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Kidney Week

Abstract: SA-OR57

Persistent DNA Damage as a Driver of CKD and Tubular Cell Senescence

Session Information

Category: CKD (Non-Dialysis)

  • 2103 CKD (Non-Dialysis): Mechanisms

Authors

  • Airik, Rannar, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
  • Airik, Merlin, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
  • Phua, Yu Leng, UPMC Children's Hospital of Pittsburgh Child Development Unit, Pittsburgh, Pennsylvania, United States
Background

Acute kidney injury (AKI) is a frequent cause of progression to chronic kidney disease (CKD) in humans. Emerging studies have shown that the transition to CKD results from impaired tubular repair due to accumulation of unresolved DNA damage in kidney tubular epithelial cells. Here we identify Fan1, a DNA repair enzyme, as a critical regulator of AKI to CKD progression in response to genotoxic and obstructive kidney injury in mice.

Methods

Ggt1-Cre mice were crossed with FAN1loxP/loxP mice to inactivate FAN1 expression in kidney proximal tubules. Kidney injury was induced by cisplatin administration (5 weekly injections of 2 mg/kg) or unilateral ureteral obstruction (UUO). Histological analysis was performed using hematoxylin and eosin, periodic acid–Schiff, or Masson’s trichrome staining. Tubular cell senescence was demonstrated by β-galactosidase staining at pH 6.0. Primary human kidney proximal tubular cells were used for modeling FAN1 loss of function in cell culture. RNA-seq analysis was performed on cisplatin-treated FAN1-deficient kidneys. Roscovitine was administered to block cell cycle activity and reduce cellular injury in cisplatin-treated FAN1 kidneys.

Results

Kidney proximal tubule cell-specific FAN1 inactivation sensitized the kidneys to tubular injury characterized by massive DNA damage response (DDR) activity. We found that persistent DDR triggers tubular cell dedifferentiation, aberrant cell cycle entry and G2 arrest which ultimately led to a failed tubular repair, tubular cell senescence and induced interstitial fibrosis in FAN1 kidneys. Transcriptional profiling of FAN1 kidneys identified that unresolved DNA damage blocks the cell cycle progression in late G2 through p53-dependent p21 upregulation. G2 cell cycle exit in FAN1-deficient cells was reinforced by nuclear cyclin D1 accumulation and DNA re-replication which gave rise to polyploid karyomegalic cells. Adminstration of roscovitine effectively blocked cell cycle activity and the formation of karyomegalic cells in cisplatin-terated FAN1-deficient kidneys.

Conclusion

Collectively, our data demonstrate that intact DNA damage response (DDR) is critical for proximal tubule regeneration after renal injury, and that Fan1 is a key effector of the DDR pathway in this process. Blocking of cell cycle activity immediately after tubular cell injury may be beneficial to augment tubular repair in the kidney.

Funding

  • NIDDK Support