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Kidney Week

Abstract: PO1708

Continuous Non-Mutagenic DNA Damage in Podocytes Activates Inflammatory Response and May Accelerate Kidney Aging

Session Information

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Nakamichi, Ran, Keio University School of Medicine Department of Internal Medicine, Tokyo, Japan
  • Hishikawa, Akihito, Keio University School of Medicine Department of Internal Medicine, Tokyo, Japan
  • Hayashi, Kaori, Keio University School of Medicine Department of Internal Medicine, Tokyo, Japan
  • Itoh, Hiroshi, Keio University School of Medicine Department of Internal Medicine, Tokyo, Japan
Background

Podocytes are suggested to contribute to kidney aging because of their terminally differentiated features. We have previously reported the association of KAT5-mediated DNA damage repair with altered DNA methylation in podocytes (Cell Rep 2019). However, the role of podocyte DNA damage itself on DNA methylation changes and kidney aging has remained to be adequately elucidated.

Methods

To investigate the significance of DNA double-strand breaks (DSBs) in podocytes, we generated podocyte-specific I-PpoI-expressing mice (podocin-Cre ROSA26-STOP- I-PpoI). I-PpoI is a homing endonuclease which causes non-mutagenic DSBs. RNA-seq and MeDIP-seq analysis were performed using isolated podocytes in I-PpoI mice and wildtype controls.

Results

I-PpoI mice showed severe albuminuria (WT 43±34.4 mg/gCr, Ip-Po1 2224±7.3 mg/gCr, p<0.01) with diffuse foot process effacement in podocytes but glomerulosclerosis and interstitial fibrosis were not observed at 12 weeks of age. Interestingly, infiltration of CD11b-positive cells was shown in I-PpoI mice, which is a similar finding in 2-year-old aged mice. The aged mice showed increased DNA damage and DNA methylation. In I-PpoI mice, rapid deterioration of renal function with glomerulosclerosis and tubulointerstitial fibrosis developed around the age of 20 weeks. RNA-seq analysis revealed that inflammatory-related genes were upregulated in podocytes of I-PpoI mice. Senescent-associated secretory phenotype (SASP)-related gene expression was also increased. MeDIP-seq analysis revealed that 5219 differentially methylated regions (DMRs) were identified in I-PpoI mice compared with controls. Interestingly, there was no significant correlation between the distance from the I-PpoI cutting site and DMRs. DNA methylation was increased in genes containing I-PpoI cutting sites or podocyte epithelial genes such as nephrin and podocin, whereas it was decreased in inflammatory related genes, suggesting gene-specific DNA methylation changes following DNA damage.

Conclusion

The phenotype of the I-PpoI mice may reflect one aspect of accelerated kidney aging. Repeated DNA damage repair in podocytes may cause altered DNA methylation independent of primary DNA damaged sites with promoted inflammation and podocyte morphological changes.