Mesenchymal stem cells participate in angiogenesis and improve heart function in rat model of myocardial ischemia with reperfusion.

OBJECTIVE

The effect of transplanted mesenchymal stem cells (MSCs) on the left ventricular (LV) function and morphology in a rat myocardial infarct heart with reperfusion model were analyzed.

METHODS

One week after 60 min of myocardial ischemia and reperfusion by left anterior descending artery (LAD) occlusion, 1.0x10(7) 6-diamidino-2-phenylindole (DAPI)-labeled MSCs were injected into the infarcted myocardium and compared with controls, and sham-operated rats, in which a cell-free serum medium was injected into the infarcted region or the myocardial wall, respectively. Measurement of vascular endothelial growth factor (VEGF) expression 1 week after MSC injection using Western blot analysis (n=5), and immunohistochemical staining using HE staining and fluorescent microscopy of the DAPI-positive regions from MSC implantation, cTnT immunostaining of potential myocardial-like cells, and SM-actin and CD31 immunostaining demonstrating neovascular transformation of implanted MSCs 1 week, 2 weeks and 4 weeks after transplantation (n=5). Hemodynamic measurements were performed after 4 weeks in vivo. Subsequently, hearts were quickly removed and cut for histological analysis using HE staining with measurement of the infarcted LV-area, the LV-wall thickness within the scar segment compared to non-infarcted scar segments, and the capillary density counting capillary vessels with 400x light microscopy (n=10).

RESULTS

Measurement of hemodynamics 4 weeks after transplantation in vivo showed LV function to be significantly greater in MSCs than in the control group. Semi-quantitative histomorphometric examinations showed a significantly lower infract size, a greater LV-wall thickness, and a lower Hochman-Choo expansion index in the MSC-treated group compared to the control group. Immunofluorescence demonstrated that transplanted MSCs were positive for cTnT, suggesting that a small number of transplanted MSCs can differentiate into cardiomyocytes. Other MSCs were positive for CD31 and SM-actin. The transplanted MSCs in MI area had significantly higher expression rates of cTnT, CD31 and SM-actin 2 weeks after transplantation. HE staining showed marked augmentation of neovascularization in the MSC group. Semi-quantitative analysis demonstrated that capillary density was significantly higher in the MSC group than in the control group.

CONCLUSION

Implanted MSCs could improve cardiac structure and function through the combined effect of myogenesis and angiogenesis.