Background and objectives Glucose-6-phosphate isomerase (G6PI) immunisation induces acute self-limiting arthritis in DBA/1 mice. Upon depletion of regulatory T cells (Tregs) it is possible to deliberately switch the outcome towards a chronic, destructive and non-remitting disease. Fibroblast-like synoviocytes (FLS) are important effector cells in rheumatoid arthritis (RA). The objective of this work is to unravel differences at the transcriptomic and miRNomic level between FLS from Treg-depleted mice (chronic) and FLS from not-depleted mice (acute).
Materials and methods FLS were isolated from the small joints of G6PI immunised mice either Treg-depleted (chronic) or not-depleted (acute) at day 56 post-immunisation or from healthy mice as a baseline control. A transepitelial resistance assay (MATRIN) was used to test FLS collagen destructive potential, while apoptosis was assessed by serum starvation for 5 days followed by flow cytometry staining. Whole genome expression analysis was realised using mouse 430 2.0 array (Affymetrix). Whole microRNA expression was assessed using TaqMan® Rodent MicroRNA A Array v2.0 (Applied Biosystems).
Results FLS from chronic mice at late stages of arthritis show an increased collagen destructive potential and their sensitivity to apoptosis is reduced. Transcriptomic analysis reveals a strong difference in gene expression between FLS from chronic mice and FLS from acute mice. Stimulation with pro-inflammatory cytokines at different time points modulates gene expression differently in cells from chronic mice, enhancing the expression of genes related to cell adhesion, regulation of apoptosis, cell motion and inflammatory response. Comprehensive miRNA analysis shows a panel of overexpressed and down regulated miRNAs that could have an important role in the regulation of arthritis chronicity.
Conclusions FLS from chronic mice are more aggressive and less sensitive to cell death than FLS from acute mice. Whole genome expression analysis confirmed their profound differences at a molecular level. Moreover, stimulation with pro-inflammatory cytokines differentially activates gene expression in FLS from mice with chronic, destructive arthritis. Differences in microRNA expression also confirm these findings. G6PI-induced arthritis mouse model is a useful tool to unravel the role of differentially expressed genes and microRNAs in FLS from chronic mice, in order to discover potential candidates for therapeutic intervention in humans.