In April of 2013, the results of three clinical trials that examined the effects of bone marrow-derived stem cell treatments in patients with acute myocardial infarction (translation – a recent heart attack) or chronic heart failure. These trials were the SWISS-AMI trial, the CELLWAVE trial, and the C-CURE trial.
The SWISS-AMI trial (Circulation. 2013;127:1968-1979), which stands for the Swiss Multicenter Intracoronary Stem Cells Study in Acute Myocardial Infarction trial, was designed to examine the optimal time of stem cell administration at 2 different time points: early or 5 to 7 days versus late or 3 to 4 weeks after a heart attack. This trial is an extension of the large REPAIR-AMI, which showed that patients who tended to receive bone marrow stem cell treatments later rather than earlier had more pronounced therapeutic effects from the stem cell treatments.
SWISS-AMI examined 60 patients who received standard cardiological care after a heart attack, 58 who received bone marrow stem cells 5-7 days after a heart attack, and 49 patients who received bone marrow stem cells 3-4 weeks after their heart attacks. All stem cells were delivered through the coronary arteries by means of the same technology used to deliver a stent.
When the heart function of all three groups were analyzed, no significant differences between the three groups were observed. Those who received stem cell 5-7 days after a heart attack showed a 1.8% increase in their ejection fractions (the percentage of blood that is ejected from the ventricle with each beat) versus an average decrease of 0.4% in those who received standard care, and a 0.8% increase in those who received their stem cells 3-4 weeks after a heart attack. If these results sound underwhelming it is because they are. The standard deviations of each group so massive that these three groups essentially overlap each other. The differences are not significant from a statistical perspective. Thus the results of this study were definitely negative.
The second study, CELLWAVE (JAMA, April 17, 2013—Vol 309, No. 15, 1622-1631), was a double-blinded, placebo-controlled study conducted among heart attack patients between 2005 and 2011 at Goethe University Frankfurt, Germany. In this study, the damaged area of heart was pretreated with low-energy ultrasound shock waves, after which patients in each group were treated with either low dose stem cells, high-dose stem cells, or placebo. Patients also received either shock wave treatment or placebo shock wave treatment. Thus this was a very well-controlled study. Stem cells were administered through the coronary arteries, just as in the case of the SWISS-AMI study.
The results were clearly positive in this study. The stem cell + shock wave treatment groups showed definite increases in heart function above the placebo groups, and showed fewer adverse effects. The shock wave treatments seem to prime the heart tissue to receive the stem cells. The shock waves induce the release of cardiac stromal-derived factor-1, which is a potent chemoattractor of stem cells. This is an intriguing procedure that deserves more study.
The third study, C-CURE, is definitely the most interesting of the three (Bartunek et al. JACC Vol. 61, No. 23, June 11, 2013:2329–38). In this trial, mesenchymal stromal cells (MSCs) were isolated from bone marrow and primed with a cocktail of chemicals that pushed the stem cells towards a heart muscle fate. Then the cells were transplanted into the heart by direct injection into the heart muscle as guided by NOGA three-dimensional imaging of the heart.
After initially screening 320 patients with chronic heart failure, 15 were treated with standard care and the other 32 received the stem cell treatment. After a two-year follow-up, the results were remarkable: those who received the stem cell treatment showed an average 7% increase in ejection fraction versus 0.2% for receiving standard care, an almost 25 milliliter reduction in end systolic volume (measures degree of dilation of ventricle – not a good thing and the fact that it decreased is a very good thing) versus a 9 milliliter decrease for those receiving standard care, and were able to walk 62 meters further in 6 minutes as opposed to standard care group who walked 18 meters less in 6 minutes.
While these studies do not provide definitive answers to the bone marrow/heart treatment debate, they do extend the debate. Clearly bone marrow stem cells help some patients and do not help others. The difference between these two groups of patients continues to elude researchers. Also, how the bone marrow is processed is definitely important. When the cells are administered also seems to be important, but the exact time slot is not clear in human patients. It is also possible that some patients have poor quality bone marrow in the first place, and might be better served by allogeneic (someone else’s stem cells) treatments rather than autologous (the patient’s own stem cells) stem cell treatments.
Also, stem cell treatments for heart patients will probably need to be more sophisticated if they are to provide greater levels of healing. Heart muscle cells are required, but so are blood vessels to feed the new heart muscle. If mesenchymal stem cells work by activating resident heart stem cells, then maybe mesenchymal transplants should be accompanied by endothelial progenitor cell transplants (CD117+, CD45+ CD31+ cells from bone marrow) to provide the blood vessels necessary to replace the clogged blood vessels and the new heart muscle that is grown.