[microRNA in autoimmune disorders].

microRNAs, short ribonucleic acid molecules which is typically 20-25 nucleotides long, can bind to complementary sequences in the three prime untranslated regions of target mRNAs, leading to the inhibition of translation or degradation of the mRNA. Theologically, human genome may have more than 1000 microRNAs, which target about 60% of human mRNAs. Thus, microRNAs have been implicated in the pathogenesis of various disorders. This paper discusses the present day understanding about the expression and role in various autoimmune diseases including rheumatoid arthritis, Sjogren syndrome, polymyositis/dermatomyositis, systemic lupus erythematosus, scleroderma, type I diabetis, and psoriasis. For example, the expression of miR-29, which targets type I collagen mRNA, is reported to be down-regulated in cultured dermal fibroblasts derived from scleroderma skin, contributing to excessive collagen production in this disease. Supplementation of the microRNA results in the decrease of collagen expression in scleroderma fibroblasts. In addition, serum miR-29a levels are significantly decreased in the very early stage of scleroderma. Investigation of the involvement of microRNAs in the pathogenesis of each autoimmune disease may lead to develop new biomarker and new therapeutic approach.