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

Abstract

Background Fibroblast-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 study the ultrastructural characteristics and functional responses in human and mouse FLS. The objective of the study was to analyze 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 (CIA). Methods FLSs were obtained from RA patients (RA-FLSs) (n = 8) and mice with CIA (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. Results RA-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. Conclusion This study provides a comprehensive understanding of the biology of RA-FLS and CIA-FLS. The differences and similarities in ultrastructural morphology and important inflammatory cytokines shown, contribute to future in vitro studies using RA-FLS and CIA-FLS, in addition, they indicate that the adoption of CIA-FLS for studies should take careful and be well designed, since they do not completely resemble human diseases.

A Review of Advances in Molecular Imaging of Rheumatoid Arthritis: From In Vitro to Clinic Applications Using Radiolabeled Targeting Vectors with Technetium-99m

“…In RA, inflammation of the synovium, called synovitis, leads to hyperplasia of the synovial lining and destruction of the cartilage and bones in the joints [ 11 , 12 , 13 ]. A healthy synovium consists of 1–2 linings of synoviocytes [ 14 , 15 , 16 ]. During inflammation, various mononuclear cells, such as T cells, B cells, dendritic cells, plasma cells, mast cells, and macrophages, infiltrate the site of inflammation ( Figure 1 ) [ 17 , 18 , 19 , 20 ]; the synovial lining becomes hyperplastic, resulting in expansion of the synovial membrane and the formation of villi [ 21 , 22 , 23 ].…”

“…Macrophage-like synoviocytes produce various proinflammatory cytokines, such as Interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF). Fibroblast-like synoviocytes (FLSs) produce IL-6, leukotrienes and prostaglandins and migrate from joint to joint for disease propagation [ 12 , 14 , 24 , 25 ]. Synovial cell proliferation reduces capillary flow, increasing fluid volume in the synovium and resulting in hypoxia at the inflamed site [ 12 , 26 , 27 , 28 , 29 , 30 , 31 ].…”

NIH/3T3 Fibroblasts Selectively Activate T Cells Specific for Posttranslationally Modified Collagen Type II

“…So far, several fibroblast subsets with distinct surface phenotypes have been identified [ 26 ]. The THY1 membrane glycoprotein (CD90) was used as a general marker for distinguishing two pathogenic fibroblast subsets related to the RA: THY1 + fibroblasts (located in the synovial sub-lining) that increase the severity and persistence of inflammation, and THY1 − fibroblasts (located in the synovial lining) that are responsible for cartilage and bone destruction [ 6 , 25 , 26 , 28 , 29 ].…”