J ZHANG 1,2, S SARAVANABAVAN 1,2, A MUNT 1,2, A WONG 1,2, P HARRIS 3, D HARRIS 1,2, P MCKENZIE 4, Y WANG 1,2, G RANGAN 1,2
1Centre for Transplant and Renal Research, Westmead Institute for Medical Research, The University of Sydney, Sydney, Australia, 2Department of Renal Medicine, Westmead Hospital, Western Sydney Local Health District, Sydney, Australia, 3Mayo Translational PKD Center, Mayo Clinic, Rochester , U. S. A., 4Department of Tissue Pathology, NSW Health Pathology, Royal Prince Alfred Hospital, The University of Sydney, Sydney, Australia
Aim: To test the hypothesis that DNA damage and DDR signalling are increased in ADPKD and evaluate whether attenuating the DDR reduces kidney cyst formation.
Background: Susceptibility to DNA-damaging events and genomic instability are features of cystic kidney disease. Previously, we demonstrated that γ-H2AX (biomarker for double-strand DNA breaks) was upregulated in a genetic ortholog of nephronophthisis but its role in ADPKD is not known.
Methods: The DDR transcriptome was examined in human ADPKD and Pkd1RC/RC mice (a genetic ortholog of ADPKD) using publicly available datasets (GSE7869, GSE9493, GSE131277). Markers of the DDR were assessed in end-stage human ADPKD tissue and cell lines (WT9-7, WT9-12). The functional role of the DDR was evaluated by pharmacological inhibition (AZD0156) and genetic ablation of ataxia telangiectasia mutated (ATM; proximal DDR kinase regulator) in Pkd1RC/RC mice.
Results: In human ADPKD, the number of upregulated DDR-related genes was increased by 16.6-fold compared to normal kidney, and by 2.5-fold in cystic compared to minimally cystic tissue (P<0.0001). In contrast, in Pkd1RC/RC mice, DDR-related gene expression was transiently increased on postnatal day 0 but not sustained at later time-points. In human ADPKD, phosphorylated ATM was localised to cystic kidney epithelial cells and constitutively increased in WT9-7 and WT9-12 cells. In vitro, AZD0156 reduced cyst growth by up to 4.4-fold but in vivo, long-term progression of cystic kidney disease was not altered in Pkd1RC/RC/Atm+/− mice compared to Pkd1RC/RC/Atm+/+ mice.
Conclusion:DDR signalling was dysregulated in cystic epithelial cells in human ADPKD and coincided with early cyst formation in mice. Kinase inhibition of ATM reduced kidney cyst growth in vitro but attenuation of ATM protein in vivo did not alter long-term kidney cyst growth.
Jennifer recently completed her PhD on polycystic kidney disease at the Westmead Institute for Medical Research under the supervision of A/Prof Gopi Rangan. She previously completed a Master of Nutrition and Dietetics and worked as a research dietitian for the PREVENT-ADPKD study. She is currently completing a Doctor of Medicine at the University of Sydney.