Cell transplantation and cardiac recovery:myocardial regeneration from endogenous cardiac progenitor cells

Following the bone marrow or cardiac derived progenitor cells transplantation,improved left ventricular(LV) function,decreased LV remodeling, and decreased fibrosis of non-infarcted LV regions,and in some cases,the reduction of infarct scar size have been reported to occur in animal mycardial infarction(MI) models.In clinical trials, stem cell transplantation has also been associated with significant,but modest improvements of LV functional parameters.These beneficial effects do occur although in many animal studies there is often very low long term engraftment or transdifferentiation of transplanted cells into myocytes and vascular cells.Importantly,paracrine signals generated by the implanted progenitor cells seem to play an important role in limiting or reversing myocardial damage as- sociated with acute MI.Paracrine signaling effects include increased myocardial vascularization and reduced apoptosis of native cardiomyocytes;these responses are most prominent in peri-myocardial infarction (MI) boarder zone(BZ) of the heart.Although much data supports the possibility that engrafted progenitor cells can mobilize endogenous cardiac progenitor cells(CPC) to the cardiac injury site and also stimulate them to propagate and transd-ifferentiate into cardiomyocytes and vascular cells, this concept remains controversial.We and others have reported evidences supporting the view that endogenous CPC can be stimulated to differentiate and partially replace cardiomyocytes destroyed during an MI.Data from our laboratory will be reviewed.