Needling the heart to rejuvenate: The promise of intramyocardial injection of bone marrow stem cells

Abstract

BMMC-injected group and the control group. Interestingly, regional wall thickening in the injected segments increased by similar amounts in the control group, which received vehicle injection, and in BMMC-injected patients. The major difference between the 2 groups was that myocardial scar size, as assessed by magnetic resonance imaging, increased in the injected segments in the control group (median value, þ5.1%) but decreased in the BMMC-injected group (median value, –13.1%). Hence, in the traditional sense, this was a “negative” study; however, the study offers important data that are relevant to study design and to the assessment of benefit and mechanisms of BMMC therapy in ischemic heart failure. The double-blind nature of the study was ensured by performance of bone marrow aspiration in all participants and masking of the syringes used for injecting cells or vehicle. Future studies would benefit from adopting this method to ensure that the observed effects are specifi ct o BMMCs and independent of the effects of intra-myocardial injection per se and eliminate any bias in assessment of clinical and imaging end points. The initial period of optimization of heart failure therapy, during which a substantial number of participants had improvement in left ventricular ejection fraction that precluded enrollment in the study, is a strength of the study. What is not clear from the study is whether there were individuals who were on the “upward curve” of reverse remodeling who were enrolled in the study and could have influenced the results by further improvement during the study period related to recently optimized heart failure therapy. It is difficult to conclusively deduce the influence of concomitant surgical revascularization on the effect of BMMC therapy. The above-mentioned meta-analysis suggests that the effect of BMMC may have been enhanced by revascularization; however, it is also possible, as the authors contend, that the independent effects of revascularization may have limited the BMMC effect. A weakness of the study is the lack of measurement of left ventricular structure and function soon after the study