Introduction: We have previously observed that rat synovial membranes incubated in medium containing cartilage interstitial fluid (CIF) responded by changes in the expression of hyaluronan synthases (HAS1 and HAS2), collagen type I, versican, aggrecan, lubricin, matrix metalloproteinases 2 and 3 (MMP2 and MMP3), tissue inhibitors of metalloproteinases (TIMP1, 2 and 3), transforming growth factor β1 (TGFβ1), tumor necrosis factor (TNF), interleukin (IL) 1β and IL-6. The aim of the study was to evaluate the influence of particular cytokines found in CIF on the gene expression of extracellular matrix (ECM) proteins in synovial membrane cells.
Material and methods: Synovial membranes (SMs) were removed from the knee joints of inbred, male Lewis rats and incubated with insulin-like growth factor 1 (IGF1), TGFβ1, basic fibroblast growth factor (bFGF) and granulocyte- macrophage colony-stimulating factors (G-CSF and M-CSF), either individually or in the combinations TGFβ1/IGF1, TGFβ1/IGF1/bFGF or G-CSF/M-CSF. Next, total RNA was isolated and the studied genes' expression was evaluated by real-time PCR.
Results: TGFβ1/IGF1 stimulated expression of HAS1, lubricin, collagen type I, aggrecan and TGFβ1, inhibited expression of MMP3 and TNF and had no effect on TIMP1 and IL-6 mRNA levels. TGFβ1/IGF1/bFGF stimulated the expression of HAS1, lubricin and TGFβ1 genes, inhibited the expression of TNF and had no effect of the expression of collagen 1, aggrecan, MMP3, TIMP1 and IL-6 genes. G-CSF/M-CSF stimulated the expression of aggrecan. TGFβ1, bFGF, and IGF1 applied individually exerted inhibitory effect on the expression of lubricin. TGFβ1 and bFGF inhibited expression of MMP3 and bFGF inhibited also the expression of aggrecan and TNF.
Conclusions: The response of the studied genes represents a resultant activity of all major cell types building the synovial membrane, i.e. highly specialized synovial fibroblasts, macrophages, epithelial cells and adipocytes. The results of our study can improve understanding of synovial membrane responses to the intraarticular injections of platelet-rich plasma (PRP) used for the treatment of joint ailments, since PRP contains factors which are also present in CIF.
Keywords: ECM proteins; cartilage interstitial fluid; gene expression; growth factors; qPCR; synovial membrane.