Inhibiting the bone-specific protein osteopontin (OPN) may prevent wear debris–induced osteolysis, according to a study of OPN-deficient mice presented at the annual meeting of the Orthopaedic Research Society in Chicago.1

In this study, researchers placed 30 mg of titanium particles under the surface of the bone in both OPN-deficient and wild-type mice and observed that OPN-deficient mice were protected from particle-induced osteolysis, whereas the wild-type animals were not. Specifically, the osteoclasts of OPN-deficient mice displayed smaller bone resorption pits than those of the control mice.

"The OPN-deficient mice suppressed titanium particle-induced osteolysis in our murine calvarial model," explains lead researcher Sadanori Shimizu, a graduate student at the Medical Research Institute of the Tokyo Medical and Dental University in Japan. Shimizu and colleagues indicate that these effects may be mediated by secretion of tumor necrosis factor-alpha (TNF-a), and the new findings suggest that "OPN is a candidate for therapeutic targets of periprosthetic osteolysis."

Findings still preliminary

"Debris-induced osteolysis is a big problem in total joint arthroplasty, and if osteopontin is able to influence that, then it may lead to knowledge that will help prevent osteolysis," says CIAOMed editorial board member Stephen Trippel, MD, professor of orthopaedic surgery at Indiana University School of Medicine in Indianapolis, Indiana.

Commenting on the new findings, Paul H. Wooley, PhD, director of biomedical research and professor of orthopaedic surgery, immunology, and biomedical engineering at Wayne State University School of Medicine in Detroit, Michigan, indicates "This is very early on. I am not convinced that [osteopontin] works through a TNF-a-mediated mechanism at this point," he says, adding that "it's an interesting approach, but it is quite a ways away [from clinical use]." Moreover, he tells CIAOMed, "treatments with biologic and pharmacologic treatments to block OPN could have quite significant side effects."

Reference

  1. Shimizu S, Asou Y, Okuda N, et al. Osteopontin deficiency impairs wear debris-induced osteolysis. Presented at: 52nd Annual Meeting of the Orthopaedic Research Society. March 18–22, 2006; Chicago, Ill. Abstract 92.