December 15, 2020

A study by an interdisciplinary team of researchers at Cornell University is challenging conventional assumptions about the lubricin protein and mammalian joint disease.

The team’s findings, published Oct. 7 in Scientific Reports, indicate that in 30 dogs with a ligament tear in the knee, lubricin concentrations actually increased within the joint.

“The dogma in this field has been that lubricin decreases in joint disease,” said Heidi Reesink, PhD, assistant professor in equine health at the Cornell University College of Veterinary Medicine and senior author of the paper, in a press release.

The Cornell study is the first investigation of lubricin’s role in cruciate ligament injuries in dogs. In three of the canine patients with a joint injury, researchers found lubricin concentration dramatically increased in the time between the initial injury and development of radiographic signs of arthritis.

“This indicates that the presence of increased lubricin might actually be a biomarker for predicting future osteoarthritis,” Dr. Reesink explained.

“We also saw increased lubricin in dogs months to years after they injured their ACLs, suggesting that lubricin might be an indicator of ongoing joint instability,” she added, saying that increased lubricin concentration could potentially be a trigger for clinicians to intervene or try a different treatment approach.

Dr. Reesink and her collaborators laid the groundwork for this study by completing a systematic review of the literature surrounding lubricin in both human and veterinary medicine.

The review, published this summer in the journal Osteoarthritis and Cartilage, looked at human and animal studies, finding two types of results on the topic.

First, rodent studies showed a decrease in lubricin concentration, which is what has led to the predominant theory in the field.

“There is a citation bias for these studies, and we think it might be motivated by those looking at lubricin as a therapeutic,” Dr. Reesink said.

Second, the horse studies showed an increase in lubricin concentration, while the human studies were equally divided. Consequently, there is no unified consensus on how lubricin concentration is altered in other domestic veterinary species and in human joint injury.

“In looking at horses and dogs, we’re seeing the same pattern,” Dr. Reesink said. “The strongest piece of data would be to show it in humans as well.”

“It’s worth looking at in canine patients, both for the benefit of the dogs and also for potentially drawing links between canine patients with this disease and similar injuries in humans like ACL tears,” Dr. Reesink said.

Her team plans a follow-up longitudinal study in dogs, examining multiple time points in a patient’s injury, treatment, and recovery process. The team also hopes to draw similar connections in human ACL tears and other orthopedic injuries.

Dr. Reesink is currently examining parallel samples from both the Cornell Veterinary Biobank and the Hospital for Special Surgery in New York City, using funding from a pilot grant from the Weill Cornell Medicine Clinical and Translational Science Center.