Roles of SATB2 in site-specific stemness, autophagy and senescence of bone marrow mesenchymal stem cells. 
Craniofacial bone marrow mesenchymal stem cells (BMSCs) display some site-specific properties that differ from those of BMSCs derived from the trunk and appendicular skeleton, but the characteristics of craniofacial BMSCs and the mechanisms that underlie their properties are not completely understood.  Previous studies indicated that special AT-rich binding protein 2 (SATB2) may be a potential regulator of craniofacial skeletal patterning and site-specific osteogenic capacity.  Here, we investigated the stemness, autophagy, and anti-aging capacity of mandible-derived BMSCs (M-BMSCs) and tibia-derived BMSCs (T-BMSCs) and explored the role of SATB2 in regulating these properties.  M-BMSCs not only possessed stronger expression of SATB2 and stemness markers (pluripotency genes, such as Nanog, OCT-4, Sox2, and Nestin) but also exhibited stronger autophagy and anti-aging capacities under normal or hypoxia/serum deprivation conditions compared to T-BMSCs.  Exogenous expression of SATB2 in T-BMSCs significantly enhanced the expression of pluripotency genes as well as autophagy and anti-aging capacity.  Moreover, SATB2 markedly enhanced osteogenic differentiation of BMSCs in vitro, and promoted bone defect regeneration and the survival of BMSCs that were transplanted into mandibles with critical size defects.  Mechanistically, SATB2 upregulates pluripotency genes and autophagy-related genes, which in turn activate the mechanistic target of rapamycin signaling pathway.  Collectively, our results provide novel evidence that site-specific BMSCs have distinct biological properties and suggest that SATB2 plays a potential role in regulating the stemness, autophagy, and anti-aging properties of craniofacial BMSCs.  The application of SATB2 to manipulate stem cells for the reconstruction of bone defects might represent a new approach.