Abstract: BACKGROUND: The previous study of the research group confirmed that Bushen Zhuangjin Decoction can regulate bone metabolism and play an anti-osteoporosis role, and nanocrystalline collagen-based bone can assist in the repair of limb bone defects. 
OBJECTIVE: To explore the repair effect of nanocrystalline collagen-based bone combined with Bushen Zhuangjin Decoction on osteoporotic bone defects. 
METHODS: Totally 84 female SD rats were randomly divided into a sham operation group (n=6, no modeling) and a bilateral ovariectomy group (n=78). After 12 weeks of bilateral ovariectomy, the sham operation group (n=6) and the bilateral ovariectomy group (n=6) were selected for osteoporosis modeling verification. The remaining 72 rats in the bilateral ovariectomy group were randomly divided into 6 intervention groups, with 12 rats in each group: groups A-E had femoral defect models (diameter 3.5 mm, depth 4 mm) established 12 weeks after bilateral ovariectomy. Group A was given double distilled water by gavage (once a day) after surgery; group B was given Bushen Zhuangjin Decoction by gavage (once a day) after surgery; group C had nanocrystalline collagen-based bone filled in the bone defect and then given double distilled water by gavage (once a day); group D had nanocrystalline collagen-based bone filled in the bone defect and then given alendronate sodium by gavage (once a week); group E had nanocrystalline collagen-based bone filled in the bone defect and then given Bushen Zhuangjin Decoction by gavage (once a day); group F had femoral defect models established at the same time after bilateral ovariectomy, and bone defect sites were filled with nanocrystalline collagen-based bone and then given Bushen Zhuangjin Decoction by gavage (once a day). All drugs were given continuously for 12 weeks. 12 hours after the last administration, serum levels of type I procollagen amino-terminal propeptide, type I collagen cross-linked C-terminal peptide, and estradiol were detected; bone volume in the bone defect area was detected by Micro-CT. The expression of type I collagen and vascular endothelial growth factor in the bone defect area was detected by immunohistochemical staining. 
RESULTS AND CONCLUSION: (1) Compared with group A, the serum level of type I procollagen amino-terminal propeptide in groups D and E was decreased (P < 0.05). Compared with groups A and C, the serum estradiol level in groups D, E, and F was increased (P < 0.05). There was no significant difference in the bone volume in the defect area between groups A-F (P > 0.05). (2) Immunohistochemical staining showed that compared with group A, the expression of type I collagen and vascular endothelial growth factor in groups B, D, and E increased (P < 0.05). Compared with group C, the expression of type I collagen in groups B, D, E, and F increased (P < 0.05), and the expression of vascular endothelial growth factor in groups D, E, and F increased (P < 0.05). (3) The results show that nanocrystalline collagen-based bone combined with Bushen Zhuangjin Decoction may have the potential to repair bone defects in ovariectomized osteoporotic rats.

Key words: Bushen Zhuangjin Decoction">, osteoporotic bone defect">, nanocrystalline collagen-based bone">, type I collagen">, vascular endothelial growth factor">, engineered bone material