Cells expressing the panleukocyte marker CD45 are mainly found in the bone marrow (BM) but are also present in skeletal muscle, where they contribute to muscle repair. How are these two populations of CD45+ cells related and what regulates the migration of BM-derived CD45+ cells to skeletal muscle? On , Mickie Bhatia and colleagues report that hepatocyte growth factor (Met) signalling controls the migration of a unique subset of BM-derived CD45+ cells to skeletal muscle. In in-vivo transplantation assays, the authors show that BM-derived CD45+ cells can fully replace the skeletal-muscle CD45+ compartment of sublethally irradiated mice. Then, using transwell migration assays, they discover that a subset of BM-derived cells migrates exclusively to mature skeletal muscle cells; this migration is dependent on Met but not on stromal-derived factor 1, which is required for the migration of CD45+ cells to stroma. This new knowledge about distinct pools of BM-derived CD45+ cells and the factors that govern their migration could prove useful to those designing treatments for muscle degeneration and damage.
