Glucocorticoid induces osteonecrosis of the femoral head in rats through GSK3β-mediated osteoblast apoptosis

Objective: One of the important causes of glucocorticoids (GCs)-induced osteonecrosis of the femoral head (ONFH) is osteoblast apoptosis. Glycogen synthase kinase 3 beta (GSK3 beta) has been reported to be related to dexamethasone (Dex)-induced osteoblast apoptosis. This study aimed to determine whether GSK3 beta plays role in GC-induced ONFH and investigate the underlying mechanism. Methods: 18 male Sprague-Dawley rats were divided into 3 groups. Rats from ONFH group underwent lipopolysaccharide and methylprednisolone injection. Lithium chloride (LiCl, a GSK3 beta inhibitor) group were fed with LiCl solution. The control group were untreated. Osteonecrosis, apoptosis and bone loss were evaluated by HE staining, TUNEL staining and micro-CT respectively. Protein expressions were examined by western blotting. In addition, primary osteoblast cells were transfected by GSK3 beta-siRNA and related signaling pathway and proteins were examined. Results: ONFH group showed a relative high percentage of empty lacunae and apoptotic cells, whilst LiCI treatment markedly decreased the percentage. LiCI treatment decreased GC-induced bone loss. Immunoblot analysis for GSK3 beta showed decreased level of Ser9-phosphorylated GSK3 beta in ONFH group compared with control group. Knockdown of GSK3 beta by siRNA in primary osteoblast cells attenuated DEX-induced apoptosis and loss of mitochondrial transmembrane potential (Delta psi m). GSK3 beta knockdown also reversed the release of cytochrome C (Cyt C) from mitochondria to the cytosol. GSK3 beta decreased apoptosis-related protein expression both in vitro and in vivo. Conclusion: Our findings suggest that GC induces ONFH in rats through GSK3 beta-mediated osteoblast apoptosis, with involvement of mitochondrial apoptotic pathway. (C) 2019 Elsevier Inc. All rights reserved.