β-gal/LacZ positive cells can proliferate and contribute to myotube formation in vitro, and blood vessel formation in vivo.

BrdU incorporation assay showed that (β-gal/LacZ)+ cells can proliferate (A–C). A myogenic differentiation assay, which deprives the cultures of serum, showed that (β-gal/LacZ)+ cells, in both cell populations without purification [ around 6% of cells were (β-gal/LacZ)+] (D) and after purification with Fluorescence-activated cell sorting (E), can participate in myotube formation (F). In vivo, ten days after laceration-injury of GM muscles that were transplanted with Cre-cells and Lox-cells for 3 weeks, some (β-gal/LacZ)+ signal was also found to co-localize with CD31+ signal in the blood vasculature (G–L). Images G–I or J–L are of the same location in tissue, and result of β-gal/LacZ staining and immunofluorescent CD31/Utrophin staining are shown here (G–I); arrowheads indicate β-gal+/CD31+ cells, and arrows indicate β-gal+ myofibers (G–I). Fluorescent co-staining of β-gal and Pax7 are also shown (J–L); arrowheads indicate β-gal+/Pax7+ cells, and arrows indicate CD31+ cells (J–L).