Assessing the mechanical energy costs of various tissue reshaping mechanisms
Assessing the mechanical energy costs of various tissue reshaping mechanisms
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DOI：
10.1007/s10237-012-0411-x
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发表时间：
2012-11-01
影响因子：
3.5
通讯作者：
Veldhuis, Jim H.
中科院分区：
文献类型：
--
作者：
Brodland, G. Wayne;Veldhuis, Jim H.
早期胚胎必须重塑组织，使其成为器官和其他维持生命的结构;如果非哺乳动物胚胎在蛋黄提供的能量耗尽之前未能完成这些任务，它们就会死亡。本研究的目的是使用一个细胞级的计算模型来研究各种机制的能量成本，这些机制可以驱动一个被称为会聚扩展的平面内重塑模式-一个组织在一个平面内方向变窄并在另一个方向扩展的主题。考虑的机制包括定向板状伪足，定向有丝分裂，应力纤维，和各向异性的外部张力。孤立的组织块和使相邻被动区域变形的主动收缩的组织都被考虑。这里使用的细胞水平有限元模型假设细胞膜及其相关蛋白质沿每个细胞-细胞界面产生净张力γ沿着，并且细胞质及其嵌入的网络和结构具有有效粘度μ。工作成本完全基于诸如边缘长度和张力的机械考虑，并且由于传统的机械效率无法计算，因此基于它们必须对组织做的工作来比较机构，以引起指定的平面内重塑速率。虽然该模型包含了一些简化相比，真实的胚胎组织，它能够表明，有丝分裂和板状伪足的组织重塑的工作要求是相同的顺序。当它们的张力大约是周围细胞中界面张力的两倍时，片状伪足在能量上最有效。该模型还表明，应力纤维或其他直接拉伸或压缩机制对组织重塑的效率至少是有丝分裂或板状伪足的五倍，并且使典型细胞组织变形所需的功比不包含细胞边界的组织大30倍以上。总的来说，这些发现表明，常见的组织重塑机制的机械效率不到1%，机械效率并不是胚胎使用哪种机制重塑其组织的主要决定因素。
Early-stage embryos must reshape the tissues of which they are made into organs and other life-sustaining structures; and if non-mammalian embryos fail to complete these tasks before the energy provided by their yolk runs out, they die. The aim of this study is to use a cell-level computational model to investigate the energetic cost of a variety of mechanisms that can drive an in-plane reshaping pattern known as convergent extension-a motif in which a tissue narrows in one in-plane direction and expands in another. Mechanisms considered include oriented lamellipodia, directed mitosis, stress fibers, and anisotropic external tension. Both isolated patches of tissue and actively contracting tissues that deform adjacent passive areas are considered. The cell-level finite element model used here assumes that the cell membrane and its associated proteins generate a net tension gamma along each cell-cell interface and that the cytoplasm and its embedded networks and structures have an effective viscosity mu. Work costs are based exclusively on mechanical considerations such as edge lengths and tensions, and because a traditional mechanical efficiency cannot be calculated, mechanisms are compared on the basis of the work they must do to the tissue to cause a specified rate of in-plane reshaping. Although the model contains a number of simplifications compared to real embryonic tissues, it is able to show that the work requirements for tissue reshaping by mitoses and by lamellipodia are of the same order. Lamellipodia are energetically most effective when their tensions are approximately twice as large as the interfacial tensions in the surrounding cells. The model also shows that stress fibers or other direct stretch or compression mechanisms are at least five times more efficient for tissue reshaping than are mitoses or lamellipodia and that the work needed to deform a typical cellular tissue is more than thirty times greater than if it did not contain cell boundaries. Collectively, these findings indicate that common tissue reshaping mechanisms have mechanical efficiencies of less than one percent and that mechanical efficiency is not the primary determinant of which mechanism(s) an embryo uses to reshape its tissues.