Inhibition of Lipopolysaccharide-Induced Inflammatory Bone Loss by Saikosaponin D is Associated with Regulation of the RANKL/RANK Pathway.

Abstract

BackgroundOsteolytic diseases such as osteoporosis are featured with accelerated osteoclast differentiation and strong bone resorption. Considering the complications and other limitations of current drug treatments, it is necessary to develop a safer and more reliable drug to deal with osteoclast-related diseases. Saikosaponin D (SSD) is the active extract of Bupleurum, which has anti-inflammation, anti-tumor and liver protection functions. However, the role of SSD in regulating the differentiation and function of osteoclasts is not clear.PurposeTo explore whether SSD could prevent osteoclast differentiation and bone resorption induced by M-CSF and RANKL, and further evaluate the potential therapeutic properties of SSD in LPS-induced inflammatory bone loss mouse models.MethodsBMMs were cultured in complete medium stimulated by RANKL with different concentrations of SSD. TRAP staining, bone resorption determination, qRT-PCR, immunofluorescence and Western blotting were performed. A mouse model of LPS-induced calvarial bone loss was established and treated with different doses of SSD. The excised calvaria bones were used for TRAP staining, micro-CT scan and histological analysis.ResultsSSD inhibited the formation and bone resorption of osteoclasts induced by RANKL in vitro. SSD suppressed LPS-induced inflammatory bone loss in vivo.ConclusionSSD inhibited osteoclastogenesis and LPS-induced osteolysis in mice both which served as a new potential agent for the treatment of osteoclast-related conditions.