BACKGROUND - Adult endothelial progenitor cells (EPCs) reduce myocardial infarct size and improve postischemic myocardial function. We have recently shown that clonal embryonic EPCs (eEPCs), derived from 7.5-day-old mice, home specifically to hypoxic areas in tumor metastasis mouse models but spare normal organs and do not form carcinomas. Here, we assessed the potential of eEPCs to limit organ dysfunction after ischemia and reperfusion in a preclinical pig model.
METHODS AND RESULTS - Pigs were subjected to ischemia (60-minute left anterior descending [LAD] artery occlusion) and reperfusion (7 days). At the end of ischemia, we applied medium with or without 5 x 10(6) eEPCs by either pressure-regulated retroinfusion or intravenous transfusion. One hour after reperfusion, 99Tc-labeled eEPCs engrafted to a 6-fold higher extent in the ischemic myocardium after retroinfusion than after intravenous application. Regional myocardial function (subendocardial segment shortening [SES] at 150/min, given in percent of nonischemic circumflex region) and infarct size (TTC viability and Methylene-blue exclusion) were determined 24 hours and 7 days later. Compared with medium-treated animals, retroinfusion of eEPCs decreased infarct size (35+/-4% versus 51+/-6%) and improved regional myocardial reserve of the apical LAD region (SES 31+/-4% versus 6+/-8%), whereas intravenous application displayed a less pronounced effect (infarct size 44+/-4%; SES 12+/-3%). Retroinfusion of an equal amount of neonatal coronary endothelial cells (rat) did not affect infarct size (49+/-5%) nor regional myocardial reserve (16+/-7%). The eEPC-dependent effect was detected at 24 hours of reperfusion (infarct size 34+/-7% versus 58+/-6%) and was sensitive to Wortmannin coapplication (50+/-5%).
CONCLUSIONS - Our findings show that eEPCs reduce ischemia-reperfusion injury in a preclinical pig model. The rapid effect (as early as 24 hours) indicates a role for enzyme-mediated cardioprotection, which involves, at least in part, the phosphatidylinositol 3-kinase/AKT pathway.