Objective: We have recently shown that mice lacking one allele of β-catenin in osteocytes do not respond to anabolic loading (Javaheri et al, JBMR 2013). The purpose of this study was to determine if these mice respond to unloading.
Method: Dmp1-Cre β-catenin fl/+ mice, HET, (n = 30) were randomly divided into 3 different housing conditions; normal, not suspended but with tail ring insertion, and suspended. Suspension was initiated at 15 weeks of age for 4 weeks. Mice were then sacrificed and their tibiae were analyzed using μCT and histomorphometry.
Result: Male trabecular bone volume and female cortical bone density significantly decreased while female trabecular bone separation significantly increased with suspension compared with non-suspended animals. (1-way ANOVA and Tukey post-hoc test, p< 0.05). Also, in the suspended animals, decreasing trends were observed in bone area and bone perimeter, while increasing trends were seen in osteoclast number and osteoclast surface.
Conclusion:
The results show that mice lacking one allele of β-catenin respond to unloading with bone loss. The loss of bone observed with suspension may be due to an increase in osteoclastic number and activity, but requires further analysis.
Funded by UMKC SOD Summer Scholars Program and NIH NIA PO1AG039355.