The Role of the Microbiome in Gut and Joint Inflammation in Psoriatic Arthritis and Spondyloarthritis

Spondyloarthiltis (SpA) encompasses a group of diseases characterized by an inflammatory arthritis involving both joints and entheses. However extraarticular symptoms constitute a large element of the pathology and should not be underestimated. Microscopic gut inflammation is observed in 50% of patients with SpA and has been linked to disease activity, underscoring the effect of gut inflammation in SpA. In this review, we discuss the influence of gut microbiota on SpA pathogenesis. A change m microbiota composition has been linked to the development of various inflammatory arthriti des, and dysbiosis is a potential factor in the pathogenesis of multiple inflammatoty diseases. In this context, several groups have reported the modulatory effects of gut microbiota-derived metabolites on the effect of immune cells. The gut mucosa is populated by several types of regulatory T cells, but also some specialized unconventional innate-like T cells. These cells are predominantly found at mucosal and epithelial barrier sites, wheie they serve an essential lole in modulating host-microbial interplay. Apart from the close association between the composition of the microbiota and inflammatoiy diseases, the therapeutic value of dysbiosis needs further investigation and the identification of a causal inflammatory pathway between gut dysbiosis and musculoskeletal inflammation could revolutionize the therapeutic approach in SpA.