The therapeutic potential of progenitor cells in ischemic heart disease--Past, present and future.

Within the recent past, it has become increasingly evident that adult bone marrow and peripheral blood do not only contain diverse hematopoietic precursors but also stem- and progenitor cells with some properties resembling those of embryonic cells. These adult progenitor cells can contribute to the regeneration of injured tissue as has been revealed by in vitro experiments and subsequent animal studies. Over the last four years, several clinical studies employing such a hypothesis in the context of myocardial repair after acute infarction or during chronic ischemic failure have been published. These studies have used autologous bone marrow cells as well as peripheral blood-derived progenitor cells, which were delivered via intracoronary or intramyocardial routes near the infarct area. The initial results demonstrated the safety and possible benefit of this strategy, which appear to be relatively simple, inexpensive and free of side effects. However, the present clinical studies were small in size so that the overall therapeutic efficacy remains open to debate and evaluation. Furthermore, a major part of the molecular mechanisms underlying progenitor cell-mediated repair has been proposed but not yet elaborated. Hence, larger controlled randomized and double-blinded trials in addition to experimental investigations on the primary mechanisms of repair are keenly anticipated.