Abstract: Objective: To analyze the effect of total flavonoids of Rhizomadrynariae on the expression of sclerostin (SOST) in bone tissue of the osteoporosis rats, and to explore the mechanism of tatal flavonoids of Rhzomadrynariae in the anti-osteoporosis process. Methods: A total of 40 female rats aged 8 months were divided into normal control group (fed daily with saline by gavage), osteoporosis model group(administrated with 90 mg·kg^-1·d^-1 retinoic acid by gavaged for 14 d),positive drug group (administrated with retinoic acid by gavage for 14 d and subcutaneously injected with 0.1 mg·kg^-1·d^-1 alendronare for 30 d),and total flavonoid of Rhizomadrynariae group (administrated with retinoic acid by gavaged for 14 d and 58 mg·kg^-1·d^-1 total flavonoids of Rhizomadrynariae by gavage for 30 d);there were 10 rats in each group. The vein blood samples of the rats were collected after administratration, and the levels of calcium, phosphorus and alkaline phosphatase (ALP) and the indexes of liver and kidney function were detected, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine (Crea) and blood urea nitrogen (BUN); one sides of the femurs of the rats were taken and the pathomorphology of bone tissue was observed by HE staining. The expression levels of SOST mRNA in bone tissue of the rats in various groups were detected by qRT-PCR and the expression levels of SOST protein in bone tissue of the rats were detected by Western blotting method. Results: Compared with osteoporosis model group, the serum calcium and phosphorus levels of the rats in positive drug group were significantly decreased(P<0.05 or P<0.01), however, the serum calcium level of the rats in total flavonoids of Rhizomadrynariae group was significantly increased (P<0.05); compared with positive drug group, the serum levels of calcium, phosphorus and ALP in total flavonoids of Rhizomadrynariae group were significantly increased (P<0.05 or P<0.01). Compared with normal control group, the serum Crea levels of the rats in osteoporosis model group, positive drug group and total flavonoids of Rhizomadrynariae group were significantly decreased (P<0.01). Compared with osteoporosis model group and positive drug group, the serum Crea level of the rats in total flavonoids of Rhizomadrynariae group was significantly reduced (P<0.01); there were no significant differences in the serum ALT, AST,and BUN levels of the rats among various groups (P>0.05). Under the light microscope, the metaphysis trabeculae of the rats in osteoporosis model group were atrophy, thin and broken, but the trabeculae in positive group and total flavonoids of Rhizomadrynariae group were obviously thickened and continuity enhancement. Compared with osteoporosis model group, the expression levels of SOST mRNA in bone tissue of the rats in positive drug group and total flavonoids of Rhizomadrynariae group were significantly decreased(P<0.01).The expression level of SOST protein in bone tissue of the rats in positive drug group was significantly lower than those in normal control group and osteoporosis model group (P<0.01). The expression level of SOST protein in bone tissue of the rats in total flavonoids of Rhizomadrynariae group was lower than those in normal control group and osteoporosis model group, but the differences were not statistically significant (P>0.05). Conclusion: The mechanism of anti-osteoporosis of total flavonoids of Rhizomadrynariae may be related to inhibiting the synthesis of SOST by osteocytes to promote the bone formation.

Key words: osteoporosis, bone metabolism, Rhizomadrynariae, sclerostin