Session Title: Rheumatoid Arthritis - Human Etiology and Pathogenisis
Session Type: Abstract Submissions (ACR)
Wnt (wingless) pathway signaling has been implicated in patterning in embryogenesis and in adult wound healing and homeostasis. A canonical Wnt antagonist, Dickkopf-1 (DKK-1), has been described as an embryonic bone morphogen. DKK-1 expression is stimulated by TNF in inflammatory disease and is elevated in the sera of rheumatoid arthritis patients. This Wnt signaling antagonist has been linked to the depression osteoblast activity and bone loss. Here we examined a novel role for the pathogenic activity of this protein by virtue of its ability to activate JNK and increase migration of fibroblast-like synoviocytes (FLS).
Human and mouse FLS were cultured and the plates were scratched. Migration was measured by serial photography of a marked area and Image J quantification. Results were confirmed with an Oris™ stopper assay, and cell entry into the central clearing was measured by calcein AM fluorescence. FLS were treated with rDKK-1, rWnt5a, PDGF, SB216763 (a GSK3ß inhibitor), SP600125 (a JNK inhibitor), and IWP-2 (a porcupine inhibitor). In some cases, FLS were lysed for Western blot and qPCR analyses.
Human and mouse FLS exhibited faster migration in the scratch wound assay and the stopper assay when stimulated with DKK-1 (50, 100 or 150ng/ml). DKK-1 increased percent wound closure from 31+4to 46+5 (p<0.04) for human and 41+4 to 58+18 (p<0.04) for mouse FLS. DKK-1-induced migration was inhibited by the JNK inhibitor SP600125. On the other hand, SB216763 and IWP-2 had minimal or no effect, indicating that it is independent of endogenously produced Wnt. DKK-1 stimulated JNK phosphorylation in FLS within 10 minutes, which was also not abrogated by IWP-2. To determine which JNK isoform is responsible, JNK1 null and JNK2 null mouse FLS were studied in the migration assays. Unexpectedly, DKK-1 treatment still induced the migration of JNK1 deficient, but not JNK2 deficient cells. In association with increased migration, DKK-1 treated FLS increased expression of MMP-1 (1.4 fold), MMP2 (1.4 fold) and MMP13 (1.6 fold). In contrast, MMP9 and MMP3 expression was decreased.
Conclusion: DKK-1 stimulates migration of FLS, which is associated with JNK phosphorylation and increased expression of selected metalloproteinases. DKK-1-induced migration was mediated by JNK2 signaling, suggesting that this pathway plays a critical role in synoviocyte migration and cartilage damage in rheumatoid arthritis
J. S. Song,
D. L. Boyle,
G. S. Firestein,
arthritis foundation NIH,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/dickkopf-1-stimulates-fibroblast-like-synoviocyte-migration-through-janus-kinase-activation/