Vitamin D-Deficient Mouse Model

Inbred C57BL/6JJ female mice were purchased from Japan SLC, Inc. (Hamamatsu, Japan). Because a previous study indicated that female mice were more sensitive than male mice to vitamin D supplementation by UV irradiation^{24 (link)}, we used only female mice in the present study. They were kept at a temperature of 25 °C with a 12-h light–dark cycle and shielded from UVB of an ordinary fluorescent light. To create a 25-hydroxyvitamin D [25(OH)D]-starved mouse group for the experiments, mice were weaned from their mothers and fed the standard wheat-based mouse diet until 12 weeks of age. Then they were fed a vitamin D-deficient diet (AIN93GA-2, Oriental Yeast Co ltd., Tokyo, Japan) until the study termination^{25 (link)}, at 32 weeks of age. AIN93GA-2 contains no vitamin D, 0.50% calcium, 0.20% phosphorus, and 7.00% total fat.