The present inventors revealed the following for the first time in the world: 1) a large amount of bone marrow-derived cells are mobilized to grafted skin； 2) the mobilized bone marrow-derived cells are differentiated into any of dermal fibroblasts, adipocytes, muscle cells, vascular endothelial cells, and epidermal keratinocytes in the grafted skin, and the mobilized bone marrow-derived cells include bone marrow-derived mesenchymal stem cells； 3) the factors which mobilize bone marrow-derived mesenchymal stem cells from peripheral blood to the grafted skin are HMGB1, HMGB2, and HMGB3 released from the necrosed tissue of recipient skin； 4) purified HMGB1, HMGB2, and HMGB3 promote the migration of mesenchymal stem cells isolated and cultured from bone marrow； 5) activators containing HMGB1 which allows the migration of bone marrow mesenchymal stem cells can be conveniently purified from several organ extracts including skin, brain, and heart； 6) activators which allow the migration of bone marrow mesenchymal stem cells can be conveniently extracted from cultured cells； and 7) a heparin-column purified fraction of skin extract mobilizes a large amount of bone marrow-derived cells in case of brain injury.
