Abstract 3175: Injection of GSK-3β Overexpressing Mesenchymal Stem Cells Attenuates Cardiac Dysfunction After Myocardial Infarction Through Cardiomyocyte Differentiation and Secretion of Angiogenic Factors
Glycogen synthase kinase-3β (GSK-3β) induces cardiomyocyte (CM) differentiation of mesen-chymal stem cells (MSCs). We have shown previously that injection of GSK-3β overexpressing MSCs into the border zone in the mouse model of myocardial infarction (MI) improves cardiac function and attenuates cardiac remodeling. However, it is currently unknown whether the therapeutic effect of MSCs is mediated through differentiation of MSCs into CM, paracrine effects, or both. In order to evaluate whether MSCs injected into the MI heart differentiate into CM in vivo, we isolated MSCs from transgenic mice harboring Nkx2.5-LacZ, a genetic reporter of CM differentiation. MSCs isolated from the reporter mice were transduced with adenovirus harboring LacZ or GSK-3β and injected into the border zone after coronary ligation. Three months later, MI size was significantly smaller in mice injected with GSK-MSCs (19.1±2.9%, p<0.001) than in mice injected with saline (38.5±3.7%) or LacZ-MSCs (27.5±2.7%). Cardiac function was significantly better in GSK-MSC mice than in saline or LacZ-MSC mice. In order to evaluate whether the injected MSCs differentiate into the CM lineage, double staining with X-Gal and anti-troponin I (TnI) antibody was conducted. Although very few X-gal/TnI-double positive myocytes were observed in the saline or LacZ-MSC group, many double positive cells (109±15/one vertical cut) were found in the GSK-MSC group, suggesting that GSK-MSCs differentiate into the CM-lineage in the injected area. The capillary density (cells/10000μm2) determined by von Willebrand factor staining was significantly increased in the GSK-MSC group (9.9±0.7, p<0.01) compared to the LacZ-MSC (2.3±1.9) and the saline groups (1.7±0.9). PCR array analysis showed that angiogenic factors, including platelet factor 4, fibroblast growth factor, and vascular endothelial growth factor A (Vegfa), were significantly upregulated in the peri-infarct area of GSK-MSC mice. In vitro, GSK-3β increased 3-fold of Vegfa protein expression in MSCs, suggesting that upregulation is cell autonomous. In conclusion, ex-vivo overexpression of GSK-3β in MSCs enhances the efficacy of cell therapy through CM differentiation as well as stimulation of angiogenesis via upregulation of Vegfa.