BACKGROUND: The heart is a highly vascular organ and prolonged interruption of 
myocardial blood flow initiates events that culminate in cardiac myocyte death. 
Proposed experimental reparative strategies include harvesting potent cells 
followed by direct injection into ischemic myocardium to achieve myogenesis and 
angiogenesis.
METHODS: Accordingly, we set out to isolate and expand a purified population of 
adult rat putative cardiomyocyte precursors, and to identify their 
characteristics in vitro. By using an acute myocardial infarction model and 
direct cell implantation, we further tested the hypothesis that these cells are 
an ideal cell source for myocardial regeneration and can enhance cardiac repair 
after implantation into the ischemic rat heart.
RESULTS: We describe here the identification of a subpopulation of primitive 
cells from rat heart, processing stem cell marker, c-kit and myogenic 
transcriptional factors, GATA-4 and MEF 2C, and cardiac specific proteins, 
troponin-I, alpha-sarcomeric actinin and connexin-43. They exhibited a high in 
vitro proliferative potential. These findings strongly suggest that these cells 
are putative cardiomyocyte precursors. After transplantation, they were able to 
be retained and proliferate (13.63 +/- 5.97% after 2 weeks) within the ischemic 
heart. Progeny of implanted cells migrated along the infarcted scar, 
reconstituted regenerated cardiomyocytes with incorporation into host 
myocardium, and inhibited cardiac remodeling with decreased scar formation.
CONCLUSION: Our findings suggest that putative cardiomyocyte precursors isolated 
from adult heart could potentially be an autologous cell source for myocardial 
regeneration cell therapy.