Histological analysis 12 weeks after therapy. A: The GFP signal of transplanted cells was determined by PCR (A). B and C: CD31-positive capillaries in the peri-infarct zone. C, Histogram of data shown in D. All values represent mean ± SEM. * p< 0.05 vs. PBS group. The capillary density in the MSCs-MK group was significantly greater than that of the PBS group. GFP, Green fluorescent protein; MSCs-MK, Mesenchymal stem cells-midkine.