Abstract 21185: The Molecular Mechanisms Of Sca-1 Signaling In Cardiac Repair In Response To Myocardial Injury
We have previously reported that an increased percentage of stem cell antigen-1/PECAM-1 (Sca-1+/CD31-, S) cell population is essential for the favorable cardiac remodeling following myocardial infarction (MI). However, little is known about the molecular mechanisms of how Sca-1 signaling participates in cardiovascular regeneration in response to injury and how its signaling input is transplated into cellular activities. Using Sca-1 mutant (MT) mice, here we determined the role of Sca-1 signaling in cardiovascular regeneration after MI. We found that vascular densities and BrdU incorporated cardiomyocytes were decreased in the left ventricle of Sca-1 MT mice as compared to that of wild type (WT) mice 4 weeks after ligation of left anterior descending coronary artery. Supperarray profiling of 96 stem cell associated genes of heart tissues revealed that cell cycle regulators like retinoblastoma protein Rb1 and adenomatous polyposis coli (APC) were up-regulated, whereas insulin like growth factor I (IGF1) and frequently rearranged in advanced T-cell lymphomas (Frat1) gene expressions were down-regulated in Sca-1 MT mice 14 days after MI. Western blotting demonstrated expression of cell proliferation markers including PCNA and Ki67 was significantly inhibited in Sca-1 MT mice compared to WT mice. S cells knocking down with Sca-1 shRNA by lentivirus transfection confirmed the protein changes of cell cycle regulators (Rb1, APC, IGF1, Frat1). Flow cytometric analysis showed that Sca-1 interference inhibited S cell proliferation at baseline (S1 phase, 6.80+/−0.26% vs 2.98+/−0.55%; n=6, P<0.01) and in response to IGF+HGF treatment (8.84+/−0.13 vs 6.69+/−0.41; n=6, P<0.01). Moreover, we observed these cells were more susceptible to serum free induced apoptosis with Annexin-V staining (9.6+/−2.3% vs 15.4+/−3.1%; n=10, P<0.01). We also showed a significant morphological alteration of S cells after knock down of Sca-1 antigen. Double strand small RNAs designed to target Sca-1 promoter region partially recapitulated the phenotypes of Sca-1 interference. Thus, Sca-1 signaling plays a critical role in governing cardiovascular regeneration following myocardial injury by regulation of S cell proliferation, survival and differentiation.
- © 2010 by American Heart Association, Inc.