J ZHANG1, M LUCIUK1, P HARRIS3, Y WANG1,2, D HARRIS1,2, G RANGAN1,2
1Centre for Transplant and Renal Research, Westmead Institute for Medical Research, University of Sydney, Westmead, Australia, 2Department of Renal Medicine, Westmead Hospital, Westmead, Australia, 3Mayo Translational PKD Centre, Mayo Clinic, Rochester, USA
Aim: To determine if DNA damage is present in cyst-lining epithelial cells of Pkd1 mice.
Background: Kidney cyst formation in autosomal dominant polycystic kidney disease (ADPKD) is focal and random, coinciding with reduced PKD gene dosage. We hypothesised that DNA damage might be a trigger for this event, and that it might be detected in renal cysts.
Methods: Pkd1 (homozygous for hypomorphic Pkd1 allele R3277C; n=12 per timepoint), and wild-type (WT) mice (n=8 per timepoint), were examined at 1, 3 and 6 months of age. DNA damage was assessed by immunohistochemistry using H2AX and γ-H2AX (specific biomarkers of DNA damage).
Results: Focal and sporadic kidney cysts were evident throughout the cortex and outer medulla from 1 month of age. The two kidney to body weight ratio was 1.4, 1.6 and 1.6-fold higher in Pkd1 compared to WT mice at 1, 3 and 6 months respectively, and %cyst area increased from 6.9% at 1 month to 10.8% at 6 months. In WT kidneys, qualitative histological analysis demonstrated that H2AX was diffusely expressed in the majority of nuclei, whereas γ-H2AX was rare and present only in scattered nuclei. In Pkd1 mice, H2AX and γ-H2AX staining was similar to WT in non-cyst lining cells at all time points. However, H2AX and γ-H2AX staining was stronger in the majority of cyst-lining cells. In addition, γ-H2AX staining was stronger at 1 month compared to 3 and 6 months, and in smaller rather than larger cysts.
Conclusions: These data support the hypothesis that DNA damage is present in the early stages of cystic renal disease, and suggest that it may be a factor in triggering kidney cyst formation in ADPKD.
Jennifer is currently a PhD student in the Polycystic Kidney Disease Group at the Westmead Institute for Medical Research, University of Sydney, under the supervision of Associate Professor Gopi Rangan. She previously completed a Bachelor of Science (Physiology and Nutrition & Metabolism), followed by a Master of Nutrition and Dietetics. Her PhD is focused on preclinical research into what triggers cyst formation in autosomal dominant polycystic kidney disease. She is also currently working as a research dietitian on the PREVENT-ADPKD study.