SFEBES2009 Poster Presentations Bone (25 abstracts)
1Academic Endocrine Unit, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; 2Max-Delbrück-Centre for Molecular Medicine, Berlin, Germany; 3Mary Lyon Centre, Medical Research Council, Harwell, UK; 4Mammalian Genetics Unit, Medical Research Council, Harwell, UK.
Renal stone disease is a common disorder for which the underlying causes remain largely unknown. We have investigated a hereditary renal calcification mouse model, Rcalc1, that is not associated with hypercalciuria for underlying mechanisms. Kidney RNA from 30 to 33 week-old Rcalc1 and control BALB/c and C3H female mice (n=4/group) was extracted and hybridised to Mouse Genome 430 2.0 arrays (Affymetrix). Following Robust Multichip Average normalization, pair-wise comparisons of expression data was performed using Students t-test. Due to the small number of genes that were significantly different between Rcalc1 and both wild-type strains at a 5% false discovery rate level, a less stringent selection criteria of transcripts that were ≥1.2-fold up- or down-regulated in Rcalc1 mice relative to both wild-type strains, at P value≤0.01, were selected for further investigation. Amongst the 45 101 probesets, 56 genes met these criteria, 33 genes were up-regulated and 23 genes were down-regulated in Rcalc1 kidneys compared with both wild-type strains. Analyses revealed that the vitamin D3-24-hydroxylase (Cyp24a1) transcript was up-regulated by 1.9- to 3.1-fold, and mRNA levels of calcium-binding protein calbindin-D28k (Calb1) and vitamin D-binding protein (Gc) were down-regulated by 1.4- to 1.5-fold in Rcalc1 kidneys, whereas other genes involved in systemic vitamin D-mediated calcium regulation were not affected. However, cell survival genes were down-regulated (Id1: −1.92- to −3.26-fold, Id3: −1.77- to −2.63-fold) in Rcalc1 kidneys when compared to those from control mice. These results were validated by quantitative real-time PCR, and suggest vitamin D-mediated cell survival is suppressed. Furthermore, TUNEL staining of kidney sections from Rcalc1 mice (n=7), when compared to control mice (n=4), revealed that calcified lesions in Rcalc1 kidneys are associated with apoptotic cells. Thus, our results show that Rcalc1 calcification in the renal papillae is associated with suppressed vitamin D-mediated cell survival.