Anti-apoptotic Bcl-2 gene modified rat MSCs improves heart function after myocardial infarction

Objective: Engraftment of mesenchymal stem cells (MSCs) in the infarcted heart for replenishing the local stem cell pool has been proposed as therapeutic approach to degenerative heart diseases. However, cells transplanted into the myocardium typically exhibit limited survival. Bcl-2 is a well-established inhibitor of apoptosis. We transfected MSCs with Bcl-2 and evaluated cellular survival, engraftment, angiogenesis and functional improvement after intracardiac injection in a rat myocardial infarction model.

Methods: Rat MSCs from bone marrow were transfected with Bcl-2 using nanopolymers and transfection efficiency was determined by rt-PCR. The anti-apoptotic effect was evaluated by cell proliferation and caspase-3 activity assays in vitro. In vivo, Bcl-2 transfected MSCs were injected into the myocardial infarct border zone after LAD ligation in rats (N=24). Cell survival was tracked by CFSE. The anti-apoptosis effect was evaluated by TUNEL, while cellular engraftment and angiogenesis were investigated by immunostaining. Pressure-volume loops (conductance catheter) were recorded to measure LV function.

Results: Bcl-2 mRNA level was upregulated for 7 days post-transfection. Both cell proliferation and capase-3 activity showed that Bcl-2 prevents apoptosis in MSCs. In vivo, transplantation with MSCs overexpressing Bcl-2 increased the survival of transplanted MSCs by more than 70%. The cardiomyocyte-like differentiation (myosin a heavy chain co-localization with CSFE) and angiogenesis (FVIII) was increased approximately 10-fold while fewer apoptotic cells were detected (TUNEL) in myocardial tissue treated with Bcl-2 transfected MSCs. Furthermore, Bcl-2 MSC treated hearts showed better functional recovery than animals treated with unmodified MSCs

Conclusion: Transplantation with Bcl-2 transfected MSCs enhances recovery after myocardial infarction.