New insights into the structural changes associated with osteoarthritis

Osteoarthritis is the most common degenerative joint disease, affecting 22% of adults over age 40 globally. Although the condition has been extensively studied, the molecular changes associated with osteoarthritis remain unclear. In a new study, researchers at the University of Illinois Urbana-Champaign and other institutions used a combination of techniques to track the progression of the disease and the changes associated with it.

The study was published in Biointerphases and was funded by the U.S. National Science Foundation.

"Osteoarthritis is a result of the degradation of cartilage and changes in lubricant characteristics in the orthopedic joint," said Khershed Cooper, a program director in NSF's Directorate for Engineering. "To study the nature of these changes, this team is applying the understanding of friction, wear and lubrication in manufacturing processes."

The cartilage in joints, along with a lubricant known as the synovial fluid, provides a smooth surface that helps withstand weight-bearing movements. The fluid contains several molecules, including hyaluronan (HA) and phospholipids. Since the cartilage environment cannot be quickly healed or repaired, researchers have tried to diagnose the early stages of joint disease by monitoring the molecular weight and concentration of HA.

"Although we know that in healthy joints there is very low friction, it is unclear which other molecules are involved and how they change during osteoarthritis," said Rosa Espinosa-Marzal, an engineer at the University of Illinois. "During the early stages of osteoarthritis, cartilage starts degrading, and the molecular composition of the synovial fluid changes. We wanted to see if the two changes are related to each other."

In diseased joints, HA is broken down, with its concentration reduced by 10 times. The study looked at how the concentration and molecular weight of HA influences the structure of healthy and diseased joints.

Next, the researchers are interested in studying the other molecular components found in joints to build a more comprehensive model of the changes associated with osteoarthritis.