Objective Osteoarthritis (OA) is a degenerative and most common joint disease which shows characteristic features like loss of cartilage, formation of osteophytes and alteration of subchondral bone leading to joint impairment and pain. The pathogenesis of OA is still not fully understood. Fibroblast-like synoviocytes (FLS), occurring in the intimal lining layer of the synovial membrane, were shown to promote secondary synovitis by the release of pro-inflammatory cytokines and matrix-metalloproteinases (MMPs). The objective of this study was to analyse the possible anti-inflammatory potential of hydrogen sulphide (H2S) on activated FLS cultured in three-dimensional micromass culture.
Methods Primary cell lines based on FLS derived from patients with OA were cultivated in spherical extracellular matrix micromasses. Micromass cultures were stimulated for 1 h with IL-1β (10 ng/ml) only or with IL-1β plus either 0.125 mM or 1 mM of sodium hydrogen sulphide (NaHS). As a control, cultures were treated with PBS only. Treatments were applied on day three, five, seven, nine, 12, 14, 16 and 19. Micromasses were cultured for 21 days, fixed with paraformaldehyde, sectioned and stained for hematoxylin and eosin (H&E), IL-6 or MMP-3. Secretion of IL-6 was analysed by enzyme-linked immunosorbent assay (ELISA).
Results We observed the spontaneous formation of a compacted, lining layer-like architecture by OA-FLS, already described for rheumatoid arthritis (RA)-FLS. Untreated cultures, in addition, showed clusters of elongated cells underneath the condensed cell layer.
A cellular response, which included increased formation of synovial lining as well as changes in cell morphology, could be seen after stimulation with the pro-inflammatory cytokine IL-1β. Treatment with 1 mM of NaHS had the potential to inhibit structural changes caused by cell activation induced by IL-1β. Furthermore, H2S treatment reduced the IL-1β stimulation-related elevated levels of IL-6 secretion.
Conclusions The ability of NaHS to inhibit the development of cellular responses to pro-inflammatory IL-1β could be considered a cartilage protective effect and has to be elucidated in more detail.