Figure 1. Individual human muscle cells express muscle stem cell markers including Pax7, c-Met and α7 integrin in vivo.

Human fetal (21 week) skeletal muscle (A-D) and adult skeletal muscle (E) were analyzed for expression of skeletal muscle and muscle stem cell markers. (A) Co-immunostaining for Pax7 and philloidin show a Pax7⁺ cell (arrow) located adjacent to individual muscle fibers. (B) Co-immunostaining for Pax7 and c-Met shows an individual cell (arrow) positive for both. Inserts in top right corner show a magnified image of the cell indicated by the arrow. (C) Immunostaining shows that α7 integrin expression is present both at the sarcolemma of fetal myofibers and in individual, cMet⁺ muscle cells (arrow). (D) Co-immunostaining for desmin and CXCR4 shows an individual cell within a muscle bundle co-expressing both (arrow). Inserts in top right corner show a magnified image of the cell indicated by the arrow. (E) Immunostaining of adult human myofibers shows an individual cMet⁺ muscle cell (arrow) located outside myofibers labeled with antibodies to laminin α2 chain. Scale Bar = 20μM