Faculty of Physics, Southern Federal University, Zorge 5, Rostov-on-Don, 344090, Russian Federation.
ISEM, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France.
Sci Rep. 2020 May 6;10(1):7652. doi: 10.1038/s41598-020-64598-w.
Since Robert Hooke studied cork cell patterns in 1665, scientists have been puzzled by why cells form such ordered structures. The laws underlying this type of organization are universal, and we study them comparing the living and non-living two-dimensional systems self-organizing at the spherical surface. Such-type physical systems often possess trigonal order with specific elongated defects, scars and pleats, where the 5-valence and 7-valence vertices alternate. In spite of the fact that the same physical and topological rules are involved in the structural organization of biological systems, such topological defects were never reported in epithelia. We have discovered them in the follicular spherical epithelium of ascidians that are emerging models in developmental biology. Surprisingly, the considered defects appear in the epithelium even when the number of cells in it is significantly less than the previously known threshold value. We explain this result by differences in the cell sizes and check our hypothesis considering the self-assembly of different random size particles on the spherical surface. Scars, pleats and other complex defects found in ascidian samples can play an unexpected and decisive role in the permanent renewal and reorganization of epithelia, which forms or lines many tissues and organs in metazoans.
自罗伯特·胡克（Robert Hooke）于 1665 年研究软木细胞模式以来，科学家们一直对细胞为何形成如此有序的结构感到困惑。这种组织类型的规律是普遍存在的，我们通过比较生活和非生活的二维系统在球面的自组织来研究它们。这种类型的物理系统通常具有特定的拉长缺陷、疤痕和褶皱的三角有序，其中 5 价和 7 价顶点交替出现。尽管生物系统的结构组织涉及相同的物理和拓扑规则，但在表皮中从未报道过这种拓扑缺陷。我们在尾索动物的滤泡球形上皮中发现了它们，这些动物是发育生物学中的新兴模型。令人惊讶的是，即使上皮细胞的数量明显少于先前已知的阈值，也会出现这些考虑到的缺陷。我们通过细胞大小的差异来解释这个结果，并通过考虑在球面上自组装不同大小的随机粒子来检验我们的假设。在尾索动物样本中发现的疤痕、褶皱和其他复杂缺陷可能在表皮的永久更新和重组中发挥意想不到的决定性作用，表皮形成或排列许多后生动物的组织和器官。
