelengths of 320-400 nanometers), and ultraviolet C (shorter than 290 nm). In addition, when exposed to an inflammatory mediator, interleukin β (ILβ), AAGP exposure reduced COX-2 expression three-fold. COX-2 is an enzyme that is induced by the various stimuli that stimulate Inflammation. It is, therefore, an excellent read-out of the degree to which inflammation has been induced. The fact that AAGP prevented the induction of COX-2 shows that this protein can inhibit the induction of inflammation. These data suggest that AAGP™ may not just be usable in cell and organ storage but also in pharmacological treatments.

Induced Pluripotent Stem Cells – Addressing Safety Concerns

In 2012, John B. Gurdon and Shinya Yamanaka won the Nobel Prize in Physiology or Medicine “for the discovery that mature cells can be reprogrammed to become pluripotent.” Since that time, induced pluripotent stem cells (iPSCs) have largely taken the stem cell scene by storm. Because of the ease with which iPSCs can be made from just about any mature cell type, and because they can be made so more cheaply and faster than embryonic stem cells, they are the perfect pluripotent stem cell for laboratory use. The additional advantage to iPSCs is that can instantly reflect the genetic defect of the patient from whom they are made. Therefore, they are provide excellent model systems for a variety of genetic diseases and provide a kind of “disease in a dish” system by which the cellular and molecular characteristics of a disease can be modeled in cell culture.

In addition to their experimental utility, many scientists have sought to promote iPSCs for clinical purposes. However, before iPSCs can be used in the clinic, their safety must be established beyond question. Despite their success in many animal models (most in rodents), the long-term safety of iPSC derivatives has yet to be firmly demonstrated.

To that end, three different experiments have added to our concerns about the safety of iPSCs. For these and other reasons, several scientists have hypothesized that if iPSCs derivatives are going to be used in a clinical setting, they will need to come from young, healthy donors. In particular, blood cells from umbilical cord blood can be matched to just about any tissue and can be easily converted into iPSCs. Therefore, allogeneic iPSC derivatives seem to be the best way to go about treating particular diseases.

That being said, there are three studies about the safety of iPSC derivatives that make important contributions to the debate.

The first study comes from the laboratory of Shoukhrat Mitalipov at the Oregon Health and Science University. Mitalipov and his team have examined the mitochondrial genomes of iPSCs made from older patients.

Mitochondria are small, vesicles surrounded by two membranes, within cells that are the energy-production structures of most cells (not bacteria). Mitochondria also contain their own DNA molecules that express a variety of mitochondrial-specific genes and their own bacterial-like ribosomes that synthesized the mRNAs made from those genes into proteins. However, the vast majority of mitochondrial proteins are encoded on genes housed in the nucleus.

Mutations in genes encoded by the mitochondrial genome are rather devastating and are responsible for several really nasty (albeit rare) genetic diseases. These mitochondrial genetic diseases include: Mitochondrial myopathy, diabetes and deafness, Leber’s hereditary optic neuropathy (includes visual loss beginning in young adulthood, progressive loss of central vision due to degeneration of the optic nerves and retina), Leigh syndrome subacute sclerosing encephalopathy (disease usually begins late in the first year of life, although onset may occur in adulthood; a rapid decline in function occurs and is marked by seizures, altered states of consciousness, dementia, ventilatory failure), neuropathy, ataxia, retinitis pigmentosa, and ptosis (progressive symptoms as described and dementia), Myoneurogenic gastrointestinal encephalopathy (gastrointestinal pseudo-obstruction and neuropathy), Myoclonic epilepsy with ragged red fibers (progressive myoclonic epilepsy, “Ragged Red Fibers” or clumps of diseased mitochondria accumulate in the muscle fiber, short stature, hearing loss, lactic acidosis, exercise intolerance), mitochondrial myopathy, encephalomyopathy, lactic acidosis, stroke-like symptoms (MELAS).

Mitochondrial DNA mutations have long been thought to be a driving force in aging and age-onset diseases. Therefore, if iPSCs are made from older patients, will their starting cells have these mitochondrial mutations?

Taoseng Huang from Cincinnati Children’s Hospital Medical Center said: “If you want to use iPS cells in a human, you must check for mutations in the mitochondrial genome. Every single cell can be different. Two cells next to each other could have different mutations or different percentages of mutations.”

In this study from Mitalipov’s laboratory, his team derived and sequenced 10 iPS clones from each patient tissue sample to get a better understanding of mitochondrial DNA mutations rates. They took samples of blood and skin samples from healthy subjects and patients with degenerative diseases, who ranged in age from 24-72 years old. In these pools of these sampled cells, the rate of mitochondrial DNA mutations was low.

20 iPS cell lines per patient were profiled. Ten of these lines were derived from skin cells and the other 10 were derived from blood cells. Sequencing of the mitochondrial genomes of the iPSC lines revealed higher numbers of mitochondrial DNA mutations, particularly in cells from patients older than 60 years old. Of the 130 iPSC lines analyzed, 80 percent of them showed mitochondrial mutations and higher percentages of the mitochondria per cell contained mutations.

Such mitochondrial mutations can seriously compromise the ability of derivatives of these iPSC lines to carry out their desired function. Mitalipov in his paper, which was published in Cell Stem Cell, 2016; DOI: 10.1016/j.stem.2016.2016.02.005, that all iPSC lines for use in human patients should be screened for mitochondrial mutations.

Graphical abstract-2

One feature not addressed by Mitalipov and his colleagues is whether or not cells that may not show the signs of aging should be used to derived iPSCs, such as particular bone dormant marrow stem cells.

If mitochondrial mutations aren’t bad enough Jennifer E. Phillips-Cremins and her coworkers at the University of Pennsylvania School of Engineering and Applied Science have found that the chromatin structures of iPSCs might prevent them from properly differentiating into particular derivatives.

As previously mentioned in other blog posts, the DNA in the nuclei of our cells is packaged into a compact structure known as chromatin. Chromatin helps cells express those genes it needs to express and shut down other genes whose expression is not needed.

Occasionally, iPSC lines show an inability to differentiate into particular cell types while others have the ability to differentiate into many cell types. According to this study by Phillips-Cremins and her team, defects in DNA packaging might explain these disparities in iPSC lines.

By using experimental and computational techniques, Phillips-Cremins and her graduate student Jonathan Beagan identified chromatin conformations in a variety of iPSC lines. The DNA topology of embryonic stem cells and neural stem cells were also analyzed as comparisons.

“We know there is a link between the topology of the genome and gene expression,” Jennifer Phillips-Cremins, said in a press release. “So this motivated us to explore how the genetic material is reconfigured in three dimensions inside the nucleus during the reprogramming of mature brain cells to pluripotency. We found evidence for sophisticated configurations that differ in important ways between iPS cells and embryonic stem cells.”

The three-dimensional DNA conformations of pluripotent stem cells are reorganized during differentiation. Phillips-Cremin and others discovered that when mature cells are reprogrammed to pluripotent cells, most pluripotency genes reconnect to their enhancers (which are crucial for their expression). However, when these same iPSCs are differentiated into neural progenitor cells, the interactions between pluripotency gene and their enhancers remain in some lines, which should not occur.

“We found marked differences among the heatmaps we generated for each cell type,” said Jonathan Beagan, a graduate student in Phillips-Cremin’s laboratory at the University of Pennsylvania. “Our observations are important because they suggest that, if we can push the 3D genome conformation of cells that we are turning into IPSCs to be closer to that of embryonic stem cells, then we can possibly generate IPSCs that match gold-standard pluripotent stem cells more rapidly and efficiently.”

This paper was published in Cell Stem Cell (2016), 18(5): 611–624. Therefore, the chromatin structure of iPSCs is also important.

Finally, another paper reports some good news for iPSCs. Research from the Wellcome Trust Sanger Institute tracked the genetic mutations acquired by iPSCs when they are made in the laboratory. These cells came from the blood of a 57-year-old male subject.

This research, led by Allan Bradley, showed that mutations arise 10 times less often in iPSCs than they do in cultured laboratory-grown blood cells. Furthermore, non of the iPSC-acquired mutations were in genes known to cause cancer.

Bradley and his colleagues were able to trace the history of every mutation that each cell acquired from its extraction from the body to its reprogramming in the laboratory and propagation in culture.

The techniques utilized in the Bradley laboratory can surely help scientists evaluate the genetic integrity of laboratory-derived iPSCs.

This work was published in PLOS Genetics, 2016; 12(4): e1005932 DOI: 10.1371/journal.pgen.1005932.

All in all, it seems that it is possible to make sound iPSC lines, but those lines must be properly screened before they can be used in a clinical setting to treat live patients. These three papers provide new ways to screen iPSC lines for ensure high levels of safety and efficacy.

Skin Cell to Eye Transplantation Successful

A presentation at the annual meeting of the Association for Research in Vision and Ophthalmology in Seattle, Washington has reported the safe transplantation of stem cells derived from a patient’s skin to the back of the eye in an effort to restore vision. The subject for this research project suffered from advanced wet age-related macular degeneration that did not respond to current standard treatments.

A small skin biopsy from the patient’s arm was collected and reprogrammed into induced pluripotent stem cells (iPSCs). The iPSCs were then differentiated into retinal pigmented epithelial (RPE) cells, which were transplanted into the patient’s eye. The transplanted cells survived without any adverse events for over a year and resulted in slightly, though significantly, improved vision.

iPSCs are adult cells that have been reprogrammed to an embryonic stem cell-like state, which can then be differentiated into any cell type found in the body.

Abstract Title: #3769: Transplantation of Autologous induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium Cell Sheets for Exudative Age Related Macular Degeneration: A Pilot Clinical Study by Yasuo Kurimoto and others from the laboratory of Masayo Takahashi’s laboratory at the RIKEN Center for Developmental Biology in Kobe, Japan.

Unfortunately, this clinical trial has been suspended because iPSCs made from other patients proved to possess too many genetic abnormalities.  Therefore, Takahashi and her colleagues have decided that allogeneic iPSCs differentiated into RPEs will probably do a better job than the patient’s own skin cell-derived iPSCs.

Insulin-Secreting Beta Cells from Human Fat

In a study led by Martin Fussenegger of ETH Zurich, stem cells extracted from the fat of a 50-year-old test subject were transformed into mature, insulin-secreting pancreatic beta cells.

Fussenegger and his colleagues isolated stem cells from the fat of a 50-year-old man and used these cells to make induced pluripotent stem cells (iPSCs). These iPSCs were then differentiated into pancreatic progenitor cells and then into insulin-secreting beta cells but means of a “genetic software” approach.

Genetic software refers to the complex synthetic network of genes required to differentiate pancreatic progenitor cells into insulin-secreting beta cells. In particular, three genes, all of which expression transcription factors, Ngn3, Pdx1, and MafA, are particularly crucial for beta cell differentiation.

Fussenegger and his team designed a a protocol that would express within these fat-based stem cells the precise concentration and combination of these transcription factors. This feature is quite important because the concentration of these factors changes during the differentiation process. For example, MafA is not present at the start of beta cells maturation, but appears on day four on the final data of maturation when its concentration rises precipitously. The concentration of Ngn3 rises and then falls and the levels of Pdx1 rise at the beginning and towards the end of maturation.

The Zurich team used ingenious genetic tools to reproduce these vicissitudes of gene expression as precisely as possible. By doing so, they were able to differentiate the iPSC-derived pancreatic progenitor cells into insulin-secreting beta cells.

This work was published in Nature Communications 7, doi:10.1038/ncomms11247.

The fact that Fussenegger’s team was able to use a synthetic gene network to form mature beta cells from adult stem cells is a genuine breakthrough. The genetic network approach also seems to work better than the traditional technique of adding various chemicals and growth factors to cultures cells. “It’s not only really hard to add just the right quantities of these components (growth factors) at just the right time, it’s also inefficient and impossible to scale up,” said Fussenegger.

This new process can successfully transform three out of four fat stem cells into beta cells. Also the beta cells made with this method have the same microscopic appearance of natural beta cells in that they contain internal granules full of insulin. They also secrete insulin in response to increased blood glucose concentrations. Unfortunately the amount of insulin made by these cells is lower than that made by natural beta cells.

Pancreatic islet transplants have been performed in diabetic patients, but such transplantations also require treatment with potent antirejection drugs that have potent side effects.

“With our beta cells, there would likely be no need for this action (administering antitransplantation drugs), since we can make them using endogenous cell material taken from the patient’s own body. This is why our work is of such interest in the treatment of diabetes,” said Fussenegger.

Fussenegger and his group have made these beta cells in the laboratory, but they have yet to transplant them into a diabetic patient. However, the success of this synthetic genetic software technology might also be useful in the reprogramming of adult cells into other types of cells that are useful for therapeutic purposes.

A Faster, Less Expensive Way to Create Heart Tissue for Testing

Researchers from the University of California, San Francisco (UCSF) have designed new stem cell-based procedure that can make three-dimensional heart tissue that can serve as a model system for drug testing and particular diseases. This new technique reduces the number of cells required to make a mini-three-dimensional heart tissue patch. Thus, this procedure can produce a cheaper, more efficient system that is also easier to set up and use.

Bruce Conklin and his colleagues published their results in the internationally acclaimed Proceedings of the National Academy of Sciences USA (DOI:10.1073/pnas.1519395113). This bioengineered microscale heart tissue provides the means for heart researchers to study heart cells in their proper context.

To design their protocol, Conklin and his colleagues used induced pluripotent stem cells (iPSCs), which are made from the mature, adult cells of patients by means of genetic engineering cell culture techniques.  Induced pluripotent stem cells can be differentiated into heart muscle cells, but the cells made iPSCs tend to be rather immature.  Furthermore, experiments with these immature heart muscle cells often requires large quantities of cells that take time and expense to cultivate.

Conklin’s microheart muscles are stretched into highly organized clusters that drive their further differentiation.  After the iPSCs are differentiated into heart muscle cells, they are grown in dog bone-shaped culture dishes that spreads the cells out and forces them to organize properly. This physical arrangement drive their differentiation.  Within a couple of days, the miniheart tissues structurally and functionally resemble heart muscle.  These more mature heart muscles cells provide more realistic information about how a particular experimental drug might affect the heart.  These microscale hearts require up to 1000-fold fewer cells, which allows for more tests, better data, and less hassle all for less expense.

As a demonstration of the maturity of the microscale heart tissue system, Conklin and his group treated their cells with a drug called verapamil.  Verapamil is a member of the “calcium channel blocker” family of drugs.  It inhibits the so-called “L-type” calcium channels, which lowers the delayed rectifier current potassium channel.  The upshot is that heart blood vessels dilate, which send more blood and oxygen to heart muscle, and the activity of the heart muscle is slowed.  However, fetal heart muscle cells are impaired by verapamil, but adult cells, while slowed, are not impaired.  Conklin’s minihearts showed a more adult response to verapamil, which strongly suggests that the cells in this structure are more adult than they are fetal.

The Gladstone Institute researcher, Bruce Conklin, and senior author of this article, said: “The beauty of this technique is that it is very easy and robust, but it still allows you to create three-dimensional miniature tissues that function like normal tissues.  Our research shows that you can create these complex tissues with a simple template that exploits the inherent properties of these cells to self-organize.  We think that the microheart muscle will provide a superior resource for conducting research and developing therapies for heart disease.”

Pluripotent Stem Cells Used to Make a Functional Thyroid

The thyroid gland sits over the main cartilage of the larynx and produces thyroid hormone (thyroxine); a hormone that regulates the basal metabolic rate. When the thyroid slows down and fails to make sufficient amounts of thyroid hormone, the result is a condition called hypothyroidism. The symptoms of hypothyroidism are fatigue, weakness, weight gain or increased difficulty losing weight, coarse, dry hair, dry, rough pale skin, hair loss, cold intolerance, muscle cramps and frequent muscle aches, constipation, depression, irritability, memory loss, abnormal menstrual cycles and decreased libido.

If someone has any evidence of a thyroid tumor, then the thyroid is removed, and the patient must take oral thyroid hormone. Because getting the dose right can be difficult, we might ask, “Can we replace the thyroid with stem cell treatments?”

Human pluripotent stem cells can differentiate into balls of cells that are mini-organs called “organoids.”  Unfortunately, if left to themselves, the formation of these organoids is rather haphazard and the cells tend to differentiate into a whole host of different cell types. This is not fatal, however, since the differentiation of these stem cells can be orchestrated by using growth factors or certain culture conditions. Can we use such innovations to make a minithyroid?

Darrell Kotton and his group at Boston University School of Medicine Pulmonary, Allergy, Sleep and Critical Care Medicine have spent their time tweaking the conditions to drive human pluripotent stem cells to form thyroid cells. A new study of theirs that appears in the journal Cell Stem Cell details how the use of two growth factors, BMP4 and FGF2 can drive pluripotent stem cells to commit to thyroid cell fates.

In order to make thyroid cells from embryonic stem cells (ESCs), Kotton and his group had to make endodermal progenitors from them first. Fortunately, a study from Kotton’s own laboratory that was published in 2012 employed a technique used in several other papers that grew ESCs in a serum-free medium with a growth factor called activin. Christodoulou, C., and others (J. Clin. Invest. 121, 2313–2325) showed that over 80 percent of the ESCs grown under these conditions differentiated into endodermal progenitors.  When Kotton and his colleagues cultured these endodermal progenitors in BMP4 and FGF2, some of them differentiated into thyroid progenitor cells. Interestingly, this mechanism by which thyroid-specific cell fates are specified is conserved in creatures as disparate as frogs and mice.

To make mature thyroid cells from these progenitors, a three-dimensional culture system was used in combination with thyroid stimulation hormone and dexamethasone. Under these conditions, the cells formed spherical thyroid follicles that secreted thyroid hormone. To perfect their protocols, Kotton’s group used mouse ESCs, but they additionally showed that this same strategy can make mature thyroid cells from human induced pluripotent stem cells (iPSCs).

Thyroid specification

The appearance of cells in a culture system that look like mature thyroid follicles and express many of the same iodine-metabolizing enzymes as mature thyroid cells is exciting, but can such cells stand in for thyroid tissue in an animal that lacks sufficient thyroid tissue?

Kotton’s laboratory took this to the next step by transplanting their cultured thyroid follicles into laboratory mice that lacked a functional thyroid. These transplants were not inserted into the neck of the animal, but instead were place underneath the kidney, which is area rich in blood vessels. Interestingly, the implanted thyroid “organoids” or little organs did not fall apart upon transplantation. Instead they retained their characteristic structure. More interestingly, these organoids kept expressing iodine-metabolizing enzymes and made thyroid hormone. The synthesis and release of thyroid hormone was also regulated by the hypothalamic hormone thyroid stimulating hormone (TSH). TSH is made and released in response to insufficient thyroid hormone levels. The thyroid responds to TSH by making a releasing more thyroid hormone, which causes a feed-back inhibition of the release of TSH. The fact that these implanted organoids were properly regulated by TSH bespeaks of the maturity of these cells. Also, significantly, none of the laboratory animals showed any signs that the implanted cells had formed any tumors.

Kotton and his coworkers were also able to used human ESCs and human iPSCs to make thyroid organoids. Human iPSCs-derived thyroid organoids were made from human patients with normal thyroid function and from hypothyroid children who carry a loss-of-function mutation in the NKX2-1 gene. This show that Kotton’s system can be used as a model to study inherited thyroid deficiencies. However, there is even more excitement that this system or something similar to it might be useful to safely treat thyroid loss in patients who have lost their thyroid as a result of cancer, or injury.

Accelerated Reprogramming and Gene Editing Protocol Can Make Fixed Cells Much Faster

Sara Howden and her colleagues at the Morgridge Institute for Research and the Murdoch Children’s Research Institute in Australia have devised a protocol that can significantly decrease the time involved in reprogramming mature adult cells while genetically repairing them at the same time. Such an advance is essential for making future therapies possible.

Howden and others demonstrated that genetically repaired cells can be derived from patient skin cells in as little as two weeks. This is much shorter than the multistep approaches that take more than three months.

How were they able to shorten the time necessary to do this? They combined two integral steps in the procedure. Adult cells were reprogrammed to an embryonic stem cell-like state in order to be differentiated into the cells that we want. Secondly, the cells must undergo gene editing in order to correct the disease-causing mutation.

By in this new protocol developed by Howden and her colleagues, they combined the reprogramming and gene editing steps.

To test their new protocol, Howden and her team used cells isolated from a patient with an inherited retinal degeneration disorder, and an infant with severe immunodeficiency. In both cases, the team not only derived induced pluripotent stem cell lines from the adult cells of these patients, but they were also able to repair the genetic lesion that causes the genetic disease.

This protocol might advance transplant medicine by making gene-correction therapies available to patients in a much timelier fashion and at lower cost.

Presently, making induced pluripotent stem cell lines from a patient’s cells, genetically repairing those cells, expanding them, differentiating them, and then isolating the right cells from transplantation, while checking the cells all along the way and properly characterizing them for safety reasons would take too long and cost too much.

With this new approach, however, Howden and others used the CRISPR/Cas9 technology to edit the damaged genes while reprogramming the cells, greatly reducing the time required to make the cells for transplantation.

Faster reprogramming also decreases the amount of time the cells remain in culture, which minimizes the risks of gene instability or epigenetic changes that can sometimes occur when culturing cells outside the human body.

Howden’s next goal is to adapt her protocol to work with blood cells so that blood samples rather than skin biopsies can be used to secure the cells for reprogramming/gene editing procedure. Blood cells also do not require the expansion that skin cells require, which would even further shorten the time needed to make the desired cell types.

The accelerated pace of the reprogramming procedure could make a genuine difference in those cases where medical interventions are required in as little time as possible. For example, children born with severe combined immunodeficiency usually die within the first few years of life from massive infections.

Howden cautioned, however, that she and her team must first derive a long-term source of blood cells from pluripotent stem cells before such treatments are viable and demonstrate the safety of such treatments as well.

See Stem Cell Reports, 2015: DOI: 10.1016/j.stemcr.2015.10.009.