Engraftment of wild-type and MyoD−/− myoblasts after myocardial injection into infarcted heart.

(A) These panels show MI induced by left coronary artery ligation. Wild-type and MyoD−/− myoblasts were directly injected into the peri-infarct regions of LV. After 1 week, X-gal staining of whole heart indicated that more MyoD−/− myoblasts engrafted than wild-type myoblasts (arrows). Arrowheads indicate left coronary artery ligation points. X-gal staining of cross sections indicated that more MyoD−/− myoblasts than wild-type myoblasts engrafted in both injured and uninjured areas of the heart. Arrows indicate engrafted lacZ+ wild-type and MyoD−/− myoblasts. Scale bars = 1 mm. (B) Engraftment of injected cells in the infarcted heart. More MyoD−/− myoblasts than wild-type myoblasts engraft in the infarcted heart 3 day to 4 weeks post-transplantation. Y-axis indicates the survival rates of engrafted cells after an injection of 1×106 wild-type or MyoD−/− myoblasts. (C) By day 3, anti-activated caspase-3 (Casp-3) and anti-phospho-histone H3 (p-His-H3) antibody staining demonstrated that lacZ+ wild-type and MyoD−/− myoblasts proliferate or undergo apoptotic cell death (n = 4). Nuclei were counter-stained with DAPI (blue). Scale bar = 50 µm. (D) Comparison of the relative numbers of lacZ+/activated caspase-3+ or lacZ+/phospho-histone H3+ cells for wild-type and MyoD−/− myoblasts 3 days after transplantation.