Matrilin-3 MATN3) inhibition of ADAMTS-5 gene expression require IL-1Ra. Knocking down IL-1Ra in primary human chondrocytes (PHCs) only partially affects MATN3-induced inhibition of ADAMTS-5 (A) and does not seem to significantly affect MMP-13 gene expression (B). The concentration of recombinant human MATN3 protein used was 200 ng/ml and of IL-1β was 5.0 ng/ml. Gene expression analysis was conducted 36 hours post exposure to cell culture treatment conditions. #P ≤ 0.05 for statistically significant differences from the untreated group; *P ≤ 0.05 for statistically significant differences between groups. Individual experiments were done in biological triplicate per patient sample. Data are representative of five individual experiments.