Department of Biomedical Engineering, Ohio State University, Columbus, OH, United States of America.
Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, United States of America.
PLoS One. 2021 Jun 9;16(6):e0248256. doi: 10.1371/journal.pone.0248256. eCollection 2021.
Assembly of the extracellular matrix protein fibronectin (FN) into insoluble, viscoelastic fibrils is a critical step during embryonic development and wound healing; misregulation of FN fibril assembly has been implicated in many diseases, including fibrotic diseases and cancer. We have previously developed a computational model of FN fibril assembly that recapitulates the morphometry and mechanics of cell-derived FN fibrils. Here we use this model to probe two important questions: how is FN fibril formation affected by the contractile phenotype of the cell, and how is FN fibril formation affected by the stiffness of the surrounding tissue? We show that FN fibril formation depends strongly on the contractile phenotype of the cell, but only weakly on in vitro substrate stiffness, which is an analog for in vivo tissue stiffness. These results are consistent with previous experimental data and provide a better insight into conditions that promote FN fibril assembly. We have also investigated two distinct phenotypes of FN fibrils that we have previously identified; we show that the ratio of the two phenotypes depends on both substrate stiffness and contractile phenotype, with intermediate contractility and high substrate stiffness creating an optimal condition for stably stretched fibrils. Finally, we have investigated how re-stretch of a fibril affects cellular response. We probed how the contractile phenotype of the re-stretching cell affects the mechanics of the fibril; results indicate that the number of myosin motors only weakly affects the cellular response, but increasing actin velocity results in a decrease in the apparent stiffness of the fibril and a decrease in the stably-applied force to the fibril. Taken together, these results give novel insights into the combinatorial effects of substrate stiffness and cell contractility on FN fibril assembly.
细胞外基质蛋白纤维连接蛋白 (FN) 组装成不溶性、粘弹性纤维是胚胎发育和伤口愈合过程中的关键步骤；FN 纤维组装的失调与许多疾病有关，包括纤维化疾病和癌症。我们之前开发了一种纤维连接蛋白纤维组装的计算模型，该模型再现了细胞来源的纤维连接蛋白纤维的形态和力学特性。在这里，我们使用该模型来探讨两个重要问题：细胞的收缩表型如何影响 FN 纤维的形成，以及周围组织的刚度如何影响 FN 纤维的形成？我们发现 FN 纤维的形成强烈依赖于细胞的收缩表型，但仅弱依赖于体外基质的刚度，这是体内组织刚度的模拟。这些结果与之前的实验数据一致，并提供了对促进 FN 纤维组装的条件的更好理解。我们还研究了两种以前确定的不同 FN 纤维表型；我们表明，两种表型的比例取决于基质的刚度和收缩表型，中等收缩力和高基质刚度为稳定拉伸纤维创造了最佳条件。最后，我们研究了纤维的重新拉伸如何影响细胞反应。我们探测了重新拉伸的细胞的收缩表型如何影响纤维的力学；结果表明，肌球蛋白马达的数量仅对细胞反应有微弱影响，但增加肌动蛋白速度会导致纤维的表观刚度降低，并导致纤维上稳定施加的力降低。总之，这些结果为基质刚度和细胞收缩性对 FN 纤维组装的组合效应提供了新的见解。
