A variant of the gene that controls production of a cartilage component increases susceptibility to osteoarthritis, Japanese researchers report

Dr. Shiro Ikegawa of The Institute of Physical and Chemical Research, Tokyo, and colleagues note in the research journal Nature Genetics that the function of joints is maintained “through a delicate balance between degradation and synthesis” of cartilage that cushions the bones in joints.

The researchers saw that a protein called asporin, used in building the matrix that holds cartilage together, is found in high amounts in joints damaged by osteoarthritis. This prompted the team to see if asporin might have a role in causing the condition.

By comparing people with and without knee osteoarthritis, Ikegawa’s group found that a variant of the gene encoding asporin occurred more frequently among those affected by osteoarthritis. A similar pattern was seen in patients with hip osteoarthritis.

The researchers then established in lab experiments that the presence of asporin ratchets down the production of collagen by cells called chondrocytes. The higher the levels of asporin, the less collagen there is to replace that lost by wear and tear.

The investigators say that “taken together,” these findings could lead to new treatment strategies for osteoarthritis.”

SOURCE: Nature Genetics, online January 2, 2005.