Vainio S, Thesleff I
Department of Pedodontics and Orthodontics, University of Helsinki, Finland.
Dev Dyn. 1992 Jun;194(2):105-17. doi: 10.1002/aja.1001940204.
Epithelial-mesenchymal interactions induce the expression of syndecan, a cell surface proteoglycan, and tenascin, an extracellular matrix glycoprotein in the mesenchymal component of many organ rudiments including the tooth. Experimental recombination cultures of early dental epithelium and mesenchyme were analysed by double immunostaining to compare the distribution of syndecan, tenascin, and proliferating cells (BrdU incorporation) in the induced dental mesenchyme. After 5-9 hr in culture expression of syndecan and tenascin as well as an increase in BrdU incorporation were evident in the mesenchymal cells adjacent to the epithelium and the positive area enlarged with time. Syndecan and tenascin were colocalized only partially in some explants. The expression of syndecan and tenascin in the recombinants correlates with their stage-dependent expression pattern during early tooth development in vivo (Vainio and Thesleff, 1992). The area of increased cell proliferation in the mesenchyme correlated closely with syndecan expression. In none of the explants was increased BrdU incorporation observed in syndecan negative areas. Epithelium induced also condensation of the mesenchymal cells. Induction and spread of the syndecan-positive zone in the dental mesenchyme required close and continuous contact with the epithelium. The mechanism by which the induction of syndecan expression spreads in the mesenchyme was studied in rat-mouse interspecies recombination cultures, using syndecan antibodies that recognize mouse but not rat syndecan. The rat mesenchyme and epithelium were first cultured in contact for 24 hr. Then the epithelium was removed and freshly dissected, "uninduced" mouse mesenchyme was placed in contact with different aspects of the rat mesenchyme. The rat mesenchymal cells that had located next to the epithelial tissue stimulated syndecan expression in adjacent mouse mesenchyme. The induction potential was gradually lost toward the periphery of the rat mesenchyme. Based on these findings we suggest that diffusible signal molecules mediate the spread of syndecan induction in the mesenchyme and that syndecan plays a role in the regulation of cell proliferation.
上皮-间充质相互作用可诱导多器官原基（包括牙齿）间充质成分中syndecan（一种细胞表面蛋白聚糖）和腱生蛋白（一种细胞外基质糖蛋白）的表达。通过双重免疫染色分析早期牙上皮和间充质的实验重组培养物，以比较syndecan、腱生蛋白和增殖细胞（BrdU掺入）在诱导的牙间充质中的分布。培养5-9小时后，上皮相邻的间充质细胞中syndecan和腱生蛋白的表达以及BrdU掺入增加明显，且阳性区域随时间扩大。syndecan和腱生蛋白仅在一些外植体中部分共定位。重组体中syndecan和腱生蛋白的表达与其在体内早期牙齿发育过程中的阶段依赖性表达模式相关（Vainio和Thesleff，1992）。间充质中细胞增殖增加的区域与syndecan表达密切相关。在任何外植体的syndecan阴性区域均未观察到BrdU掺入增加。上皮还诱导了间充质细胞的凝聚。牙间充质中syndecan阳性区域的诱导和扩散需要与上皮紧密且持续接触。利用识别小鼠而非大鼠syndecan的syndecan抗体，在大鼠-小鼠种间重组培养物中研究了syndecan表达诱导在间充质中扩散的机制。大鼠间充质和上皮首先接触培养24小时。然后去除上皮并新鲜解剖，将“未诱导”的小鼠间充质与大鼠间充质的不同部位接触。位于上皮组织旁边的大鼠间充质细胞刺激相邻小鼠间充质中syndecan的表达。诱导潜能朝着大鼠间充质的周边逐渐丧失。基于这些发现，我们认为可扩散的信号分子介导了syndecan诱导在间充质中的扩散，且syndecan在细胞增殖调控中发挥作用。
