High-mobility group box chromosomal protein-1 deletion alleviates osteoporosis in OVX rat model via suppressing the osteoclastogenesis and inflammation

Abstract

Abstract Background Osteoporosis is a skeletal metabolic disease that constitutes a great threaten to human health. However, there is currently no gold standard for its treatment. High-mobility group box chromosomal protein-1 (HMGB-1) has been reported to play an important role in various orthopedic diseases. Till now, its role in osteoporosis remains elusive. Methods Rats underwent ovariectomy (OVX) were used to construct a postmenopausal model of osteoporosis. Then, rats were divided into sham groups without OVX surgery, OVX model group, HMGB-1 knockdown (HMGB-1 KD) OVX model groups. The expression of HMGB1 was evaluated by qRT-PCR and western blotting. Subsequently, the changes of trabeculae were evaluated by micro-computed tomography (CT) assay. Skeletal necrosis and metabolism were further analyzed by hematoxylin–eosin (HE) staining, Alcian blue staining and Masson’s trichrome staining. The contents of serum alkaline phosphatase (ALP) and osteocalcin were detected by ELISA assay. Expression of osteoclast-associated receptor (OSCAR) and tartrate-resistant acid phosphatase (TRAP) were determined to investigate the effects of HMGB-1 loss on osteoclastogenesis. Results Single HMGB-1 deletion exerted no significant effect on rat trabeculae, serum ALP and osteocalcin. Noticeably, HMGB1 knockdown dramatically ameliorated OVX-induced changes in above indexes. Trabeculae structures of OVX rats were sparse with disorder arrangement, which were greatly recovered after HMGB-1 deletion. Enhanced osteoclastogenesis was observed in OVX rats by increasing number of TRAP + cells and expression of TRAP and OSCAR, and loss of HMGB1 ameliorated osteoclastogenesis in OVA rats. Moreover, HMGB-1 deletion antagonized OVX-evoked downregulation of osteoblast activity markers osterix (OSX), collagen type I alpha 1(COL1A1) and distal-less homeobox 2 (DLX2) protein. Furthermore, loss of HMGB-1 attenuated fluctuation of inflammatory factors in OVX rats. Additionally, HMGB-1 deficiency inhibited OVX-evoked activation of the Toll-like receptor (TLR) 4/NF-κB signaling pathway. Moreover, reactivating the TLR4 signaling further aggravated OVX-induced osteoporosis, which was reversed by HMGB1 knockdown. Conclusion HMGB-1 deletion alleviated OVX-triggered osteoporosis by suppressing osteoclastogenesis and inflammatory disorder via the inhibition of the TLR4 signaling. Therefore, HMGB-1 may be a promising therapeutic target for osteoporosis.