DHEA promotes osteoblast differentiation by regulating the expression of osteoblast-related genes and Foxp3(+) regulatory T cells.

Several studies have reported that dehydroepiandrosterone (DHEA) promotes osteoblast proliferation and inhibits osteoblast apoptosis and that DHEA inhibits osteoclast maturation. However, whether DHEA regulates osteoblast differentiation remains unclear. The present study first examined the effect of DHEA on bone morphology in vivo. DHEA was found to increase bone volume (BV), bone mineral density (BMD), and the number of trabeculae in bone (Th.N) and it was found to decrease trabecular spacing in bone (Th.sp) in ovariectomized (OVX) mice. Next, the effect of DHEA on osteoblast differentiation was examined in vitro and osteoblastogenesis-related marker genes, such as Runx2, Osterix, Collagen1, and Osteocalcin, were also detected. DHEA increased osteoblast production in mesenchymal stem cells (MSCs) cultured in osteoblastogenic medium, and DHEA increased the expression of Runx2 and osterix, thereby increasing the expression of osteocalcin and collagen1. Immune cells and bone interact, so changes in immune cells were detected in vivo. DHEA increased the number of Foxp3(+) regulatory T cells (Tregs) in the spleen but it did not affect CTLA-4 or IL-10. When MSCs were treated with DHEA in the presence of Tregs, alkaline phosphatase (ALP) activity increased. Osteoblasts and adipocytes are both generated by MSCs. If osteoblast differentiation increases, adipocyte differentiation will decrease, and the reverse also holds true. DHEA was found to increase the number of adipocytes in osteoblastogenic medium but it had no effect on the number of adipocytes and expression of PPARγ mRNA in adipogenic medium. This finding suggests that osteoblasts may be involved in adipocyte production. In conclusion, the current results suggest that DHEA can improve postmenopausal osteoporosis (PMO) by up-regulating osteoblast differentiation via the up-regulation of the expression of osteoblastogenesis-related genes and via an increase in Foxp3(+) Tregs.