Fig. 4.

Myotube formation by α7-positive human myogenic cells. Human fetal muscle tissue were dissociated and sorted for high α7 integrin expression. The unsorted population and the α7-positive population were then allowed to differentiate into myotubes by culturing in low serum-differentiation medium. High α7-integrin-expressing myoblasts (Tongue, 19 wk) show a high frequency of differentiating myotubes (B), whereas the unsorted α7-expressing cells did not (A). Bar, 50 μm. (A2) and (B2) are enlargements. Bar, 25 μm. Note presence of cell fusion and multinucleation in (B1, 2). α7-positive (D) and α7-negative (C) fetal muscle cells (tongue, 20 wk) were cultured under differentiation conditions as above, and processed for staining with anti-desmin antibody. Bar, 25 μm. Strong desmin staining was detected in the α7-positive population. Myotube formation by α7-positive (F) and α7-negative (E) myoblasts at ectopic sites in nude mice. Fetal muscle cells (Tongue, 22 wk) were injected subcutaneously into the flank of NIH nude mice as described in Materials and Methods. The resulting tissue was harvested, sectioned and evaluated by hematoxylin and eosin staining. Myotubes were formed by α7-positive cells (arrows), while no myotubes were detected with α7-negative cells. Bar, 50 μm.