| Cell transplantation has emerged as a promising approach for improving the failing heart in the past decade. Many kinds of cells have been investigated as donors for transplantation in myocardium, including cardiac muscle cells, smooth muscle cells, embryonic stem cells, bone marrow mesenchymal stem cells (MSCs), skeletal myoblast cells, liver stem cells and so on. MSCs are the most promising candidate and many researchers prefer to MSCs both in basical research and clinical application. Until now, cell transplantation research has focused on improving the function of the regionally impaired myocardium, such as after a myocardial infarction. Little is known about the effect of cell transplantation on the contractile function of globally dysfunctional hearts, especially in dilated cardiomyopathy. In this study, cultured MSCs were transplanted into the left ventricular free wall of adult cardiomyopathic rabbits to see its differtation and effects on impaired heart function.Objectives: To investigate the factors that govern MSCs differentiate into cardiomyocytes in vitro and to investigate the effects of MSCs on heart function after transplanted into dilated cardiomyopathy.Methods: Firstly, rabbit MSCs were aspirated from tibia and the cells were incubated with 10μmol/L 5-azacytiding on the third day for 24 hours. At the end of fourteenth day, cardiac specific protein Troponin T and protein a-actin was detected through immunocytochemistry; Secondly, Rabbits were randomized into 4 groups: (1) DCM cell transplantation group (n=12); (2) DCM control group (n=12); (3) DCM sham-operated rabbits (n=12); (4) normal rabbits (n=10). Doxorubicin was applied to create rabbit DCM model. Animals for cell transplantation were received intramyocardial injection of autologous MSCs in the left ventricular free wall. Echocardiography and hemodynamic studies were performed to evaluate cardiac structure and function following 28 days of transplantation. Histologic sections of the transplanted sites were examined under fluorescent microscope to identify the transplanted MSCs and to investigate its differentitation. Some other heart sections were fixed in 10% methanol, embedded in paraffin, and cut into 5-μm-thick slices. The slices were stained with hematoxylin and eosin for pathological examination.Results: ①During the primary passage, after attaching to the culture dish MSCs were spindle-shaped, resembling fibroblasts in morphology, and grew in the forms of colonies dispersely. ② Morphology of cells induced by 5-aza was similar to that ofcardiomyocytes. In addition, the cells stained positively for cardiac Troponin T and protein a-actin, the positive rate was 34.1% and 35.8% respectively. ?Compared to the normal rabbits, Doxorubicin resulted in significant dilatation of the LV and impaired LV function; The pathological examination demonstrated that severe focal myocardial necrosis was present in the all DCM groups; ? 4 weeks after the cells transplantation, the transplanted cells were found in the trasplantation group and some appeared to differentiate into cardiomyocytes and vascular endothelial cells, which was not founded in the other groups. Comparison among all DCM groups showed that impaired LV functions were improved by autologous MSCs transplantation, as revealed by decreased LVEDP and increased EF, LVSP and dp/dtmax (all P<0.05).Conclusions: Rabbit MSCs can be induced into cardiomyocyte by 5-aza, which provide a good source for autologous cell transplantation. MSCs appeared to differentiate into cardiomyocytes and vascular endothelial cells after autologous transplantation into DCM and improve impaired cardiac function.
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