Adeno‐associated virus–mediated osteoprotegerin gene transfer protects against particulate polyethylene–induced osteolysis in a murine model

Abstract

Objective Osteoprotegerin (OPG), a natural negative regulator of osteoclastogenesis and bone resorption, may be a potential therapeutic agent for treatment of osteolysis‐associated prosthetic joint loosening. Using an in vivo adeno‐associated virus (AAV)–mediated gene transfer technique, this study was designed to evaluate the protective effects of OPG transgene against orthopedic wear debris–induced bone loss in a murine model of osteolysis. Methods Bone tissue was implanted into established pouches on BALB/c mice, followed by the introduction of ultra‐high‐molecular‐weight polyethylene (UHMWPE) particles to provoke inflammation and osteolysis. The viruses encoding human OPG gene (rAAV‐hOPG) or β‐galactosidase marker gene (rAAV‐LacZ) were injected into the air pouches, and the tissue was harvested 7 days after viral infection for histologic and molecular analyses. Results Successful transgene expression was confirmed by the detection of OPG by enzyme‐linked immunosorbent assay and positive X‐Gal staining of pouch tissue (LacZ). Real‐time polymerase chain reaction indicated significant diminishment of messenger RNA expression of osteoclast markers in OPG‐transduced pouches compared with rAAV‐LacZ–transduced pouches. The transduction and expression of OPG also markedly decreased the gene copies of the biologic receptor activator of nuclear factor κB. The expression of OPG in the bone‐implanted pouch reduced bone calcium release by a mean of 39% compared with the calcium release in the other 2 groups. Computerized image analysis revealed that expression of OPG significantly protected against bone collagen loss. Conclusion OPG gene transfer mediated by rAAV effectively protects against particulate polyethylene–induced bone resorption in this experimental model. Data suggest that gene transfer using rAAV‐OPG may be a feasible and effective therapeutic candidate to treat or prevent wear debris–associated osteolysis and aseptic loosening.