Background/Purpose:

The primary cilium is a microtubule-based, polarized, antenna structure that emanates from the cell surface of most mammalian cell types. It serves as a sensor that mediates reactions to mechanical and chemical signals from the environment and is therefore, a crucial factor in the communication with neighbouring cells and the environment.

We aimed to investigate the functional role of the primary cilium expressed on synovial fibroblasts (SF) in the pathogenesis of rheumatoid arthritis (RA).

Methods:

The expression of the primary cilium was verified in serum- starved RASF by immunofluorescence microscopy using acetylated tubulin as a marker and by transmission electron microscopy. Ciliogenesis of RASF was disrupted by transfection of siRNA targeting the ciliary components kinesin family member 3a (KIF3a) and intraflagellar transport 88 homolog (IFT88). RASF were stimulated with TNF-α (10ng/ml) and IL-1β (1ng/ml). Differentially expression of transcripts in RASF transfected with KIF3a siRNA with and without cytokine stimulation was screened using Microarrays (Affymetrix). Migration and adhesion properties of transfected RASF were analysed by scratch assay (n=3) and a fibronectin-based adhesion assay (n=7), respectively.

Results:

The primary cilium was detected on the surface of RASF.  Migration of RASF with blocked formation of the primary cilium due to transfection with siRNA targeting KIF3a or IFT88 was reduced compared to RASF transfected with scrambled siRNA. RASF adhesion to fibronectin was induced by TNF-α (2.1 fold ± 0.9, n.s.) and IL-1β (2.3 fold ± 1.3, p<0.05), and was reduced in KIF3a siRNA transfected RASF (TNF-α: 1.2 fold ± 0.7, p<0.05; IL-1β: 1.3 fold ± 0.7, p=0.1142). In the whole genome expression analysis, 1321 transcripts were more than 2-fold up or down regulated in RASF transfected with KIF3A siRNA and 1243 transcripts were more than 2-fold up or down regulated in the KIF3AsiRNA transfected group stimulated with cytokines compared to control groups. 213 transcripts appeared to be differentially expressed under stimulated as well as under unstimulated conditions.

Conclusion:

Our data show a functional role of the primary cilium in the migratory and adhesive properties of RASF.  Since disruption of ciliogenesis in RASF altered their response to stimulation with TNF-α and IL-1β, we hypothesise that the primary cilium also plays a key role in the transmission of pro-inflammatory signals in RASF.

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« Back to 2012 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/functional-analysis-of-the-primary-cilium-in-rheumatoid-arthritis-synovial-fibroblasts/