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; and7) a 
heparin-column purified fraction of skin extract mobilizes a large amount of bone marrow-derived cells in case of brain injury.