Arthritis, a joint condition that affects 52 million people or about 23 percent of adults in the US, also affects fish, according to a study to be published this month in the journal eLife. The research team led by the University of Southern California found that zebra fish, Paracanthurus (Dory’s species) and other ray-finned fish have synovial joints prone to arthritis like ours.

The research team found that some joints in zebrafish jaw and fins resemble the synovial joints that mammals have. These joints allow movements. They suggest that arthritis may stem from the stress on joints caused by water resistance.

The team had to use CT scans and genetic tools to study the aforementioned ray-finned fish species as well as the three-spined stickleback and the spotted gar. They found that the animals’ synovial joints produced a protein called Lubricin that is similar to the protein in humans used to lubricate the joints.


This is a magnification of the adult zebrafish jaw skeleton. The jaw joint (middle) functions as a lubricated hinge. Credit: USC/Gage Crump Lab

As shown in other research, the reduced amount of Lubricin results in poor joint lubrication and early onset of arthritis in humans and mice. Now, the team observed that removing this protein also caused poor lubrication and the joint condition in fish jaws and fins.

This could lead the way to arthritis management and possibly even a cure. As of now, no cure has been found for this disease.

“Developing the first arthritis model in the zebrafish — an emerging regenerative model for medical research — opens up fundamentally new approaches toward finding a cure for arthritis,” said the study’s senior author Gage Crump, an associate professor of stem cell biology and regenerative medicine at the Keck School of Medicine at the University of Southern California . “While arthritis is the leading cause of disability in the United States, there are no treatments beyond artificial joint replacement. Our research offers new hope for finding a biological cure.”

The findings also have implications on how animals evolved. Previously, scientists thought that the synovial joints evolved when vertebrates came to land but the findings contradict this theory, suggesting that these joints are as old as bone itself.