Abstract: BACKGROUND: Although aromatase inhibitors significantly improve the clinical benefit of patients with hormone receptor-positive breast cancer, its associated adverse event - osteoporosis seriously affects the quality of life of patients. Huangqi Bushen Huoxue Decoction can effectively prevent the occurrence of aromatase inhibitor-induced osteoporosis, but its mechanism of action is unclear.
OBJECTIVE: To investigate the effects of Huangqi Bushen Huoxue Decoction on osteoclast activity in a mouse model of osteoporosis induced by aromatase inhibitors and relevant mechanisms. 
METHODS: Sixty 8-week-old female C57BL/6J mice were randomly divided into sham operation group, model group, high-, medium- and low-dose Huangqi Bushen Huoxue Decoction, and positive control group, with 10 mice in each group. Bilateral ovaries were removed to establish postmenopausal animal models in all the groups except for the sham operation group. After 1 week of recovery, letrozole was injected subcutaneously to establish postmenopausal osteoporosis models via subcutaneous injection of letrozole (an aromatase inhibitor). The high-, medium- and low-dose Huangqi Bushen Huoxue Decoction groups were intragastrically given 19.24, 9.62 and 4.81 g/kg/d Huangqi Bushen Huoxue Decoction (once a day), respectively. The positive control group was given alendronate 5mg/kg once a week. After 3 months of administration, Micro-CT was used to detect tibial bone mineral density and bone microstructure. Hematoxylin-eosin staining and tartrate-resistant acid phosphatase staining of the femur were performed. Immunohistochemistry was used to detect the protein expression of receptor activator of nuclear factor-κB ligand and osteoprotectin in the femur. ELISA was used to detect the serum levels of carboxyterminal cross-linked telopeptides of type I collagen and tartrate-resistant acid phosphatase 5b.
RESULTS AND CONCLUSION: (1) Compared with the sham operation group, the model group showed a significant decrease in bone mineral density, sparse and fractured trabecular morphology, and a significant increase in serum levels of carboxyterminal cross-linked telopeptides of type I collagen and tartrate-resistant acid phosphatase 5b, indicating that the model of aromatase inhibitor-induced osteoporosis was successfully constructed. (2) Compared with the model group, the high-, medium-, and low-dose Huangqi Bushen Huoxue Decoction groups showed significant improvement in bone mineral density and bone microstructure, thickening and densification of trabecular morphology, significantly decreased serum levels of carboxyterminal cross-linked telopeptides of type I collagen and tartrate-resistant acid phosphatase 5b, a decrease in the number of osteoclasts and the expression of receptor activator of nuclear factor-κB ligand proteins, and an increase in the expression of osteoprotegerin. To conclude, Huangqi Bushen Huoxue Decoction may regulate the receptor activator of nuclear factor-κB ligand/receptor activator of nuclear factor-κB/osteoprotegerin signaling pathway, inhibit osteoclast activity, improve trabecular morphology and bone microstructure, and increase bone mineral density, thus preventing the occurrence and development of aromatase inhibitor-induced osteoporosis.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: Huangqi Bushen Huoxue Decoction, aromatase inhibitor, osteoporosis, osteoclast activity, receptor activator of nuclear factor-κB ligand, receptor activator of nuclear factor-κB, osteoprotegerin, signaling pathway