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Nanoparticle injections may be future of osteoarthritis treatment

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Researchers at Washington University School of Medicine in St. Louis have found that injecting nanoparticles into an injured joint can inhibit the inflammation that contributes to the cartilage damage seen in osteoarthritis. Shown in green is an inflammatory protein in cartilage cells. After nanoparticles are injected, the inflammation is greatly reduced. (Image: Pham Laboratory)

Researchers at Washington University School of Medicine in St. Louis have shown in mice that they can inject nanoparticles into an injured joint and suppress inflammation immediately following an injury, reducing the destruction of cartilage. In the study, the nanoparticles were injected shortly after an injury, and within 24 hours, the nanoparticles were at work taming inflammation in the joint. But unlike steroid injections that are quickly cleared, the particles remained in cartilage cells in the joints for weeks. The nanoparticles used in the study are more than 10 times smaller than a red blood cell, which helps them penetrate deeply into tissues. The particles carry a peptide derived from a natural protein called melittin that has been modified to enable it to bind to a molecule called small interfering RNA (siRNA). The melittin delivers siRNA to the damaged joint, interfering with inflammation in cells. The peptide-based nanoparticle was designed by study co-investigators Hua Pan, PhD, an assistant professor of medicine, and Samuel Wickline, MD, the James R. Hornsby Family Professor of Biomedical Sciences. The nanoparticles were injected shortly after injury to prevent the cartilage breakdown that eventually leads to osteoarthritis. Whether such a strategy will work years after an injury, when osteoarthritis is established and there is severe cartilage loss, still needs to be studied.  But the findings suggest that the nanoparticles, if given soon after joint injuries occur, could help maintain cartilage viability and prevent the progression to osteoarthritis.