MiR-20b promotes osteocyte apoptosis in rats with steroid-induced necrosis of the femoral head through BMP signaling pathway

OBJECTIVE: To study the effect of micro-ribonucleic acid (miR)-20b on osteocyte apoptosis in rats with steroid-induced necrosis of the femoral head (SNFH) and to analyze whether the bone morphogenetic protein (BMP) signaling pathway is involved in the regulation. MATERIALS AND METHODS: A total of 36 Sprague-Dawley rats were randomly divided into control group (n=12), model group (n=12) and intervention group (n=12). The rat model of SNFH was established in the model and intervention groups, while the rats in the intervention group were intraperitoneally injected with the bone morphogenetic protein (BMP) signaling pathway inhibitor. After modeling, the femoral head in each group was taken, and the morphology of osteocytes was observed via hematoxylin-eosin (HE) staining. The apoptosis level of femoral head cells was detected via terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining. The miR-20b expression level in femoral head cells in each group was detected via quantitative Polymerase Chain Reaction (qPCR). The expression levels of inflammatory factors in femoral head cells in each group were detected via enzyme-linked immunosorbent assay (ELISA). The expression levels of apoptotic proteins and BMP signaling pathway-related proteins in femoral head cells in each group were detected via Western blotting. RESULTS: Compared with those in the control group, the bone trabecula was sparse, the number of osteocytes significantly declined and the number of apoptotic osteocytes markedly increased (p<0.01); the expression level of miR-20b in bone tissues remarkably increased (p<0.01), the content of interleukin-1 beta (IL-1 beta), IL-6 and tumor necrosis factor-alpha (TNF-alpha) in bone tissues increased (p<0.01), the content of IL-10 significantly declined (p<0.01), the expression level of cleaved caspase-3 protein in bone tissues markedly increased (p<0.01), the Bcl-2/Bax expression level evidently declined (p<0.01) and the expression levels of anaplastic lympho-ma kinase3 (ALK3), GATA4 and NKX2.5 in bone tissues remarkably increased (p<0.01) in the model group. Compared with those in the model group, the necrosis of bone tissues significantly decreased, the apoptosis level of osteocytes remarkably declined (p<0.01), the content of IL-1 beta, IL-6 and TNF-alpha in bone tissues markedly decreased (p<0.01), the content of IL-10 increased (p<0.01), the expression level of cleaved caspase-3 protein in bone tissues significantly declined (p<0.01), the B-cell lymphoma 2/BCL2-Associated X (Bcl-2/Bax) expression level markedly increased (p<0.01) and the expression levels of ALK3, GATA4 and NKX2.5 in bone tissues significantly decreased (p<0.01) in the intervention group. CONCLUSIONS: SNFH will significantly increase the expression level of miR-20b in bone tissues, thereby activating the BMP signaling pathway, promoting the release of inflammatory factors and leading to osteocyte apoptosis. Inhibiting the BMP signaling pathway can effectively reduce the osteocyte apoptosis level.