Abstract. Osteoporosis is one of the leading metabolic bone diseases affecting adults. Young bones are in equilibrium with bone resorption by osteoclasts and new bone deposition by osteoblasts. Osteoporosis occurs when this equilibrium disappears. Reduced bone density increases the risk for fracture, also decreases the candidacy for those individuals to receive implants.

The purpose of this study is using siRNA technology to inhibit expression of RANK (a transmembrane signaling receptor on osteoclasts and their precursors which modulates osteoclast formation and function). Reduction of RANK should suppress bone resorption by osteoclast on bone surfaces ultimately increasing bone density and preventing bone degradation after implantation. As the first step in our analysis, we created an in vitro assay to confirm the inactivation of osteoclasts in vitro. We generated osteoclasts using treatment of RAW 264.7 cells with RANKL and its phenotype was confirmed by using TRAP assay. The effects of siRNA transfection have been tested and its efficacy was determined by analyzing the decrease in pit formation assay on bone slides. After optimizing conditions for siRNA transfection, the formation and function of osteoclast was significantly inhibited by siRNA targeting RANK. The supporting Q-PCR results showed that the RANK gene expression decreased dramatically after transfection. A continuous examination of transfection on primary cells would strengthen our conclusion. Future studies will include an in vivo model of siRNA delivery in the context of osteoporosis.