Background: We hypothesized that overexpression of cGMP-dependent protein kinase type 1α (PKG1α) 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 PKG1α ((PKG1α)MSCs).Controls included native MSCs ((Nat)MSCs) and MSCs transduced with an empty vector ((Null)MSCs). PKG1α activity was increased approximately 20, 5 and 16 fold respectively in (PKG1α)MSCs. (PKG1α)MSCs 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, pGSK3β, and Bcl-2 were significantly increased in (PKG1α)MSCs compared to (Nat)MSCs and (Null)MSCs. Higher release of multiple prosurvival and angiogenic factors such as HGF, bFGF, SDF-1 and Ang-1 was observed in (PKG1α)MSCs before and after OGD. In a female rat model of acute myocardial infarction, (PKG1α)MSCs group showed higher survival compared with (Null)MSCs 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 (PKG1α)MSCs. At 4 weeks after transplantation, compared to DMEM group and (Null)MSCs group, (PKG1α)MSCs 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 (PKG1α)MSCs group.
Conclusion: Overexpression of PKG1α transgene could be a powerful approach to improve MSCs survival and their angiomyogenic potential in the infarcted heart.