Turning Stem Cells into Drug Factories


Wouldn’t it be nice to have cells that express the right molecules at the right place and the right time to augment or even initiate healing?

Researchers at the Brigham and Women’s Hospital and Harvard Stem Cell Institute have inserted modified messenger RNA to induce mesenchymal stem cells to produce adhesive proteins  (PSGL-1)and secrete interleukin-10, a molecule that suppresses inflammation. When injected into the bloodstream of mice, these modified stem cells home to the right location, stick to that site, and secrete interleukin-10 (IL-10) to suppress inflammation.

Improving MSC therapeutic potential viamRNA transfection with homing ligands and immunomodulatory factors. Illustration of (A) mRNA-engineered MSCs that express a combination of homing ligands (PSGL-1 and SLeX) and an immunomodulatory factor (IL-10), and (B) targeting mRNA-engineered MSCs to site of inflammation.
Improving MSC therapeutic potential viamRNA transfection with homing ligands and immunomodulatory factors. Illustration of (A) mRNA-engineered MSCs that express a combination of homing ligands (PSGL-1 and SLeX) and an immunomodulatory factor (IL-10), and (B) targeting mRNA-engineered MSCs to site of inflammation.

Jeffrey Karp, Harvard Stem Cell Institute principal faculty member and leader of this research, said this about this work: “If you think of a cell as a drug factory, what we’re doing is targeting cell-based, drug factories to damaged tissues, where the cells can produce drugs at high enough levels to have a therapeutic effect.”

Karp’s paper reports a proof-of-principle study has piqued the interest of several biotechnology companies, since it has the potential to target biological drug to disease sites. While ranked as the top sellers in the drug industry, biological drugs are still challenging to use. Karp’s approach might improve the clinical applications of biological drugs and improve the somewhat mixed results of clinical trials with mesenchymal stem cells.

Mesenchymal stem cells (MSCs) have emerged as one of the favorite sources for stem cell therapies. The attractiveness of MSCs largely lies with their availability, since they are found in bone marrow, fat, liver, muscle, and many other places. Secondly, MSCs can be grown in culture for a limited period of time without a great deal of difficulty. Third, MSCs tend to be ignored by the immune system when injected. For these reasons, MSCs have been used in many clinical trials, and they appear to be quite safe to use.

To genetically modify MSCs, Karp and his co-workers made chemically modified messenger RNAs (mRNAs) whose bases differed slightly from natural mRNAs. These chemical modifications did not affect the recognition of the mRNA by the protein synthesis machinery of the MSCs, but did affect the recognition of these mRNAs by those enzymes that degrade mRNAs. Therefore, these synthetic mRNAs are very long-lived and the transfected cells end up making the proteins encoded by these mRNAs for a very long time. RNA transfection does not modify the genome of the host cells, and this makes it a very safe procedure, since the engineered cells will express the desired protein for some time, but not indefinitely.

The mRNAs introduced into the cultured MSCs included mRNAs that encode the IL-10 protein, which is cytokine that suppresses inflammation, the PSGL-1 protein, a cell-surface protein that sticks to the P-and E-selectin receptors, and the Fut7 gene product.  FUT7 encodes an enzyme called fucosyltransferase 7, which adds a sugar called “fucose” to the PSGL-1 protein and without this sugar, PSGL-1 cannot bind to the selectins.  Selectins are stored by cells and during inflammation, they are sent to the cell surface where they can bind cells and keep them there to mediate inflammation.  By expressing PSGL-1 in the MSCs, Karp and his group hoped to that the engineered MSCs would bind to the surfaces of blood vessels and not be washed out.

e-selectin_binding

Oren Levy, lead author of this paper, said, “This opens the door to thinking of messenger RNA transfection of cell populations as next generation therapeutics in the clinic, as they get around some of the delivery challenges that have been encountered with biological agents.”

A problem that constantly troubles clinical trials that use MSCs is that they are rapidly cleared from the bloodstream within a few hours or days after they are introduced. The Harvard team showed that rapid targeting of MSCs to inflamed tissue produced a therapeutic effect despite rapid clearance of the MSCs.

Karp and his colleagues would like to extend the lifespan of these cells in the bloodstream and they are presently experimenting with new synthetic mRNAs that encode pro-survival factors.

“We’ve interested to explore the platform nature of this approach and see what potential limitations it may have or how far we can actually push it. Potentially we can simultaneously deliver proteins that have synergistic therapeutic impacts,” said Weian Zhao, another author of this paper.

Keeping Implanted Stem Cells in the Heart


Globally, thousands of heart patients have been treated with stem cells from bone marrow and other sources. While many of these patients have been helped by these treatments, the results have been inconsistent, and most patients only show a modest improvement in heart function.

The reason for these sometimes underwhelming results seems to result from the fact that implanted stem cells either die soon after they are delivered to the heart or washed out. Since the heart is a pump, it is constantly contracting and having fluid (blood) wash through it. Therefore, it is one of the last places in the body we should expect implanted stem cells to stay put.

To that end, cardiology researchers a Emory University in Atlanta, Georgia have packaged stem cells into small capsules made of alginate (a molecule from seaweed) to keep them in the heart once they are implanted there.

alginate_formel

W. Robert Taylor, professor of medicine and director of the cardiology division at Emory University School of Medicine, and his group encapsulated mesenchymal stem cells in alginate and used them to male a “patch” that was applied to the hearts of rats after a heart attack. Taylor’s group compared the recovery of these animals to those rats that had suffered heart attacks, but were treated with non-encapsulated cells, or no cells at all. The rats treated with encapsulated cells not only showed a more robust recovery, but they had larger numbers of stem cells in their hearts and showed better survival.

Histological appearance of encapsulated human mesenchymal stem cells (hMSCs). Light microscopic appearance of encapsulated hMSCs at the time of implantation with approximately 200 cells within each 250 μm capsule. (Scale bar=100 μm)
Histological appearance of encapsulated human mesenchymal stem cells (hMSCs). Light microscopic appearance of encapsulated hMSCs at the time of implantation with approximately 200 cells within each 250 μm capsule. (Scale bar=100 μm)

Of this work, Taylor said, “This approach appears to be an effective way to increase cell retention and survival in the context of cardiac cell therapy. It may be a strategy applicable to many cell types for regenerative therapy in cardiovascular medicine.

Readers of this blog might remember that I have detailed before the inhospitable environment inside the heart after a heart attack. Oxygen levels are low because blood vessels have died, and roving white blood cells are gobbling up cell debris and releasing toxic molecules while they do it. Also the dying cells have released a toxic cocktail of molecules that make the infarcted area very inhospitable. Injecting stem cells into this region is an invitation for more cells to die. Previous experiments have shown that preconditioning stem cells either by genetically engineering them to withstand high stress levels of by growing them in high-stress conditions prior to implantation can increase their survival in the heart.

Taylor also pointed out that the mechanical forces of the contracting heart can squeeze them and displace them from the heart, much like pinching a watermelon seed between your fingers causes it to slip out. “These cells are social creatures and like to be together,” said Taylor. “From some studies of cell therapy after myocardial infarction, one can estimate that more than 90 percent of the cells are lost in the first hour. With numbers like that, it’s easy to make the case that retention is the first place to look to boost effectiveness.”

Encapsulation keeps the mesenchymal stem cells together in the heart and “keeps them happy.” Encapsulation, however, does not completely cut off the cells from their environment. They can still sense the cardiac milieu and release growth factors and cytokines while they are protected from marauding white blood cells and antibodies that might damage, destroy, or displace them.

Alginate already has an impressive medical pedigree as a biomaterial. It is completely non-toxic, and chefs use it to make edible molds to encase other types of tasty morsels. Dentists use alginate to take impressions of a patient’s teeth and it is also used a component of wound dressings. One of Taylor’s co-authors, an Emory University colleague named Collin Weber has used alginate to encapsulate insulin-producing islet-cells that are being tested in clinical trials with diabetics.

Encasing cells in alginate prevents them from replacing dead cells, but mesenchymal stem cells tend to do the majority of their healing by means of “paracrine” mechanisms; that is to say, mesenchymal stem cells tend to secrete growth factors, cytokines and other healing molecules rather than differentiating into heart cells. Mesenchymal stem cells can be isolated from bone marrow or fat.

One month after suffering from a heart attack, those rats that had suffered a heart attack saw their ejection fractions (a measure of how much volume the heart pumps out with every beat) fell from an average of 72% to 34%. However, rats treated with encapsulated mesenchymal stem cells saw an increase in their ejection fractions from 34% to 56%. Those treated with unencapsulated mesenchymal stem cells saw their ejection fractions rise to 39%.

Detailed cardiac functional analysis by cardiac magnetic resonance imaging (CMR) and transthoracic echocardiography (TTE) showed improvement in animals treated with encapsulated human mesenchymal stem cells (hMSCs). A, Representative short axis CMR at end systole of animals treated with encapsulated hMSCs or controls. Myocardial thinning and chamber dilation, delineated by traced endocardium (red) and epicardium (green) was reduced in the encapsulated hMSC group (arrow). Quantification of end systolic volume (B) and ejection fraction (C) by CMR at day 28 showed improved contractile function in the encapsulated hMSC treated group (n=4 per group). D, TTE comparison of untreated animals (n=9) to animals treated with encapsulated hMSCs (n=7) or hMSCs delivered by direct injection (n=7) into the infarcted myocardium showed greater benefit of treatment with encapsulated cells. Data represent mean±SEM. *P<0.05 by Dunnett's test of multiple comparisons; #P<0.05 by analysis of variance (ANOVA). LVESV indicates left ventricular end systolic volume; MI, myocardial infarction.
Detailed cardiac functional analysis by cardiac magnetic resonance imaging (CMR) and transthoracic echocardiography (TTE) showed improvement in animals treated with encapsulated human mesenchymal stem cells (hMSCs). A, Representative short axis CMR at end systole of animals treated with encapsulated hMSCs or controls. Myocardial thinning and chamber dilation, delineated by traced endocardium (red) and epicardium (green) was reduced in the encapsulated hMSC group (arrow). Quantification of end systolic volume (B) and ejection fraction (C) by CMR at day 28 showed improved contractile function in the encapsulated hMSC treated group (n=4 per group). D, TTE comparison of untreated animals (n=9) to animals treated with encapsulated hMSCs (n=7) or hMSCs delivered by direct injection (n=7) into the infarcted myocardium showed greater benefit of treatment with encapsulated cells. Data represent mean±SEM. *P

One of the main effects of implanted stem cells is the promotion of the growth of new blood vessels.  In capsule-treated rats, the damaged area of the heart had a blood vessel density that was several times that of the hearts of control animals.  Also, the area of cell death was much lower in the hearts treated with encapsulated MSCs.

Treatment of hearts with encapsulated human mesenchymal stem cells (hMSC) post myocardial infarction reduced myocardial scarring at 28 days. A, Representative sections of infarcted hearts stained with Masson's Trichrome and treated with encapsulated hMSCs or control gels. Blue indicates fibrotic scar. ×15, scale bar=1 mm. B, Animals treated with encapsulated hMSCs showed reduced scar area (7±1%; n=6) at 28 days compared to control treated hearts (MI: 12±1%, n=8; MI+Gel: 14±2%, n=7; MI+Gel+hMSC: 14±1%, n=7; MI+Gel+Empty Caps: 12±2%, n=5). Data represent mean±SEM. *P<0.05. MI indicates myocardial infarction.
Treatment of hearts with encapsulated human mesenchymal stem cells (hMSC) post myocardial infarction reduced myocardial scarring at 28 days. A, Representative sections of infarcted hearts stained with Masson’s Trichrome and treated with encapsulated hMSCs or control gels. Blue indicates fibrotic scar. ×15, scale bar=1 mm. B, Animals treated with encapsulated hMSCs showed reduced scar area (7±1%; n=6) at 28 days compared to control treated hearts (MI: 12±1%, n=8; MI+Gel: 14±2%, n=7; MI+Gel+hMSC: 14±1%, n=7; MI+Gel+Empty Caps: 12±2%, n=5). Data represent mean±SEM. *P

The encapsulated stem cells seem to stay in the heart for just over ten days, which is the time is takes for the alginate hydrogels to break down.  Taylor said that he and his lab would like to test several different materials to determine how long these capsules remain bound to the patch.

The goal is to use a patient’ own stem cells as a source for stem cell therapy.  Whatever the source of stem cells, a patient’s own stem cells must be grown outside the body for several days in a stem cell laboratory, much like Emory Personalized Immunotherapy Center in order to have enough material for a therapeutic effect.

Foregut Stem Cells


Scientists from Cambridge University have designed a new protocol that will convert pluripotent stem cells into primitive gut stem cells that have the capacity to differentiate into liver, pancreas, or some other gastrointestinal structure.

Nicholas Hannan and his colleagues at the University of Cambridge Welcome Trust MRC Stem Cell Institute have developed a technique that allows researchers to grow a pure, self-renewing population of stem cells that are specific to the human foregut, which is the upper section of the human digestive system. These types of stem cells are known as “foregut stem cells” and they can be used to make liver, pancreas, stomach, esophagus, or even parts of the small intestine. Making these types of gastrointestinal tissues can provide material for research into gastrointestinal abnormalities, but might also serve as a source of material to treat type 1 diabetes, liver disease, esophageal and stomach cancer, and other types of severe gastrointestinal diseases.

“We have developed a cell culture system which allows us to specifically isolate foregut stem cells in the lab,” said Hannan. “These cells have huge implications for regenerative medicine, because they are the precursors to the thyroid upper airways, lungs, liver, pancreas, stomach, and biliary systems.”

Hannan did this work in the laboratory of Ludovic Vallier, and they think that their technique will provide the means to analyze the precise embryonic development of the foregut in greater detail. “We now have a platform from which we can study the early patterning events that occur during human development to produce intestines, liver, lungs, and pancreas,” said Hannan.

To make foregut stem cells, Hannan begins with a pluripotent stem cell line; either an embryonic stem cell line or an induced pluripotent stem cell line. Then he differentiated them into definitive endoderm by treating them with CDM-PVA and activin-A (100 ng/ml), BMP4 (10 ng/ml), bFGF (20 ng/ml), and LY294002 (10 mM) for 3 days. Once they differentiated into endoderm, the endodermal cells were grown in RPMI+B27 medium with activin-A (50 ng/ml) for 3-4 days in order to generate foregut stem cells.

(A) GFP-expressing hPSCs were differentiated into hFSCs. (B) Single GFP-positive hFSCs were seeded onto a layer of non-GFP hFSCs and then expanded for five passages. The resulting population was then split into culture conditions inductive for liver or pancreatic differentiation. (C and D) GFP-hFSCs differentiated for 25 days were found to respectively generate cells expressing liver markers (ALB, LDL-uptake) and pancreatic markers (PDX1, C-peptide) from both hESC-derived (C) and hIPSC-derived (D) hFSCs.
(A) GFP-expressing hPSCs were differentiated into hFSCs.  (B) Single GFP-positive hFSCs were seeded onto a layer of non-GFP hFSCs and then expanded for five passages. The resulting population was then split into culture conditions inductive for liver or pancreatic differentiation.  (C and D) GFP-hFSCs differentiated for 25 days were found to respectively generate cells expressing liver markers (ALB, LDL-uptake) and pancreatic markers (PDX1, C-peptide) from both hESC-derived (C) and hIPSC-derived (D) hFSCs.

These foregut stem cells (FSCs) can self-renew, and can also differentiate into any part of the foregut. Thus, FSCs can grow robustly in culture, and they can also differentiate into foregut derivatives. However, these cells also do not form tumors. When injected into mice, they failed to form tumors.

(A) Large cystic hFSC outgrowth under the kidney capsule of a NOD-SCID mouse. (B) Cryosection of a hFSC outgrowth showing large cystic structures lined with epithelial cells. (C) Immunocytochemistry showing foregut outgrowths expressing EpCAM, PDX1, AFP, and NKX2.1. Scale bars, 100 μm or 50 μm as shown. See also Figure S4.
(A) Large cystic hFSC outgrowth under the kidney capsule of a NOD-SCID mouse.  (B) Cryosection of a hFSC outgrowth showing large cystic structures lined with epithelial cells.  (C) Immunocytochemistry showing foregut outgrowths expressing EpCAM, PDX1, AFP, and NKX2.1.  Scale bars, 100 μm or 50 μm as shown. See also Figure S4.

What are the advantages to FSCs as opposed to making pancreatic cells or liver cells from pluripotent stem cells? These types of experiments always create cultures that are impure. Such cultures are difficult to use because not all the cells have the same growth requirements and they would be dangerous for therapeutic purposes because they might contain undifferentiated cells that might grow uncontrollably and cause a tumor. Therefore, FSCs provide a better starting point to make pure cultures of pancreatic tissues, liver tissues, stomach tissues and so on.

Ludovic Vallier, the senior author of this paper said this of his FSCs, “What we have now is a better starting point – a sustainable platform for producing liver and pancreatic cells. It will improve the quality of the cells that we produce and it will allow us to produce the large number of uncontaminated cells we need for the clinical applications of stem cell therapy.”

Vallier’s groups is presently examining the mechanisms that govern the differentiation of FSCs into specific gastrointestinal cell types in order to improve the production of these cells for regenerative medicine.

Human Umbilical Cord Mesenchymal Stem Cells and Rheumatoid Arthritis


A collaborative study between physicians at the Hospital of Chinese People’s Liberation Army and the University of Oklahoma Health Sciences Center has examined the efficacy of umbilical cord mesenchymal stem cell treatments in combination with drugs in patients with active rheumatoid arthritis (RA).

RA may exist in 0.5-1.0% of the general population. In 2005, an estimated 1.5 million US adults aged ≥ 18 (0.6%) had RA. RA is characterized by chronic inflammation of the joints that causes cartilage and bone damage and deformity. It occurs in women two to three times more often than men.

Treatment of RA requires the administration of disease-modifying antirheumatic drugs (DMARDs), Unfortunately, these drugs have sizable side effects, and less debilitating treatments would be a welcome addition to the treatment options for RA patients.

A paper by Liming Wang and colleagues that was published in Stem Cells and Development examines the efficacy of combining DMARDs with infusions of umbilical cord mesenchymal stem cells (MSCs). Since MSCs have the ability to suppress an overactive immune response, such treatments might provide relief from the symptoms of RA and decrease the dependence on DMARDs.

In this study, Wang and others enrolled 172 RA patients and divided them into two groups: 36 of them were treated with DMARDs alone and 136 were treated with DMARDs plus umbilical cord MSCs (UC-MSCs). Of these 136 patients, 76 were treated for 3 months, 45 for 6 months, and 15 for 8 months. Each of these groups consisted of patients who could and who could not tolerate DMARDs. All patients in the second group received 4 x 10[7] UC-MSCs in 40 milliliters of liquid, but the first group received stem cell “solvent” (whatever that is) without UC-MSCs.

The results clearly showed that UC-MSCs treatments are safe. Patients blood work-ups before and after treatment show no significant differences. Secondly, the DMARD-only group did not show any improvements, but they did not get worse either. The DMARD + UC-MSC group showed quantifiable improvements. These patients reported feeling better in health assessment questionnaires, their serum levels of C-reactive protein and rheumatoid factor went down and their numbers of regulatory T-cells went up. The joint evaluations of these patients also improved (the so-called DAS28 score). All of these are measures of the severity of RA, and in the DMARD + UC-MSC groups, all the these markers improved.

Other markers of RA severity such as IL-6 and TNF-alpha also decreased in the DMARD + UC-MSC patients.

From these data, Wang and others conclude that “UC-MSCs are suitable pllications in the clinic and provide an additional choice to many RA patients.”

The data in this paper are rather clear. The benefits of a single UC-MSC treatment are significant. For this reason, umbilical cord MSCs should be regarded as a potential adjuvant treatment for RA patients.

Inhibition of a Heart-Specific Enzyme After a Heart Attack Decreases Heart Damage and Prevents Remodeling


Cardiac Troponin I-interacting Kinase or TNNI3K is an enzyme that was initially identified in fetal and adult heart tissue, but was undetectable in other tissues. The function of this enzyme remains unknown, but Chinese scientists showed that overexpression of TNNI3K in cultured heart muscle cells causes them to blow up and get large (hypertrophy). Earlier this year, a research team from Peking Union Medical College showed that overexpression of TNNI3K in mice caused enlargement of the heart (Tang H., et al., J Mol Cell Cardiol 54 (2013): 101-111). These results suggested that TNNI3K is a potential therapeutic target for heart attack patients.

To that end, Ronald Vagnozzi and his colleagues in the laboratory of Thomas Force at Temple University School of Medicine and their collaborators designed small molecules that can inhibit TNNI3K activity, and these small molecules decrease cardiac remodeling after a heart attack in rodents. Large animal trials are planned next.

In the first experiments of this paper, Vagnozzi and others showed that the levels of TNNI3K in the heart increase after a heart attack. Measurements of TNNI3K protein levels failed to detect it in all tissue other than the heart. Furthermore, it was present throughout the heart, and mainly in heart muscle and not in blood vessels, fibroblasts, and other types of non-muscle heart tissues.

Next, Vagnozzi and others measured TNNI3K protein levels in heart transplant patients. The heart tissues of these patients, who had badly dysfunctional hearts showed higher than usual levels of TNNI3K protein. Thus, TNNI3K is associated with heart tissue and is up-regulated in response to heart dysfunction.

The next experiment examined the effects of overexpressing the human TNNI3K gene in mice. While the overexpression of TNNI3K did not affect heart function of structure under normal circumstances, under pathological conditions, however, this is not he case. If mice that overexpressed TNNI3K where given heart attacks and then “reperfused,” means that the blood vessel that was tied off to cause the heart attack was opened and blood flowed back into the infarcted area. In these cases, mice that overexpressed TNNI3K had a larger area of cell death in their hearts than their counterparts that did not overexpress TNNI3K. The reason for this increased cell death had to do with the compartment in the cell that generated most of the energy – the mitochondrion. TNNI3K causes the mitochondria in heart muscle cells to go haywire and kick out all kinds of reactive oxygen-containing molecules that damage cells.

Cell damage as a result of reactive oxygen-containing molecules (known as reactive oxygen species or ROS) activates a pathway in heart cells called the “p38” pathway, which leads to programmed cell death.

p38 signaling

Once Vagnozzi and his colleagues nailed down the function of TNNI3K in heart muscle cells after a heart attack, they deleted the gene that encodes TNNI3K and gave those TNNI3K-deficient mice heart attacks. Interestingly enough, after a heart attack, TNNI3K-deficient mice showed much small dead areas than normal mice. Also, the levels of the other mediators of TNNI3K-induced cell death (e.g., oxygen-containing molecules, p38, ect.) were quite low. This confirms the earlier observations that TNNI3K mediates the death of heart muscle cells after a heart attack, and inhibiting TNNI3K activity decreases the deleterious effects of a heart attack.

And now for the pièce de résistance – Vagnozzi and his crew synthesized small molecules that inhibited TNNI3K in the test tube. Then they gave mice heart attacks and injected these molecules into the bellies of the mice. Not only were the infarcts, or areas of dead heart muscle cells small in the mice injected with these TNNI3K inhibitors, but the heart of these same mice did not undergo remodeling and did not enlarge, showed reduced scarring, and better ventricular function. This is a proof-of-principle that inhibiting TNNI3K can reduce the pathological effects of a heart attack.

This strategy must be tested in large animals before it can move to human trials, but the strategy seems sound at this point, and it may revolutionize the treatment of heart attack patients.

Primed Fat-Based Stem Cells Enhance Heart Muscle Proliferation


A Dutch group from the University of Groningen has shown that fat-based stem cells can enhance the proliferation of cultured heart muscle cells. The stem cells used in these experiments were preconditioned and this pretreatment greatly enhanced their ability to activate heart muscle cells.

This paper, by Ewa Przybyt, Guido Krenning, Marja Brinker, and Martin Harmsen was published in the Journal of Translational Medicine. To begin, Przybyt and others extracted human adipose derived stromal cells (ADSC) from fat tissue extracted from human liposuction surgeries. To do this, they digested the fat with enzymes, centrifuged and washed it, and then grew the remaining cells in culture.

Then they used rat neonatal heart muscle cells and infected them with viruses that causes them to glow when certain types of light was shined on them. Then Przybyt and others co-cultured these rat heart cells with human ADSCs.

In the first experiment, the ADSCs were treated with drugs to prevent them from dividing and then they were cultured with rat heart cells in a one-to-one ratio. The heart muscle cells grew faster with the ADSCs than they did without them. To determine if cell-cell contact was required for this stimulation, they used the culture medium from ADSCs and grew the heart cell on this culture medium. Once again, the heart cells grew faster with the ADSC culture medium than without it. These results suggest that the ADSCs stimulate heart cell proliferation by secreting factors that activate heart cell division.

Another experiment subjected the cultured heart cells to the types of conditions they might experience inside the heart after a heart attack. For example, heart cells were subjected to low oxygen tensions (2% oxygen), and inflammation – two conditions found within the heart after a heart attack. These treatments slowed heart cell growth, but this heart cell growth was restored by adding the growth medium of ADSCs. Even more remarkably, when ADSCs were grown in low-oxygen conditions or treated with inflammatory molecules (tumor necrosis factor-alpha or interleukin-1beta), the culture medium increased the fractions of cells that grew. Therefore, ADSCs secrete molecules that increase heart muscle cell proliferation, and increase proliferation even more after the ADSCs are preconditioned by either low oxygen tensions or inflammation.

In the next experiment, Przybyt and others examined the molecules secreted by ADSCs under normal or low-oxygen tensions to ascertain what secreted molecules stimulated heart cell growth. It was clear that the production of a small protein called interleukin-6 was greatly upregulated.

Could interleukin-6 account for the increased proliferation of heart cells? Another experiment showed that the answer was yes. Cultured heart cells treated with interleukin-6 showed increased proliferation, and when antibodies against interleukin-6 were used to prevent interleukin-6 from binding to the heart cells, these antibodies abrogated the effects of interleukin-6.

Przybyt and others then took these results one step further. Since the signaling pathways used by interleukin-6 are well-known, they examined these pathways. Now interleukin-6 signals through pathways, once of which enhances cell survival, and another pathway that stimulated cell proliferation. The cell proliferation pathway uses a protein called “STAT3” and the survival function uses a protein called “Akt.” Both pathways were activated by interleukin-6. Also, the culture medium of ADSCs that were treated with interleukin-6 induced the interleukin-6 receptor proteins (gp80 and gp130) in cultured heart muscle cells. This gives heart muscle cells a greater capacity to respond secreted interleukin-6.

This paper shows that stromal stem cells from fat has the capacity, in culture, to activate the growth of cultured heart muscle cells. Also, if these cells were preconditioned with low oxygen tensions or pro-inflammatory molecules, those fat-based stem cells secreted interleukin-6, which enhanced heart muscle cell survival, and proliferation, even if those heart muscle cells are exposed to low-oxygen tensions or inflammatory molecules.

This suggests that preconditioned stem cells from fat might be able to protect heart muscle cells and augment heart healing after a heart attack. Alternatively, cardiac administration of interleukin-6 after a heart attack might prove even more effective to protect heart muscle cells and stimulate heart muscle cell proliferation. Human trials anyone?

Radio Interview About my New Book


I was interviewed by the campus radio station (89.3 The Message) about my recently published book, The Stem Cell Epistles,

Stem Cell Epistles

It has been archived here. Enjoy.