Markers of proliferation and of differentiating cardiac cells. (A-C) Immunophenotypic characterization of cells of endothelial lineage demonstrated in treated animals versus control animals (A), diffuse increase in capillaries (B) > 100 micrometer diameter or (C) of 12 to 100 micrometers; (D-F) double immunostaining showed that cycling Ki67⁺ cells expressed FVIII (Ki67 appeared in brown and was revealed by DAB-peroxidase reaction and FVIII appeared in red and was revealed by Fastred-alkaline phosphatase reaction) (F), most of endothelial lineage cells did not express Ki67 (E), control animals (D). (G-I) In the healthy myocardium, cardiac myocytes are characterized by the organization of the contractile proteins into striated myofibrils, resulting from repeating units arranged in series, the sarcomeres (G). Myosin was expressed in some sections of the infarcted area, but a disorganization of cardiac sarcomeres was observed in treated animals (H) as well as in control animals (I). Original magnifications: A-F, × 40; G-I, × 60.