Injecting nanoparticles into a joint immediately after an injury may suppress inflammation, reduce destruction of cartilage and lower the risk for osteoarthritis, a new study in mice suggests.
“I see a lot of patients with osteoarthritis, and there’s really no treatment,” said Christine Pham from Washington University School of Medicine in St Louis in the US.
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“We try to treat their symptoms, but even when we inject steroids into an arthritic joint, the drug only remains for up to a few hours, and then it’s cleared. These nanoparticles remain in the joint longer and help prevent cartilage degeneration,” said Pham.
Frequently, osteoarthritis patients suffer an earlier injury – a torn meniscus or anterior cruciate ligament (ACL) injury in the knee, a fall, car accident or other trauma.
The body naturally responds to such injuries in the joints with robust inflammation.
Patients typically take drugs such as acetaminophen and ibuprofen, and as pain gets worse, injections of steroids also can provide pain relief, but their effects are short-lived.
In the new study, the nanoparticles were injected shortly after an injury, and within 24 hours, the nanoparticles were at work taming inflammation in the joint.
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, an assistant professor of medicine, and Samuel Wickline, Professor of Biomedical Sciences.
“The nanoparticles are injected directly into the joint, and due to their size, they easily penetrate into the cartilage to enter the injured cells,” Wickline said.
“Previously, we’ve delivered nanoparticles through the bloodstream and shown that they inhibit inflammation in a model of rheumatoid arthritis. In this study, they were injected locally into the joint and given a chance to penetrate into the injured cartilage,” he said.
The nanoparticles were injected shortly after injury to prevent the cartilage breakdown that eventually leads to osteoarthritis.
The findings suggest that the nanoparticles, if given soon after joint injuries occur, could help maintain cartilage viability and prevent the progression to osteoarthritis.
“The inflammatory molecule that we’re targeting not only causes problems after an injury, but it’s also responsible for a great deal of inflammation in advanced cases of osteoarthritis,” said Linda J Sandell, from Washington University’s Centre for Musculoskeletal Research. The findings were published in the journal PNAS.