Osteoblast CFTR inactivation reduces differentiation and osteoprotegerin expression in a mouse model of cystic fibrosis-related bone disease

Michael S. Stalvey, Katrina L. Clines, V. Havasi, Christopher R. McKibbin, Lauren K. Dunn, W. Joon Chung, Gregory A. Clines

Research output: Contribution to journalArticle

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Abstract

Low bone mass and increased fracture risk are recognized complications of cystic fibrosis (CF). CF-related bone disease (CFBD) is characterized by uncoupled bone turnover-impaired osteoblastic bone formation and enhanced osteoclastic bone resorption. Intestinal malabsorption, vitamin D deficiency and inflammatory cytokines contribute to CFBD. However, epidemiological investigations and animal models also support a direct causal link between inactivation of skeletal cystic fibrosis transmembrane regulator (CFTR), the gene that when mutated causes CF, and CFBD. The objective of this study was to examine the direct actions of CFTR on bone. Expression analyses revealed that CFTR mRNA and protein were expressed in murine osteoblasts, but not in osteoclasts. Functional studies were then performed to investigate the direct actions of CFTR on osteoblasts using a CFTR knockout (Cftr-/-) mouse model. In the murine calvarial organ culture assay, Cftr-/- calvariae displayed significantly less bone formation and osteoblast numbers than calvariae harvested from wildtype (Cftr+/+) littermates. CFTR inactivation also reduced alkaline phosphatase expression in cultured murine calvarial osteoblasts. Although CFTR was not expressed in murine osteoclasts, significantly more osteoclasts formed in Cftr-/- compared to Cftr+/+ bone marrow cultures. Indirect regulation of osteoclastogenesis by the osteoblast through RANK/RANKL/OPG signaling was next examined. Although no difference in receptor activator of NF-κB ligand (Rankl) mRNA was detected, significantly less osteoprotegerin (Opg) was expressed in Cftr-/- compared to Cftr+/+ osteoblasts. Together, the Rankl:Opg ratio was significantly higher in Cftr-/- murine calvarial osteoblasts contributing to a higher osteoclastogenesis potential. The combined findings of reduced osteoblast differentiation and lower Opg expression suggested a possible defect in canonical Wnt signaling. In fact, Wnt3a and PTH-stimulated canonical Wnt signaling was defective in Cftr-/- murine calvarial osteoblasts. These results support that genetic inactivation of CFTR in osteoblasts contributes to low bone mass and that targeting osteoblasts may represent an effective strategy to treat CFBD.

Original languageEnglish
Article numbere80098
JournalPLoS One
Volume8
Issue number11
DOIs
Publication statusPublished - Nov 13 2013

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bone diseases
Osteoprotegerin
osteoblasts
cystic fibrosis
Bone Diseases
Osteoblasts
Cystic Fibrosis
inactivation
Bone
animal models
Osteogenesis
osteoclasts
mice
Osteoclasts
bones
bone formation
Skull
Bone and Bones
vitamin D deficiency
Messenger RNA

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Osteoblast CFTR inactivation reduces differentiation and osteoprotegerin expression in a mouse model of cystic fibrosis-related bone disease. / Stalvey, Michael S.; Clines, Katrina L.; Havasi, V.; McKibbin, Christopher R.; Dunn, Lauren K.; Chung, W. Joon; Clines, Gregory A.

In: PLoS One, Vol. 8, No. 11, e80098, 13.11.2013.

Research output: Contribution to journalArticle

Stalvey, Michael S. ; Clines, Katrina L. ; Havasi, V. ; McKibbin, Christopher R. ; Dunn, Lauren K. ; Chung, W. Joon ; Clines, Gregory A. / Osteoblast CFTR inactivation reduces differentiation and osteoprotegerin expression in a mouse model of cystic fibrosis-related bone disease. In: PLoS One. 2013 ; Vol. 8, No. 11.
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