Protein Kinase G1 α Overexpression Increases Stem Cell Survival and Cardiac Function after Myocardial Infarction

Background: We hypothesized that overexpression of cGMP-dependent protein kinase type 1 alpha (PKG1 alpha) could mimic the effect of tadalafil on the survival of bone marrow derived mesenchymal stem cells (MSCs) contributing to regeneration of the ischemic heart. Methods and Results: MSCs from male rats were transduced with adenoviral vector encoding for PKG1 alpha ((MSCs)-M-PKG1 alpha). Controls included native MSCs ((MSCs)-M-Nat) and MSCs transduced with an empty vector ((MSCs)-M-Null). PKG1 alpha activity was increased approximately 20, 5 and 16 fold respectively in (MSCs)-M-PKG1 alpha. (MSCs)-M-PKG1 alpha showed improved survival under oxygen and glucose deprivation (OGD) which was evidenced by lower LDH release, caspase-3/7 activity and number of positive TUNEL cells. Anti-apoptotic proteins pAkt, pGSK3 beta, and Bcl-2 were significantly increased in (MSCs)-M-PKG1 alpha compared to (MSCs)-M-Nat and (MSCs)-M-Null. Higher release of multiple prosurvival and angiogenic factors such as HGF, bFGF, SDF-1 and Ang-1 was observed in (MSCs)-M-PKG1 alpha before and after OGD. In a female rat model of acute myocardial infarction, (MSCs)-M-PKG1 alpha group showed higher survival compared with (MSCs)-M-Null group at 3 and 7 days after transplantation as determined by TUNEL staining and sry-gene quantitation by real-time PCR. Increased anti-apoptotic proteins and paracrine factors in vitro were also identified. Immunostaining for cardiac troponin I combined with GFP showed increased myogenic differentiation of (MSCs)-M-PKG1 alpha. At 4 weeks after transplantation, compared to DMEM group and (MSCs)-M-Null group, (MSCs)-M-PKG1 alpha group showed increased blood vessel density in infarct and peri-infarct areas (62.5 +/- 7.7; 68.8 +/- 7.3 per microscopic view, p < 0.05) and attenuated infarct size (27.2 +/- 2.5%, p < 0.01). Heart function indices including ejection fraction (52.1 +/- 2.2%, p < 0.01) and fractional shortening (24.8%+/- 1.3%, p < 0.01) were improved significantly in (MSCs)-M-PKG1 alpha group. Conclusion: Overexpression of PKG1 alpha transgene could be a powerful approach to improve MSCs survival and their angiomyogenic potential in the infarcted heart.