[Stem-cell therapy following large acute myocardial infarction].

In just a few years, research into the use of stem cells for treating patients with acute myocardial infarction has become a reality in Spain. Since the first safety studies we have moved on to the design of randomized trials to determine whether this therapy works. To understand why the paper by Suárez de Lezo et al1 deserves to be discussed in an editorial, the short history of cell therapy in patients with acute myocardial infarction needs to be told. The first stem cell therapy experiments in this area were performed some five years ago with the main aim of determining whether such an approach was safe, and whether this new therapeutic possibility was feasible.2-7 All were small studies without controls. As it remains to this day, two ways of using these cells were contemplated: their intracoronary injection, or the stimulation of their proliferation in the bone marrow through the use of growth factors. The latter substances, which are in daily hematological use, increase spectacularly the number of stem cells the bone marrow produces. This in turn promotes their mobilization into the blood stream, which theoretically they then leave in order to colonize damaged tissues. Once the absence of important secondary effects and the feasibility of such treatment was confirmed, efficacy studies were undertaken using surrogate endpoints (generally the development of remodeling in the post-infarction left ventricle). In this second phase, experimental designs now contemplated control groups, but work did not go beyond comparing the two routes of administering these cells (mentioned above). At this point the number of types of stem cell used was increased, although all came from the bone marrow subpopulations.8 These comparative studies raised the first doubts regarding the mechanism of action of these stem cells. It was found that after the intracoronary infusion of stem cells they did indeed settle in the myocardium, and that the more stem cells added, the more myocardium that became Stem-Cell Therapy Following Large Acute Myocardial Infarction