Introduction:  Lubricin, a heavily glycosylated proteoglycan, has provoked much enthusiasm amongst investigators involved with orthopedic medicine.  First described in what have become seminal studies involving bovine synovial fluid; lubricin, an endogenous product of the Proteoglycan-4 (PRG-4) gene, is now thought to be the primary boundary lubricant of diarthrodial joints.  As such, lubricin has been shown to significantly reduce the frictional coefficient in ambulating joints.  The PRG-4 gene has also been implicated in the autosomal recessive disorder camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP) in which PRG-4 mutations result in the manifestations of precocious arthropathy, pericarditis and coxa vara.  Likewise, PRG-4 knock-out mice have demonstrated analogous joint pathology as that seen in their CACP counterparts.

Student Project:  The student will test if lubricin is expressed within articular and non -articular tissue.  Lubricin mRNA transcripts are speculated to be found in pericardium, peripleura, mesothelium and peritoneum.  We will be targeting these tissues as they are continuously exposed to frictional forces, making them prime candidates for tissue adhesions and cell damage.  Lubricin may play a role in circumventing these untoward consequences in healthy subjects due to its boundary lubricating ability.  Justification for investigation comes from the extra-articular manifestations seen in CACP and the strikingly similar findings seen in studies involving PRG-4 knock-out mice.  Compromised lubricin expression may contribute to the intra- and extra-articular manifestations of CACP.