Mineral content of calcified tissues in cystic fibrosis mice |
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Authors: | Lara R Gawenis Paulette Spencer Laura S Hillman Matthew C Harline J Steven Morris Lane L Clarke |
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Institution: | (1) Dalton Cardiovascular Research Center and the Department of Veterinary Biomedical Sciences, USA;(2) Missouri University Research Reactor Center, USA;(3) Department of Child Health, University of Missouri-Columbia, 65211 Columbia, MO;(4) the Department of Oral Biology, University of Missouri-Kansas City School of Dentistry, 64108 Kansas City, MO |
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Abstract: | Although abnormal hard tissue mineralization is a recognized complication of cystic fibrosis (CF), the pathogenesis leading
from the defective cystic fibrosis transmembrane conductance regulator (CFTR) protein is poorly understood. We hypothesized
that CFTR plays a direct role in the mineralization of bone and teeth and tested the hypothesis using CF mouse models CFTR(−)
mice]. In vivo measurements by dual-emission X-ray absorpitometry (DEXA) indicated that bone mineral density (BMD) was reduced
in CF mice as compared to gender-matched littermates. However, no change was evident after correction of BMD for the covariant
of body weight. The latter finding was confirmed in isolated femurs and nasal bones by standard dry-ashing and instrumental
neutron activation analysis (INAA). INAA of the continuously growing hypsodont incisor teeth from CFTR(−) mice revealed reduced
Ca and normal P in the enamel layer—a finding consistent with changes in the deciduous teeth of CF children. Interestingly,
enamel fluoride was increased in the CFTR(−) incisors and may associate with abnormal enamel crystallite formation. The iron
content of the incisor enamel was reduced, explaining the loss of yellow pigmentation in CFTR(−) incisors. In contrast to
the incisors, the mineral content of the slow-growing brachydont molar teeth was not different between CFTR(−) and CFTR(+)
mice. It was concluded that CFTR does not play a direct role in the mineralization of bones or brachydont teeth in mice. Functional
CFTR is apparently required for normal mineralization of the hypsodont incisors. However, multiple changes in the mineral
composition of the CF incisors suggest an indirect role for CFTR, perhaps by maintaining a normal salivary environment for
continuous tooth eruption.
Preliminary reports published in Pediatric Pulmonology, 14, 253A (1997) and 15, 253A (1998). |
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Keywords: | Femurs nasal bone bone teeth incisors molars enamel CFTR calcium phosphorus fluoride iron neutron activation |
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