Characterization of proteoglycan-4 (PRG4): Estrogen regulation in the female temporomandibular joint

About 10-15% of the North American population is affected by Temperomandibular Joint Disorders (TMD), a major percentage of them are women in their reproductive ages. TMDs are mainly caused by the TMJ articular disc displacement. The mechanism underlying development of TMD is not known, however one hypothesis is a failure in the TMJ lubrication system leads to TMD [Nitzan et al., 2002, 2003]. Proteoglycan 4 (PRG4) is a major component of the lubricating synovial fluid of many articular joints. It is mucinous extracellular glycoprotein that has anti-adhesive and chondroprotective properties. The lack of this protein is shown to increase friction and thereby cause irreversible damage to the disc in articular joints [Jay et al., 1992].

Interestingly at the time of my study, PRG4 had not been studied in the TMJ. Studies have also shown the presence of estrogen receptors only in female baboons and not in male baboons [Aufdemorte et al., 1986]. All these have led us to research on the lubrication mediated by PRG4 in the TMJ and also elucidating the role of estrogen on PRG4 expression that leads to sexual disparity in TMDs.