The Role Of Interleukin-17A In The Pathogenesis Of Thyroid-associated Ophthalmolpathy

ObjectivesThe development of thyroid-associated ophthalmopathy(TAO)is associated with self-immune dysfunction.Recent findings in TAO and Graves’disease indicate that IL-17A may also be involved in the autoimmunity of TAO.In this study,we sought to investigate the pathogenic function of IL-17A-producing T cells in TAO and examine how Th17 cells affect different subsets of orbital fibroblasts(OF)and fibrocytes.Materials and Methods1.Blood samples were obtained from TAO patients and healthy controls and were subjected to ELISA and flow cytometry analysis.Primary human OFs cultured from surgical wastes were stimulated with IL-17A were examined by real-time PCR,cytokine-specific ELISA,flow cytometry,and Western blotting assays.2.We analyzed Th17,Treg,and fibrocyte phenotypes in blood samples and orbital tissues from TAO patients and healthy controls.We also studied inflammatory reactions,fibrotic and adipogenic processes in OFs and fibrocytes modulated by IL-17A.Luminex and pathscan intracellular signaling assays were conducted to unravel the regulatory loops among Th17 cells,OFs,and fibrocytes in TAO.Results1.We showed a significantly higher proportion of IL-17A-producing T cells in TAO patients and the recruitment of both CD4~+and CD8~+T cells in TAO orbits.TAO orbital tissues expressed more IL-17A receptor,IL-17A and its related cytokines,with severe fibrotic change compared with normal controls.Furthermore,we validated that IL-17A could enhance the proinflammatory function of orbital fibroblasts and stimulate the production of extracellular matrix proteins in orbital fibroblasts,but not eyelid fibroblasts.The mechanisms involved in this enhancement mainly relied on MAPK activation.Finally,we observed that the deubiquitinase inhibitor vialinin A could down-regulate RORγt expression and decrease IL-17A level in TAO patients.2.We reported that pathogenic Th17 cells and cytokine-producing fibrocytes were increased in TAO patients.Costimulatory molecules were highly expressed in TAO orbits and could be elevated with IL-17A stimulation.The majority of TAO orbital connective tissue derived OFs were CD34~+CD90~+.We demonstrated that the CD34~+subpopulation exhibited more aggressive function under IL-17A incubation or with Th17 cell co-culture treatment in vitro,and Th17 cells could be activated after direct contact with fibrocytes or OFs.We also showed that the cell surface expression of CD90on OFs influenced their terminal differentiation into myofibroblasts or adipocytes.Whereas IL-17A promoted fibrosis in CD90~+OFs,it inhibited TAO adipogenesis via different pathways.Conculsions1.Our observations illustrate the potential pathogenic role of IL-17A-producing T cells in the inflammatory response and fibrosis of TAO.The effect of vialinin A on the reduction of RORγt level implicates its potential role as a novel therapeutic agent for TAO and other autoimmune disorders in the future.2.The interplay among pathogenic Th17 cells,fibrocytes and orbital fibroblasts leads to orbital inflammation and tissue remodeling in TAO.Understanding the heterogeneity of OFs monitored by IL-17A will help to afford a novel approach to better therapeutic strategies for TAO.