Abstract: Objective To explore the effect and molecular mechanism of proanthocyanidins on the improvement of osteoporosis based on Wnt signaling pathway. Methods The osteoporosis rat model was constructed in 50 SD female rats by ovariectomy, then they were randomly divided into model group, alendronate sodium group, proanthocyanidins low-, medium-, and high- dose groups. Another 10 SD rats were recorded as the control group, and the bilateral ovaries of rats in the control group were turned over only without resection. Rats in the alendronate sodium group were given 1 mg / kg alendronate sodium by gavage. Rats in the procyanidins low-, medium-, and high dose groups were given procyanidins by gavage at the dose of 15, 25 and 35 mg / kg respectively. Rats in the control group and the model group were given the same amount of normal saline injection by gavage, once a day for 12 weeks. The levels of serum oxidative stress indexes [malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px)] and bone metabolism indexes [tartrate resistant acid phosphatase (TRAP), type I procollagen carboxyl-terminal peptide (PICP), bone Gla-protein (BGP)] in rats of each group were measured by enzyme-linked immunosorbent assay ( ELISA). Bone density scanner was used to determine the value of femoral bone mineral density (BMD). Hematoxylin-eosin (HE) staining was used to observe the morphological changes of bone tissues in rats. Real time fluorescence quantitative polymerase chain reaction (RT-qPCR) and Western blotting (WB) were used to detect the mRNA and protein expression levels of Wnt, β-catenin, and osteogenic marker proteins [runt related transcription factor 2 (Runx2), Osterix]. Results Compared with the control group, the serum MDA and TRAP levels in the model group, the alendronate sodium group and the procyanidins low-, medium- , and high-dose groups were increased, the levels of SOD, GSH-Px, PICP and BGP were decreased (P< 0. 05). Compared with the model group, the serum MDA and TRAP levels in the alendronate sodium group and the procyanidins low-, medium-, and high-dose groups were decreased, the levels of SOD, GSH-Px, PICP and BGP were increased (P < 0. 05). In the control group, the bone trabeculae were arranged reticulated and formed a dense network. In the model group, the number of trabeculae was decreased, the arrangement was sparse and disordered, and the continuity was poor. Compared with the model group, the number and structure of the bone trabeculae in the alendronate group and the procyanidins low-, medium-, and high-dose groups were improved to varying degrees. Compared with the control group, the mRNA and protein expression levels of Wnt, β-catenin, Runx2, Osterix bone tissues of the model group, the alendronate sodium group and the procyanidins low-, medium-, and high-dose groups were decreased (P < 0. 05). Compared with the model group, the mRNA and protein expression levels of Wnt, β-catenin, Runx2, Osterix in the alendronate sodium group and the procyanidins low-, medium-, and high-dose groups were increased (P < 0. 05). Conclusion Procyanidins can effectively improve the oxidative stress and bone metabolism in osteoporosis rats, and play a role in the treatment of osteoporosis. It is speculated that this effect is achieved by the inhibition of the peroxidative stress response and the promotion of the expressions of Wnt, β-catenin and osteogenic marker proteins Runx2 and Osterix through Wnt pathway.

Key words: Wnt signaling pathway, proanthocyanidins, osteoporosis