Genetic lineage tracing of Sca-1 cells reveals endothelial but not myogenic contribution to the murine heart

-The adult mammalian heart displays a cardiomyocyte turnover rate of ~1% per year throughout postnatal life and after injuries such as myocardial infarction (MI), but the question of which cell types drive this low level of new cardiomyocyte formation remains contentious. Cardiac-resident stem cells marked by stem cell antigen-1 (Sca-1, gene name ) have been proposed as an important source of cardiomyocyte renewal. However, the contribution of endogenous Sca-1 cells to the heart at baseline or after MI has not been investigated. -Here we generated gene-targeted mice containing either a constitutive or inducible Cre recombinase to perform genetic lineage tracing of Sca-1 cells -We observed that the contribution of endogenous Sca-1 cells to the cardiomyocyte population in the heart wa