Session Type: Poster Session (Sunday)
Session Time: 9:00AM-11:00AM
Background/Purpose: Anti-citrullinated protein antibodies (ACPAs) play an important role in rheumatoid arthritis (RA) pathogenesis. ACPAs have different amino acid motif recognition patterns and show cross-reactivity to other protein modifications. We aimed to investigate the effect of different monoclonal ACPAs on RA synovial tissue derived fibroblast-like synoviocytes (FLS).
Methods: FLS were isolated from synovial tissue of RA patients by enzymatic digestion. ACPA and control monoclonal antibodies (mAbs) were derived from single B cells isolated from RA patients. Whole antibodies and F(ab’)2 fragments were tested in synovial fibroblast migration (IncuCyte live-cell analysis) and osteoclast formation assays. Blocking experiments were performed with soluble citrullinated proteins in SF migration. The role of mAbs cross-reactivity was tested in fibroblast migration assays using antibodies with distinct cross-reactivities, inhibitors of peptidylarginine deiminases (Cl-amidine and GSK199), histone acetyltransferase (anacardic acid) and histone deacetylase (trichostatin A). Binding patterns of monoclonal ACPAs were tested in synovial biopsies obtained from both healthy donors and RA patients.
Results: Three monoclonal ACPAs (1325:01B09, 14T+:02D09 and14T+:02H12) enhanced fibroblast migration significantly compared to control mAb 1362:01E02-treated samples (mean±SD fold increase of 1.9±0.5, 1.7±0.4 and 1.8±0.6, respectively, p< 0.05), whereas the same antibodies showed no effect on osteoclast formation. Clone 1325:01B09 but neither 14T+:02D09 nor 14T+:02H12 is cross reactive with homo-citrullinated and acetylated targets (acetylated histone). The effect of 1325:01B09 on fibroblast migration was completely abolished by Cl-amidine or by pre-incubating the antibody with citrullinated fibrinogen or histone but not by citrullinated enolase or vimentin. Despite the cross-reactivity with acetylated epitopes, neither anacardic acid nor trichostatin A could modulate the 1325:01B09 effect on fibroblast migration. The fibroblast-promoting ACPA clone 1325:01B09 but not the osteoclastogenic 1325:04C03 co-localized with podoplanin-positive fibroblasts in the inflamed rheumatoid synovium. On the contrary to RA samples, healthy synovia were not stained by ACPAs. F(ab’)2 fragments of mAbs show similar effects on synovial fibroblast migration, osteoclast formation and a similar tissue binding pattern as the intact antibodies, indicating an Fc-independent mediated effect.
Conclusion: Some but not all ACPA clones could stimulate synovial fibroblast migration through a mechanism that was dependent on protein citrullination but no other protein modifications or FcR binding. Different clones acted on fibroblasts and osteoclasts suggesting unique pathological roles associated with individual ACPA specificities.
To cite this abstract in AMA style:Sun M, Rethi B, Krishnamurthy A, Joshua V, Circiumaru A, Hensvold A, Engström M, Catrina S, Steen J, Malmström V, Grönwall C, Klareskog L, Wähämaa H, Catrina A. Monoclonal ACPA Promote Synovial Fibroblasts Migration Through a Peptidylarginine Deiminases (PAD) Dependent Pathway [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/monoclonal-acpa-promote-synovial-fibroblasts-migration-through-a-peptidylarginine-deiminases-pad-dependent-pathway/. Accessed February 26, 2021.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/monoclonal-acpa-promote-synovial-fibroblasts-migration-through-a-peptidylarginine-deiminases-pad-dependent-pathway/