Sca-1-positive cardiac stem cell migration in a cardiac infarction model.

Adult myocardium has the capacity for repair and regeneration, which is derived from cardiac stem cells (CSCs). In this study, we assessed the migration and changes in numbers of Sca-1-positive CSCs after myocardial infarction (MI) in vivo and in vitro. In this study, we showed that in a rat MI model the CSCs emerged around the vessels near the peri-infarct zone and in the epicardium of the infarcted area. Four weeks after infarction, no differences in the expression of connexin 43 (Cx43) were observed in the peri-infarct and infarct zones. In vitro, we mimicked tissue ischemia and hypoxia by using a culture environment of 5 % O₂ and a wound healing assay to monitor the migration of CSCs. In conclusion, under hypoxic conditions, the CSCs, conveyed by blood vessels, migrated from the niche to the infarct zone for repairing the damaged myocytes. The number of endogenous migrating CSCs was proportionate to the repair time after infarction, rather than the degree of infarction. Four weeks after MI, the expression of Cx43 was not altered in migratory CSCs, namely no enhanced gap-junctional communication with cardiomyocytes was seen in the CSCs. Further studies are necessary to delineate the molecular mechanisms that drive the migration of CSCs after MI.