Ezh2 knockout in mesenchymal cells causes enamel hyper-mineralization.

Enhancer of zeste homolog 2 (EZH2) is the catalytic core of polycomb repressive complex 2 (PRC2), which primarily methylates lysine 27 on histone H3 (H2K27me3), generating transcriptionally suppressed heterochromatin. Since EZH2 suppresses expression of genes involved in dentin formation, we examined the role of EZH2 in tooth development. Intriguingly, microCT analysis of teeth from mice with conditional Ezh2 knockout in uncommitted mesenchymal cells showed hyper-mineralization of enamel, which is produced by the epithelial-lineage cells, ameloblasts. Scanning electron microscopy analysis and nano-indentation of the incisor enamel from knockout mice revealed smaller inter-rod spaces and higher hardness compared to wild type enamel, respectively. Interestingly, expression of the calcium channel subunit gene, Orai2, was decreased compared to its competitor, Orai1, both in knockout mouse incisors and the ex vivo culture of ameloblasts with the surrounding tissues under EZH2 inhibition. Moreover, histological analysis of incisor from knockout mice showed decreased ameloblastin and expedited KLK4 expression in the ameloblasts. These observations suggest that EZH2 depletion in dental mesenchymal cells reduces enamel matrix formation and increases enamel protease activity from ameloblasts, resulting in enamel hyper-mineralization. This study demonstrates the significant role of the suppressive H3K27me3 mark for heterochromatin on enamel formation.

Estudio in vitro del Efecto Antibacteriano de la Oleorresina de Copaifera reticulata y el Aceite Esencial de Origanum majoricum Frente a Streptococcus mutans y Enterococcus Faecalis Bacterias de Importancia en Patologías Orales / In vitro Study of the Antibacterial Effect of Oleoresin of Copaifera reticulata and the Essential Oil of Origanum majoricum against Streptococcus mutans and Enterococcus faecalis Bacteria of Importance in Oral Pathologies

RESUMEN: El objetivo del estudio fue determinar el efecto antibacteriano in vitro de la oleorresina de Copaifera reticulata (C. reticulata) "copaiba" y del aceite esencial de Oreganum majoricum (O. majoricum) "orégano" frente a Streptococcus mutans (S. mutans) y Enterococcus faecalis (E. faecalis). Se desarrollaron pruebas de sensibilidad activando primero las cepas bacterias a enfrentar. La oleorresina de copaiba fue diluida con dimetilsulfósido (DMSO), obteniéndose al final concentraciones a probar de 100 %, 50 %, 25 %, y 12,5 %. En relación al aceite esencial de orégano este se probó solamente al 100 %. Para la prueba de difusión en agar con discos, se tomaron inóculos 100 µL de cada cepa bacteriana a una turbidez de 0,5 de Mc Farlam, para ser sembrados por diseminación en placas de tripticasa soya agar, para luego colocar los discos de forma equidistante cargados con las diferentes concentraciones de los productos naturales, se utilizaron como control positivo a la clorhexidina al 0,12 % y al DMSO como control negativo. Se incubaron las placas por el método de la vela en extinción a 37 °C, por un periodo de 24 horas, pasado el tiempo se realizó la lectura de los halos de inhibición. Los resultados obtenidos por la copaiba, determinaron un efecto antibacteriano en sus cuatro concentraciones, siendo los mayores halos de inhibición a la concentración del 100 %, copaiba genero mayores halos promedios para S, mutans de 30,00 ± 0,00 mm y para E. faecalis de 8,3 ± 0,50 mm. Para el caso del orégano se producen halos a la concentración del 100 % con un promedio de 25,3 ± 0,96 mm para S. mutans y para E. faecalis de 9,5 ± 1,29 mm. Se concluye del estudio que tanto copaiba como el orégano presentan un efecto antibacteriano para ambas bacterias, siendo su mayor efecto antibacteriano para ambos productos naturales sobre S. mutans.

ABSTRACT: The objective of the study was to determine the in vitro antibacterial effect of the oleoresin of Copaifera reticulata (C. reticulata) "copaiba" and of the essential oil of Oreganum majoricum (O. majoricum) "oregano" against Streptococcus mutans (S. mutans) and Enterococcus faecalis (E. faecalis). Sensitivity tests were developed by first activating the bacteria strains to be confronted. The oleoresin of copaiba was diluted with dimethylsulphoside (DMSO), obtaining final concentrations to be tested of 100 %, 50 %, 25 %, and 12.5 %. In relation to the essential oil of oregano, it was only 100 % tested. For the disk agar diffusion test, 100 mL of each bacterial strain was taken at a turbidity of 0.5 of Mc Farlam, to be planted by dissecting trypticase soy agar plates, and then placing the disks equidistantly loaded with the different concentrations of natural products; 0.12 % chlorhexidine was used as a positive control and DMSO as negative control. The plates were incubated by the candle method in extinction at 37 °C, for a period of 24 hours, after which time the inhibition halos were read. The results obtained by the copaiba, determined an antibacterial effect in its four concentrations, being the biggest halos of inhibition at the concentration of 100 %, copaiba genus higher average halos for S. mutans of 30.00 ± 0.00 mm and for E. faecalis of 8.3 ± 0.50 mm. In the case of oregano, haloes are produced at a concentration of 100 % with an average of 25.3 ± 0.96 mm for S. mutans and for E. faecalis 9.5 ± 1.29 mm. It is concluded from the study that both copaiba and oregano present an antibacterial effect for both bacteria, being its greater antibacterial effect for both natural products on S. mutans.

La importancia de las ciencias básicas en la formación del cirujano dentista / The importance of basic science in the training of dental surgeons

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Expression patterns of nestin and dentin sialoprotein during dentinogenesis in mice.

Differentiated odontoblasts could not be identified by one unique phenotypic marker, but the combination of expression of dentin phosphoprotein (Dpp), dentin sialoprotein (Dsp), dentin matrix protein 1 (Dmp1), and nestin may be valuable for the assessment of these cells. However, the findings using these proteins remain controversial. This study aimed to compare two odontoblast differentiation markers: nestin and Dsp in the process of dentinogenesis in mice. We performed immunohistochemistry and/or in situ hybridization technique for nestin and Dsp using 3-week-old incisors as well as postnatal 1-day- to 8-week-old molars. Preodontoblasts began to express nestin and Dsp proteins and Dsp mRNA, which increased in their intensity according to the progress of odontoblast differentiation in both incisors and developing molars. Nestin was consistently expressed in the differentiated odontoblasts even after the completion of dentin matrix deposition. The expression of Dsp mRNA coincided with the odontoblast secretory activity for dentin matrix deposition. In contrast, other pulpal cells, predentin matrix and dentinal tubules also showed a positive reaction for Dsp protein in addition to differentiated odontoblasts. In conclusion, nestin is valuable as a differentiation marker for odontoblasts, whereas Dsp mRNA is a functional marker for their secretory activity.