Association of glomerular DNA damage and DNA methylation with one-year eGFR decline in IgA nephropathy

Accumulation of DNA double-strand breaks (DSBs) is linked to aging and age-related diseases. We recently reported the possible association of DNA DSBs with altered DNA methylation in murine models of kidney disease. However, DSBs and DNA methylation in human kidneys was not adequately investigated. This study was a cross-sectional observational study to evaluate the glomerular DNA DSB marker γH2AX and phosphorylated Ataxia Telangiectasia Mutated (pATM), and the DNA methylation marker 5-methyl cytosine (5mC) by immunostaining, and investigated the association with pathological features and clinical parameters in 29 patients with IgA nephropathy. To evaluate podocyte DSBs, quantitative long-distance PCR of the nephrin gene using laser-microdissected glomerular samples and immunofluorescent double-staining with WT1 and γH2AX were performed. Glomerular γH2AX level was associated with glomerular DNA methylation level in IgA nephropathy. Podocytopathic features were associated with increased number of WT1(+)γH2AX(+) cells and reduced amount of PCR product of the nephrin gene, which indicate podocyte DNA DSBs. Glomerular γH2AX and 5mC levels were significantly associated with the slope of eGFR decline over one year in IgA nephropathy patients using multiple regression analysis adjusted for age, baseline eGFR, amount of proteinuria at biopsy and immunosuppressive therapy after biopsy. Glomerular γH2AX level was associated with DNA methylation level, both of which may be a good predictor of renal outcome in IgA nephropathy.