Abstract: BACKGROUND: Previous studies have found that for postmenopausal osteoporosis patients, the Bushen Jianpi Formula can help regulate serum osteoclast- and osteoblast-related factors and intestinal flora levels, improve clinical symptoms of patients and further improve efficacy.
OBJECTIVE: To investigate the effect of Bushen Jianpi Formula on bone metabolism and bone microarchitecture in ovariectomized rats.
METHODS: Twenty-four female SD rats were randomly divided into four groups by random number table method: sham operation group (n=6) was subjected to periovarian fat removal, and bilateral ovariectomy was performed in model group (n=6), alendronate group (n=6), and Bushen Jianpi Formula group (n=6). Five days after modeling, the Bushen Jianpi Formula group was given Bushen Jianpi Formula by intragastric administration (once a day). The alendronate sodium group was given alendronate by intragastric administration (once a week). The sham operation group and model group were given an equal volume of normal saline by intragastric administration (once a day) for 12 consecutive weeks. After intragastric administration, serum levels of procollagen I N-terminal peptide, β-isomerized C-terminal telopeptide of type I collagen degradation product, and tumor necrosis factor α were detected. The distal femur microstructure was detected by Micro-CT. The femoral tissue morphology was observed by hematoxylin-eosin staining. The expression of type I collagen and tumor necrosis factor α in the femur was detected by immunohistochemical staining. 
RESULTS AND CONCLUSION: (1) The serum ELISA test showed that compared with the sham operation group, the level of procollagen I N-terminal peptide in the model group decreased (P < 0.05), and the levels of degradation products of β-isomerized C-terminal telopeptide of type I collagen and tumor necrosis factor α increased (P < 0.05). Compared with the model group, the levels of the procollagen I N-terminal peptide in the Bushen Jianpi Formula group and the alendronate sodium group increased (P < 0.05), and the levels of β-isomerized C-terminal telopeptide of type I collagen degradation products and tumor necrosis factor α decreased (P < 0.05). (2) Micro-CT three-dimensional reconstruction showed that compared with the sham operation group, the number of bone trabeculae in the model group was significantly reduced, the continuity was worsened, and the gaps were increased. Both alendronate sodium and Bushen Jianpi Formula had a positive improvement effect on this phenomenon. (3) Hematoxylin-eosin staining showed that compared with the sham operation group, the number of bone trabeculae in the model group was reduced and the shape became thinner, and the network structure was destroyed. Compared with the model group, the number of bone trabeculae in the Bushen Jianpi Formula group and the alendronate sodium group increased, the shape became thicker, and the reticular structure was restored. (4) Immunohistochemical staining showed that compared with the sham operation group, the expression of type I collagen was reduced and tumor necrosis factor α expression was increased in the model group. Compared with the model group, the expression of type I collagen increased and the expression of tumor necrosis factor α decreased in the Bushen Jianpi Formula group and the alendronate sodium group. The results show that the Bushen Jianpi Formula can effectively improve bone metabolism and bone microstructure in ovariectomized rats.

Key words: Bushen Jianpi Formula, ovariectomized rat, osteoporosis, bone metabolism, bone microarchitecture, Micro-CT, engineered tissue construction