Impact of three endocrine disruptors, Bisphenol A, Genistein and Vinclozolin on female rat enamel

Concerns about the potential adverse effects of endocrine disruptors (EDs) have been increasing over the last three decades. Bisphenol A (BPA), genistein (G) and vinclozolin (V) are three widely used EDs sharing similar effects.Since populations are exposed to many diverse EDs simultaneously, we demonstrated recently their impact alone or combined on male rat tooth enamel. The purpose of this study was therefore to assess their effects on female rat tooth enamel in order to understand why they are differentially sensitive. Rats were exposed daily in utero and after birth to low doses of EDs during the critical fetal and suckling periods when amelogenesis takes place. Enamel of rats exposed to EDs presented opaque areas of hypomineralization. The proportion of affected rats was the highest in the groups of rats treated with BPA alone and higher in males than in females (in all the groups). Comparison of enamel key gene expression levels showed modulations of Klk4 and Enamelin in males but no significant variations in females. These findings show that female rats are less affected than males by the three EDs chosen in this study and suggest that enamel hypomineralization may differ between males and female

Tracking Endogenous Amelogenin and Ameloblastin In Vivo

Research on enamel matrix proteins (EMPs) is centered on understanding their role in enamel biomineralization and their bioactivity for tissue engineering. While therapeutic application of EMPs has been widely documented, their expression and biological function in non-enamel tissues is unclear. Our first aim was to screen for amelogenin (AMELX) and ameloblastin (AMBN) gene expression in mandibular bones and soft tissues isolated from adult mice (15 weeks old). Using RT-PCR, we showed mRNA expression of AMELX and AMBN in mandibular alveolar and basal bones and, at low levels, in several soft tissues; eyes and ovaries were RNA-positive for AMELX and eyes, tongues and testicles for AMBN. Moreover, in mandibular tissues AMELX and AMBN mRNA levels varied according to two parameters: 1) ontogenic stage (decreasing with age), and 2) tissue-type (e.g. higher level in dental epithelial cells and alveolar bone when compared to basal bone and dental mesenchymal cells in 1 week old mice). In situ hybridization and immunohistodetection were performed in mandibular tissues using AMELX KO mice as controls. We identified AMELX-producing (RNA-positive) cells lining the adjacent alveolar bone and AMBN and AMELX proteins in the microenvironment surrounding EMPs-producing cells. Western blotting of proteins extracted by non-dissociative means revealed that AMELX and AMBN are not exclusive to mineralized matrix; they are present to some degree in a solubilized state in mandibular bone and presumably have some capacity to diffuse. Our data support the notion that AMELX and AMBN may function as growth factor-like molecules solubilized in the aqueous microenvironment. In jaws, they might play some role in bone physiology through autocrine/paracrine pathways, particularly during development and stress-induced remodeling

Impact de trois perturbateurs endocriniens, le bisphénol A, la génistéine et la vinclozoline sur l'amélogenèse

Notre environnement contient de plus en plus de polluants dont les perturbateurs endocriniens (PE), associés à une augmentation de la prévalence de pathologies graves et à l'émergence de nouvelles pathologies. Récemment, une nouvelle pathologie amélaire appelée hypominéralisation des molaires et des incisives (MIH) a été décrite. Cette pathologie, dont l'étiologie est inconnue, est devenue un véritable problème de santé publique avec une prévalence d'environ 18%. L'objectif de ce travail fut de rechercher des relations potentielles entre l'exposition aux PE et le MIH. Pour cela, des rats Wistar ont été exposés à de faibles doses de trois PE, le bisphénol A (BPA), la génistéine et la vinclozoline, seuls ou en association, de la conception jusqu'au sacrifice. 75% des rats traités au BPA seul, présentaient des taches d'hypominéralisation amélaire dont les caractéristiques structurales et biochimiques étaient comparables à celles des dents humaines atteintes par le MIH analysées en parallèle. Ainsi, nous proposons d'utiliser les dents MIH comme biomarqueur précoce d'exposition aux PE agissant comme le BPA. Par ailleurs, nos résultats ont montré que l'action du BPA sur la prolifération des précurseurs améloblastiques et les modulations d'expression de deux gènes cibles clé, l'énaméline et la kallikréine 4, ne semble emprunter qu'en partie la voie œstrogénique suggérant que dans l'épithélium dentaire, le BPA interagit avec d'autres récepteurs que ERa et ERß. La combinaison du BPA avec les deux autres PE impacte apparemment moins l'amélogenèse. Les trois PE étudiés ici modulent chacun différemment l'expression des gènes codant les protéines matricielles amélaires et les protéases spécifiques de l'émail, réduisant l'effet des autres PE. Ceci explique, au moins en partie, l'impact différentiel sur l'émail de substances exogènes hypominéralisantes dont la relation avec le développement de certaines pathologies sera intéressante à étudier dans le futur.Our environment has become increasingly contaminated by pollutants including endocrine disruptor Chemicals (EDCs), associated with an increased prevalence of serious diseases and the emergence of new diseases. Recently, a new dental pathology called molar incisor hypomineralization (MIH) has been described. This pathology, whose etiology is unknown, has become a real public health problem with a prevalence of roughly 18%. The aim of this work was to investigate potential relationships between exposure to EDCs and MIH. For this purpose, Wistar rats were treated from the conception to the sacrifice, with low doses of three EDCs, bisphenol A (BPA), genistein and vinclozolin, alone or in combination. 75% of rats treated with BPA alone have shown enamel hypomineralized spots sharing similar biochemical and structural characteristics with human teeth affected by MIH analyzed in parallel. Thus, we propose to use MIH teeth as an early biomarker o exposure to EDCs acting as BPA. The effects of BPA on pre-ameloblast prolifération and enamelin and klk4 expression seem to use the estrogenic pathway only in part suggesting that BPA could interact with other receptors than ERa and ERp in dental epithelial cells. Each combination of BPA with other EDCs affects specifically the amelogenesis explaining the lower impact of the combination compared with BPA alone. This explains, at least in part, the différentiel impact of exogenous hypomineralizing substances on enamel whose relationship with the development of certain diseases will be interesting to study in the future.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Expression of steroid receptors in ameloblasts during amelogenesis in rat incisors

Endocrine disrupting chemicals (EDCs) play a part in the modern burst of diseases and interfere with the steroid hormone axis. Bisphenol A (BPA), one of the most active and widely used EDCs, affects ameloblast functions, leading to an enamel hypomineralization pattern similar to that of Molar Incisor Hypomineralization (MIH). In order to explore the molecular pathways stimulated by BPA during amelogenesis, we thoroughly investigated the receptors known to directly or indirectly mediate the effects of BPA. The expression patterns of high affinity BPA receptors (ERRγ, GPR30), of ketosteroid receptors (ERs, AR, PGR, GR, MR), of the retinoid receptor RXRα and PPARγ were established using RT-qPCR analysis of RNAs extracted from microdissected enamel organ of adult rats. Their expression was dependent on the stage of ameloblast differentiation, except that of ERβ and PPARγ which remained undetectable. An additional large scale microarray analysis revealed three main groups of receptors according to their level of expression in maturation stage ameloblasts. The expression level of RXRα was the highest, similar to the vitamin D receptor (VDR), whereas the others were 13 to 612 fold lower, with AR and GR being intermediate. Immunofluorescent analysis of VDR, ERα and AR confirmed their presence mainly in maturation- stage ameloblasts. These data provide further evidence that ameloblasts express a specific combination of hormonal receptors depending on their developmental stage. This study represents the first step towards understanding dental endocrinology as well as some of the effects of EDCs on the pathophysiology of amelogenesis

MSX2 in ameloblast cell fate and activity

International audienceWhile many effectors have been identified in enamel matrix and cells via genetic studies, physiological networks underlying their expression levels and thus the natural spectrum of enamel thickness and degree of mineralization are now just emerging. Several transcription factors are candidates for enamel gene expression regulation and thus the control of enamel quality. Some of these factors, such as MSX2, are mainly confined to the dental epithelium. MSX2 homeoprotein controls several stages of the ameloblast life cycle. This chapter introduces MSX2 and its target genes in the ameloblast and provides an overview of knowledge regarding its effects in vivo in transgenic mouse models. Currently available in vitro data on the role of MSX2 as a transcription factor and its links to other players in ameloblast gene regulation are considered. MSX2 modulations are relevant to the interplay between developmental, hormonal and environmental pathways and in vivo investigations, notably in the rodent incisor, have provided insight into dental physiology. Indeed, in vivo models are particularly promising for investigating enamel formation and MSX2 function in ameloblast cell fate. MSX2 may be central to the temporal-spatial restriction of enamel protein production by the dental epithelium and thus regulation of enamel quality (thickness and mineralization level) under physiological and pathological conditions. Studies on MSX2 show that amelogenesis is not an isolated process but is part of the more general physiology of coordinated dental-bone complex growth

MIH and Dental Caries in Children: A Systematic Review and Meta-Analysis

(1) Background: Molar-incisor hypomineralization (MIH) is a clinical condition affecting permanent teeth in children, with a documented rising trend in the last two decades. The aim of the present study was to analyze and synthesize the available evidence on caries experience (dmft/DMFT) and MIH in children. (2) Methods: A systematic review and meta-analysis were conducted according to the PRISMA statement. (3) Results: 59 papers published between 2007 and 2022 were included in the qualitative synthesis and 18 in the meta-analysis. The total sample of subjects was 17,717 (mean: 896), of which 2378 (13.4%) had MIH (mean: 119), with a girl/boy ratio of 1:1. The mean age of the enrolled participants was 8.6 (age range 7–10 years). Meta-analysis showed that MIH has a positive correlation with both dmft (effect size of 0.67, 95% CI [0.15, 1.19]) and DMFT (effect size of 0.56, 95% CI [0.41, 0.72]); (4) Conclusions: Children with MIH should be diagnosed correctly and on time. Treatment and management options for moderate and severe forms of MIH should consider prognosis based on known risk factors, and secondary and tertiary prevention policies should also consider the multifactorial nature of caries etiology