Influence of LPS, TNF, TGF-ß1 and IL-4 on the expression of MMPs, TIMPs and selected cytokines in rat synovial membranes incubated in vitro.

Synovial membranes are formed by four main types of cells, i.e. fibroblasts, macrophages, epitheliocytes and adipocytes. To study the combined effect of various factors on these cell populations, synovial membranes dissected from rat knee joints were incubated in control medium or medium with lipopolysaccharide (LPS), TNF, TGF-ß1 or IL-4 for 12 h. LPS stimulated TNF secretion and both agents stimulated secretion of IL-6. TGF-ß1 slightly increased IL-6 secretion. LPS increased the mRNA levels of IL-6, IL-1ß, TGF-ß1, MMP1a, MMP1b, MMP3, MMP9, MMP13, MMP14, TIMP1 and TIMP3 while the mRNA levels of MMP2, TIMP2 and TIMP4 were significantly decreased. Expression of IL-1ß, MMP1a, MMP1b, MMP3, MMP9, MMP13 and TIMP1 increased after TNF treatment, while mRNA levels of MMP2, MMP14, TIMP2, TIMP3 and TIMP4 were decreased. TGF-ß1 decreased the mRNA levels of IL-1ß, all MMPs, TIMP1, TIMP2, TIMP4 and increased mRNA levels of itself and TIMP3. IL-4 decreased mRNA levels of IL-1ß, TGF-ß1, MMP2, MMP9, MMP13 and all TIMPs. Only LPS decreased the amount and activity of MMP2. The effect of LPS and cytokines on most of the MMPs and TIMPs produced by whole synovial membrane was in good agreement with previous studies on their action on similar types of cells as those present in synovial membranes, but originating from other tissues. All tested agents decreased MMP2 mRNA expression levels and in the case of LPS also the protein level and its activity determined by zymography, contrary to previous observations on isolated cell populations. This indicates that the response of the organized tissue is an interplay of all components and cannot be deduced from the individual reactions.