Expression of phosphate transporters in optimized cell culture models for dental cells biomineralization

Phosphate is a key component of dental mineral composition. The physiological role of membrane proteins of dental cells is suspected to be crucial for mineralization mechanisms. Contrary to published data related to calcium, data on regulation of phosphate flux through membrane of mineralizing cells are scarce. To address this lack of data, we studied the expression of six membranous phosphate transporters in two dental cell lines: a rat odontoblastic cell line (M2H4) and a mouse ameloblastic cell line (ALC) for which we optimized the mineralizing culture conditions

Slc20a2, Encoding the Phosphate Transporter PiT2, Is an Important Genetic Determinant of Bone Quality and Strength.

Osteoporosis is characterized by low bone mineral density (BMD) and fragility fracture and affects over 200 million people worldwide. Bone quality describes the material properties that contribute to strength independently of BMD, and its quantitative analysis is a major priority in osteoporosis research. Tissue mineralization is a fundamental process requiring calcium and phosphate transporters. Here we identify impaired bone quality and strength in Slc20a2-/- mice lacking the phosphate transporter SLC20A2. Juveniles had abnormal endochondral and intramembranous ossification, decreased mineral accrual, and short stature. Adults exhibited only small reductions in bone mass and mineralization but a profound impairment of bone strength. Bone quality was severely impaired in Slc20a2-/- mice: yield load (-2.3 SD), maximum load (-1.7 SD), and stiffness (-2.7 SD) were all below values predicted from their bone mineral content as determined in a cohort of 320 wild-type controls. These studies identify Slc20a2 as a physiological regulator of tissue mineralization and highlight its critical role in the determination of bone quality and strength. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc

Phosphate and dental mineralization : what role for phosphate transporters ?

La place essentielle du phosphate dans la composante minérale dentaire laisse supposer un rôle physiologique déterminant pour les protéines membranaires permettant son entrée dans les cellules dentaires. Contrairement aux données disponibles pour le calcium, les molécules permettant la production et la régulation du flux de phosphate aux sites de formation du minéral par les cellules minéralisantes dentaires sont peu connues. Ces informations sont pourtant déterminantes pour la compréhension des mécanismes de minéralisation dentaire. La première étape dans la compréhension du rôle des six transporteurs de phosphate connus (SLC17A1, SLC34A1, SLC34A2, SLC34A3, SLC20A1 et SLC20A2) pendant l’odontogenèse et la minéralisation dentaire a été de déterminer leur expression spatio temporelle par différentes techniques. Nos résultats ont montré que SLC34A2, SLC20A1 et SLC20A2 sont les transporteurs de phosphate exprimés pendant le développement dentaire. Cependant le schéma spatiotemporel d’expression de ces transporteurs ne coincidant pas avec la cinétique de minéralisation la question de leur implication fonctionnelle dans les processus de minéralisation, en tant que transporteurs de phosphate dans la dent, ou en tant que protéines multifonctionnelles restait ouverte. Pour répondre à cette question, nous avons mis en place plusieurs modèles d’analyse in vitro, ex vivo et in vivo. Les résultats les plus importants, issus de l’analyse phénotypique des dents des souris Slc20a2- /- ont montré que l’absence de Slc20a2 entraîne des anomalies de la dentine avec des calcosphérites au front de minéralisation avec un retard de minéralisation dentinaire.The importance of phosphate in dental mineralization suggests a key role for membrane proteins controlling Pi uptake into dental cells. In contrast to calcium, there is no study assessing the functional implication of the different sodium-phosphate transporters in tooth mineralization and odontogenesis. As a first step to determine the functional involvement of the six known phosphate transporters (Npt1/SLC17A1, Npt2a/SLC34A1, Npt2b/SLC34A2, Npt2c/SLC34A3, PiT1/SLC20A1 and PiT2/SLC20A2) during tooth development and mineralization, we have determined their spatiotemporal expression in mouse model during large timescale of odontogenesis by different techniques. Our results obtained by Real Time PCR as well as by in situ hybridization, immunohistochemistry and Xgal staining unravel that SLC34A2, SLC20A1 and SLC20A2 are the main phosphate transporters expressed during tooth development. These results coincide with our results on human dental samples. Considering the spatiotemporal pattern of expression, it remains so to be determined the functional implication of these transporters in mineralization processes, and whether these proteins act indeed as transporters of phosphate in the tooth, or as multifunctional proteins. To answer this question we adressed several models: in vitro (cell lines culture) ex vivo (dental germ culture) and in vivo ( trasngenic mouse models). Multimodal analysis (histology, microCT, SEM, EDX, immunohistochemistry) on Slc20a2-/- mice dental structures show that absence of Slc20a2 leads to abnormal dentin structures displaying calcospherites at the mineralization front, together with delayed dentin mineralization

Utilisation du laser pour le traitement et la prévention des mucités chimio et radio induites chez l'enfant

RENNES1-BU Santé (352382103) / SudocSudocFranceF

Oro-dental phenotype in patients with RUNX2 duplication

International audienceRunt-related transcription factor 2 (RUNX2) is well-known for its role in bone development and tooth mor-phogenesis. Most RUNX2 mutations described in the literature result in loss-of-function mutations of RUNX2 responsible for cleidocranial dysplasia, an autosomal dominant disorder. We describe here the oro-dental phenotype of four patients of a unique family with a 285 kb duplication including the entire sequence of RUNX2, likely responsible for three functional copies of the gene, leading to an increased RUNX2 dosage. Several dental anomalies of number (hypodontia or oligodontia), morphology (microdontia, radiculomegaly, taurodontism or dens invaginatus) and tooth position (rotation) were found in these patients