Timing of intracoronary bone-marrow-derived stem cell transplantation after ST-elevation myocardial infarction.

It is still unclear whether the timing of intracoronary stem cell therapy affects the therapeutic response in patients with reperfused myocardial infarction. The natural course of healing the infarction and the presence of putative homing signals within the damaged myocardium appear to favor cell engraftment during the transendothelial passage in the early days after reperfusion. However, the adverse inflammatory environment, with its high oxidative stress, might be deleterious if cells are administered too early after reperfusion. In addition, current studies use mostly unfractionated cells and it remains to be addressed whether specific cell types, and their enrichment, would be better suited to augmenting the recovery at later time points. Here we highlight several aspects of the timing of intracoronary stem cell therapy and focus on time-related questions that are relevant to the design of future experimental and basic studies.