ICCBH2019 Poster Presentations (1) (226 abstracts)
Rescue diet restores bone matrix mineralization in mice with a non-functioning vitamin D receptor
Barbara Misof 1 , Stéphane Blouin 1 , Markus Hartmann 1 , Jochen Hofstaetter 2 , Klaus Klaushofer 1 , Jochen Zwerina 1 , Paul Roschger 1 & Reinhold Erben 3
1Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, Wien, Austria; 2Orthopaedic Hospital Vienna Speising, Wien, Austria; 3Department of Biomedical Sciences, University of Veterinary Medicine, Wien, Austria.
Objectives: Mice with a non-functioning vitamin D receptor (VDR mutants) develop severe secondary hyperparathyroidism, which can be rescued by a diet enriched with calcium, phosphate and lactose. In this work, we studied the effects of a low calcium challenge (CD), normal calcium (ND) and a calcium enriched rescue diet (RD) on the bone mineralization density distribution (BMDD) and osteocyte lacunae sections (OLS) in these mice.
Methods: BMDD and OLS were measured in femoral bone from male VDR mutants (n=22) and wildtype (WT, n=11) mice based on quantitative backscattered electron imaging. Mice were fed with RD for 4 months (baseline), subsequently switched to CD for 2 months and afterwards fed 3 months either with CD, ND or RD (9 months age-groups).
Results: At baseline no difference in BMDD or OLS parameters between VDR mutants and WT could be observed. After 2 months with CD distinct differences in BMDD were observed, for instance average degree of mineralization CaMean was decreased by −7.6% and the percentage of low mineralized bone area CaLow was 3-fold (P≤0.001) in metaphyseal spongiosa in VDR mutants versus WT, while OLS-parameters were similar. Comparison among the VDR mutant mouse groups revealed no differences in OLS but differences in BMDD. Of the 9 months old mice, only those on RD had similar BMDD compared to baseline.
Conclusion: Switching the VDR mutant mice from RD to CD for 2 months caused severe effects on BMDD showing a large percentage of bone area with poor mineralization consistent with histologic signs of rickets. These detrimental effects on bone mineralization could be rescued by following 3 months with RD which is in line with the previously reported correction of hyperparathyroidism. Our findings further suggest no change in osteocyte lacunae size, shape and density independent of differences in bone mineralization in VDR mutants.
Disclosure: The authors declared no competing interests.
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Bone Abstracts
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