Characterization and differentiation of the derived myogenic mesenchymal cells.

<p>(A) Morphology of the derived myogenic mesenchymal progenitors 2 days (day 7+14+2) and 4 weeks (day 7+14+28) after replating. Homogeneous spindle-shaped fibroblastic cells were observed. (B) Surface marker analysis of myogenic mesenchymal progenitors. Representative data from KhES1 differentiation are shown. Note that CD56 in addition to mesenchymal markers CD73, CD105, CD166, and CD29 was exclusively expressed. (C) Changes in the expression of myogenic markers were analyzed by immunofluorescence. The number of Cy3-positive nuclei was divided by the total number of nuclei stained by DAPI. The expression of myogenic progenitor markers decreased after exposure to serum-free medium, whereas the number of MYOG-positive cells substantially increased after serum deprivation. (D) Changes in the number of MYOG-positive nuclei were observed up to 3 weeks after serum deprivation. hES/iPS-derived myofibers tended to detach from tissue culture plates during long-term culture in serum-free medium. (E) Serum deprivation increased the number of skeletal myosin-positive fibers and MYOG-positive nuclei for more than 2 weeks. KhES1 was used in this figure. (F) Multinucleated myofibers denoted by MYOG myogenin-positive nuclei aligned in skeletal myosin-positive fibers. (G) Morphology of mature myofibers, which were stained with skeletal myosin, MYOG, and dystrophin, from both KhES1 and 253G4 cells. Skeletal myosin was visualized with fluorescein isothiocyanate (FITC) (Green), myogenin was visualized with Cy3 (red), and nuclei were counterstained with DAPI (blue). Scale bars = (C, E) 100 µm, (D) 50 µm.