Characterization of fibroblast-like synoviocytes from the synovial fluid of patients affected by juvenile idiopathic arthritis

Objectives The objectives of this study were to characterize some phenotypic and functional aspects of fibroblast-like synoviocytes isolated from the Synovial Fluid (SF-FLSs) of patients affected by Juvenile Idiopathic Arthritis (JIA) with active disease and to compare SF-FLS characteristics with those reported in the literature for FLSs of the SM (Synovial Membrane) in adult rheumatic patients. Methods FLSs were isolated from the SF of JIA patients with active disease by therapeutic arthrocentesis. SF-FLS surface marker expression was assessed by cytofluorimetry; proinflammatory cytokine and MMP gene expression was investigated by quantitative RT-PCR (qRT-PCR); and chondrogenic properties were evaluated by staining with Alcian-Blue. Results SF-FLSs display a CD45-,CD34-,CD90+,PDPN+ phenotype and exhibit a significant increase in the expression of genes coding for pro-inflammatory cytokines, but not MMPs, when treated with TNF-α, a cytokine present in the joint environment. In addition, SF-FLSs express the chondrogenic genes BMP4 and Aggrecan (AGG) and show the ability to differentiate towards a chondrocyte-like phenotype when cultured in TGF-β-enriched medium. Conclusion FLSs from the SF of JIA patients display a phenotype that has pro-inflammatory, rather than tissue-disruptive, activity; this is similar to what is observed in cells from the sublining region of the SM in adult arthritis patients. In addition, they show chondrogenic ability, indicating the potential for SF-FLSs as an in vitro model for chondrocytes.