CCN2/CTGF increases expression of miR-302 microRNAs, which target the TGFβ type II receptor with implications for nephropathic cell phenotypes.

Signalling interplay between transforming growth factor-β (TGFβ) and CCN2 [also called connective tissue growth factor (CTGF)] plays a crucial role in the progression of diabetic nephropathy and has been implicated in cellular differentiation. To investigate the potential role of microRNAs (miRNAs) in the mediation of this signalling network, we performed miRNA screening in mesangial cells treated with recombinant human CCN2. Analysis revealed a cohort of 22 miRNAs differentially expressed by twofold or more, including members of the miR-302 family. Target analysis of miRNA to 3'-untranslated regions (3'-UTRs) identified TGFβ receptor II (TβRII) as a potential miR-302 target. In mesangial cells, decreased TβRII expression was confirmed in response to CCN2 together with increased expression of miR-302d. TβRII was confirmed as an miR-302 target, and inhibition of miR-302d was sufficient to attenuate the effect of CCN2 on TβRII. Data from the European Renal cDNA Biopsy Bank revealed decreased TβRII in diabetic patients, suggesting pathophysiological significance. In a mouse model of fibrosis (UUO), miR-302d was increased, with decreased TβRII expression and aberrant signalling, suggesting relevance in chronic fibrosis. miR-302d decreased TGFβ-induced epithelial mesenchymal transition (EMT) in renal HKC8 epithelial cells and attenuated TGFβ-induced mesangial production of fibronectin and thrombospondin. In summary, we demonstrate a new mode of regulation of TGFβ by CCN2, and conclude that the miR-302 family has a role in regulating growth factor signalling pathways, with implications for nephropathic cell fate transitions.