Induction of bone marrow-derived cells myogenic identity by their interactions with the satellite cell niche

BACKGROUND: Skeletal muscle regeneration is possible thanks to unipotent stem cells, which are satellite cells connected to the myofibers. Populations of stem cells other than muscle-specific satellite cells are considered as sources of cells able to support skeletal muscle reconstruction. Among these are bone marrow-derived mesenchymal stem cells (BM-MSCs), which are multipotent, self-renewing stem cells present in the bone marrow stroma. Available data documenting the ability of BM-MSCs to undergo myogenic differentiation are not definitive. In the current work, we aimed to check if the satellite cell niche could impact the ability of bone marrow-derived cells to follow a myogenic program. METHODS: We established a new in-vitro method for the coculture of bone marrow-derived cells (BMCs) that express CXCR4 (CXCR4(+)BMCs; the stromal-derived factor-1 (Sdf-1) receptor) with myofibers. Using various tests, we analyzed the myogenic identity of BMCs and their ability to fuse with myoblasts in vitro and in vivo. RESULTS: We showed that Sdf-1 treatment increased the number of CXCR4(+)BMCs able to bind the myofiber and occupy the satellite cell niche. Moreover, interaction with myofibers induced the expression of myogenic regulatory factors (MRFs) in CXCR4(+)BMCs. CXCR4(+)BMCs, pretreated by the coculture with myofibers and Sdf-1, participated in myotube formation in vitro and also myofiber reconstruction in vivo. We also showed that Sdf-1 overexpression in vivo (in injured and regenerating muscles) supported the participation of CXCR4(+)BMCs in new myofiber formation. CONCLUSION: We showed that CXCR4(+)BMC interaction with myofibers (that is, within the satellite cell niche) induced CXCR4(+)BMC myogenic commitment. CXCR4(+)BMCs, pretreated using such a method of culture, were able to participate in skeletal muscle regeneration.