Led by Dr. Denis Evseenko, scientists from the University of Southern California's Keck School of Medicine have developed a molecule that could be used to treat arthritis. If applied in the form of an injection at the affected joint, it might conceivably make joint replacement surgery unnecessary.

The molecule is known as RCGD 423 – the first part of which stands for "Regulator of Cartilage Growth and Differentiation" – and it promotes cartilage growth while also stopping the inflammation that leads to cartilage degeneration.

It works by communicating with a molecule in the body, called the glycoprotein 130 (Gp130) receptor. The Gp130 is capable of receiving two types of signals from the body, namely those that promote cartilage development in the embryo, and those that trigger chronic inflammation in the adult. RCGD 423 boosts the Gp130's ability to receive the cartilage development signals (which leads to cartilage regeneration, even in adults), and blocks the inflammatory signals.

When applied to joint cartilage cells in the lab, RCGD 423 caused those cells to proliferate more and die less than would otherwise be the case. Additionally, when it was injected into the knees of rats that had damaged cartilage, the injuries healed more effectively.

Plans now call for RCGD 423 (or a similar molecule) to be the subject of a clinical trial, in which it will be used to treat osteoarthritis or juvenile arthritis.

"The goal is to make an injectable therapy for an early to moderate level of arthritis," says Evseenko. "It's not going to cure arthritis, but it will delay the progression of arthritis to the damaging stages when patients need joint replacements, which account for a million surgeries a year in the US."

The research is described in a paper that was recently published in the journal Annals of Rheumatic Diseases.