Abstract 3872: Clonal Variation Reveals Subpopulations of Stem Cells Committed to Myogenic and Vasculogenic Lineages in Adult Mouse Myocardium
Multipotent cardiac stem/progenitor cells (CSCs) have been identified in adult myocardium, but their biological properties and differentiation potential remain incompletely defined. We isolated c-kit+, sca-1+ CSCs from adult mouse left ventricles and obtained >40 clones by serial dilution, of which 8 –10 were characterized in detail. The clones exhibited distinct and stable morphologies, but globally similar gene expression profiles by microarray. All clones expressed stem cell-associated genes, including Oct-4, and Myc, and were pluripotent. However there were striking differences among clones in the propensity to adopt myogenic vs. vasculogenic fates. Upon differentiation, one clone almost exclusively adopted a smooth muscle phenotype with high expression of sm22-alpha and smooth muscle actin proteins. Under the same culture conditions, 2 other clones produced negligible levels of smooth muscle markers, but expressed high levels of GATA4 protein, suggesting a cardiomyogenic fate. Cells from 3 other clones expressed GATA4 and smooth muscle markers at similar levels, suggesting an intermediate or embryonic cardiomyocyte phenotype. Vasculogenic potential was confirmed in the original clones and in 4 more clones using a tube formation assay in Matrigel. Five clones with the highest vasculogenic differentiation potential had a distinctive stellate morphology and formed tubes as well or better than HUVECs. Five other formed tubes more slowly (between 5–20 hours) or remained dispersed in the gel matrix as individual cells. Expression analysis revealed that vasculogenic and myogenic clones could be distinguished by expression of SDF-1 (CXCL12), as well as by other genes encoding cell adhesion and migration molecules. Indeed, SDF-1 protein levels correlated both with number of tubes formed in Matrigel (CF=0.691) as well as with tube length (CF=0.529), suggesting that SDF-1 can be used as a marker of the angiogenic potential of CSCs. Our results demonstrate for the first time that c-kit+, sca-1+ CSCs in adult hearts are heterogeneous, with large and clonally stable differences in myogenic vs. vasculogenic potential that can be predicted in part by expression of SDF-1. These findings have important implications for the therapeutic use of CSCs.
This research has received full or partial funding support from the American Heart Association, National Center.