FGF7 as an essential mediator for the onset of ankylosing arthropathy related to psoriatic skin lesions

IL-17A plays an important role in the pathology of psoriasis and psoriatic arthritis (PsA). However, the pathogenic association between the skin and joint manifestations in PsA is not completely understood. In this study, we initially observed that IL-17A and fibroblast growth factor (FGF) 7 induced endochondral ossification in the mouse entheseal histoculture. Importantly, the responses of endochondral ossification by IL-17A stimulation were strongly inhibited by the treatment of a blocking antibody to FGF receptor 2IIIb (FGFR2IIIb), which is the receptor of FGF7, suggesting that FGF7 acts as a downstream factor of IL-17A in the endochondral ossification in the culture. Next, using the animal PsA model, the administration of anti-FGFR2IIIb antibody resulted in significant suppression of ankylosing enthesitis but not dermatitis. Collectively, our findings indicate that augmented IL-17A in PsA dermatitis induces the elevation of FGF7 levels in joint enthesis, and results in the development of ankylosing enthesitis via FGF7 signaling in PsA. Gene expression analysis of entheseal tissues of C57BL/6J mice. Organs were stimulated with or without IL-17A (10 ng/mL) for 72 h (n = 3 per sample).