Bone marrow stromal cells (mesenchymal stem cells) retain differentiation capacity to multiple connective tissue lineages including osteoblasts, chondrocytes, skeletal muscle, smooth muscle cells, cardiac muscle cells, adipocytes, and fibroblasts. The extensive proliferative capacity of bone marrow stromal cells in vitro suggests that these cells could be a valuable source of myoblast transplantation in the therapy of Duchenne Muscular Dystrophy (DMD), as well as other genetic and acquired disorders of the musculoskeletal system. Phenotypic characterization of human bone marrow stromal cells, specifically, the Strol+ subset reveals heterogeneity of clonogenic expansion capacity and specifically osteoblast differentiation capacity. We have also demonstrated that single Strol+ human bone marrow stromal cells cultured in a novel single cell combinatorial cell culture system, with sequential imaging in real time are heterogeneous with respect to differentiation to alkaline phosphatase-positive (AlkP+) osteoblasts and clonagenic capacity declines with age of the donor. We have demonstrated myofibroblast phenotype of clonal bone marrow stromal cell lines from human and murine culture systems. We will now elucidate the common and unique myogenic properties of murine bone marrow stromal cells compared to muscle-derived stem cells from skeletal muscle. The present development and feasibility project is designed to generate preliminary data for each of three specific aims for an eventual NIH R01 grant application. The first specific aim tests the hypothesis that the surface phenotype of muscle-derived stem cells from adult mouse skeletal muscle is distinguishable from bone marrow stromal cells by different biological parameters, including movement along extracellular matrix in vitro. and differential expression on stromal cells of Scal, c-kit, and other markers common to hematopoietic stem cells. The second specific aim tests he hypothesis that skeletal muscle cell differentiation capacity of murine bone marrow stromal cells can be induced in single cells and maintained during multiple cell divisions using a defined medium and/or transgene expression. Murine isolates of marrow stromal cells and muscle-derived stem cells will be compared. The third specific aim tests the ability of bone marrow stromal cells which display myogenic differentiation capacity in vitro and in vivo can deliver dystrophin in cell therapy to improve muscle strength in MDX mice. These data should lead to use of bone marrow stromal cells as a valuable resource in cellular therapies for genetic and acquired diseases of skeletal muscle.