Identification and characterization of proteoglycan 4 splice variants in the baboon temporomandibular joint

Proteoglycan 4 (PRG4) is an extracellular matrix molecule known to be a critical component of the lubrication system in articular joints yet its presence and function in the TMJ has not been characterized. At least four splice variants of PRG4 are expressed in articular joints and there is compelling evidence suggesting that one or more of these variants are critical for normal lubrication of joints. A common disorder of the TMJ results from displacement of the articular disc (TMJ derangement) leading to degenerative joint disease. Recent evidence suggests that a defect in the lubricating system of the joint may be responsible for the development of TMJ derangement and subsequent degenerative TMJ disease (TMD). Unfortunately, the mechanisms underlying TMDs are not well understood therefore effective clinical treatments for patients are limited.

TMDs affect up to 15% of the adult population in North America, however 80% of those seeking treatment are women predominately of reproductive age. This clinical observation paired with early studies indicating a sexual dimorphism in estrogen receptor distribution in the female versus male TMJ of baboons suggests the possibility that estrogen regulates the PRG4 gene accounting for at least some of the disparity seen between males and females. Therefore, the purpose of the following research was to better understand the lubricating system of the TMJ in an effort to identify causative factors responsible for common TMJ disorders and shed light on the gender differences observed clinically in TMDs.