Osthole Promote Differentiation and Inhibit Proliferation of Osteoblast by Activating Wnt Signaling and Endoplasmic Reticulum Stress

Background: Osthole is extracted from Fructus Cnidii and is proved to be effective in the treatment of osteoporosis in rats. However, data are still scarce and the mechanism remains elusive. Objective: To investigate the effect of Osthole on proliferation and differentiation of osteoblast. Materials and Methods: Cells were divided into five groups: control group, β‑estradiol group (10−8 M), and Osthole groups (10−6 M, 10−5 M, and 10−4 M). Osteoblast proliferation was evaluated by Cell Counting Kit‑8 (CCK- 8) assay. Alkaline phosphatase (ALP) activity was detected by ALP staining and enzymatic measurement. Mineralization was detected by alizarin‑red staining. The level of osteocalcin was measured by enzyme‑linked immunosorbent assay (ELISA). The expression of key proteins of Wnt/ β‑catenin signaling pathway and endoplasmic reticulum stress (ERS) was analyzed by Western blot. Results: Cell proliferation was retarded in moderate‑dose and high‑dose Osthole group at 1d, 2d and 3d and in low‑dose Osthole group at 1d and 2d (P < 0.05). ALP activity was enhanced in high‑dose Osthole group from 1d to 3d and in moderate‑dose Osthole group at 2d (P < 0.05). Mineralization of bone matrix was promoted in high‑dose Osthole group at 21d (P < 0.05). The secretion of osteocalcin was promoted in Osthole groups at 21d (P < 0.05). Expression of CHOP, GRP78, PDI, Wnt1, and β‑catenin was upregulated in high‑dose Osthole group at 2d, indicating that both of ERS and Wnt/β‑catenin signaling pathway were activated. Conclusion: It can be concluded that the effect of Osthole on inhibition of proliferation is relevant with activation of ERS, and activation of Wnt/β‑catenin signaling pathway is one of the mechanisms how Osthole promotes osteoblast differentiation. In summary, this study provided more evidence for Osthole as a potential anti‑osteoporosis medicine.