Transgenic Mice Expressing Fibroblast Growth Factor 23 under the Control of the alpha 1 (I) Collagen Promoter Exhibit Growth Retardation, Osteomalacia, and Disturbed Phosphate Homeostasis
Mutations in the fibroblast growth factor 23 gene, FGF23, cause autosomal dominant hypophosphatemic rickets (ADHR). The gene product, FGF-23, is produced by tumors from patients with oncogenic osteomalacia (OOM), circulates at increased levels in most patients with X-linked hypophosphatemia (XLH) an...
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Veröffentlicht in: | Endocrinology (Philadelphia) 2004-07, Vol.145 (7), p.3087-3094 |
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Sprache: | eng |
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Zusammenfassung: | Mutations in the fibroblast growth factor 23 gene, FGF23, cause autosomal dominant hypophosphatemic rickets (ADHR). The gene product, FGF-23, is produced by tumors from patients with oncogenic osteomalacia (OOM), circulates at increased levels in most patients with X-linked hypophosphatemia (XLH) and is phosphaturic when injected into rats or mice, suggesting involvement in the regulation of phosphate (Pi) homeostasis. To better define the precise role of FGF-23 in maintaining Pi balance and bone mineralization, we generated transgenic mice that express wild-type human FGF-23, under the control of the alpha 1(I) collagen promoter, in cells of the osteoblastic lineage. At 8 wk of age, transgenic mice were smaller (body weight = 17.5 plus or minus 0.57 vs. 24.3 plus or minus 0.37 g), exhibited decreased serum Pi concentrations (1.91 plus or minus 0.27 vs. 2.75 plus or minus 0.22 mmol/liter) and increased urinary Pi excretion when compared with wild-type littermates. The serum concentrations of human FGF-23 (undetectable in wild-type mice) was markedly elevated in transgenic mice (>7800 reference units/ml). Serum PTH levels were increased in transgenic mice (231 plus or minus 62 vs. 139 plus or minus 44 pg/ml), whereas differences in calcium and 1,25-dihydroxyvitamin D were not apparent. Expression of Npt2a, the major renal Na super(+)/Pi cotransporter, as well as Npt1 and Npt2c mRNAs, was significantly decreased in the kidneys of transgenic mice. Histology of tibiae displayed a disorganized and widened growth plate and peripheral quantitative computerized tomography analysis revealed reduced bone mineral density in transgenic mice. The data indicate that FGF-23 induces phenotypic changes in mice resembling those of patients with ADHR, OOM, and XLH and that FGF-23 is an important determinant of Pi homeostasis and bone mineralization. |
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ISSN: | 0013-7227 |
DOI: | 10.1210/en.2003-1768 |