Are endothelial progenitor cells mobilized by myocardial ischemia or myocardial necrosis? A cardiac magnetic resonance study

Background: In ST-elevation myocardial infarction (STEMI) patients, the main stimuli involved in endothelial progenitor cells (EPCs) mobilization are not fully understood. We aimed to assess by cardiac magnetic resonance (CMR) whether the extent of ischemic myocardium (area at risk (AAR)) or of necrotic myocardium (infarct size (IS)) can be correlated to levels of circulating EPCs. Methods: Peripheral EPCs were measured in fifteen STEMI patients at 24. h after successful primary percutaneous coronary intervention (pPCI). Between two and four days after pPCI all patients underwent CMR assessment of myocardial AAR, IS, myocardial salvage (MS) and microvascular obstruction at late gadolinium enhancement CMR (LG-MVO). Results: CD34+/KDR+, CD34+/KDR+/CD45dim, CD34+/KDR+/CD45-, EPCs were related to extent of AAR (rho = 0.51, p= 0.05; rho = 0.55, p= 0.03; rho = 0.72, p= 0.002, respectively), while no relationships were detected with IS, MS or LG-MVO. Conclusions: Our data show that EPCs were strongly correlated to extent of myocardial AAR, thus suggesting that progenitor cells mobilization in STEMI develops in response to myocardial ischemia and not to myocardial necrosis