[Transcription factor activator protein 2C contribute to molar development in mice].

Objective: Explore the expression pattern of transcription factor activator protein 2C (TFAP2C) and identify the roles of Tfap2c during tooth development. Methods: Real-time fluorescence quantitative PCR (RT-qPCR) was used to analyze the relative expression level of Tfap2c in various organs of embryonic day(E)14.5 mouse embryos and mouse molar germs at E12.5-E18.5 and postnatal day (P)0-P7. The expression position of Tfap2c in mouse molar germs was demonstrated by frozen section immunofluorescence staining. Cultured mandibular molar germs were transfected with control small interfering RNA (siRNA) or Tfap2c siRNA to evaluate the effect of Tfap2c on tooth molar germs development, and RT-qPCR was used to detect the relative expression level of genes related to odontoblast expression. Dental mesenchymal cells were isolated from E14.5 molar germs and transfected with control siRNA or Tfap2c siRNA, cell counting kit 8 (CCK-8) and scratch healing test were applied to detect dental mesenchymal cell viability and migration. Results: Tfap2c was highly expressed in the early development period of mouse molar germs. Tfap2c was expressed in the epithelial and mesenchymal tissues of E13.5 mouse molar germs and there was no significant difference of relative expression of Tfap2c between them (t=1.06, P=0.472). Tfap2c was expressed in mesenchymal tissues of E14.5 mouse molar germs and the relative expression of Tfap2c in mesenchymal tissues was significantly higher than epithelial tissues (t=37.29, P<0.0001). For molar germs transfected with Tfap2c siRNA, the relative height of cusps (0.708±0.171) and the ratio of cusp height and crown height (0.321±0.068) was significantly lower than control group (1.000±0.287 and 0.483±0.166) (t=2.79, P=0.012; t=2.85, P=0.015). But there was no significant difference in relative height (1.078±0.206, 0.993±0.254, t=0.83, P=0.419)and relative width (1.000±0.116, 0.999±0.122, t=0.01, P=0.992) of crowns between two groups. The relative expression level of genes related to odontoblast expression was decreased (Dspp: t=15.33, P<0.001; Dmp1: t=13.81, P<0.001). Tfap2c siRNA hinders cell migration in dental mesenchymal cells (t=29.86, P=0.001), but there was no significant difference in CCK-8 absorbance value between two groups. The relative expression level of genes related to odontoblast expression was also decreased in dental mesenchymal cells transfected with Tfap2c siRNA (Dspp: t=3.86, P=0.031; Dmp1; t=4.36, P=0.022). Conclusions: Tfap2c highly expressed in the early morphogenesis period of mouse molar germs, mainly in mesenchymal tissues. Tfap2c affected the cusps formation of mouse molar germs and migration of dental mesenchymal cells.

Fibroblast growth factor signalling regulates the development of tooth root.

Fibroblast growth factor (FGF) signalling plays a crucial role in the morphogenesis of multiple tissues including teeth. While the role of the signal has been studied in tooth crown development, little is known about root development. Of several FGF ligands involved in hard tissue formation, we suggest that FGF18 regulates the development of murine tooth roots. We implanted FGF18-soaked heparin beads into the lower first molar tooth buds at postnatal day 6 (P6), followed by transplantation under the kidney capsule. After 3 weeks, FGF18 significantly facilitated root elongation and periodontal tissue formation compared to the control. In situ hybridisation showed that Fgf18 transcripts were initially localised in the dental pulp along Hertwig's epithelial root sheath at P6 and P10 and subsequently in the dental follicle cells at P14. Fgf receptors were expressed in various dental tissues during these stages. In vitro analysis using the dental pulp stem cells revealed that FGF18 inhibited cell proliferation and decreased expression levels of osteogenic markers, Runx2, Alpl and Sp7. Consistently, after 1 week of kidney capsule transplantation, FGF18 application did not induce the expression of Sp7 and Bsp, but upregulated Periostin in the apical region of dental mesenchyme in the grafted molar. These findings suggest that FGF18 facilitates molar root development by regulating the calcification of periodontal tissues.

Irrompimento do primeiro molar permanente em crianças da zona urbana e rural do município de Santa Helena - Paraná / Irrompement of the first permanent molar in children from the urban and rural area of the city of Santa Helena - Paraná

O objetivo deste trabalho foi comparar a cronologia de erupção do primeiro molar permanente em crianças de ambos os sexos, residentes na zona urbana e rural do munícipio de Santa Helena - PR, Brasil. Foi realizado um estudo transversal com 154 crianças da zona rural e 300 crianças da área urbana de 04 a 07 anos (48 a 84 meses). Os primeiros molares avaliados foram considerados irrompidos quando qualquer porção de sua coroa estivesse clinicamente visível. A média de idade para erupção do primeiro molar permanente se mostrou de 72 a 83 meses. Destes, o grupo da zona rural apresentou uma média para idade de erupção mais precoce. Contudo, verificou-se um resultado considerável em crianças na faixa de 48 a 59 meses (4 anos), mostrando mais uma vez a erupção precoce nas crianças da zona rural. Este dente irrompeu primeiro na mandíbula, irrompendo primeiro nas meninas do que nos meninos, e o dente 46 foi o que mais se mostrou presente. A média de idade para erupção do primeiro molar permanente correspondeu àquela descrita pela literatura aos seis anos, mas não correspondeu ao atraso na erupção das crianças residentes em zona rural. Bem como este dente irrompeu primeiro na mandíbula... (AU)

The objective of this study was to compare the chronology of eruption of the first permanent molar in children of both sexes, living in the urban and rural areas of the city of Santa Helena-PR, Brazil. A cross-sectional study was carried out with 154 children from the rural area and 300 children from the urban area from 4 to 7 years old (48 to 84 months). The first molars evaluated were considered erupted when any portion of their crown was clinically visible. The average age for eruption of the first permanent molar was 72 to 83 months. Of these, the rural group had an earlier average age for eruption than the urban group. However, a considerable result was found in children 48-59 months showing once again the early eruption in rural children. This tooth erupted first in the jaw, erupting first in girls rather than boys, and tooth 46 was most present. The mean age of eruption of the first permanent molar corresponded to that described in the literature at age six, but did not correspond to the delayed eruption of children living in rural areas. Just like this tooth erupted in the jaw first... (AU)

First molar development in Calomys callosus / Desenvolvimento do primeiro molar em Calomys callosus

Due to an increased use of Calomys callosus as a laboratory animal, the present study purposed to describe morphologically the embryonic development of the first molar, seeking to determine for this rodent, the age in which each odontogenesis phase occurs. In this experiment fetuses of Calomys callosus obtainde during a gestational period of 11 to 20 days were used. The heads of the fetuses were removed and fixed in 10% formol and in a 0.1 M phosphate buffer for 15 hours, decalcified in 10% EDTA and embedded in glycol metacrilate (Historesin-Leica). Serial frontal sections of the upper first molar were cut at 2 micrometers of thickness and stained with 1% toluidine blue for light microscope analysis. At day 11, no indications of odontogenesis were found. On the 12th day, epithelial ingrowths compatible with primary epithelial bands were observed. On the 13th day of development, the dental lamina and the beginning of the bud stage were seen, becaming well defined in the 14th day. On the 15th and 16th days the cap stage was observed. On the 17th , 18th and 19th days the bell stage were observed. On the 20th day the beginning of the crown stage was seen. The results obtained indicate that the odontogenesis of the Calomys callosus is similar to the one of other rodents used in laboratory, which justifies its use as a biological model for studies related to the dental development.

Devido ao aumento crescente de utilização do Calomys callosus como animal de laboratório, o presente estudo teve como objetivo descrever morfologicamente o desenvolvimento embrionário do primeiro molar, visando determinar a idade em que ocorre cada fase da odontogênese. Neste experimento foram utilizados fetos de Calomys callosus obtidos durante o período gestacional de 11 a 20 dias. As cabeças deos fetos foram removidas e fixadas em formal 10% por 15 horas, descalcificadas em EDTA 10% e processadas para inclusão em glicol metacrilato (Historesin-Leica). Cortes frontais da região do primeiro molar superior, com 2 micrometro de espessura, corados em azul de toluidina 1%, foram analisados ao microscópio de luz. As 11 dias não houve indício de odontogênese. Com 12 dias de desenvolvimento observou-se crescimento epitelial compatível com a banda eoitelial primária. Aos 13 dias observou-se a lâmina dental e início da fase em botão, que se tornou definida no 14º dia. A fase em capus foi observada no 15º e 16º dias de desenvolvimento. A fase em campânula foi observada no 17º, 18º, 19º dias. No 20º dia foi observado o início da fase em coroa. Os resultados encontrados indicam que as fases da odontogênese em C. callosus são similares a de outros roedores usados em laboratório, o que justifica o uso desse animal como modelo biológico para estudos relacionados ao desenvolvimento dental.