Matrilin-3 MATN3) regulation of type II collagen (COL2A1) and aggrecan (ACAN) gene expression, as well as COL2A1 protein expression requires IL-1Ra. Knocking down IL-1Ra abolishes the ability of recombinant human (rh) MATN3 protein to maintain COL2A1 gene expression in primary human chondrocytes (PHCs) that are challenged with IL-1β (A). A significant reduction in the basal gene expression of COL2A1 is also observed in IL-1Ra knock-down PHCs. PHCs cultured for 48 hours in media supplemented with rh MATN3 protein (200 ng/ml) exhibit increased COL2A1 protein levels; however, upon suppressing IL-1Ra via siRNA-based gene knock-down, MATN3 enhancement of collagen is diminished according to western blot analysis (B). Relative quantification of band intensity is the accumulated result of three individual experiments (n = 3). Knocking down of IL-1Ra also abolishes MATN3 stimulation of ACAN gene expression (C). The concentration of rh MATN3 protein used was 200 ng/ml and of IL-1β was 5.0 ng/ml for all experiments. (A, C) 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. (B) *P ≤ 0.05 for statistically significant differences from the untreated control group. Individual experiments were done in biological triplicate per patient sample. Data are representative of five individual experiments.
Jayasuriya et al. Arthritis Research & Therapy 2012 14:R197 doi:10.1186/ar4033