IADR Abstract Archives
Phospho1 Phosphatase Functions to Facilitate Enamel Biomineralization and Prism Structure
Objectives: To determine the function of PHOSPHO1 during amelogenesis.
Methods: Phospho1 was localized in 3 days postnatal enamel organs using immunohistochemistry. Mouse mandibular first molar structure was compared between Phospho1-/- mutant mice and wild-type controls using electron microscopy and elemental analysis. Another group of mandibles was formalin fixed and processed for ground sections to perform von Kossa and Alizarin red staining.
Results: Immunoreactions demonstrated PHOSPHO1 staining in wild-type ameloblasts. Phospho1 mutant mice revealed densely stained deposits in the stratum intermedium. Wild-type EDX elemental analysis revealed a significant 7.3% reduction in phosphate content in Phospho1-/- mutant mice when compared to wild-type controls (p<0.05) while the difference in calcium was not statistically significant. Scanning electron microscopy of EDTA-etched enamel surface revealed classic picket fence patterns in wild-type controls, while the prism structure of mutant mice was obscured, in part because of a 1.56-fold increase in enamel prism width in Phospho1-/- mutant mice (p<0.0001). Moreover, individual prisms were less separated from each other as a result of a 45.3% reduced mineral-free inter-prism space between individual prisms in Phospho1-/- mutant mice compared to controls. As revealed by von Kossa staining, Phospho1 mutant enamel was less mineralized and contained more organic matrix when compared to WT enamel. Moreover, incisal tips of mutant mice were more rounded, thicker, and less sharp than those of WT mice.
Conclusions: Together, these data indicate that the matrix vesicle-associated phosphatase PHOSPHO1 is essential for physiological enamel mineralization. Our findings prompt us to speculate that matrix vesicle-like organelles may not only be involved in the formation of mesenchymal mineralized tissues but also in amelogenesis.
Methods: Phospho1 was localized in 3 days postnatal enamel organs using immunohistochemistry. Mouse mandibular first molar structure was compared between Phospho1-/- mutant mice and wild-type controls using electron microscopy and elemental analysis. Another group of mandibles was formalin fixed and processed for ground sections to perform von Kossa and Alizarin red staining.
Results: Immunoreactions demonstrated PHOSPHO1 staining in wild-type ameloblasts. Phospho1 mutant mice revealed densely stained deposits in the stratum intermedium. Wild-type EDX elemental analysis revealed a significant 7.3% reduction in phosphate content in Phospho1-/- mutant mice when compared to wild-type controls (p<0.05) while the difference in calcium was not statistically significant. Scanning electron microscopy of EDTA-etched enamel surface revealed classic picket fence patterns in wild-type controls, while the prism structure of mutant mice was obscured, in part because of a 1.56-fold increase in enamel prism width in Phospho1-/- mutant mice (p<0.0001). Moreover, individual prisms were less separated from each other as a result of a 45.3% reduced mineral-free inter-prism space between individual prisms in Phospho1-/- mutant mice compared to controls. As revealed by von Kossa staining, Phospho1 mutant enamel was less mineralized and contained more organic matrix when compared to WT enamel. Moreover, incisal tips of mutant mice were more rounded, thicker, and less sharp than those of WT mice.
Conclusions: Together, these data indicate that the matrix vesicle-associated phosphatase PHOSPHO1 is essential for physiological enamel mineralization. Our findings prompt us to speculate that matrix vesicle-like organelles may not only be involved in the formation of mesenchymal mineralized tissues but also in amelogenesis.