Renal cysts are the defining feature of autosomal dominant polycystic kidney disease (ADPKD); however, the substantial interstitial inflammation is an often-overlooked aspect of this disorder. Recent studies suggest that immune cells in the cyst microenvironment affect ADPKD progression. Here we report that microRNAs (miRNAs) are new molecular signals in this crosstalk. We found that miR-214 and its host long noncoding RNA Dnm3os are upregulated in orthologous ADPKD mouse models and cystic kidneys from humans with ADPKD. In situ hybridization revealed that interstitial cells in the cyst microenvironment are the primary source of miR-214. While genetic deletion of miR-214 does not affect kidney development or homeostasis, surprisingly, its inhibition in Pkd2- and Pkd1-mutant mice aggravates cyst growth. Mechanistically, the proinflammatory TLR4/IFN-γ/STAT1 pathways transactivate the miR-214 host gene. miR-214, in turn as a negative feedback loop, directly inhibits Tlr4. Accordingly, miR-214 deletion is associated with increased Tlr4 expression and enhanced pericystic macrophage accumulation. Thus, miR-214 upregulation is a compensatory protective response in the cyst microenvironment that restrains inflammation and cyst growth.
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