LRP6 Conditional Knockout Mice Protocol

Lrp6^f/f mice were obtained from Van Andel Research Institute. ^{60 (link), 61 (link)} Transgenic mice expressing the Cre recombinase under the control of a 3.9-kb fragment of the human osteocalcin promoter (OC-Cre) were obtained from T. Clemens (Baltimore, MD).^{62 (link)} The generation of homozygous deletion Cre^+/−;Lrp6^f/f mice (LRP6-KO hereafter) and control Cre^−/−;Lrp6^f/f (WT hereafter) were described previously.^{23 (link)} Mice were maintained on a mixed background of C57Bl/6J, 129, and FVB/N. All animals were maintained in the Animal Facility of the Johns Hopkins University School of Medicine. The experimental protocol was reviewed and approved by the Institutional Animal Care and Use Committee of the Johns Hopkins University, Baltimore, MD. Genomic DNA extraction and genotyping of the animals were prepared as described previously.^{23 (link)} Primers for Cre recombinase and the loxP sites were used for PCR. For PTH treatment, two month-old male WT mice and KO mice were randomized into four groups: WT-vehicle, WT-PTH, KO-vehicle, and KO-PTH. Six mice of each treatment group were used. Mice were subcutaneously injected with either Human PTH1–34 or vehicle (1 mM acetic acid in phosphate buffered saline (PBS)) at a dosage of 80 μg/kg daily, five days per week, for 4 weeks. Human PTH1–34 was purchased from Bachem Bioscience Inc. (King of Prussia, PA).