Sclerostin antibody promotes bone formation through the Wnt/β-catenin signaling pathway in femoral trochlear after patellar instability.

Purpose: The molecular mechanism of patellar instability (PI) remains unknown. The purpose of this study was to explore the function of SOST/sclerostin in PI and examine the effect of sclerostin antibody (Scl-Ab).

Materials and methods: We randomly divided 60 male 3-week-old C57Bl/6 mice into four groups: sham, PI, Scl-Ab intraperitoneal injection (Scl-Ab IP), Scl-Ab intraarticular injection (Scl-Ab IA). PI was established in the latter three groups. The Scl-Ab IP/IA groups were administered with an intraperitoneal/intraarticular Scl-Ab injection (100 mg/kg, 20 µl), respectively, at 5-day intervals. Distal femurs were collected 30 days after the surgery. The SOST/sclerostin, β-catenin, ALP, OPG and RANKL expression in distal femur were determined. Trochlear morphology and structural parameters of the trabecular and cortical bone compartments were determined by micro-CT. Further sub-regional analysis was performed. HE staining and Masson's trichrome staining were performed to evaluate cartilage changes.

Results: PI increased the expression of SOST/sclerostin and RANKL, and decreased β-catenin, ALP and OPG levels, while Scl-Ab IP reversed these changes. Scl-Ab IP brought trochlear morphology closer to normality. Additionally, Scl-Ab IP significantly improved most of the bone parameters. Importantly, both PI and Scl-Ab IP acted mainly on trabecular bone. Histological analysis showed that Scl-Ab IP protected cartilage from degeneration. However, Scl-Ab IA did not protect against bone loss or cartilage degradation.

Conclusions: SOST/sclerostin plays an important role in PI and systemic Scl-Ab use promotes bone formation through the Wnt/β-catenin signaling pathway in the femoral trochlear after PI.