小鼠早期牙胚发育的三维结构重建研究

Three-dimensional reconstruction of the early development of tooth germ:An experimental study in the mouse

目的:三维重建小鼠牙发育早期牙胚的形态结构,对比无牙区发育不全的牙胚(rudimentary bud 2,R2)与磨牙区第一磨牙(the first molar,M1)牙胚的形态差异。方法:选取胚胎12.5 d(E12.5)及胚胎13.5 d(E13.5)小鼠胚胎头部标本,经冠状面连续石蜡切片、苏木精-伊红(hematoxylin and eosin,HE)染色后,获取组织学图像数据。图像经Photoshop CC 2018软件处理并配准,用Fiji软件再配准与赋予虚拟CT值后,导入Mimics Research 19.0软件进行三维重建和分析。结果:在重建的三维图像中观察到无牙区R2上皮可向间充质内陷形成蕾状,但其下方无明显的间充质细胞团形成。赋予无牙区R2和磨牙区M1虚拟CT值后,对重建图像进行半定量测量,发现凝聚在无牙区R2蕾状上皮周围的间充质细胞密度较低,凝聚面积较小。此现象可能与无牙区细胞增殖不如磨牙区活跃有关。结论:基于组织学切片的三维重建结果提示,发育早期小鼠无牙区丧失了形成间充质细胞团的能力。

Objective:To reconstruct the structure of mouse tooth germ in the early stage of development,and to compare the morphological differences between the rudimentary bud 2(R2)in the diastema region and the first molar(M1)in the molar region.Methods:After being fixed,the head specimens of E12.5 and E13.5 mouse embryos were embedded in paraffin,serially sectioned in the frontal plane,and stained with hematoxylin and eosin(HE).All images were processed with Photoshop CC 2018 software and Fiji software,then imported into Mimics Research 19.0 software for three-dimensional reconstruction and analysis.Results:It was observed in the reconstructed three-dimensional model that the epithelium of the tooth germ in the diastema forms a bud shape,but there was no obvious condensation of mesenchyme cells below it.After assigning virtual CT values to the R2 and M1,semi-quantitative measurements of the reconstructed images revealed that the mesenchymal cells coalescing around the bud-like epithelium of R2 were less dense and had a smaller condensation area.This phenomenon may be related to less cell proliferation in the diastema region.Conclusion:Three-dimensional reconstructions based on histological sections revealed a loss of the ability to form the condensational mesenchymal cell cluster in the diastema region of mice during early tooth development.