Peter Muir, Susan L. Schaefer, Paul A. Manley, John P Svaren,William E. Oldenhoff, Zhengling Hao.
University of Wisconsin-Madison, Madison, WI, United States

ACVS Abstract 2007 

Chronic synovitis and development of inflammatory stifle arthritis is likely an important factor promoting degenerative rupture of the cranial cruciate ligament (CCL). To further understanding of the pathogenesis of this arthropathy, we studied expression of immune response genes in affected stifles. Blood and stifle synovial fluid samples were collected from 32 CCL rupture dogs, 8 normal dogs, and 9 dogs with degenerative osteoarthritis (OA).

Using real-time quantitative RT-PCR, mRNA expression was determined in synovial fluid cells relative to peripheral blood mononuclear cells (PBMC) for immune response genes [cathepsin S, tartrate-resistant acid phosphatase (TRAP), and invariant chain] and matrix turnover genes [cathepsin K,MMP-9, cathepsin S]. Data were analyzed using the -DDCt method; the 18S rRNA gene was used as the housekeeping gene.

Relative expression of MMP-9, TRAP, and invariant chain was increased in the stifle synovial fluid of dogs with CCL rupture, compared with normal dogs (P _ 0.05); TRAP expression was increased in CCL rupture joints, when compared with OA joints (Po0.05). In the CCL rupture dogs, expression of immune response and matrix turnover genes was increased in synovial fluid, when compared with PBMC (Po0.05), whereas in OA dogs only expression of matrix turnover genes was increased.

These data suggest that expression of TRAP may be a useful biomarker for chronic synovitis. These findings also suggest that antigen-specific immune responses may be an important factor in the pathogenesis of synovitis in dogs with inflammatory stifle arthritis and associated degenerative CCL rupture.