When Is the Best Time to Treat Heart Attack Patients With Stem Cells?

Several preclinical trials in laboratory animals and clinical trials have definitively demonstrated the efficacy of stem cell treatments after a heart attack. However, these same studies have left several question largely unresolved. For example, when is the best time to treat acute heart attack patients? What is the appropriate stem cell dose? What is the best way to administer these stem cells? Is it better to use a patient’s own stem cells or stem cells from someone else?

A recent clinical trial from Soochow University in Suzhou, China has addressed the question of when to treat heart attack patients. Published in the Life Sciences section of the journal Science China, Yi Huan Chen and Xiao Mei Teng and their colleagues in the laboratory of Zen Ya Shen administered bone marrow-derived mesenchymal stromal cells at different times after a heart attack. Their study also examined the effects of mesenchymal stem cells transplants at different times after a heart attack in Taihu Meishan pigs. This combination of preclinical and clinical studies makes this paper a very powerful piece of research indeed.

The results of the clinical trial came from 42 heart attack patients who were treated 3 hours after suffering a heart attack, or 1 day, 3 days, 2 weeks or 4 weeks after a heart attack. The patients were evaluated with echocardiogram to ascertain heart function and magnetic resonance imaging of the heart to determine the size of the heart scar, the thickness of the heart wall, and the amount of blood pumped per heart beat (stroke volume).

When the data were complied and analyzed, patients who received their stem cell transplants 2-4 weeks after their heart attacks fared better than the other groups. The heart function improved substantially and the size of the infarct shrank the most. 4 weeks was better than 2 weeks,

The animal studies showed very similar results.

Eight patients were selected to receive additional stem cell transplants. These patients showed even greater improvements in heart function (ejection fraction improved to an average of 51.9% s opposed to 39.3% for the controls).

These results show that 2-4 weeks constitutes the optimal window for stem cell transplantation. If the transplant is given too early, then the environment of he heart is simply too hostile to support the survival of the stem cells. However, if the transplant is performed too late, the heart has already experiences a large amount of cell death, and a stem cell treatment might be superfluous. Instead 2-4 weeks appears to be the “sweet spot” when the heart is hospitable enough to support the survival of the transplanted stem cells and benefit from their healing properties. Also, this paper shows that multiple stem cell transplants a two different times to convey additional benefits, and should be considered under certain conditions.

Major Clinical Trial Finds Bone Marrow Stem Cell Treatments Provide No Benefits After a Heart Attack

A large and very well designed and carefully controlled clinical trial known as TIME has failed to demonstrate any benefit for infusions of bone marrow stem cells into the heart 3-7 days after a heart attack.  This study comes on the heals of a similar clinical study known as LateTIME, which stands for Late Timing In Myocardial infarction Evaluation, and tested the effects of bone marrow stem cells infusions into the heart of heat attack patients 2-3 weeks after a heart attack.

LateTIME enrolled 87 heart attack patients, and harvested their bone marrow stem cells.  The stem cells were delivered into the hearts through the coronary arteries, but some received a placebo.  All patients had their ejection fractions measured, their heart wall motions in the damaged areas of the heart and outside the damaged areas and the size of their infarcts.  There were no significant changes in any of these characteristics after six months. Because another large clinical study known as the REPAIR-AMI study showed significant differences between heart attack patients that had received the placebo and those that had received bone marrow stem cells 3-7 days after a heart attack, this research group, known as the Cardiovascular Cell Therapy Research Network (CCTRN), sponsored by the National Institutes of Health, decided the test their bone marrow infusions at this same time frame.

TIME was similar in design to LateTIME.  This study enrolled 120 patients that had suffered a heart attack and all patients received either an infusion of 150 million bone marrow stem cells or a placebo within 12 hours of bone marrow aspiration and cell processing either 3 days after the heart attack to 7 days.  The researchers examined the changes in ejection fraction, movement of the heart wall, and the number of major adverse cardiovascular events plus the changes in the infarct size.

The results were resoundingly negative.  At 6 months after stem cell infusion, there was no significant increase in ejection fractions versus the placebo and no significant treatment effect on the function of the left ventricle in either the infarct or the border zones.  These findings were the same for those patients that received bone marrow stem cell infusions 3 days after their heart attack or 7 days after their heart attacks.  Fortunately, the incidence of major adverse events were rare among all treatment groups.

Despite the negative results for these clinical trials, there are a few silver linings.  First of all, the highly controlled nature of this trial sets a standard for all clinical trials to come.  A constant number of stem cells were delivered in every patient, and because the stem cells were delivered soon after they were harvested, there were no potential issues about bone marrow storage.

Jay Traverse, the lead author of this study, made this point about this trial:  “With this baseline now set, we can start to adjust some of the components of the protocol to grow and administer stem cell [sic] to find cases where the procedure may improve function.  For example, this therapy may work better in different population groups, or we might need to use new cell types or new methods of delivery.”

When one examines the data for this study, it is clear that some patients definitely improved dramatically, whereas others did not.  Below is a figure from the Traverse et al paper that shows individual patient’s heart function data 6 months after the stem cell infusions.

BMC indicates bone marrow mononuclear cell; MI, myocardial infarction.

From examining these data even cursorily, it is clear that some patients improved dramatically while others tanked.  Traverse is convinced that bone marrow stem cell infusions help some people, but not others (just like any other treatment).  He is convinced that by mining these data, he can begin to understand who these patients are who are helped by bone marrow stem cell transplants and who are not.  Also, the stem cells of these patients have been stored.  Hopefully, further work with them will help Traverse and his colleagues clarify what, if anything, about the bone marrow of these patients makes them more likely to help their patients and so on.

There are some possible explanations for these negative results.  Whereas the positive REPAIR-AMI used the rather labor-intensive Ficoll gradient protocols for isolating mononculear cells from bone marrow aspirates, the TIME trials used and automated system for collecting the bone marrow mononuclear cells.  Cells isolated by the automated system have neither been tested in an animal model of heart attacks, nor established as efficacious in a human study of heart disease.  Therefore, it is possible that the bone marrow used in this study was largely dead.  Secondly, the cell products were kept in a solution that had a heparin concentration that is known to inhibit the migratory properties of mononuclear cells (See Seeger et al., Circ Res 2012 111(7): 1385-94).  Therefore, there is a possibility that the bone marrow used in this study was no good.  Until the bone marrow stem cells collected by this method are confirmed to be efficacious, judgment must be suspended.

Engineered Mesenchymal Stem Cells Make Blood Vessels that Help Heal Ailing Hearts

Another term for a heart attack is a myocardial infarction (MI). A heart attack or an MI occurs when the blood supply to the heart that flows through coronary blood vessels is interrupted. The interruption of blood flow deprives the heart of nourishment and oxygen, and the downstream blood vessels and heart muscle die as a result. The decrease in blood vessel density after a MI can increase cell death, which increases the amount of cell death and the size of the heart scar. Therefore, growing more blood vessels in the heart after a heart attack, which is known as therapeutic angiogenesis, is a potentially strategy in treating an MI (see Ziebart T, et al., (2008) Circ Res 103: 1327–1334)..

To this end, a few clinical trials have attempted to used stem cells that can make blood vessels to reverse heart damage caused by an MI (see Ripa RS, et al. (2007) Circulation 116: I24–I30 and Schachinger V, et al. (2006) N Engl J Med 355: 1210–21).

Among those therapeutic agents for heart attack patients, mesenchymal stem cells (MSCs) are considered excellent candidates. MSCs have the ability to differentiate into smooth muscle, or blood vessels, which means that they can help revascularize the heart after a MI. The problem with MSCs is their tendency to die off rapidly after transplantation into the heart after a heart attack (see Ziegelhoeffer T, et al. (2004) Circ Res 94: 230–38 & O’Neill TT, et al., Circ Res 97: 1027–35; & Perry TE, et al. (2009) Cardiovasc Res 84: 317–25).

To fix this problem, MSCs can be either preconditioned before implantation (see previous posts) or genetically engineered to withstand the hostile conditions inside the heart after a heart attack.

Previously, Muhammad Ashraf and Yigang Wang from the University of Cincinnati genetically engineered MSCs to express a surface protein called CXCR4.  CXC4R is the receptor for a chemokine known as CXCL12/SDF-1.  SDF-1 is a rather potent stem cell recruitment molecule.

When transplanted into the hearts of rodents that had just experienced a heart attack, MSCs that expressed CXCR4 showed increased mobilization and engraftment into the damaged areas of the heart. Also, the pumping abilities of the heart regions into which the MSC-CXCR4s were infused increased, and the MSC-CXCR4 cells cranked up their secretion of blood vessel-inducing growth factors (vascular endothelial growth factor-A or VEGF-A), This led to increased formation of new blood vessels and a decrease in the early signs of left ventricular remodeling (see Zhang D, et al. (2010) Am J Physiol Heart Circ Physiol 299: H1339– H1347; Huang W, et al. (2010) J Mol Cell Cardiol 48: 702–712; &.Zhang D, et al. (2008) J Mol Cell Cardiol 44: 281–292). While these papers show truly stunning results, it was still, even after all this work, unclear if the MSCs were actually differentiating into blood vessel cells and making blood vessels.

To nail this down, Wang and his group used a clever little technique. They engineered MSCs to express CXCR4 and the viral TK gene. TK stands for “thymidine kinase,” which is an enzyme involved in nucleotide synthesis from a virus. The TK enzyme is not found in human cells, and is therefore a target for antiviral drugs. If treated with antiviral drugs that target the TK enzyme, only cells with the TK gene will be killed.

When Wang and his group used their CXCR4-engineered MSCs to treat the heart of mice that had recently suffered a heart attack, they found that their hearts improved and that these same heart were covered with new blood vessels. However, when this experiment was repeated with CXCR4-MSCs that also had the TK gene, Wang his co-workers fed the mice a drug called ganciclovir, which kills only those cells that possess the TK gene. In these mice, their heart failed to improve and also were completely devoid of the new blood vessels.

This paper nicely shows that without viable MSCs, no new blood vessels were made. This strongly suggests that the engineered MSCs are differentiating into blood vessel cells and making new blood vessels, which helps the heart recover from the heart attack and shrinks the size of the dead area of the heart.

What are the implications for human clinical trial\? This is difficult to say. Before clinical trials with genetically engineered cells are approved those cells will need to go through piles of safety tests before they can be used in clinical trials. Once that hurdle is passed, then they can be used in human clinical trials, and they will certainly prove efficacious for human patients.

Blood Vessel-Making Stem Cells Reprogrammed into Heart Muscle Cells That Improve Heart Function After a Heart Attack

Douglas Losardo at Northwestern University, Chicago, IL has done some extremely innovative work with transplanting bone marrow stem cells into the heart of human heart attack patients. His clinical trials have shown that human heart attack patients that receive infusions of their own bone marrow stem cells, on the average, show improved heart function, abatement of symptoms and improved prognosis.

In particular, Losardo has used CD34+ stem cells from bone marrow. CD34 is a cell surface protein that marks blood cell-making stem cells. CD34+ stem cells have been intensely studied and can form blood vessels in addition to red and white blood cells. The formation of new blood vessels in a sick heart improves the delivery of oxygen and blood to the heart, which improves heart function and recovery after a heart attack. Additionally, the CD34+ stem cells release a host of molecules that help the heart recover and function better.

The downside of CD34+ stem cells, is that they show limited ability to differentiate into heart muscle cells, and also do not survive terribly well in the heart after a heart attack. Therefore, Losardo has been on the hunt for a better technique for healing sick hearts, and a recent paper from his laboratory with mice provides a proof-of-concept of using reprogramming to form cells that can be used for regenerative therapies for the heart.

In this paper, Losardo and his team used a bone marrow stem cell called and “EPC,” which is short for “endothelial progenitor cell.” Endothelial cells compose blood vessels and EPCs make blood vessels. EPC infusions into a heart after a heart attack can improve heart function, but only modestly.

The first author of this paper, Melissa A. Thal, and her colleagues from Losordo’s laboratory treated EPCs isolated from mouse bone marrow with a cocktail of chemicals to move their gene expression patterns away from an EPC-specific pattern to that of a heart muscle cell. Their chemical cocktail contained either 5-Azacytidine, which changes the epigenetic profile of cells, and valproic acid, another epigenetic modifier, or a G9a histone dimethyltransferase called BIX-01294, which is also an epigenetic modifier. After soaking their EPCs in these chemicals for 48 hours, Genomic expression studies showed that pluripotency genes were expressed in these cells, as were genes for heart muscle and blood vessels. When cultured under the right conditions, these reprogrammed EPCs also formed good heart muscle cells.

These results were so remarkable that Losardo and his team decided to test these reprogrammed cells in the hearts of mice that have just experienced a heart attack. Transplantations of EPCs, or reprogrammed (REPCs) definitively showed that mice that had experienced heart attacks and did not have any interventions continued to deteriorate. However, EPC transplantations slightly improved the functional characteristics of the heart and tended to arrest the degradation of the heart. However, mice that had received REPCs had almost twice the % of blood ejected from the heart, significant reduction in the size of the damaged area, much less blood left in the heart after each pumping cycle, and better heart muscle function. Tissue examinations of the hearts showed that the REPC-transplanted hearts had grown new heart muscle whereas the EPC-transplanted hearts did not.

Thus this paper shows that it is feasible to reprogram EPCs from bone marrow into heart muscle cells and that it is also feasible to use these cells to repair the heart after a heart attack.

There were no significant side effects seen in the laboratory animals with the REPC transplantations. There were no tumors, no funky heart rhythms, and no sign of immunological rejection. Further work in animals will hopefully lead to human clinical trials and maybe even a commercially available treatment for heart attacks that use your own bone marrow stem cells. While that is a long way off, it is a hope that we all share.

Slow Adhering Skeletal Muscle Cells Improve Function of Sick Hearts

Skeletal muscles consist of cells that have fused together to form a so-called “myotube.” Myotubes, upon closer examination, are filled with contractile proteins that help them contract. These rows of contractile proteins are organized into stripes, and for this reason, skeletal muscle is often called “striated muscle” because of its stripped appearance under the microscope. Skeletal muscles are collections of these myotubes all bound together, and attached to bones by means of tendons.

Skeletal muscles also contain a stem cell population called muscle satellite cells. Muscle satellite cells divide and form new muscle in response to increase demand on the muscles. Muscle satellite cells are responsible for the increase in muscle size when you lift heavy weights.

Because muscle satellite cells are easily isolated from patients, and they resist the hostile conditions of a heart that has had a heart attack, they were one of the first stem cells used to treat heart attack patients. Preclinical work on laboratory animals produced hopeful results. The implanted satellite cells did not become heart muscle cells (Reinecke H, Poppa V, Murry CE (2002) J Mol Cell Cardiol. 34(2):241-9). However, the hearts that had received satellite transplants after a heart attack showed functional improvements and no deterioration in comparison to the control animals (rats – CE Murray, et al., J. Clin. Invest. 98(11): 2512–2523; rabbits – Blatt A,, et al., Eur J Heart Fail. 2003 Dec;5(6):751-7). These positive results were the impetus for the first human clinical trials that used a patient’s own satellite muscle stem cells as a treatment for acute heart attacks.

Early trials were quite small but the implanted patients seemed to improve. Unfortunately, these early studies were not controlled terribly well, and the results somewhat hopeful, but not completely conclusive (Siminiak T., et al., Am Heart J. 2004;148(3):531-7). More controlled clinical trials, the MAGIC and MYSTAR trials, however, revealed a problem with satellite cells. They had a tendency to not connect with the resident heart muscle cells, and were, therefore, functionally isolated from the rest of the heart (Léobon B, et al., Proc Natl Acad Sci USA. 2003;100:7808–7811). Such isolation had a tendency to cause implanted hearts to beat irregularly, and for this reason, muscle satellite clinical trials have been tabled for the time being (Menasché P, et al., Circulation. 2008;117(9):1189-200).

However, skeletal muscles possess several distinct cell types and some of these are probably better candidates for heart treatments (Winitsky SO, et al., PLoS Biol. 2005;3:e87). To that end, Johnny Huard’s laboratory at the University of Pittsburgh has characterized a population of cells that show superior therapeutic possibilities from skeletal muscle.

Masaho Okada was the lead author of this paper, and he and his colleagues observed that most of the cells in skeletal muscle adhere very readily to the culture flasks after the muscle tissue was pulled apart. They designated these fast adhering cells as RACs or rapidly-adhering cells. A minority population of cells were slow-adhering cells or SACs.

Comparisons of SACs and RACs showed that the SACs were more resistant to cellular stresses than their RAC counterparts. SACs also more readily formed myotubes that RACs. The gene expression profiles of the two cell populations were also sufficiently different to confirm that even though these two cell populations were clearly derived from skeletal muscle, they were distinct populations.

Finally, transplantation of SACs into the heart of laboratory animals that had suffered heart attacks showed definitively, that SACs improved cardiac function better than RACs. Also, SACs decreased the quantity of scar tissue in the heart and increased the number of blood vessels that had formed since the heart attack. There was also less cell death in the SAC-implanted hearts as opposed to the RAC-implanted hearts.

From these data, it seems clear that the SAC population more effectively improves heart function than the RAC population. If such a population exists in the skeletal muscles of adult humans, then such cells might prove more effective for cardiac treatments than muscle satellite cells. The only caveat is that such cells may not exist in humans, since searches for such cells have not turned up anything useful to date (see Susanne Proksch, et al., Mol Ther. 2009; 17(4): 733–741).

High Blood Pressure Medicine Improves Mesenchymal Stem Cell Treatments of Heart Attacks

Mesenchymal stem cells (MSCs) exist in a variety of places throughout the body. They are found in bone marrow, the lower levels of the skin, umbilical cord and umbilical cord blood, placenta, amniotic membrane, muscle, blood vessels, liver, synovial membranes that surround joints, endometrial glands, fat, tendons, and other locations as well. MSCs have the ability to differentiate into cartilage-making cells, fat-making cells, muscle-making cells or bone-making cells  Other protocols exist to differentiate MSCs into heart muscle (Williams AR, Hare JM. Mesenchymal stem cells: biology, pathophysiology, translational findings, and therapeutic implications for cardiac disease.Circ Res. 2011 Sep 30;109(8):923-40; Song YH, Pinkernell K, Alt E.Stem cell induced cardiac regeneration: fusion/mitochondrial exchange and/or transdifferentiation? Cell Cycle. 2011 Jul 15;10(14):2281-6.), neurons (Scuteri A, Miloso M, Foudah D, Orciani M, Cavaletti G, Tredici G.Mesenchymal stem cells neuronal differentiation ability: a real perspective for nervous system repair? Curr Stem Cell Res Ther. 2011 Jun;6(2):82-92), and liver cells (Al Battah F, De Kock J, Vanhaecke T, Rogiers V. Current status of human adipose-derived stem cells: differentiation into hepatocyte-like cells. ScientificWorldJournal. 2011;11:1568-81).  The therapeutic possibilities of MSCs has been widely recognized by stem cell scientists and MSCs have been the subject of many past and ongoing clinical trials.

The use of MSCs to treat heart attack patients has been the subject of several clinical trials (Mazo M, Araña M, Pelacho B, Prosper F. Mesenchymal stem cells and cardiovascular disease: a bench to bedside roadmap. Stem Cells Int. 2012;2012:175979).  While MSCs do provide a modicum of healing to damaged hearts, the ability of MSCs to differentiate into heart muscle is low.  Many experiments have focused upon increasing the percentage of implanted MSCs  that differentiate into heart muscle cells.  However, a recent paper from a research group at the Keio University School of Medicine and the National Institute for Child Health and Development in Tokyo, Japan has taken a different approach to this problem.

Drugs that treat blood pressure include the “angiotensin II receptor blockers” or ARBs.  ARBs prevent a small polypeptide called angiotensin II from binding its receptor.  WHen it binds to its receptor, angiotensin II causes rather substantial constriction of blood vessels throughout the body, and this raises blood pressure.  By preventing blood vessel constriction, ARBs can lower blood pressure.  Also, many heart attack patients are on blood pressure medicines, and ARBs are one of the those normally given to heart attack patients.

One particular ARB is called candesartan, and the commercial names are Atacand, Amias, Blopress, and Ratacand.  In this paper by Yohei Namasawa and colleagues in the laboratories of Kaoru Segawa, Satoshi Ogawa, and Akihiro Umezawa, determined if treating human MSCs from bone marrow could increase the ability of these cells to form heart muscle cells.  To induce heart muscle cells, they used a popular technique from the literature that grows MSCs in culture with mouse heart muscle cells.  The interaction between the MSCs and the heart muscle cells in culture drives the MSCs to form heart muscle-like cells at a somewhat low-frequency.  This group determined if MSCs became heart muscle cells by testing for the presence of heart muscle-specific proteins (cardiac-specific troponin-I).  To prevent them from confusing MSCs with the mouse heart muscle cells, the MSCs were pre-labeled with a fluorescent protein.

Candesartan treatment of MSCs more than doubled the ability of MSCs to form heart muscle cells in culture.  When these same cells were transplanted into the hearts of rats that had suffered heart attacks, the results were even more interesting.  MSC transplantation into the hearts of rats that had recently suffered a heart attack.  Those animals that had undergone surgery but were not given any heart attacks, showed an average reduction of about 3% in their ejection fraction (percentage of blood that pumped from the heart during each heart beat).  Given that the standard deviation was close to this number, this change is not significant.  The control animals that were not given MSC treatments showed an average decrease of just over 10% in their ejection fraction.  Animals treated with MSCs that had suffered heart attacks showed a decrease of about 6-7%.  This is significantly less of a decrease than in the control, but it is still a decrease.  When the rat hearts were treated with MSCs that had been pretreated with candesartan, they showed an average 3-4% increase in ejection fraction.  If the rats were given candesartan after the heart attack, it raised the ejection fraction 1-2%.  If the rats were given candesartan, and treated with bone marrow cells after the heart attack, their ejection fractions decreased by the same as the sham group.  However, if the rats were given candesartan and MSCs that had been pretreated with candesartan after the heart attack, their ejection fractions increased by 10-12%.  Other heart function indicators improved too, since transplantation of the candesartan-treated bone marrow cells improved the “end systolic dimension,” which is an indication of how well the heart contracts.

When hearts were examined after the animals died, those animals that had received transplantations of the candesartan-pretreated bone marrow cells had 2-3 times more heart muscle cells derived from the implanted MSCs than did the controls transplanted with non-treated bone marrow.  Also, post-mortem examination of hearts from the treated rats showed that the rats treated with candesartan-pretreated bone marrow cells had much small heart scars than the other groups (5%-7% smaller).

These experiments, though pre-clinical, suggest that pre-treatment of MSCs with compounds like candesartan can increase their ability to differentiate into heart muscle cells.  This would certainly augment their ability of heal the hearts of patients after a heart attack.  While further work is certainly warranted, a clinical study should be proposed to test if this efficacy applies to human hearts as well.

Highly Regarded Cochrane Library Study Shows that Bone Marrow Treatments Help Heart Attack Patients

A whole gaggle of stem cells treatments for heart attack patients have been completed. Some patients are definitely helped, but others are not. Some clinical trials have shown a definitively positive effect from stem cell infusions in combination with standard care. Other trials, however, have failed to show any positive benefits to combining stem cell infusions with standard care. What do these clinical trials as a whole tell us?

This question is the realm of “meta-analyses.” While several clinical trials that have given stem cell treatments on heart attack patients have been subjected to meta-analyses, more stem cell trials have been completed, and further analyses are necessary. Meta-analyses take data from separately published studies that were conducted at different times and places and combine these data into a giant database that is subjected to rigorous statistical analysis. One organization that excels at meta-analyses, and has a solid reputation in the field is the Cochrane Library. The Cochrane Library has just completed a systematic meta-analysis of the data generated in 33 different clinical trials that used adult stem cells to treat the hearts of heart attack patients. The Cochrane Library’s analysis revealed that heart function definitely improves after stem cell treatments. However, these same analyses showed that the data are limited by the predominance of small trials and larger clinical trials are necessary to more rigorously demonstrate if the benefit of stem cell treatments in the heart actually means that the treated patients will benefit from a longer and healthier life.

Heart attacks are caused by blocked coronary arteries that prevent life-giving oxygen from flowing to heart muscle. This lack of oxygen causes the demanding heart muscle cells to die, and this cell death damages the heart and leads to the production of a scar that does not contract or conduct electrical impulses. Clinical trials have used adult stem cells from the patient’s own bone marrow to repair and reduce this damage. Although, unfortunately, this treatment regime is only available in facilities that have close links to medical research facilities.

The Cochrane Library authors (David M Clifford and colleagues), cobbled together data from as many clinical trials that used bone marrow stem cells to treat heart attack patients as they could find. In 2008, Cochrane reviewed 13 clinical trials to address this very question. However, since that time, 20 more clinical trials have been completed, and this year, 33 clinical trials that treated 1,765 patients were analyzed. Since the earlier trials continued patient follow-up, there are new data points from many older clinical trials that were also included. These data provide a more precise indication of the effects of stem cell therapy several years after completion of stem cell treatment.

In the analyzed trials, all 1,765 patients had already undergone angioplasty, which is a conventional treatment for heart attack patients. Angioplasty uses an inflatable balloon that is fed into the coronary artery by means of a fine catheter. This catheter is inserted into a large vein and guided by imaging methods to the blocked coronary arteries. Once in place, the balloon is slowly inflated to push the obstructing material to the sides of the artery. This opens up the blocked artery and allows the flow of blood to the heart muscle. To keep the blood vessel open, sometimes a stent is inserted into the blocked vessel. If angioplasty is combined with bone marrow stem cell treatments, the Cochrane reviews finds that such treatments can produce moderate long-term improvement in heart function that is sustained for up to five years. Unfortunately, there was not enough data to reach firm conclusions about increases in survival rates.

Senior author of this review, Enca Martin-Rendon, from the Stem Cell Research laboratory at the John Radcliffe Hospital in Oxford, UK, said, “This new treatment may lead to moderate improvement in heart function over standard treatments. Stem cell therapy may also reduce the number of patients who later die or suffer from heart failure, but currently there is a lack of statistically significant evidence based on the small number of patients treated so far.”

Will such treatments become part of the treatment for a heart attack? At this point it is difficult to say with any certainty. It is simply too early to establish guidelines for standard practice, since several labs have used differing transplantation and cell isolation and storage methods. According to the Cochrane Review, further work is required to properly standardize the procedure. For instance, there is little agreement on the dosage of cells for the heart, even though several studies have shown a dose-specific effect. Secondly, a standardized protocol for when after the heart attack treatment should be given, and what methods most accurately measure heart function must be constructed before such a procedure is universally offered to patients. Martin-Rendon noted, “The studies were hard to compare because they used so many different methods. Larger trials with standardized treatment procedures would help us to know whether this treatment is really effective.

A larger trial is already in the works, since the task force of the European Society of Cardiology for Stem Cells and Cardiac Repair received a recent, sizable grant from the European Union Seventh Framework Programme for Research and Innovation (EU FP7-BAMI) to initiate such a large trials. The Principal Investigator for this trial (called BAMI) who is also a co-author of this review, Anthony Mathur, said, ”The BAMI trial will be the largest stem cell therapy trial in patients who have suffered heart attacks and will test whether this treatment prolongs the life of these patients.”