Myocardial repair achieved by the intramyocardial implantation of adult cardiomyocytes in combination with bone marrow cells

Various cytokines produced by bone marrow cells can protect adult cardiomyocytes against apoptosis. Thus, we investigated the feasibility of implanting adult cardiomyocytes in combination with bone marrow cells for myocardial repair. Ventricular cardiomyocytes were isolated from adult rats and cocultured with bone marrow cells. Using a rat model of doxorubicin-induced cardiomyopathy, we injected 6 × 10⁵ adult cardiomyocytes, 3 × 10⁷ bone marrow cells, or both into damaged hearts, for myocardial repair. Coculture of the cardiomyocytes with the bone marrow cells enhanced the expression of integrin-β1D and focal adhesion kinase in cardiomyocytes, resulting in increased survival and decreased apoptosis of the cardiomyocytes after 7 days of culture. Compared with the baseline levels, cardiac function was preserved by the implantation of bone marrow cells alone and by the implantation of cardiomyocytes in combination with bone marrow cells, but it was decreased significantly 28 days after the implantation of cardiomyocytes alone. Furthermore, apoptosis of the host cardiomyocytes was decreased significantly after the implantation of bone marrow cells alone, or in combination with cardiomyocytes, compared with that after the implantation of cardiomyocytes alone (p < 0.01). Interestingly, the implantation of adult cardiomyocytes in combination with bone marrow cells resulted in a dramatic increase in the survival of donor cardiomyocytes, and induced the myogenic differentiation of donor bone marrow stem cells. Our findings indicate that cardiomyocytes and bone marrow cells can assist and compliment each other; thus, the implantation of adult cardiomyocytes in combination with bone marrow cells shows promise as a feasible new strategy for myocardial repair.