Minneapolis Heart Institute Foundation Tests Stem Cell Combination in Heart Attack Patients

The Minneapolis Heart Institute Foundation has announced a new clinical trial that will examine the ability of a stem cell combination to treat patients with ischemic heart failure.

In patients who have suffered from former heart attacks, clogged coronary blood vessels and heart muscle that hibernates can result in a heart that no longer works well enough to support the life of the patient. The lack of blood flow to vital parts of the heart and an increasing work load can result is so-called “Ischemic heart failure.” Such heart failure after a previous heart attack is one of the leading cause of death and morbidity in the world. According to the World Health Organization, ischemic heart disease affects more than 12% of the world’s population.

Stem cell therapy has been tested as a potential treatment for ischemic heart disease. Despite flashes of remarkable success, the overall efficacy of these treatments has been relatively modest. Most clinical trials have used the patient’s own bone marrow cells. In this case, the cell population is very mixed and it might not even be stem cell populations in the bone marrow that are eliciting recovery. Also, the quality of each patient’s bone marrow is probably quite varied, which makes standardizing such experiments remarkably difficult. Other clinical trials have used bone marrow derived mesenchymal cells [MSCs]. Several clinical trials with MSCs have seen some improvement in patients. MSCs seem to induce the formation of new blood vessels and also seem to induce endogenous stem cell populations in the heart to come to life and fix the heart. Other trials have used cardiac stem cells (CSCs) that were derived from biopsies of the heart. Even though fewer clinical trials have tested the efficacy of CSCs in human patients, the trials that have been conducted suggest that these cells can truly regenerate damaged heart tissue.

The Minneapolis Heart Institute Foundation® (MHIF) has announced a new clinical trial which will examine the combination of MSCs with CSCs to treatment patients with ischemic heart failure. This clinical trial, the CONCERT study, will be led by Principal Investigator Jay Traverse, MD. The CONCERT study will implant MSC’s and CSC’s in order to determine if the combination would be more successful than using either alone based on pre-clinical studies in swine demonstrating an enhanced synergistic effect of the combination.

CONCERT is sponsored by the National Institutes of Health and the Cardiovascular Cell Therapy Research Network (CCTRN), of which MHIF is a charter member. This will be a phase II clinical trial, which means that the focus of this leg of the study is to assess the relative safety of CSCs and MSCs, delivered either alone, or in combination, in comparison to placebo, and to measure the efficacy of the stem cell cocktail as well. To that end, researchers will measure and note any change or improvement in left ventricular (LV) function by cardiac MRI as well as changes in various clinical outcomes (survival, 6-minute walking, blood pressure, etc.), and quality of life.

This phase II study is a randomized, blinded, placebo-controlled study that will enroll 160 subjects at seven different CCTRN sites throughout the U.S. All recruited subjects will have ischemic cardiomyopathy and an ejection fraction 5%). This is significant, because some work in animals suggests that CSCs can make new heart muscle tissue that can shrink the heart scar. The first 16 patients were recently enrolled in a FDA-required safety run-in phase, but the remaining patients will be enrolled in the fall after a three-month safety analysis is performed. Incidentally, this is the first cardiac stem cell trial to perform MRIs on patients with defibrillators and pacemakers

“This combination of cells represents the most potent cell therapy product ever delivered to patients,” said Dr. Traverse. “Confirming that both types of stem cells together work better than either individual cell type could lead to improved patient outcomes and better quality of life for ischemic heart failure patients.”

Small Molecule Supercharges Human Cardiac Stem Cells

HO-1 or heme oxygenase is an enzyme that degrades heme groups to biliverdin, iron, and carbon monoxide. It is induced in cells in response to oxidative stress. Overexpression of HO-1 can make cells more resistant to oxidative stress. The highest levels of HO-1 are found in the spleen, where old red blood cells are sequestrated and destroyed.

Mesenchymal stem cells (MSCs) from bone marrow have been genetically engineered to overexpress HO-1 survive much better when implanted into the hearts of animals that have recently suffered a heart attack (Zeng B, et Al, Biomed Sci. 2010 Oct 7;17:80; Yang JJ et al Tohoku J Exp Med. 2012;226(3):231-41). Such cells also increase the density of blood vessels in infarcted tissue, and HO-1 has been postulated to increase blood vessel production (Jang YB et al Chin Med J (Engl). 2011 Feb;124(3):401-7).

These previous experiments show that HO-1 can increase the survival and therapeutic abilities of MSCs. Can increasing the levels of HO-1 do the same for other types of stem cells?

Stuart Atkinson at the Stem Cell Portal web site has highlighted a new paper that was published in the journal Stem Cells that has examined increasing the levels of HO-1 in Cardiac Stem Cells (CSCs).

CSCs are a resident stem cell in the heart that can be isolated from heart patients during heart surgeries. Animal studies and clinical trials have shown that implantation of CSCs soon after a heart attack can produce significant increases in heart function (Bearzi C, et al. Proc Natl Acad Sci U S A 2007;104:14068-14073; Bolli R, et al Lancet. 2011 Nov 26;378(9806):1847-57). Unfortunately, the success of this clinical has been called into questioned by some problems with the data reported in this paper. However, animal studies suggest that the effectiveness of CSCs is compromised by their limited ability to survive in the heart after a heart attack (Hong KU, et al. PLoS One 2014;9:e96725). Therefore, increasing the survival of CSCs might increase their therapeutic efficacy.

Atkinson notes that the compound cobalt protoporphyrin (CoPP) can induce the expression of higher levels of HO-1 and thereby increase the resistance of the cells to oxidative stress and augment cell survival. Therefore, Robert Bolli from the University of Louisville, Kentucky and his colleagues, in collaboration with researchers from the Albany Medical College have treated CSCs with CoPP and these tested their ability to heal the heart after a heart attack.

Bolli and others isolated human CSCs from patients undergoing CABG (cardiac artery bypass graft) surgery, and grew them in culture to beef up the numbers of cells. After a short time in culture, the CSCs were incubated with CoPP for 12 hours. Then Bolli and his team transplanted these human CSCs that were also labeled with green fluorescent protein (GFP) into the hearts of mice that had suffered rather massive heart attacks and had undergone 35 days of reperfusion. The GFP allowed Bolli and others to detect the presence of the implanted CSCs in the rodent heart tissue.

When these hearts of these mice were examined one and five weeks after CSC transplantation, the CoPP-treated CSCs showed substantially higher levels of survival in the mouse hearts. The other two groups of mice included those transplanted with non-pretreated CSCs, and mice treated with the culture medium used to grow the CSCs, and the pretreated CSCs survival significantly better than the non-pretreated CSCs.

CoPP pretreatment seems to augment cell survival, but do the surviving cells increase heart function? Bolli and others used echocardiogram to measure heart function, and echocardiographic assessment 5 weeks after CSC transplantation showed that the CoPP-preconditioned CSCs elicited greater improvement in remodeling of the left ventricle. Additionally, the hearts of the animals that received CoPP-pretreated CSCs showed improved movement of the walls of the heart during its pumping cycle, and better overall performance of the heart in general. Both pretreated and the non-pretreated CSCs, but not CSC culture growth medium shrank the amount of scar tissue in the heart and grew new heart tissue. However, The CoPP-pretreated CSCs were obviously superior to the non-pretreated CSCs at increasing the mass of heart muscle (see here for pictures).

These experiments might very well unravel a burning controversy surrounding CSCs. Bolli’s experiment show that can definitely grow new heart muscle. However, the bulk of the experiments with CSCs strongly suggest that these cells improve heart function by secreting pro-healing molecules without directly contributing to the regrowth of heart muscle. These papers probably observed the effects of CSCs that were transplanted into the heart, but did not survive very long. Bolli and his colleagues, on the other hand, were able to implant CSCs and survived for a much longer time in the hearts. Incidentally, Bolli and his team showed that the implanted CSCs expressed heart muscle-specific genes, which corroborated that these cells were differentiating into heart muscle cells, even though the proportion of cells that formed new heart muscle was relatively small.

In summary, CoPP pretreatment of cell seems to be feasible, safe, and effective as a means to improve CSC-based therapy. Even though It is likely that paracrine mechanisms are essential for CSC-based healing, the ability of CSCs to differentiate into heart muscle cells also seems to be an essential part of the means by which CSCs heal the heart after a heart attack. Thus more work is certainly warranted, but this is a fine start to what might be a simple, but effective way to increase the effectiveness of our own CSCs.

Cardiac Stem Cells or their Exosomes Heal Heart Damage Caused by Duchenne Muscular Dystrophy

One of the research institutions that has been at the forefront of developing investigational stem cell treatments for heart attack patients is The Cedars-Sinai Heart Institute. Recently, a research team at Cedars-Sinai Heart Institute (CSHI) has injected cardiac stem cells into the hearts of laboratory mice afflicted with a rodent form of Duchenne muscular dystrophy. This disease can also adversely affect the heart, and these stem cell injections actually improved the heart function of these laboratory animals and resulted in greater survival rates for those mice. This work might provide the means to extend the lives and improve the quality of life of patients with this chronic muscle-wasting disease.

The CSHI team presented their results at the American Heart Association Scientific Sessions in Chicago. Their results clearly demonstrated that once laboratory mice with Duchenne muscular dystrophy were infused with cardiac stem cells, the animals showed progressive and significant improvements in heart function and increased exercise capacity.

Specifically, 78 lab mice that had been given laboratory-induced heart attacks were injected with their own cardiac stem cells, and over the next three months, these mice demonstrated improved pumping ability and exercise capacity in addition to a reduction in heart-specific inflammation. The CSHI team also discovered that the stem cells work indirectly, by secreting tiny vesicles called exosomes that are filled with molecules that induce tissue healing. When these exosomes were purified and administered alone, they reproduced the key benefits of the cardiac stem cells.

Apparently, this particular procedure could be ready for testing in human clinical studies as soon as next year.

Duchenne muscular dystrophy or DMD is a genetic disease that results from mutations in a gene found on the X chromosome in humans. DMD affects 1 in 3,600 boys and is a neuromuscular disease caused by abnormalities in a muscle protein called dystrophin.  Because dystrophin is an important structural protein for muscle that anchors muscle to other muscles and to the substratum, deficiencies for functional copies of the dystrophin protein cause progressive muscle wasting, destruction, and muscle weakness.

Dystrophin acts as an important link between the internal cytoskeleton and the extracellular matrix. Neuronal nitric oxide synthase (nNOS) binds to α-syntrophin but also has a binding site in repeat 17 of the rod domain of dystrophin (see Fig. 2A for details of dystrophin domains). αDG, α-dystroglycan; βDG, β-dystroglycan
Dystrophin acts as an important link between the internal cytoskeleton and the extracellular matrix. Neuronal nitric oxide synthase (nNOS) binds to α-syntrophin but also has a binding site in repeat 17 of the rod domain of dystrophin (see Fig. 2A for details of dystrophin domains). αDG, α-dystroglycan; βDG, β-dystroglycan.  See here

The majority of DMD patients lose their ability to walk by twelve years of age, although the severity of the disease varies from patient to patient. The average life expectancy is about 25, and the cause of death is usually heart failure. Dystrophin deficiency causes heart muscle weakness, and, ultimately, heart insufficiency, since the chronic weakness of the heart muscle prevents the heart from pumping enough blood to maintain a regular heart rhythm and provide for the needs of the rest of the body. Such a heart condition is called “cardiomyopathy.”

“Most research into treatments for Duchenne muscular dystrophy patients has focused on the skeletal muscle aspects of the disease, but more often than not, the cause of death has been the heart failure that affects Duchenne patients,” said Eduardo Marbán, MD, PhD, who is the director of the CSHI and the principal investigator of this particular study. “Currently, there is no treatment to address the loss of functional heart muscle in these patients.”

In 2009, Marbán and his team completed the world’s first procedure in which a patient’s own heart tissue was used to grow specialized heart stem cells. Stem cells from the heart were isolated, cultured, and then injected back into the patient’s heart in order to repair and regrow healthy heart muscle that had been injured by a heart attack. Results, Marbán and his colleagues published these results in The Lancet in 2012, and also demonstrated that one year after their patients had received the experimental stem cell treatment, they showed significant reductions in the size of the heart scar that had been produced by their heart attacks.

Earlier this year, CSHI researchers commenced a new clinical trial entitled “ALLSTAR,” which stands for Allogeneic Heart Stem Cells to Achieve Myocardial Regeneration (Clinical trial number NCT01458405). In this study, heart attack patients are given injections of stem cells from healthy donors, which should work better than the patient’s own stem cells, which were damaged by the heart attack.

CSHI has recently opened the nation’s first Regenerative Medicine Clinic, which is designed to match heart and vascular disease patients with the appropriate stem cell clinical trial being conducted at CSHI and other institutions.

“We are committed to thoroughly investigating whether stem cells could repair heart damage caused by Duchenne muscular dystrophy,” Marbán said.

The protocols for growing cardiac-derived stem cells were developed by Marbán when he was on the faculty of Johns Hopkins University. Johns Hopkins has filed for a patent on that intellectual property and has licensed it to Capricor, a company in which Cedars-Sinai and Marbán have a financial interest. Capricor is providing funds for the ALLSTAR clinical trial at Cedars-Sinai.

Growth Factor Delivery Stimulates Endogenous Heart Repair After Heart Attacks in Pigs

Steven Chamulean and his colleagues at the University Medical Center Utrecht in Holland have examined the use of growth factors to induce healing in the heart after a heart attack. Because simply applying growth factors to the heart will cause them to simply be washed out, Chamulean and his coworkers embedded the growth factors in a material called hydrogel. They were able to measure how long the implanted growth factors lasted. As it turns out, when the growth factors were embedded in the hydrogel, they lasted for four days, and the hydrogel caused the growth factors to spread out into heart tissue with a gradient with the highest concentration at the site of injection (see Bastings, et al., Advanced Healthcare Materials 2013 doi: 10.1002/adhm.201300076).

In his new publication in the Journal of Cardiovascular Translational Research, Chamulean and his group used a new hydrogen called UPy to into which they embedded their growth factors. UPy stands for ureido-pyrimidinone end-capped poly(ethylene glycol) polymer. At the pH of our bodies, UPy hydrogels form a gel-like material made of fibers. When the pH changes, the gel becomes liquid. They embedded the growth factors insulin-like growth factor-1 (IGF-1), and hepatocyte growth factor (HGF).

The experimental design of this paper used pigs that were given heart attacks and then reperfused 75 minutes later. One month later, the animals were broken into three groups: just hydrogel, hydrogel with growth factors embedded in it, and growth factors injected into other heart without hydrogel. One month later, the animals were examined for their heart function, and then the animals were sacrificed to examine their heart tissue.

In every case, the hearts treated with only the hydrogel did the poorest of the three groups. The animals injected with gel-less growth factors did better than the controls, but those animals treated with growth factors embedded in UPy hydrogel did the best. The physiological indicators of the hearts from the animals treated with UPy embedded with IGF-1 and HGF improved significantly more than the controls that were treated with only UPy hydrogel. The hearts from animals treated with IGF and HGF without hydrogels improved over controls, by not nearly as well as those treated with growth factor-embedded UPy hydrogels.

When the hearts were examined even more surprises were observed. The animals with hearts that had been treated with UPy + growth factors did not show the enlargement observed in the control hearts. This is significant, because enlargement of the heart is a side effect for a heart attack and is the sign of heart failure. The UPy + growth factor hearts also displayed many signs of dividing cells; far more than hearts from the other two groups. Since the heart has its own resident stem cell population, these growth factors stimulated these stem cells to divide and form new heart muscle, and new blood vessels. Blood vessel density was much higher in the UPy + growth factor group and the pressure against which blood flowed in these hearts was substantially less in this groups, demonstrating that not only was the blood vessel density higher, but blood flow through these vessel networks was much more efficient. There was also plentiful evidence of the formation of new muscle in the UPy + growth factor group. When these hearts were also stained for c-kit, which is a cell surface marker for cardiac stem cells, the UPy + growth factor hearts had lots of them – much more than the other two groups.

This paper reports significant findings because the resident stem cell population in the heart was actively mobilized without having to extract them by means of a biopsy. There is also evidence from Torella and others that IGF-1 and HGF can reactivate the sleeping cardiac stem cells of aged laboratory animals (Circulation Research 2004 94: 514-524). The UP{y hydrogels are well tolerated and are biodegradable. They provide a medium that stays in place and releases embedded growth factors in a sustained manner. The results in this paper provide the rationale to develop growth factor therapy for human patients.

Making Cardiac Stem Cells That are a Notch Above the Rest

The human heart has a stem cell population all its own. This stem cell population replaces heart cells at a leisurely rate throughout the life of the heart. Unfortunately, a heart attack overwhelms this repair system, and the heart simply lacks the capacity to heal itself to beyond particular limits.

However, there is the hope that physicians will one day be able to augment the healing capacity of the heart, and a few clinical trials and several animal experiments strongly suggest that this is the possible.

A new paper by Yoshiki Sawa at and his team from Osaka University has examined a way to increase the healing capabilities of human cardiac stem cells (CSCs).

In this paper, which was published in the journal Circulation, isolated CSCs from a 12-year old patient and grown in culture. However, the cells were grown in several different types of culture conditions. The density at which cells are grown can affect their biological characteristics. Therefore, Sawa and his group plated these cells at four different densities; single, low, mid and high densities. The single, low and med density-grown cells divided faster than the cells grown as high density. Also, the cells grown at lower cell densities retained their ability to form either heart muscle or blood vessels whereas the cells grown at high densities stated to make blood vessels en mass.

When scientists from Sawa’s group examined why the cells grown at high densities turned into blood vessel cells, they discovered that these cells activated a signaling pathway called the NOTCH pathway. Activation of the NOTCH pathway turned the cells into blood vessel-making cells and slowed their growth in culture.

JCS slide template

Presumably, the faster-growing, more plastic cells would be better for regenerative treatments that the slower-growing, less plastic cells. To test this hypothesis, Sawa and others transplanted cultured CSCs grown as different densities into the hearts of rats that had suffered a recent heart attack. They are used CSCs grown at high densities, but had been treated with a drug that inhibits the NOTCH pathway.

The results were remarkable. The lower the densities at which the cells were grown, the better they repaired the heart. However, the high-density cells grown in the presence of a NOTCH inhibitor (called GSI), were just as good at repairing the heart as the cells grown at low density. While the cells grown in the presence of GSI at high density still grew slowly, they showed an enhanced capacity to induce the formation of new blood vessels in the damaged heart tissue and form new heart muscle.

In conclusion these authors state: “Therapeutic effects of CSC-transplantation for heart disease may be enhanced by reducing NOTCH signaling in CSCs.”

Taiwanese Group Identifies Stem Cell-Based Drug to Rejuvenate Aged Hearts

A southern Taiwan-based National Cheng Kung University research team led by Patrick Ching-Ho Hsieh has discovered that a molecule called prostaglandin E2 can regenerate aged hearts in rodents.

This discovery provides a useful new perspective on heart regeneration and presents an effective option for heart disease patients other than heart transplant.

According to Hsieh, congestive heart disease and other cardiovascular diseases are a leading cause of morbidity and mortality throughout the world. There are some six million patients with congestive heart failure in the US alone and some 400,000 in Taiwan. Despite intensive drug, surgical and other medical interventions, 80 percent of all heart patients die within 8 years of diagnosis.

Even though several experiments and clinical trials have established that heart regeneration can take place, the means by which the heart regenerates is still not completely clear, and there are also no drugs to stimulate heart regeneration by the resident stem cell population in the heart.

Now, after seven years of hard work, Hsieh’s team has identified the critical time period and the essential player that directs heart repair.

Hsieh and his colleagues used genetically engineered mice that Hsieh had developed as a postdoctoral research fellow at Harvard Medical School. By using this transgenic mouse strain, Hsieh and others showed that the self-repair process of the heart begins 7 days after injury and peaks at 10 days after injury.

The “director” of this self-repair process is the molecule PGE2. PGE2 regulates heart-specific stem cell activities.


“More importantly, both young and old mice have significant improvements for cardiac remodeling if you treat both of them [with] PGE2,” said Hsieh.

Hsieh’s team also established that PGE2 decreases expression of a gene associated with aging, TGF-beta1. PGE2 also rejuvenates the micro-environment of the aged cells, according to Hsieh.

Umbilical Cord Stem Cells Preserve Heart Function After a Heart Attack in Mice

A consortium of Portuguese scientists have conducted an extensive examination of the effects of mesenchymal stromal cells from umbilical cord on the heart of mice that have suffered a massive heart attack. Even more remarkable is that these workers used a proprietary technique to harvest, process, and prepare the umbilical cord stem cells in the hopes that this technique would give rise to a commercial product that will be tested in human clinical trials,

Human umbilical cord tissue-derived Mesenchymal Stromal Cells (MSCs) were obtained by means of a proprietary technology that was developed by a biomedical company called ECBio. Their product,, UCX®, consists of clean, high-quality, umbilical cord stem cells that are collected under Good Manufacturing Practices. The use of Good Manufacturing Practice means that UCX is potentially a clinical-grade product. Thus, this paper represents a preclinical evaluation of UCX.

This experiments in this paper used standard methods to give mice heart attacks that were later received injections of UCX into their heart muscle. The same UCX cells were used in experiments with cultured cells to determine their effects under more controlled conditions.

The mice that received the UCX injections into their heart muscles after suffering from a large heart attack showed preservation of heart function. Also, measurements of the numbers of dead cells in the heart muscle of heart-sick mice that did and did not receive injections of umbilical cord cells into their hearts showed that the umbilical cord stem cells preserved heart muscle cells and prevented them from dying. Additionally, the implanted umbilical cord MSCs induced the growth and formation of many small blood vessels in the infarcted area of the heart. This prevented the heart from undergoing remodeling (enlargement), and preserved heart structure and function.

When subjected to a battery of tests on cultured cells, UCX activated cardiac stem cells, which are the resident stem cell population in the heart. Implanted UCX cells activated the proliferation of cardiac stem cells and their differentiation into heart muscle cells. There was no evidence that umbilical cord MSCs differentiated into heart muscle cells and engrafted into the heart. Rather UCX seems to help the heart by means of paracrine mechanisms, which simply means that they secrete healing molecules in the heart and help the heart heal itself.

In conclusion, Diana Santos Nascimento, the lead author of this work, and her colleagues state that, “the method of UCX® extraction and subsequent processing has been recently adapted to advanced therapy medicinal product (ATMP) standards, as defined by the guideline on the minimum quality data for certification of ATMP. Given that our work constitutes a proof-of-principle for the cardioprotective effects UCX® exert in the context of MI, a future clinical usage of this off-the-shelf cellular product can be envisaged.”

Preclinical trials with larger animals should come next, and after that, hopefully, the first human clinical trials will begin.

Heart Regeneration and the Heart’s Own Stem Cell Population

For years scientists were sure that the heart virtually never regenerated.

Today this view has changed, and researchers at the Max Plank Institute for Heart and Lung Research have identified a stem cell population that is responsible for heart regeneration. Human hearts, as it turns out, do constantly regenerate, but at a very slow rate.

This finding brings the possibility that it might be possible to stimulate and augment this self-healing process, especially in patients with diseases or disorders of the heart, with new treatments.

Some vertebrates have the ability to regenerate large portions of their heart. For example zebrafish and several species of amphibians have the ability to self-heal and constantly maintain the heart at maximum capacity. This situation is quite different for mammals that have a low capacity for heart regeneration. Heart muscle cells in mammals stop dividing soon after birth.

However, mammalian hearts do have a resident stem cell population these cells replace heart muscle cells throughout the life of the organism, In humans, between 1-4% of all heart muscle cells are replaced every year.

Experiments with laboratory mice have identified at heart stem cells called Sca-1 cells that replace adult heart muscle cells and are activated when the heart is damaged. Under such conditions, Sca-1 cells produce significantly more heart muscle.

Unfortunately, the proportion of Sca-1 cells in the heart is very low, and finding them has been likened to searching for a diamond at the bottom of the Pacific Ocean.

Shizuka Uchida, the project leader of this research, said, “We also faced the problem that Sca-1 is no longer available in the cells as a marker protein for stem cells after they have been changed into heart muscle cells. To prove this, we had to be inventive.”

This inventiveness came in the form of a visible protein that was made all the time in the Sca-1 cells that would continue being made even if the cells differentiated into heart muscle.

Uchida put it this way: “In this way, we were able to establish that the proportion of the heart muscle cells originating from Sca-1 stem cells increased continuously in healthy mice. Around five percent of the heart muscle cells regenerated themselves within 18 months.”

When the same measurements were taken in mice with heart disease, the number of heart muscle cells made from Sca-1 stem cells increased three-fold.

“The data show that in principle the mammalian heart is able to trigger regeneration and renewal processes. Under normal circumstances, however, these processes are not enough to ultimately repair cardiac damage,” said Thomas Braun, the principal investigator in whose laboratory this work was done.

The aim is to devise and test strategies to improve the activity and number of these stem cells and, ultimately, to strengthen and augment the heart’s self-healing powers.

Encapsulation of Cardiac Stem Cells and Their Effect on the Heart

Earlier I blogged about an experiment that encapsulated mesenchymal stem cells into alginate hydrogels and implanted them into the hearts of rodents after a heart attack. The encapsulated mesenchymal stem cells showed much better retention in the heart and survival and elicited better healing and recovery of cardiac function than their non-encapsulated counterparts.

This idea seems to be catching on because another paper reports doing the same thing with cardiac stem cells extracted from heart biopsies. Audrey Mayfield and colleagues in the laboratory of Darryl Davis at the University of Ottawa Heart Institute and in collaboration with Duncan Steward and his colleagues from the Ottawa Hospital Research Institute used cardiac stem cells extracted from human patients that were encased in agarose hydrogels to treat mice that had suffered heart attacks. These experiments were reported in the journal Biomaterials (2013).

Cardiac stem cells (CSCs) were extracted from human patients who were already undergoing open heart procedures. Small biopsies were taken from the “atrial appendages” and cultured in cardiac explants medium for seven days.

atrial appendage

Migrating cells in the culture were harvested and encased in low melt agarose supplemented with human fibrinogen. To form a proper hydrogel, the cells/agarose mixture was added drop-wise to dimethylpolysiloxane (say that fast five times) and filtered. Filtration guaranteed that only small spheres (100 microns) were left. All the larger spheres were not used.

Those CSCs that were not encased in hydrogels were used for gene profiling studies. These studies showed that cultured CSCs expressed a series of cell adhesion molecules known as “integrins.” Integrins are 2-part proteins that are embedded in the cell membrane and consist of an “alpha” and “beta” subunit. Integrin subunits, however, come in many forms, and there are multiple alpha subunits and multiple beta subunits.


This mixing and matching of integrin subunits allows integrins to bind many different types of substrates. Consequently it is possible to know what kinds of molecules these cells will stick to based on the types of integrins they express. The gene prolifing experiments showed that CSC expressed integrin alpha-5 and the beta 1 and 3 subunits, which shows that CSC can adhere to fibronectin and fibrinogen.



When encapsulated CSCs were supplemented with fibrinogen and fibronectin, CSCs showed better survival than their unencapsulated counterparts, and grew just as fast ans unencapsulated CSCs. Other experiments showed that the encapsulated CSCs made just as many healing molecules as the unencapsulated CSCs, and were able to attract circulating angiogenic (blood vessel making) cells. Also, the culture medium of the encapsulated cells was also just as potent as culture medium from suspended CSCs.

With these laboratory successes, encapsulated CSCs were used to treat non-obese diabetic mice with dysfunctional immune systems that had suffered a heart attack. The CSCs were injected into the heart, and some mice received encapsulated CSCs, other non-encapsulated CSCs, and others only buffer.

The encapsulated CSCs showed better retention in the heart; 2.5 times as many encapsulated CSCs were retained in the heart in comparison to the non-encapsulated CSCs. Also, the ejection fraction of the hearts that received the encapsulated CSCs increased from about 35% to almost 50%. Those hearts that had received the non-encapsulated CSCs showed an ejection fraction that increased from around 33% to about 39-40%. Those mice that had received buffer only showed deterioration of heart function (ejection fraction decreased from 36% to 28%). Also, the heart scar was much smaller in the hearts that had received encapsulated CSCs. Less than 10% of the heart tissue was scarred in those mice that received encapsulated CSCs, but 16% of the heart was scarred in the mice that received free CSCs. Those mice that received buffer had 20% of their hearts scarred.

Finally, did encapsulated CSCs engraft into the heart muscle? CSCs have been shown to differentiate into heart-specific tissues such as heart muscle, blood vessels, and heart connective tissue. Encapsulation might prevent CSCs from differentiating into heart-specific cell types and connecting to other heart tissues and integrating into the existing tissues. However, at this point, w have a problem with this paper. The text states that “encapsulated CSCs provided a two-fold increase in the number of engrafted human CSCs as compared transplant of non-encapsulated CSCs.” The problem is that the bar graft shown in the paper shows that the non-encapsulated CSCs have twice the engraftment of the capsulated CSCs. I think the reviewers might have missed this one. Nevertheless, the other data seem to show that encapsulation did not affect engraftment of the CSCs.

The conclusion of this paper is that “CSC capsulation provides an easy, fast and non-toxic way to treat the cells prior to injection through a clinically acceptable process.”

Hopefully large-animal tests will come next. If these are successful, then maybe human trials should be on the menu.

The Use of Synthetic Messenger RNAs Augment Heart Regeneration and Healing After a Heart Attack

A collaborative effect between researchers at Harvard University and Karolinska Institutet has shown that the application of particular factors to the heart after a heart attack can heal the heart and induce the production of new heart muscle.

Kenneth Chien, who has a dual appointment at the medical university Karolinska Institutet and Harvard University, led this research teams said this about this work: “This is the beginning of using the heart as a factory to produce growth factors for specific families of cardiovascular stem cells, and suggests that it may be possible to generate new heart parts without delivering any new cells to the heart itself.”

This study builds upon previous work by Chien and his colleagues in which the growth factor VEGFA, which is known to activate the growth of endothelial cells in the adult heart (endothelial cells line blood vessels), also serves as a switch that converts heart stem cells away from making heart muscle to forming coronary vessels in the fetal heart.

To drive the expression of VEGFA in the heart, Chien and others made synthetic messenger RNAs that encoded VEGFA and injected them into the heart cells. Injections of these synthetic VEGFA messenger RNAs produced a short burst of VEGFA.

Chien induced a heart attack in mice and then administered the synthetic VEGFA messenger RNAs to some mice and buffer to others 48 hours after the heart attacks. Chien and his crew was sure to inject the synthetic VEGFA mRNAs into the regions of the heart known to harbor the resident cardiac stem cell populations.

Not only did the VEGFA-mRNA-injected mice survive better than the other mice, but their hearts had smaller heart scars, and had clear signs of the growth of new heart muscle that had been made by the resident cardiac stem cell populations. One pulse of VEGFA had long-term benefits and those cells that would have normally made the heart scar ended up making heart muscle instead as a result of one pulse of VEGFA.

Chien said of this experiment, “This moves us very close to clinical studies to regenerate cardiovascular tissue with a single chemical agent without the need for injecting any additional cells into the heart.”

At the same time, Chien also noted that this technology is in the early stages of development. Even though these mice had their chests cracked open and their hearts injected, for human patients, the challenge is to adapt heart catheter technologies to the delivery of synthetic messenger RNAs. Also, to demonstrate the safety and efficacy of this technology to humans, Chien and others will need to repeat these experiments in larger animals that serve as a better model system for the human heart than rodents. Chien’s laboratory is presently in the process of doing that.

To adapt catheter technology to deliver these reagents, Chien had co-founded a company called Moderna Therapeutics to research this problem and develop the proper platform technology for clinical use. Chien is also collaborating with the biotechnology company AstraZeneca to help expedite moving the synthetic RNA technology into a clinical setting.

Do Stem Cells from Bone Outdo Those from the Heart in Regenerating Cardiac Tissue?

Scientists at Tulane University in New Orleans, La. (US) have completed a study that suggests that stem cells derived from cortical, or compact bone do a better job of regenerating heart tissue than do the heart’s own stem cells.

The study, led by Steven R. Houser, Ph.D., FAHA, director of Tulane’s School of Medicine’s Cardiovascular Research Center (CVRC), could potentially lead to an “off the rack” source of stem cells for regenerating cardiac tissue following a heart attack.

Cortical bone stem cells (CBSCs) are considered some of the most pluripotent cells in the adult body. These cells are naïve and ready to differentiate into just about any cell type. However, even though CBSCs and similar pluripotent stem cells retain the ability to develop into any cell type required by the body, they have the potential to wander off course and land in unintended tissues. Cardiac stem cells, on the other hand, are more likely to stay in their resident tissue.

Bone cross-section

To determine how CBSCs might behave in the heart, Houser’s team, led by Temple graduate student Jason Duran, collected the cells from mouse tibias (shin bones), expanded them in the lab and then injected them into back the mice after they had undergone a heart attack.

The cells triggered the growth of new blood vessels in the injured tissue and six weeks after injection had differentiated into heart muscle cells. While generally smaller than native heart cells, the new cells had the same functional capabilities and overall improved survival and heart function.

Similar improvements were not observed in mice treated with cardiac stem cells, nor did those cells show evidence of differentiation.

“What we did generates as many questions as it does answers,” Dr. Houser said. “Cell therapy attempts to repopulate the heart with new heart cells. But which cells should be used, and when they should be put into the heart are among many unanswered questions.”

The next step will be to test the cells in larger animal models. The current study was published in the Aug. 16 issue of Circulation Research.

Cardiac Stem Cells Offer New Hope for Treatment of Heart Failure

Scientists from the United Kingdom have, for the first time, highlighted the natural regenerative abilities of a group of stem cells that live in our hearts. This particular study shows that these cells are responsible for repairing and regenerating muscle tissue that has been damaged by a heart attack. Such damage to the heart can lead to heart failure.

There is a robust debate as to the regenerative capacity of cardiac stem cells (CSCs) in the hearts a adult human beings. While many scientists are convinced that CSCs in the hearts of newborns have good regenerative ability, many remain unconvinced that adult CSCs can do similar things (see Zaruba, M.M., et al., Circulation 121, 1992–2000 and Jesty, S.A., et al., Proc. Natl. Acad. Sci. USA 109, 13380–13385). Nevertheless, an earlier paper showed that when introduced into heart muscle after a heart attack, CSCs will regenerate the lost heart muscle and blood vessels lost in the infarct (see Beltrami, A.P., et al., Cell 114, 763–776). Resolving this disagreement requires a different type of experiment.

In this paper, Bernardo Nadal-Ginard and colleagues from the and his collaborators at the Stem Cell and Regenerative Biology Unit at the Liverpool John Moores University in Liverpool and his collaborators from Italy used a different way to affect the heart. When heart attacks are experimentally induced in the heart of rodents, the infarcts are large and they kill off large numbers of CSCs. Therefore, Nadal-Ginard and others induced severe diffuse damage of the heart muscle that also spared the CSCs. They gave the mice a large dose of a drug called isoproterenol, which acts as a “sympathomimetic.” This is confusing science talk that simply means that the drug speeds the heart rate to the point where the heart muscle exhausts itself and then starts to die off. This treatment, however, spares the CSCs (see Ellison, G.M., et al., J. Biol. Chem. 282, 11397–11409).

When the heart muscle was damaged, the CSCs differentiated into heart muscle cells and other heart-specific cells and repaired the damage in the heart. Also, the repairing cells were in the heart and were not the result of bone marrow stem cells that migrated to the bone marrow, thus putting to rest a controversy that has lasted for some years that CSCs are the result of bone marrow stem cells that migrate to the heart.

Elimination of CSCs prevents heart repair after heart damage. If, however, these heart-based stem cells are replaced after damage, the heart repairs itself and the heart recovers its function, anatomical integrity, and cellular structure.

In other experiments, removal of cardiac stem cells (CSCs) and re-injection after a heart attack shows that the CSCs can home in and repair the damaged heart.

c-kit CSCs repair heart

Since Nadal-Ginard showed that CSCs have a capacity to home to the damaged heart, less invasive treatments might be possible and that these treatments might even prevent heart failure after a heart attack in the future.

In a healthy heart, the quantity of CSCs is sufficient to repair heart muscle tissue. However, once the heart is damaged many of the CSCs are also damaged and cannot multiply or produce new muscle tissue. In these cases it could be possible to replace damaged CSCs with new ones that have been grown in the laboratory and administered intravenously.,

These new approaches involved maintaining or increasing the activity of CSCs in order to renew heart muscle and replace old, damaged cells. This new strategy will only require intravenous administration of CSCs and not require open heart procedures that require such a long time to recover.

These findings are very promising. The nest step is a clinical trial, which is due to start early 2014 and is aimed at assessing the safety and effectiveness of CSCs for preventing and treating heart failure in humans.