Interleukin-17 is a critical target for the treatment of ankylosing enthesitis and psoriasis-like dermatitis in mice.

Ankylosis is a major pathological manifestation of spondyloarthropathy. The aim of this study was to evaluate the effects of anti-IL-17 therapy on spontaneous ankylosing enthesitis in mice. In this study, we used male DBA/1 mice as a spontaneous ankylosis model. Serum IL-17 concentrations were determined using enzyme-linked immunosorbent assay. Male DBA/1 mice from different litters were mixed and caged together preceding the treatment at 10 weeks (wk) of age (prophylaxis) or 21 wk of age (intervention). Treatment with anti-IL-17 antibodies or saline was initiated after caging in groups of mice and administered weekly. The onset of tarsal ankylosis was assessed by ankle swelling and histopathological examination. Pathological changes and mRNA expression levels were assessed in joints and ears obtained at the experimental end-point. We found that circulating IL-17 increased with the onset of ankylosis in male DBA/1 mice, coinciding with the onset of dermatitis. The symptoms of dermatitis corresponded to the pathological characteristics of psoriasis: acanthosis with mild hyperkeratosis, scaling, epidermal microabscess formation and augmented expression of K16, S100A8 and S100A9. Prophylactic administration of anti-IL-17 antibodies significantly prevented the development of both ankylosis and dermatitis in male DBA/1 mice caged together. On the other hand, administration of anti-IL-17 antibodies after disease onset had a lesser but significant effect on ankylosis progression but did not affect dermatitis progression. In conclusion, IL-17 is a key mediator in the pathogenic process of tarsal ankylosis and psoriasis-like dermatitis in male DBA/1 mice caged together. Thus, IL-17 is a potential therapeutic target in ankylosing enthesitis and psoriasis in humans.