Nanoparticle injection wards off osteoarthritis in injured mice

Normal knee and knee with osteoarthritis--Courtesy of Bruce Blaus CC BY-SA 4.0

While the symptoms of osteoarthritis can be managed, there is no cure for the progressive destruction of cartilage. Now, researchers from Washington University in St. Louis have prevented cartilage degeneration in mice by injecting their injured joints with nanoparticles.

Osteoarthritis, also known as degenerative joint disease, is the most common chronic joint condition. The cartilage that covers the ends of each bone breaks down, causing pain and swelling and making it difficult to move the joint. Current treatments include anti-inflammatory drugs and/or steroid injections depending on the severity of pain, but relief can be brief.

"I see a lot of patients with osteoarthritis, and there's really no treatment," said senior author Dr. Christine Pham, an associate professor of medicine at Washington University, in a statement. "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."

The nanoparticle is more than 10 times smaller than a red blood cell, which helps it penetrate tissues deeply. It contains a peptide modified to bind to small interfering siRNA, which hampers inflammation in the joint.

The mice were injected with nanoparticles containing the peptide and siRNA soon after sustaining an injury. The goal was to ward off cartilage degeneration that eventually results in osteoarthritis. Within 24 hours, the nanoparticles were reducing inflammation in the joint, according to the statement. But unlike painkillers, which are cleared quickly, the nanoparticles remained in the joints for weeks, the scientists said in the statement.

While the results show the nanoparticle treatment could effectively prevent the progression of joint injury to osteoarthritis, further studies are needed to see if the therapy could benefit a patient years after sustaining the injury and has already developed 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 Sandell, the Mildred B. Simon Research Professor of Orthopaedic Surgery and director of Washington University's Center for Musculoskeletal Research, in the statement. "So we think these nanoparticles may be helpful in patients who already have arthritis, and we're working to develop experiments to test that idea."