Inflammation induced changes in the expression levels of components of the microRNA maturation machinery Drosha, Dicer, Drosha co-factor DGRC8 and Exportin-5 in inflammatory lesions of hidradenitis suppurativa patients

Background: The inflammatory pathogenesis behind the debilitating chronic inflammatory skin disorder hidradenitis suppurativa (HS) is poorly understood. Deregulation of microRNAs (miRNAs) may contribute to the pathogenesis and chronic inflammation in autoimmune and inflammatory diseases. However, there are no data on the expression or function of miRNAs in HS. Objective: To evaluate expression of the miRNA key regulators Drosha, Drosha co-factor DGRC8, Dicer and Exportin-5 in the inflammatory microenvironment of HS. Methods: Specimens were harvested from lesional HS skin (n = 18), adjacent healthy-appearing HS skin (n = 7), lesional psoriatic skin (n = 10), and healthy subjects (n = 10). To evaluate the quantitative real-time RT-PCR data of Drosha and Dicer a subset of skin samples were studied by immunohistochemistry. Results: Drosha and DGRC8 were significantly downregulated in healthy-appearing perilesional skin from HS patients compared to healthy controls. There were no significant differences in Drosha, DGRC8 and Exportin-5 expression between lesional HS and lesional psoriatic skin. Notably, Dicer expression levels were not dysregulated in psoriatic skin. Limitations: Small sample size and descriptive study design. Conclusions: The miRNA key regulators were significantly dysregulated in HS lesions compared to healthy skin. Drosha and DGRC8 are altered in the initial, subclinical inflammatory process in healthy-appearing perilesional skin of HS patients prior to the first visible clinical manifestations. Dicer and Exportin-5 may contribute to the later inflammatory process with visible HS lesions. (C) 2016 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.