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Abstract: TH-OR003

Knockout of DNA Methyltransferases in Proximal Tubules Preserves Klotho and Improves Kidney Repair after Ischemia/Reperfusion Injury

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Guo, Chunyuan, Medical College of Georgia, Augusta University, Augusta, Georgia, United States
  • Wei, Qingqing, Medical College of Georgia, Augusta University, Augusta, Georgia, United States
  • Livingston, Man J., Augusta University Medical College of Georgia, Augusta, Georgia, United States
  • Dong, Zheng, Medical College of Georgia, Augusta, Georgia, United States
Background

DNA methylation, catalyzed by DNA methyltransferases (DNMTs), is an important epigenetic mechanism that has been implicated in renal development, function, and disease pathogenesis. However, the role of DNA methylation in renal ischemia/reperfusion (I/R) injury and subsequent kidney repair remains largely unknown.

Methods

Mice were subjected to: i) 30 minutes of bilateral renal ischemia with 48 hours of reperfusion to examine renal I/R injury, and ii) 30 minutes of unilateral renal ischemia with 2 weeks of reperfusion to analyze post-injury kidney repair. To determine the role of DNA methylation, we established kidney proximal tubule-specific DNMT1 knockout (PT-DNMT1-KO) or DNMT1 and DNMT3a double knockout (PT-DNMT1/3a-DKO) mouse models.

Results

DNMT1 and DNMT3a were markedly increased in renal tubular cells during renal I/R injury as well as post-injury kidney repair. Knockout of DNMT1 or knockout of both DNMT1 and DNMT3a in proximal tubules did not affect renal I/R injury. However, DNMT1 and DNMT3a double knockout (PT-DNMT1/3a-DKO) promoted post-injury kidney repair and attenuated renal fibroblast activation and interstitial renal fibrosis. Two weeks after I/R injury, PT-DNMT1/3a-DKO mice showed lower kidney injury molecule-1 (Kim-1) and vimentin expression than wild type mice, suggesting better kidney repair in DKO mice. Furthermore, DKO mice showed less accumulation of fibronectin and α-SMA (myofibroblast marker) with lower levels of collagen deposition in kidneys, indicating less interstitial fibrosis. Mechanistically, post-injury kidneys showed hypermethylation of Klotho, the anti-aging gene with anti-fibrosis activity. Hypermethylation of Klotho was accompanied by a dramatic decrease of Klotho expression in kidneys. Notably, DNMT1/3a-DKO prevented Klotho hypermethylation and preserved Klotho expression in post-injury kidneys.

Conclusion

These results indicate that DNMT1 and DNMT3a-dependent DNA methylation in proximal tubules plays an important role in kidney repair following renal I/R. Changes in DNA methylation in specific genes, such as Klotho, may lead to aberrant gene expression to promote maladaptive repair and interstitial fibrosis.

Funding

  • NIDDK Support