Bu-Shen-Tong-Luo decoction prevents bone loss via inhibition of bone resorption and enhancement of angiogenesis in ovariectomy-induced osteoporosis of rats

Ethnopharmacological relevance Gathering three ancient formulas, traditional Chinese medicine Bu-Shen-Tong-Luo decoction (BSTLD) has been used to treat postmenopausal osteoporosis (PMO) at the Jiangsu Province Hospital of Chinese Medicine for decades. However, the effect of BSTLD on angiogenesis and bone resorption as well as its possible mechanism are still unknown. Aim of the study This study was aimed to evaluate the preventive effect of BSTLD on ovariectomy-induced bone loss and vasculature disorder, and to investigate the possible bone protection mechanism of BSTLD in inhibiting bone resorption by enhancing angiogenesis signaling in ovariectomy-induced osteoporosis of rats. Materials and methods The animal experiment was divided into five groups. Rats underwent either sham surgery with intact ovaries (SHAM, n = 10) or bilateral ovariectomy (OVX, n = 40). OVX rats were randomly divided into four groups and gavaged by water (vehicle, 12 mL/kg, n = 10), BSTLD (6 g/kg, n = 10), BSTLD (12 g/kg, n = 10) and 17β-estradiol (E2, 100 μg/kg, n = 10) daily for 12 weeks, respectively. The bone loss and microstructure of the distal femur were observed using micro-computed tomography (μCT). The biomechanical parameters of the femur were detected using three-point bending tests. The distribution of osteoclasts and endothelial cells were analyzed by immunohistochemistry. The mRNA and protein levels of angiogenesis-related hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF), as well as osteoclast activation-related signaling calcitonin receptor (CALCR), cathepsin K (CTSK), receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG), and β-catenin were assayed by RT-PCR or Western blot. Results BSTLD protected trabecular bone mass density and trabecular bone microstructure from ovariectomy-induced osteoporosis in rats. BSTLD significantly reduced mRNA and protein levels of calcitonin receptor and CTSK in femoral metaphysis and inhibited bone resorption in ovariectomized rats. Furthermore, BSTLD stabilized HIF-1α activity and subsequently increased VEGF expression to enhance angiogenesis and modulated RANKL/OPG signaling in this animal model. Conclusions These results demonstrated that BSTLD reduced osteoclasts activation and bone resorption in ovariectomy-induced osteoporosis. Bone protection by BSTLD may be associated with its stimulation of HIF-1α/VEGF angiogenesis signaling and suppression of RANKL/OPG ratio. This study may provide evidence that BSTLD treats postmenopausal osteoporosis, especially with micro-circulation complication.