Protein loss linked to osteoarthritis ~~~~>> believe it

The loss of a single protein within the surface layer of the joint cartilage is linked to osteoarthritis.

"We have found the mechanism that begins to explain how and why ageing leads to deterioration of articular cartilage," said Scripps Institute professor Martin Lotz, an authority on arthritis who led the study with Noboru Taniguchi, senior research associate in his lab.

"Our findings demonstrate a direct link between the loss of this protein and osteoarthritis." Osteoarthritis typically begins with a disruption of the surface layer of cartilage.

The cartilage surface layer, called the superficial zone, is the most important functionally of the four layers of cartilage present in joints. In normal joints the cartilage surface is perfectly smooth, enabling joints to slide across one another without friction.

Once the cartilage of the superficial zone starts to deteriorate, though, osteoarthritis sets in, triggering an irreversible process that eventually leads to the loss of underlying layers of cartilage until bone begins to grind painfully against bone.

Osteoarthritis most commonly affects the spine, temporomandibular joints, shoulders, hands, hips and knees, said a Scripps release.

"We knew that the first phase of osteoarthritis is the destruction of cartilage in the superficial zone," said Lotz, who has spent the past five years studying the role of the single protein HMGB2 in osteoarthritis.

"Now we know that before this layer is destroyed, there is loss of the critical DNA binding protein HMGB2 and that this loss is directly related to aging."

The findings, made in collaboration with colleagues from Scripps Research, San Raffaele University in Milan, Italy, and Kagoshima University in Kagoshima, Japan, provide a promising avenue to explore the development of new osteoarthritis treatment options.

The results were published in this week's edition of the Proceedings of the National Academy of Sciences.