Comparative morphofunctional analysis of fibroblast-like synoviocytes in human rheumatoid arthritis and mouse collagen-induced arthritis

Abstract

BackgroundFibroblast-like synoviocytes (FLS) play a prominent role in rheumatoid synovitis and degradation of the extracellular matrix through the production of inflammatory cytokines and metalloproteinases (MMPs). Since animal models are frequently used for elucidating the disease mechanism and therapeutic development, it is relevant to compare ultrastructural characteristics and functional responses by human and mouse FLS. The objective of this study is to compare ultrastructural characteristics, IL-6 and MMP-3 production, and the activation of intracellular pathways in FLS from patients with RA (RA-FLS) and mice with collagen-induced arthritis (CIA-FLS). The objective of the study was to compare ultrastructural characteristics, Interleukin-6 (IL-6) and Metalloproteinase-3 (MMP-3) production and the activation of intracellular pathways in Fibroblast like synoviocytes (FLS) cultures obtained from patients with Rheumatoid Arthritis (RA) and from mice with collagen-induced arthritis.MethodsFLSs were obtained from RA patients (RA-FLSs) (n = 8) and mice with collagen-induced arthritis (CIA-FLSs) (n = 4). Morphology was assessed by transmission and scanning electron microscopy. IL-6 and MMP-3 production was measured by ELISA, and activation of intracellular signaling pathways (NF-κB and MAPK: p-ERK1/2, p-P38 and p-JNK) was measured by Western blotting in cultures of RA-FLSs and CIA-FLSs stimulated with tumor necrosis factor - alpha (TNF-α) and IL-1β.ResultsRA-FLS and CIA-FLS cultures exhibited rich cytoplasm, rough endoplasmic reticula and prominent and well-developed Golgi complexes. Transmission electron microscopy demonstrated the presence of lamellar bodies, which are cytoplasmic structures related to surfactant production, in FLSs from both sources. Increased levels of pinocytosis and numbers of pinocytotic vesicles were observed in RA-FLSs (p < 0.05). Basal production of MMP-3 and IL-6 was present in RA-FLSs and CIA-FLSs. Regarding the production of MMP-3 and IL-6 and the activation of signaling pathways, the present study demonstrated a lower response to IL-1β by CIA-FLSs than by RA-FLSs.ConclusionThere were differences between RA-FLSs and CIA-FLSs in their ultrastructural morphologies and functional responses. The differences shown in our study indicate that the adoption of an RA-FLS human model is a better alternative than the CIA-FLS animal model for in vitro studies of RA etiopathogenesis and new therapeutic targets.