Analysis of normal and osteoarthritic canine cartilage mRNA expression by quantitative polymerase chain reaction

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 assays were designed measuring the expression of selected matrix molecules (collagens and small leucine-rich proteoglycans), key mediators of the proteolytic degradation of articular cartilage (metalloproteinases, cathepsins), and their inhibitors (tissue inhibitors of matrix metalloproteinases). All data were normalised using a geometric mean of three housekeeping genes, and the results subjected 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 OA. The expression of TIMP2 and TIMP4 was significantly reduced in canine OA cartilage. The patterns of gene expression change observed in naturally occurring canine OA were similar to those reported in naturally occurring human OA and experimental canine OA. We conclude that the expression profiles of matrix-associated molecules in end-stage mammalian OA may be comparable but that the precise aetiologies of OA affecting specific joints in different species are presently unknown.

Figure 1

Graph illustrating the means and 95% confidence intervals (CIs) of the gene expression profiles. To normalise values, the mean of each control group has been used to normalise and produce fold changes in expression. The results of the COL9A3 transcript are omitted because the 95% CIs were very high. *Significant difference. ADAMTS5, ADAM metallopeptidase with thrombospondin type 1 motif, 5; AGC, aggrecan; COL9A3, type IX collagen alpha 3 chain; CTSB, cathepsin B; D, disease; DCN, decorin; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; N, normal; RPL13A, ribosomal protein L13a; SDHA, succinate dehydrogenase complex, subunit A; TBP, TATA box binding protein; TIMP2, tissue inhibitor of metalloproteinase 2; TIMP4, tissue inhibitor of metalloproteinase 4; TNC, Tenascin C; VIM, vimentin.

Figure 2

Graph illustrating the means and 95% confidence intervals (CIs) of the gene expression profiles. To normalise values, the mean of each control group has been used to normalise and produce fold changes in expression. The results of the COL9A3 transcript are omitted because the 95% CIs were very high. *Significant difference. BGN, biglycan; COL1A2, type I collagen, alpha two chain; COL2A1, type II collagen alpha 1 chain; COL3A1, type III collagen alpha 1 chain; COL5A1, type V collagen alpha 1 chain; COL9A3, type IX collagen alpha 3 chain; CSPG2, chondroitin sulphate proteoglycan 2; CTSD, cathepsin D; D, disease; LUM, lumican; MMP13, matrix metalloproteinase 13; N, normal; TIMP1, tissue inhibitor of metalloproteinase 1.