Cells isolated from adult human skeletal muscle capable of differentiating into multiple mesodermal phenotypes

Wound healing is the response of tissue to injury that results in scar formation. Tissue regeneration would be a more ideal response. Previously, we have isolated a population of cells from avian, rodent, and rabbit skeletal muscle capable of differentiating into multiple mesodermal phenotypes. The present experiments were designed to determine whether a similar population of cells exist in human skeletal muscle. Separate cell preparations from skeletal muscle on an amputated leg of a 75-year-old female and the pectoralis muscle of a 27-year-old male were enzymatically dissociated and cultured to confluence in Eagle's minimal essential medium with 10 per cent preselected horse serum, then trypsinized, filtered, and slowly frozen in 7.5 per cent dimethylsulfoxide to -80 degrees C. The cells were thawed and plated with the same media plus dexamethasone (a nonspecific differentiation agent) at 10(-10) - 10(-6) M concentrations for up to 6 weeks. Immunological and histochemical staining assays were performed. Phenotypes observed included stem cells with typical stellate morphology (control), skeletal myotubes (anti-myosin), smooth muscle (anti-a-actin), bone (von Kossa stain), cartilage (Alcec blue), and fat (Sudan black B). These experiments establish the existence of a population of mesenchymal stem cells in human skeletal muscle capable of differentiating into multiple mesodermal phenotypes. The possibility exists of manipulating the mesenchymal stem cells to achieve appropriate regeneration of mesenchymal tissues in the injured patient.