Kidney Week

Abstract: TH-PO902

Proximal Tubule ATR in Humans and Mice Is a Key Regulator of the DNA Repair Response Protecting the Kidney Against Maladaptive Repair and Fibrosis After Tubular Injury

Session Information

• Molecular Mechanisms of CKD - I
  October 25, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

• 1903 CKD (Non-Dialysis): Mechanisms

Authors

• Kishi, Seiji, Tokushima University Hospital, Tokushima, Japan

Seiji Kishi,

• Brooks, Craig R., Vanderbilt University Medical Center/Division of Nephrology & Hpertension, Nashville, Tennessee, United States

Craig R. Brooks,

• Ichimura, Takaharu, Brigham & Women's Hospital/Harvard Medical School, Boston, Massachusetts, United States

Takaharu Ichimura,

• Nishimura, Kenji, Tokushima University Hospital, Tokushima, Japan

Kenji Nishimura,

• Morizane, Ryuji, Brigham & Women's Hospital/Harvard Medical School, Boston, Massachusetts, United States

Ryuji Morizane,

• Bonventre, Joseph V., Brigham & Women's Hospital/Harvard Medical School, Boston, Massachusetts, United States

Joseph V. Bonventre,

Background

Renal proximal tubular epithelial cells (RPTECs) comprise the bulk of the renal parenchyma and are the primary target of a variety of insults to the kidney. Maladaptive repair of RPTECs has been implicated in kidney fibrosis through induction of cell cycle arrest at G2/M. The DNA damage response (DDR) is a mechanism of DNA repair that is responsible for maintaining genome integrity. We hypothesize that inhibition of DDR, through deletion of the DNA damage sensor ataxia telangiectasia and Rad3 related (ATR), would worsen the fibrotic response in RPTECs.

Methods

Human kidney biopsy tissue was analyzed from 11 patients with interstitial fibrosis and elevated serum creatinine and 9 cases with minor glomerular abnormalities and good preservation of tubules. Kidney organoids were generated from human pluripotent stem cells. An active form of ATR and the marker of DNA damage (γH2AX) were studied by immunocytochemistry along with KIM-1 to evaluate whether DDR correlates with eGFR or fibrosis. We generated RPTC-specific conditional ATR knockout (ATR^RPTC-/-) mice by crossing ATR floxed (ATR^fl/fl) with ATR^+/– and tamoxifen-inducible RPTC-CRE driver (SLC34a1-CreERT2) mice and evaluated kidney injury, fibrosis and cell cycle arrest following ischemia/reperfusion, cisplatin and ureteral obstruction-induced injury in these mice.

Results

Humans with chronic fibrotic kidney disease and human kidney organoids treated with cisplatin have activation of ATR and extensive DNA damage in proximal tubules with an inverse correlation between p-ATR and DNA damage marked by γH2AX in human biopsies. ATR^RPTC-/-mice exhibited greater kidney functional impairment, DNA damage, and fibrosis in response to kidney injury induced by either bilateral ischemia reperfusion, cisplatin or unilateral ureteral obstruction. ATR^RPTC-/-mice had increased G2/M arrested cells after these kidney injuries.

Conclusion

DDR is activated in human kidney disease and ATR plays a protective role against tubular cell injury, death and fibrotic response. Proximal tubule ATR activation is a key component of the DDR which confers a protective effect by mitigating maladaptive repair and consequent fibrosis that follows kidney injury.

Funding

• NIDDK Support