Adenoviral human BCL-2 transgene expression attenuates early donor cell death after cardiomyoblast transplantation into ischemic rat hearts

Background-Cell transplantation for myocardial repair is limited by early cell death. Gene therapy with human Bcl-2 (hBcl-2) has been shown to attenuate apoptosis in the experimental setting. Therefore, we studied the potential benefit of hBcl-2 transgene expression on the survival of cardiomyoblast grafts in ischemic rat hearts. Methods and Results-H9c2 rat cardiomyoblasts were genetically modified to express both firefly luciferase and green fluorescent protein (mH9c2). The cells were then transduced with adenovirus carrying hBcl-2 (AdCMVhBcl-2/mH9c2). Lewis rats underwent ligation of the left anterior descending artery ( LAD) to induce a sizable left ventricular (LV) infarct. Hearts were explanted and the infarcted region was restored using collagen matrix (CM) seeded with 1 x 10(6) mH9c2 cells (n = 9) or AdCMVhBcl-2/mH9c2 cells (n = 9). Control animals received CM alone (n = 6) or no infarct (n = 6). Restored hearts were transplanted into the abdomen of syngeneic recipients in a "working heart" model. Cell survival was evaluated using optical bioluminescence imaging on days 1, 5, 8, 14, and 28 after surgery. The left heart function was assessed 4 weeks postoperatively using echocardiography and magnetic resonance imaging. During 4 weeks after surgery, the optical imaging signal for the AdCMVhBCL2/mH9c2 group was significantly (P < 0.05) higher than that of the mH9c2-control group. Both grafts led to better fractional shortening (AdCMVhBcl-2/mH9c2: 0.21 +/- 0.03; mH9c2: 0.21 +/- 0.04; control: 0.15 +/- 0.03; P = 0.04) and ejection fraction (AdCMVhBcl-2/mH9c2: 47.0 +/- 6.2; mH9c2: 48.7 +/- 6.1; control: 34.3 +/- 6.0; P = 0.02) compared with controls. Importantly, no malignant cells were found in postmortem histology. Conclusion-Transduction of mH9c2 cardiomyoblasts with AdCMVhBcl-2 increased graft survival in ischemic rat myocardium without causing malignancies. Both AdCMVhBcl-2/mH9c2 and mH9c2 grafts improved LV function.