MicroRNAs in the Pathogenesis of Ankylosing Spondylitis and their Clinical Implication.

Ankylosing spondylitis (AS) is a chronic and progressive immunoinflammatory disease, which mainly affects the spine and sacroiliac joints and shows a high rate of late disability. Inflammation, bone destruction, and new bone formation are typical pathological changes of AS. AS is dominated by inflammation at the early stage. While bone destruction and heterotopic ossification, the two contradictory manifestations of AS, occur at a later stage and reflect the imbalance between osteogenesis and osteoclastogenesis in AS patients. Till now, the pathogenesis of AS remains unclear. MicroRNAs (miRNAs) are a class of highly conserved single-stranded noncoding RNAs (ncRNAs) with a length of about 22 bases characterized by temporal sequence and tissue specificity. MiRNAs are key modulators in bone formation, resorption, remodeling and regeneration by regulating the immune responses and the differentiation and functions of osteoblasts, osteoclasts and chondrocytes. The present review summarizes the roles and potential mechanisms of miRNAs' involvement in AS by regulating immuno-inflammatory responses, bone destruction, heterotopic ossification, cell death and autophagy, and the involved signaling including the Wnt/β-catenin and BMP/Smads pathways. In addition, the feasibility of miRNAs as diagnostic biomarkers and therapeutic targets for AS are also discussed.