Analysis of normal and osteoarthritic canine cartilage mRNA expression by quantitative-PCR.

ABSTRACT: The molecular basis to mammalian osteoarthritis (OA) is unknown. We hypothesised that the expression of selected proteases, matrix molecules and collagens believed to have a role in the pathogenesis of OA would be changed in naturally occurring canine OA cartilage, when compared to normal articular cartilage. Quantitative (real-time) reverse transcriptase polymerase chain reaction (RT-PCR) assays were designed measuring the expression of selected matrix molecules (collagens and small leucine rich proteoglycans), and key mediators of the proteolytic degradation of articular cartilage (metalloproteinases, cathepsins), their inhibitors (tissue inhibitors of matrix metalloproteinases). All data were normalised using a geometric mean of three housekeeping genes, and the results subject to power calculations and corrections for multiple hypothesis testing. We detected increases in the expression of BGN, COL1A2, COL2A1, COL3A1, COL5A1, CSPG2, CTSB, CTSD, LUM, MMP13, TIMP1 and TNC in naturally occurring canine osteoarthritis. The expression of TIMP2 and TIMP4 were significantly reduced in canine OA cartilage. The patterns of gene expression change observed in naturally occurring canine osteoarthritis were similar patterns of expression to that reported in naturally occurring human osteoarthritis, and experimental canine osteoarthritis. We conclude that the expression profiles of matrix associated molecules in end-stage mammalian osteoarthritis may be comparable, but the precise aetiologies of OA affecting specific joints in different species are presently unknown.