Cartilage Destruction Mediated by Synovial Fibroblasts Does Not Depend on Proliferation in Rheumatoid Arthritis

Abstract

The aim of the study was to investigate the relationship between invasion and proliferation in rheumatoid arthritis synovial fibroblasts (RASFs). In vitro, RASFs, normal synovial fibroblasts (NSFs), and RASFs transformed with SV40 T-antigen (RASF(SV40)) were analyzed for the expression of cell surface markers (Thy1, VCAM-1, ICAM-1, CD40, CD44) and their proliferation by flow cytometry. Furthermore, colony-forming unit assays were performed and the expression of matrix metalloproteinases (MMP)-14 and cathepsin K mRNA were determined by real-time polymerase chain reaction. In vivo, in the severe combined immunodeficiency (SCID) mouse co-implantation model, RASFs, NSFs, and RASF(SV40) were tested for cartilage invasion, cellular density, and for their expression of the cell cycle-associated protein Ki67. In the SCID mouse co-implantation model, RASFs invaded significantly stronger into the cartilage than NSFs and RASF(SV40). Of note, RASF(SV40) cells formed tumor-like tissues, and the cellular density adjacent to the cartilage was significantly higher than in RASFs or NSFs. In turn, the proliferation marker Ki67 was strongly expressed in the SV40-transformed synoviocytes in SCID mice, but not in RASFs, and specifically not at sites of cartilage invasion. Using the colony-forming unit assay, RASFs and NSFs did not form colonies, whereas RASF(SV40) lost contact inhibition. In vitro, the proliferative rate of RASFs was low (4.3% S phase) in contrast to RASF(SV40) (24.4%). Expression of VCAM-1 was significantly higher, whereas of ICAM-1 was significantly lower, in RASFs than in RASF(SV40). CD40 was significantly stronger expressed in RASF(SV40), whereas CD44 and AS02 were present at the same degree in almost all synoviocytes. Expression of cathepsin K and matrix metalloproteinase-14 mRNA was significantly higher in RASFs than in the RASF(SV40). Our data demonstrate clearly that invasion of cartilage is mediated by activated RASFs characterized by increased expression of adhesion molecules, matrix-degrading enzymes, but does not depend on cellular proliferation, suggesting the dissociation of invasion and proliferation in RASFs.

Emodin Inhibits Proinflammatory Responses and Inactivates Histone Deacetylase 1 in Hypoxic Rheumatoid Synoviocytes

“…35) There are many evidences that synoviocytes produce MMPs, especially MMP-1 and -13 (collagenases), and contribute to joint destruction in RA. [36][37][38] In our study, IL-1b and LPS treatment significantly induced MMP-1 and -13 expressions at secreted protein and mRNA levels, consistent with the previous papers. 39,40) Transcriptional activation of MMP-1 and -13 can be regulated by various signaling pathways.…”

Rosiglitazone induces interleukin‐1 receptor antagonist in interleukin‐1β–stimulated rat synovial fibroblasts via a peroxisome proliferator–activated receptor β/δ–dependent mechanism

“…Consistent with this idea, PPAR␥ ligands have been shown to decrease the expression of TNF␣ in activated synoviocytes (28) and macrophages (19) and the production of various matrix metalloproteinases in chondrocytes (25,38) and synoviocytes (39). Synoviocytes may play a crucial role because of their ability to proliferate under inflammatory conditions (40) and to cooperate with both macrophages in the synovial pannus and chondrocytes at the synovium-cartilage junction (41). In addition, the increased expression of proinflammatory cytokines within the rheumatoid synovium (42) is accompanied by an imbalance between IL-1 and its natural antagonist IL-1Ra in synoviocytes (13), further explaining the major contribution of IL-1 to cartilage destruction.…”

A Role for the High-Density Lipoprotein Receptor SR-B1 in Synovial Inflammation via Serum Amyloid-A

“…32 Furthermore, high levels of expression of ICAM-1 on RA FLCs are associated with a more aggressive and invasive phenotype. 33 To establish whether a relationship exists between SR-B1 expression and responsiveness to A-SAA, ICAM-l induction after A-SAA stimulation was compared with quantitative baseline SR-B1 expression on four RA FLC lines as shown in Figure 3b. Induction of ICAM-1 by A-SAA correlated closely with baseline SR-B1 expression across RA FLC lines (r 2 ϭ 0.99, P Ͻ 0.05).…”