TGF-β3 Restrains Osteoclastic Resorption Through Autophagy.

While TGF-β3 promoted defect healing in a primate baboon skull defect model and patients, it remains unclear whether TGF-β3 affects the formation of osteoclasts and bone resorption between osteogenesis and osteolysis. Analysis of the full transcriptome of hPDLSCs (human periodontal ligament stem cells) revealed that the expression of RANKL was significantly up-regulated after TGF-β3 treatment during osteogenesis, which suggests its involvement in clock-controlled autophagy in bone metabolism. TRAP staining and bone resorption lacunae were used to assess the osteoclasts formed from RANKL-induced differentiated BMMs. During osteoclast differentiation, the characteristics of autophagy regulated by TGF-β3 were observed in BMMs through MDC staining, transmission electron microscopy, and LC3 immunofluorescence. The expression of related genes and proteins were detected on the sixth day in mCherry-EGFP-LC3B lentivirus-transfected BMMs using RT-qPCR and WB. Finally, a trans-well co-culture system was used to evaluate the effects of osteogenic differentiated hPDLSCs treated with TGF-β3 on the osteoclastic differentiation of BMMs. The results showed 10 ng/mL of TGF-β3 significantly suppressed osteoclastic differentiation and bone resorption in BMMs (p < 0.05 vs. RANKL). In particular, TGF-β3 augments the expression of LC3-II to stimulate autophagy, consequently restraining osteoclastic resorption. These findings provide a molecular basis and are beneficial to illustrate the potential druggability of TGF-β3 in osteoporotic diseases.