Persistent osteopenia in adult cystic fibrosis transmembrane conductance regulator-deficient mice

Rationale A loss of function mutation in the cystic fibrosis transmembrane conductance regulator gene is believed to be an independent risk factor for bone disease inpatients with cystic fibrosis. Objectives: The objective of this work was to use congenic mice as a preclinical model to examine the bone phenotype of Cftr(-/-) mice and control littermates at 8, 12, and 28 weeks of age. Methods: The bone phenotype of control and Cftr(-/-) mice was evaluated by quantitative imaging, histologic and histomorphometric analyses, and serum levels of bone biomarkers. Measurements and Main Results: At 12 weeks of age, Cftr(-/-) mice were smaller, had lower bone mineral density, cortical bone thinning, and altered trabecular architecture compared with Cftr(+/+) or Cftr(+/-) control mice. In skeletally mature 28-week-old mice, there were persistent deficits in cortical and trabecular bone structure in Cftr(-/-) mice despite significant, quantifiable improvements. Cftr(-/-) mice also had lower serum insulin-like growth factor-I levels at 12 weeks of age than did control mice, whereas parathyroid hormone and 25-hydroxyvitamin D levels were not significantly different. Conclusions: Persistent osteopenia and structural abnormalities in adult Cftr(-/-) mice, in the absence of overt respiratory and gastrointestinal disease, suggest that loss of Cftr function has a direct impact on bone metabolism in Cftr(-/-) mice that is not sex specific or subject to haplotype insufficiency.