Bone marrow cell transfer in acute myocardial infarction.

Permanent loss of cardiomyocytes after ischemic injury often initiates the development of heart failure and adversely affects clinical outcome. The concept of progenitor-cell transfer for enhancing cardiac repair has raised new therapeutic prospects. Promising results have been reported in early studies in rodents, using various modalities of progenitor-cell transfer in the dysfunctional heart, although underlying mechanisms remain ill defined. Despite ongoing controversies over whether or not stem cells can autonomously adapt cardiomyocyte-like behavior after genetic reprogramming or whether they merely fuse with native host cardiomyocytes, early-phase clinical trials have shown a reassuring safety profile and suggest a functional benefit. However, identification of the intrinsic value of stem cell transfer in patients after myocardial infarction will require carefully designed randomized, placebo-controlled, blinded studies. While these are becoming available, a number of critical questions about the choice of progenitor-cell type, dosage regimen, and timing of administration need to be considered, and end points for future clinical trials need to be chosen carefully. There is great enthusiasm for this novel treatment paradigm in patients with ischemic cardiomyopathy, but only carefully conducted clinical trials paralleled by preclinical studies in relevant animal models will ultimately identify the best conditions and indications for cell transfer.