Laboratoire de Physique Statistique, Ecole Normale Supérieure, Université Pierre-et-Marie-Curie Paris 06, Centre National de la Recherche Scientifique, 75005 Paris, France.
Proc Natl Acad Sci U S A. 2013 Jun 25;110(26):10525-30. doi: 10.1073/pnas.1217391110. Epub 2013 Jun 10.
Embryogenesis offers a real laboratory for pattern formation, buckling, and postbuckling induced by growth of soft tissues. Each part of our body is structured in multiple adjacent layers: the skin, the brain, and the interior of organs. Each layer has a complex biological composition presenting different elasticity. Generated during fetal life, these layers will experience growth and remodeling in the early postfertilization stages. Here, we focus on a herringbone pattern occurring in fetal intestinal tissues. Common to many mammalians, this instability is a precursor of the villi, finger-like projections into the lumen. For avians (chicks' and turkeys' embryos), it has been shown that, a few days after fertilization, the mucosal epithelium of the duodenum is smooth, and then folds emerge, which present 2 d later a pronounced zigzag instability. Many debates and biological studies are devoted to this specific morphology, which regulates the cell renewal in the intestine. After reviewing experimental results about duodenum morphogenesis, we show that a model based on simplified hypothesis for the growth of the mesenchyme can explain buckling and postbuckling instabilities. Being completely analytical, it is based on biaxial compressive stresses due to differential growth between layers and it predicts quantitatively the morphological changes. The growth anisotropy increasing with time, the competition between folds and zigzags, is proved to occur as a secondary instability. The model is compared with available experimental data on chick's duodenum and can be applied to other intestinal tissues, the zigzag being a common and spectacular microstructural pattern of intestine embryogenesis.
胚胎发生为组织生长引起的模式形成、屈曲和后屈曲提供了一个真实的实验室。我们身体的每个部分都由多个相邻的层构成：皮肤、大脑和器官内部。每个层都有复杂的生物组成，具有不同的弹性。这些层是在胎儿期生成的，在受精后的早期阶段会经历生长和重塑。在这里，我们专注于发生在胎儿肠道组织中的人字形模式。这种不稳定性在许多哺乳动物中很常见，是绒毛的前体，即指状突起进入管腔。对于禽类（鸡和火鸡的胚胎），已经表明，在受精后几天，十二指肠的黏膜上皮是光滑的，然后出现褶皱，而褶皱在 2 天后呈现出明显的锯齿状不稳定性。许多争论和生物学研究都致力于这种特定的形态学，它调节了肠道中的细胞更新。在回顾了关于十二指肠形态发生的实验结果之后，我们表明，一个基于间充质生长简化假设的模型可以解释屈曲和后屈曲不稳定性。该模型完全是解析的，它基于层之间的差异生长引起的双轴压缩应力，并定量预测了形态变化。随着时间的推移，生长各向异性的增加，褶皱和锯齿的竞争被证明是二次不稳定性的发生。该模型与关于鸡十二指肠的现有实验数据进行了比较，并且可以应用于其他肠道组织，锯齿是肠道胚胎发生的常见而壮观的微观结构模式。
