Mesenchymal stem cells (MSCs) have multi-differentiation potency, and enhance wound healing in various kinds of disease. Recently MSC not only differentiate into tissue-forming cells, but also secrete various kinds of cytokines and chemokines that are anti-apoptotic, immunomodulatory, angiogenic, and the cell-mobilizing to influence extracellular environment. In addition, we show that MSC has a novel intercellular communication mechanism. It hopes to suggest ways to make safer and reliable usage of MSC in bone regeneration.