Background Chondroitin sulfate (CS) is one the most used molecules in the management of OA. Its mechanism of action remains to be detailed.
Objectives To perform a microarray analysis to identify a differential expression profile between control and IL-1β stimulated synovial fibroblast cells cultures and to investigate the effects of CS on this gene expression profile.
Methods OA synovial specimens were obtained from 12 patients undergoing knee replacement. Synovial fibroblast cells (SFC) were enzymatically isolated and used after four passages (P4). SFC were pre-treated 1 hour with highly purified bovine CS (200 µg/ml, Bioibérica S.A., Barcelona, Spain) before treatment with IL-1β (1 ng/ml) for 24 hours. Gene expression profiling was performed using Illumina’s multi-sample format Human HT-12 BeadChip (Illumina Inc.). Differential analysis was performed with the BRB array tools software. Class comparison test between control (Ctl) and interleukin (IL)-1β conditions, Ctl and Ctl/CS and IL-1β and IL-1β/CS conditions was based on paired t-test where Ctl and IL-1β, Ctl and Ctl/CS and IL-1β and IL-1β/CS were paired for each patient. The biological relevance of regulated genes was analyzed with Ingenuity Pathways Analysis (Ingenuity® Systems). Probes with a p-value below 0.001 were chosen and classified as up- or down-regulated.
Results 3308 genes were identified as differentially expressed genes between Ctl and IL-1β conditions. A differential profile of expression of major pathways involved in OA pathogenesis was observed. In the inflammatory network, the most upregulated cytokines were IL-8 and IL-6 (fold change: 156.25 and 58.8 respectively). We identified several chemokines, enzymes and metallothioneins (MTs). Complement factor B (CFB) and complement component 3 (C3) are two factors upregulated in the inflammatory complement cascade. We identified some genes implicated in the angiogenesis pathway. The most upregulated was Stanniocalcin 1 (STC1) (fold change: 9.09). The differential expression of intermediates in cartilage anabolism and catabolism revealed an imbalance in favour of catabolism. MMP-3 was largely upregulated (fold change: 62.5). Wnt 5A and low density lipoprotein receptor-related protein (LRP8) were significantly upregulated while frizzled homolog 2 (FZD2) and dickkopf homolog 3 (DKK3) were downregulated in the Wnt signaling. The class comparison test highlighted 660 differentially expressed genes between Ctl and Ctl/CS conditions and 241 genes between IL-1β and IL-1β/CS. Among them, our attention was focused on two genes upregulated in the presence of CS: lysyl oxidase-like 4 (LOXL4) and claudin 11 (CDLN11), two genes that negatively regulate cell invasion.
Conclusions We here evidenced in synovial fibroblast cells the modulation of gene expression following IL-1β stimulation. We also demonstrated the modulatory effects of CS on gene expression and isolated several CS-modulated genes of interest such as LOXL4 and CDLN11, which could constitute new mechanisms of action of the molecule and contribute to explain the symptomatic efficacy of CS in the treatment of OA.
Disclosure of Interest C. Lambert: None Declared, J.-E. Dubuc: None Declared, E. Montell Employee of: BIOIBÉRICA, S.A, Barcelona, Spain; Pre-Clinical R&D Manager, J. Vergés Employee of: BIOIBÉRICA, S.A, Barcelona, Spain; Medical Director, Y. Henrotin Grant/research support from: This study was supported by a grant from BIOIBÉRICA, S.A, Barcelona, Spain