TNF-α suppresses osteogenic differentiation of MSCs by accelerating P2Y2 receptor in estrogen-deficiency induced osteoporosis

Tumor Necrosis Factor-α (TNF-α)-inhibited osteogenic differentiation of mesenchymal stem cells (MSCs) contributes to impaired bone formation, which plays a central role in the pathogenesis of postmenopausal osteoporosis. However, the exact mechanisms of TNF-α-inhibited osteoblast differentiation have not been fully elucidated. Multiple P2 purinoceptor subtypes are expressed in several species of osteoblasts and are confirmed to regulate bone metabolism. The purpose of this study is to investigate whether P2 purinoceptors are involved in TNF-α-inhibited osteoblast differentiation. This study shows TNF-α increased P2Y2 receptor expression in the differentiation of MSCs into osteoblasts in a noticeable manner. Overexpressing or silencing of the P2Y2 receptor either impaired or promoted osteogenic differentiation of MSCs significantly. Silencing of the P2Y2 receptor attenuated the inhibitory effects of TNF-α on osteoblastic differentiation of MSCs. In addition, silencing of the P2Y2 receptor evidently alleviated TNF-α-inhibited MSC proliferation. P2Y2 receptor expression was mechanistically upregulated by TNF-α mainly through extracellular regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling pathways. Overall, our results revealed a novel function of the P2Y2 receptor and suggested suppressing the P2Y2 receptor may be an effective strategy to promote bone formation in estrogen deficiency-induced osteoporosis.