Osteoblast CFTR Inactivation Reduces Differentiation and Osteoprotegerin Expression in a Mouse Model of Cystic Fibrosis-Related Bone Disease
Figure 4
CFTR inactivation increased osteoclastogenesis and Rankl:Opg osteoblast expression.
(A) Bone marrow was flushed from Cftr+/+ and Cftr−/− mice and osteoclast formation assays performed. Osteoclasts were identified by TRAP staining as cells containing ≥3 or more nuclei. More osteoclasts were found in Cftr−/− bone marrow. (B) Rankl and Opg mRNA expression was determined by real-time RT PCR in Cftr+/+ and Cftr−/− calvarial osteoblasts with and without PTH (1–34) 10 nM treatment for 24 hours. Overall, CFTR inactivation increased the Rankl:Opg ratio in both PTH (1–34)-treated and untreated osteoblasts. (C) In long-term osteoblast cultures, decreased Opg expression persisted post-confluence despite no significant difference in Rankl. Opg expression remained significantly lower at 7 days in Cftr−/− osteoblasts, but did not reach significance at 14 days post-confluence. (* = p<0.05; ** = p<0.01; *** = p<0.001; NS = not significant)