The effect of inhibiting p38 MAPK on the expression of genes related to enamel development in mice / 口腔疾病防治

Objective@#To study the effect of p38 mitogen activated protein kinase (p38 MAPK) on the expression of genes related to enamel development in the enamel epithelium and to provide a basis for the study of the molecular mechanism of enamel development.@*Methods@#The p38 MAPK-specific inhibitor SB203580 dissolved in DMSO was added to the culture medium of mouse mandibular molar tooth germs in vitro as experiment group, and mouse mandibular molar tooth germs treated with the same amount of DMSO were used as control group. Western blot was used to detect the protein expression level of phosphorylated p38 (p-p38) in the enamel epithelium. Real-time PCR was used to detect the mRNA expression levels of runt-related transcription factor 2 (Runx2), osteoblast-specific transcription factor (Osx), ameloblast markers odontogenic ameloblast associated protein (ODAM), amelotin (AMTN), matrix metalloproteinase 20 (MMP20) and kallikrein 4 (KLK4) in the enamel epithelium. @*Results @# Western blot results showed that under the action of the inhibitor SB203580, the phosphorylation level of p38 MAPK in mouse enamel epithelium decreased, and the difference was statistically significant (P < 0.05). Real-time PCR results showed that the expression levels of the transcription factors Runx2 and Osx and the ameloblast markers ODAM, AMTN, MMP20, and KLK4 in the SB203580 group were lower than those in the control group, and the difference was statistically significant (P < 0.05).@*Conclusion@#The p38 MAPK signaling pathway can mediate enamel development by regulating the expression of the transcription factors Runx2 and Osx and the ameloblast markers ODAM, AMTN, MMP20 and KLK4 in the mouse enamel epithelium.

Immunohistochemical study of polycystin-1 in dentigerous cysts.

Background: The alterations involved in step-wise transformation of a dental follicle to dentigerous cyst (DC) is not clearly known. Primary cilium and its protein have been hypothesized to be associated with DC. Mutation of a ciliary protein, polycystin‑1 (PC1) is associated with autosomal dominant polycystic kidney disease. This study was performed to assess the immunohistochemical expression of PC1 between DC and postfunctional follicular tissue (PFFT). Materials and Methods: Thirty‑one consecutive PFFT and 15 DC formed the study group. The PFFT and DC tissues were stained with antibody against PC1. Statistical Package for Social Service was used to analyze data. Descriptive statistics and Student’s Chi‑square test were appropriately used. P ≤0.05 was taken as significant. Results: Fifteen DC (100%) and 7 (22.58%) PFFT were positive for PC1. The difference was statistically significant (P = 0.000). PC1 expression was observed in the cytoplasm with varying intensity. Discussion and Conclusion: All PC1 positive epithelial cells’ cytoplasm stained diffusely. Abnormal cytoplasmic expression of PC1 in all positive epithelial lining indicates that the PC1 probably is associated with cystic transformation.

Efectos del cloruro de cobalto sobre el epitelio de unión y epitelio reducido del esmalte del primer molar superior de rata / Effects of cobalt chloride in junctional epithelium and reduced enamel epithelium of the rat maxillary first molar

El cobalto es uno de los principales componentes de las aleaciones metálicas fundidas, usadas frecuentemente en odontología. El metal es el constituyente de 45 a 70 por ciento de los trabajos protéticos. En virtud de la existencia de evidencias que elementos metálicos pueden causar toxicidad sistémica y local, este trabajo tuvo como objetivo evaluar los efectos del cobalto sobre el epitelio de unión y el epitelio del esmalte del primer molar superior de rata, durante la lactancia. Con esa finalidad fueron usadas ratas con 1 día de vida postnatal, cuyas madres recibieron 300 mg de cloruro de cobalto por litro de agua destilada en el bebedero, durante a la lactancia. Al cabo de 21 días, las crías fueron sacrificadas con sobredosis anestésica. Las cabezas fueron separadas, fijadas en "alfac", descalcificadas e incluidas en parafina. Fueron utilizados cortes frontales seriados teñidos con hematoxilina y eosina. Fueron estimados los siguientes parámetros nucleares: diámetros mayor, menor y geométrico medio, relación entre diámetros, perímetro, área, volumen, relación entre volumen y área, excentricidad, coeficiente de forma e índice de contorno. Mediante métodos estereológicos fueron evaluados: relación núcleo/citoplasma, volumen celular, densidad numérica celular, relación superficie externa/camada basal, espesor de las camadas epiteliales y densidad de superficie. Todos los datos obtenidos fueron sometidos a análisis estadístico mediante la prueba no-paramétrica de Wilcoxon-Mann-Whitney. Los núcleos de los tejidos estudiados mostraron valores menores para diámetros, perímetro, área, volumen y relación volumen/área. Estereológicamente, fue posible observar en el epitelio de unión y en el epitelio reducido del esmalte, células menores con citoplasma más escaso, lo que se refleja en mayor número de células por mm3 de tejido. En este estudio, el cobalto ocasionó un cuadro de atrofia epitelial, sugiriendo una acción directa sobre los epitelios de unión y del esmalte.

Cobalt is one of the main components of cast metal alloys broadly used in dentistry. It is the constituent of 45 to 70 percent of numerous prosthetic works. There are evidences that metal elements cause systemic and local toxicity. The purpose of the present study was to evaluate the effects of cobalt on the junctional epithelium and reduced enamel epithelium of the first superior molar in rats, during lactation. To do this, 1-day old rats were used, whose mothers received 300mg of cobalt chloride per liter of distilled water in the drinker, during lactation. After 21 days, the rat pups were killed with an anesthetic overdose. The heads were separated, fixed in "alfac", decalcified and embedded in paraffin. Frontal sections stained with hematoxylin and eosin were employed. Karyometric methods allowed to estimate the following parameters: biggest, smallest and mean diameters, D/d ratio, perimeter, area, volume, volume/area ratio, eccentricity, form coefficient and contour index. Stereologic methods allow to evaluate: cytoplasm/nucleus ratio, cell and cytoplasm volume, cell number density, external surface/basal membrane ratio, thickness of the epithelial layers and surface density. All the collected data were subjected to statistic analysis by the non-parametric Wilcoxon-Mann-Whitney test. The nuclei of the studied tissues showed smaller values after karyometry for: diameters; perimeter, area, volume and volume/area ratio. Stereologically, it was observed, in the junctional epithelium and in the reduced enamel epithelium, smaller cells with scarce cytoplasm, reflected in the greater number of cells per mm3 of tissue. In this study, cobalt caused epithelial atrophy, indicating a direct action on the junctional and enamel epithelium.

IMMUNOHISTOCHEMICAL STUDY FOR THE DETECTION OF THE TUMOROUS CHANGES OF REMAIND ENAMEL EPITHELIUM IN THE IMPACTED HUMAN TOOTH FOLLICLE

In order to investigate the potential cellular activity of remaind enamel epithelium of impacted tooth follicle, we have examined 75 tooth follicular tissues from impacted teeth by immunohistochemical methods. Particular focus on the proliferation, differentiation and apoptosis-antiapoptosis of remaind enamel epithelium was made. Follicular tissues were removed from impacted teeth, fixed in neutral formalin and prepared for 4micrometer thick 20 serial sections. Hematoxylin & eosin staining was done routinely, and the mucopolycharide materials of myxoid odontogenic mesenchyme was detected by histochemical reactions of toluidin blue, PAS, Van Gieson, Masson's trichrome Various antibodies, i.e., PCNA(proliferating cell nuclear antigen) and Ki-67 for proliferative activity, transglutaminase-C, transglutaminase-K, transglutaminase-E, TGF-beta1, bcl-2, and p53 were used. Apop-tag staining was also done to detect the phenomenon of apoptosis. Both of the reduced enamel epithelium in the luminal side of tooth follicle and the enamel epithelial rests scattered in the wall of tooth follicle showed frequent positive reaction for the PCNA and Ki-67, and these cells were also positive for the transglutaminase-C, K, E. On the other hand the enamel epithelium was not stained by Apop-tag staining but weakly positive for bcl-2 and p53. Relatively high amount of myxoid odontogenic mesenchyme was also diffusely observed in the tooth folliclular tissue, and the distribution of the myxoid odontogenic mesenchyme was closely related with the distribution of enamel epithelial rest infiltration. Taken together, these data may suggest that the remaind enamel epithelial cells are biologically acitive rather than the dormant state after the completion of tooth formation, and that the remaind enamel epithelium may has interaction with odontogenic mesenchyme and will not be degraded easily but may have a potential for the odontogenic tumors.