2017 Volume 15 Issue 3-4 Pages 126-138
Hypophosphatasia(HPP)is caused by mutations in the gene encoding tissue-nonspecific alkaline phosphatase(ALPL). HPP patients develop deficient calcification of bones and teeth including defects in cementum, dentin, and enamel and the characteristic premature loss of primary teeth. Here, we investigated the enamel defects of knockout(Alpl-/-)mice compared with that of control wild type(Alpl+/+)mice.
No alkaline phosphatase(ALP)activity was detected by specific staining in the first molar germ of Alpl-/- mice on postnatal day 5. Hematoxylin and eosin staining revealed that the enamel layer in Alpl-/- mice was thin, undulated, and rugged. Furthermore, Alpl-/mice had abnormal ameloblasts and the dentin-predentin layer blur and the abuttal not well defined. Some enamel defects matched non-homogeneous distribution of the enamel matrix proteins(EMPs); amelogenin(AMELX), ameloblastin(AMBN), and enamelin(ENAM), as shown by immunohistochemistry. Microarray analysis revealed that several expressions of genes related to enamel development were reduced in Alpl-/- mice. Furthermore, gene expressions of both Ambn and Enam were significantly lower in Alpl-/- mice than in Alpl+/+ mice, as determined by quantitative real time PCR analysis.(p<0.05).
Our study suggests that ALP may have involvement in EMPs and enamel defects in Alpl-/- mice is caused by ameloblasts disorder. Furthermore, our study advances elucidation of the mechanisms that underlie enamel development, and will support establish the causes of enamel defects of HPP patients.
