PRG4 and synovitis: In order to assess inflammatory gene expression and expression of the genes encoding for hyaluronic acid synthases (HAS1, HAS2, HAS3), lubricin (proteoglycan 4, PRG4), TNF-α stimulated gene 6 (TSG6) and IL-1β (IL1β), quantitative RT-PCR analysis of synovial fluid cell pellets was performed at 12 and 24 h post-induction of synovitis or lavage and of synovial membrane biopsies at 5 weeks post-induction of synovitis or lavage.