Strontium ranelate promotes chondrogenesis through inhibition of the Wnt/-catenin pathway

BACKGROUND: Cartilage regeneration is a key step in functional reconstruction for temporomandibular joint osteoarthritis (TMJ-OA) but is a difficult issue to address. Strontium ranelate (SrR) is an antiosteoporosis drug that has been proven to affect OA in recent years, but its effect on chondrogenesis and the underlying mechanism are still unclear. METHODS: Bone mesenchymal stem cells (BMSCs) from SpragueDawley (SD) rats were induced in chondrogenic differentiation medium with or without SrR, XAV-939, and LiCl. CCK-8 assays were used to examine cell proliferation, and alcian blue staining, toluidine blue staining, immunofluorescence, and PCR analysis were performed. Western blot (WB) analyses were used to assess chondrogenic differentiation of the cells. For an in vivo study, 30 male SD rats with cartilage defects on both femoral condyles were used. The defect sites were not filled, filled with silica nanosphere plus gelatine-methacryloyl (GelMA), or filled with SrR-loaded silica nanosphere plus GelMA. After 3months of healing, paraffin sections were made, and toluidine blue staining, safranin O/fast green staining, and immunofluorescent or immunohistochemical staining were performed for histological evaluation. The data were analyzed by SPSS 26.0 software. RESULTS: Low concentrations of SrR did not inhibit cell proliferation, and the cells treated with SrR (0.25mmol/L) showed stronger chondrogenesis than the control. XAV-939, an inhibitor of -catenin, significantly promoted chondrogenesis, and SrR did not suppress this effect, while LiCl, an agonist of -catenin, strongly suppressed chondrogenesis, and SrR reversed this inhibitory effect. In vivo study showed a significantly better cartilage regeneration and a lower activation level of -catenin by SrR-loaded GelMA than the other treatments. CONCLUSION: SrR could promote BMSCs chondrogenic differentiation by inhibiting the Wnt/-catenin signaling pathway and accelerate cartilage regeneration in rat femoral condyle defects.