Background/Purpose:

Fibroblast-like synoviocytes (FLS) play an important role in the progression of rheumatoid arthritis (RA). Particularly, FLS of RA patients (RA-FLS) exhibit pro-migratory and invasive characteristic reminiscent of cancer cells, destroying cartilage and bone. However, key regulators or signaling molecules responsible for this characteristic are not fully documented. Recently, we have demonstrated that nuclear factor of activated T cell 5 (NFAT5), an osmo-protective transcription factor, is crucial to the development of experimentally-induced arthritis in mice (Kim WU, et al. Arthritis Rheum 2011). Here, we investigated if NFAT5 controls migration and invasion of RA-FLS.

Methods:

The FLS were obtained from synovial tissues of RA patients. Messenger RNA (mRNA) in RA-FLS and embryonic fibroblasts, which were deficient of NFAT5 gene, were profiled using microarray technology. NFAT5 expression in the presence of interleukin 1β (IL-1β) or transforming growth factor β (TGFβ) was analyzed by western blot analysis and real-time PCR. The expression levels of tissue factor and CCL2 were measured by flow cytometry analysis and ELISA, respectively. Wound migration assay and invasion assay using matrigel chamber were conducted in vitro.

Results:

The mRNA profiling of RA-FLS transfected with NFAT5 short interfering RNA (siRNA) and embryonic fibroblasts of NFAT5 knockout mouse revealed that NFAT5 is involved in the migration and invasion in RA-FLS. Transcriptome analysis also suggested that tissue factor and CCL2 were the key target genes of NFAT5 responsible for these processes. Consistent with these results, NFAT5 was up-regulated in RA-FLS stimulated with pro-migratory and pro-invasive cytokines, including IL-1β and TGFβ. Interestingly, tissue factor and CCL2 were independently increased by TGFβ and IL-1β, respectively, although both of which were commonly regulated by NFAT5. Moreover, knockdown of NFAT5 or tissue factor using siRNAs resulted in a marked suppression of migration and invasion of RA-FLS; particularly, TGFβ-induced RA-FLS invasion and lamellipodia formation were blocked by knockdown of NFAT5 or tissue factor transcripts. SB203580, a p38 inhibitor, down-regulated TGFβ-induced NFAT5 expression, suggesting that p38 is an up-stream regulator of NFAT5 under high TGFβ conditions.

Conclusion:

The present study demonstrates first that NFAT5 is a critical regulator responsible for the migration and invasion of RA-FLS. These data also provide the evidence for a novel role of the TGFβ-NFAT5-tissue factor axis in RA-FLS invasiveness, which could be a potential target for anti-FLS therapy retarding cartilage and bone destruction.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/crucial-role-of-nuclear-factor-of-activated-t-cell-5-nfat5-an-osmo-protective-factor-in-migration-and-invasion-of-rheumatoid-synoviocytes/