Myoblast sheets repaired the impaired myocardium, reduced fibrosis, and prevented remodeling in association with recruitment of hematopoietic stem cells through the release of stromal-derived factor 1 and other growth factors. Our experiment indicates a therapy for patients with severe heart failure.

Cardiomyocyte sheets integrated with the impaired myocardium and improved cardiac performance in a model of ischemic myocardium. Techniques using such tissue-engineered cell sheets are introducing the promising concept of tissue cardiomyoplasty to the field of regenerative medicine.

It is reported that ischemia-reperfusion induces apoptotic cell death in myocardium. It is also demonstrated that heat shock protein 70 (HSP70) enhances myocardial tolerance. Therefore, it is hypothesized that HSP70 may play a role in the attenuation of myocardial apoptosis. To elucidate this goal, HSP70-overexpressing and control-transfected rat hearts were prepared using gene transfection by intra-coronary infusion of the hemagglutinating virus of Japan-liposome. In vivo experiment Hearts of both groups were subjected to global ischemia, followed by reperfusion in situ. Shorter recovery time to spontaneous beating (HSP70-transfected vs. control-transfected; 46.7+/-4.6 vs. 67.5+/-7.0 s, p = 0.033) and lower serum CPK levels (415+/-27 vs. 533+/-36 IU, p = 0.027) were observed in the HSP70-transfected group. The HSP70-transfected group also showed a lower percentage of cardiac myocytes positively stained by nick end labeling after ischemia-reperfusion (17.5+/-4.9 vs. 40.0+/-5.1%, p = 0.010). In vitro experiment Cardiac myocytes isolated from the hearts of both groups (prepared separately from the in vivo experiment) were subjected to hypoxia-reoxygenation. Flow cytometry was used to identify the cells that showed sub-G1 DNA content as apoptotic cells. Apoptotic cells as a percentage of viable cells increased more in the control-transfected group after hypoxia-reoxygenation (13.0+/-0.77 vs. 21.9+/-1.18%, p<0.0001). In conclusion, we demonstrated that apoptosis after ischemia-reperfusion was decreased in the HSP70-overexpressing heart in vivo and in vitro, leading to the suggestion that HSP70 could be associated with the reduction in myocardial apoptosis.

Background — We hypothesized that transfection of the gene for human hepatocyte growth factor (hHGF) combined with cellular cardiomyoplasty might regenerate the impaired myocardium. Methods and Results — We used a ligation model of proximal left anterior descending coronary artery (LAD) of Lewis rats. Two weeks after LAD ligation, 3 different treatments were conducted: (1) neonatal rat cardiomyocytes group (10 6 cells, T group, n=11), (2) HVJ-liposomes bearing the hHGF gene group (H group, n=10), and (3) combined (T-H group, n=10). The injection site was the scar area of myocardial infarction. For control, culture medium was injected (C group, n=13). Echocardiography demonstrated that cardiac performance was significantly ameliorated in the T-H group 4 and 8 weeks after injection. Contrast echocardiography also showed a marked increase in myocardial perfusion in the T-H group but not in the other groups. In the T-H group, neovascularization and a marked reduction of fibrosis were observed histologically. In an immunohistochemical study, strong staining for β 1 -integrin, α-, and β-dystroglycan were found principally in the basement membrane of myocytes in the T-H group 8 weeks after transplantation, although there was weak immunoreactivity in the T group. Conclusions — hHGF gene transfection enhanced the cellular cardiomyoplasty possibly by stimulating angiogenesis, restoring the impaired ECM, and promoting the integration of the dissociated grafted myocytes. The combined effects might have lead to the improved cardiac performance. Thus, combined therapy may be a promising strategy for the treatment of heart failure caused by myocardial infarction.

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