SOST gene suppression stimulates osteocyte Wnt/ß-catenin signaling to prevent bone resorption and attenuates particle-induced osteolysis

The most common cause for prosthetic revision surgery is wear particle-induced periprosthetic osteolysis, which leads to aseptic loosening of the prosthesis. Both SOST gene and its synthetic protein, sclerostin, are hallmarks of osteocytes. According to our previous findings, blocking SOST induces bone formation and protects against bone loss and deformation caused by titanium (Ti) particles by activating the Wnt/beta-catenin cascade. Although SOST has been shown to influence osteoblasts, its ability to control wear-particleinduced osteolysis via targeting osteoclasts remains unclear. Mice were subjected to development of a cranial osteolysis model. Micro CT, HE staining, and TRAP staining were performed to evaluate bone loss in the mouse model. Bone marrow-derived monocytemacrophages (BMMs) made from the C57BL/6 mice were exposed to the medium of MLO-Y4 (co-cultured with Ti particles) to transform them into osteoclasts. Bioinformatics methods were used to predict and validate the interaction among SOST, Wnt/beta-catenin, RANKL/OPG, TNF-alpha, and IL-6. Local bone density and bone volume improved after SOST inhibition, both the number of lysis pores and the rate of skull erosion decreased. Histological research showed that beta-catenin and OPG expression were markedly increased after SOST inhibition, whereas TRAP and RANKL levels were markedly decreased. In-vitro, Ti particle treatment elevated the expression of sclerostin, suppressed the expression of beta-catenin, and increased the RANKL/OPG ratio in the MLO-Y4 cell line. TNF-alpha and IL-6 also elevated after treatment with Ti particles. The expression levels of NFATc1, CTSK, and TRAP in osteoclasts were significantly increased, and the number of positive cells for TRAP staining was increased. Additionally, the volume of bone resorption increased at the same time. In contrast, when SOST expression was inhibited in the MLO-Y4 cell line, these effects produced by Ti particles were reversed. All the results strongly show that SOST inhibition triggered the osteocyte Wnt/beta-catenin signaling cascade and prevented wear particle-induced osteoclastogenesis, which might reduce periprosthetic osteolysis.

Automated summary

It has been found that inhibiting SOST gene can trigger the osteocyte Wnt/β-catenin signaling cascade, inhibit osteoporosis, and reduce periprosthetic osteolysis. The study results show that inhibiting SOST can significantly improve bone density and volume, reduce the number of osteolysis pores, and decrease the extent of skull erosion. In addition, inhibiting SOST can reverse the effects of titanium particles on bone cells, preventing particle-induced bone resorption and destruction.