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Abstract: SA-PO340

miR-17/-20a Alleviates Renal Interstitial Fibrosis by Repressing Frmd6 Expression in Renal Epithelia

Session Information

Category: Development, Stem Cells, and Regenerative Medicine

  • 600 Development, Stem Cells, and Regenerative Medicine

Authors

  • Malta C.S Santos, Debora, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States
  • Tayeb, Maliha, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States
  • Bodnar, Andrew J., Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States
  • Appolonia, Corynn, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States
  • Tan, Roderick J., University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States
  • Subramanya, Arohan R., University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States
  • Bitzer, Markus, University of Michigan Department of Internal Medicine, Ann Arbor, Michigan, United States
  • Ho, Jacqueline, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States
Background

An estimated 37 million Americans have chronic kidney disease (CKD), and its prevalence is increasing with higher rates of diabetes mellitus, hypertension and obesity. Regardless of the underlying etiology, renal fibrosis is the final manifestation of CKD. microRNAs (miRNAs) are endogenous, small non-coding RNAs that bind to target mRNAs and regulate their expression. In this study, we investigated the role of the miR-17~92 cluster (comprises miR-17, -18a, -19a, -19b, -20a and -92a) in renal fibrosis.

Methods

Genetic mouse models of inducible epithelial-specific miR-17~92 loss-of-function (imiR-17~92EpiLOF) or gain-of-function (imiR-17~92EpiGOF) were generated by crossing Pax8Cre-rtTA; LC1-cre mice with miR-17~92 floxed mice or with a mouse line containing a constitutively active CAG promoter ahead of a loxP-flanked STOP cassette preventing transcription of the downstream miR-17~92 sequence, respectively. Unilateral ureteral obstruction (UUO) and acute kidney injury (AKI) to CKD model were performed. Renal fibrosis was assessed by immunostaining with anti-collagen III and anti-α-SMA antibodies, followed by semi-quantitative analyses with ImageJ. The human proximal tubular epithelial cell line HK2 was transfected with either empty vector or a vector containing the Frmd6 cDNA. HK2 cells were used for experimental identification of miR-17~92 target genes using PAR-CLIP.

Results

miRs-17, -18a, and -20a were upregulated in UUO and the AKI to CKD model. Interestingly, imiR-17~92EpiLOF mice exhibited increased predisposition to renal fibrosis with aging and after UUO, which was accompanied by increased expression of known miR-17~92 profibrotic targets, p-Stat3 and p-Smad3. Conversely, UUO-induced fibrosis was ameliorated in imiR-17~92EpiGOF kidneys. Frmd6, an activator of Hippo signaling, was identified as a novel miR-17/-20a target. Frmd6 was increased in the tubular epithelium of obstructed imiR-17~92EpiLOF kidneys compared to controls. Finally, overexpression of Frmd6 in HK2 cells resulted in increased expression of the mesenchymal markers SNAI1 and FN1, and elevated secretion of collagen III in conditioned media.

Conclusion

Together, our findings indicate that the miR-17~92 cluster in renal epithelia functions to limit fibrosis by regulating multiple pro-fibrotic pathways.

Funding

  • NIDDK Support