John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138.
Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138.
Proc Natl Acad Sci U S A. 2018 Sep 4;115(36):E8368-E8377. doi: 10.1073/pnas.1802568115. Epub 2018 Aug 17.
Variations in a multitude of material microenvironmental properties have been observed across tissues in vivo, and these have profound effects on cell phenotype. Phenomenological experiments have suggested that certain of these features of the physical microenvironment, such as stiffness, could sensitize cells to other features; meanwhile, mechanistic studies have detailed a number of biophysical mechanisms for this sensing. However, the broad molecular consequences of these potentially complex and nonlinear interactions bridging from biophysical sensing to phenotype have not been systematically characterized, limiting the overall understanding and rational deployment of these biophysical cues. Here, we explore these interactions by employing a 3D cell culture system that allows for the independent control of culture substrate stiffness, stress relaxation, and adhesion ligand density to systematically explore the transcriptional programs affected by distinct combinations of biophysical parameters using RNA-seq. In mouse mesenchymal stem cells and human cortical neuron progenitors, we find dramatic coupling among these substrate properties, and that the relative contribution of each property to changes in gene expression varies with cell type. Motivated by the bioinformatic analysis, the stiffness of hydrogels encapsulating mouse mesenchymal stem cells was found to regulate the secretion of a wide range of cytokines, and to accordingly influence hematopoietic stem cell differentiation in a Transwell coculture model. These results give insights into how biophysical features are integrated by cells across distinct tissues and offer strategies to synthetic biologists and bioengineers for designing responses to a cell's biophysical environment.
体内不同组织中的物质微环境特性存在多种变化，这些变化对细胞表型有深远影响。现象学实验表明，物理微环境的某些特征，如硬度，可以使细胞对其他特征敏感；同时，力学研究详细描述了许多用于这种传感的生物物理机制。然而，这些潜在复杂和非线性相互作用的广泛分子后果，从生物物理传感到表型，尚未得到系统表征，限制了对这些生物物理线索的整体理解和合理应用。在这里，我们通过使用 3D 细胞培养系统来探索这些相互作用，该系统允许独立控制培养基底的刚度、应力松弛和粘附配体密度，使用 RNA-seq 系统地探索受不同生物物理参数组合影响的转录程序。在小鼠间充质干细胞和人皮质神经元祖细胞中，我们发现这些基底特性之间存在显著的耦合，并且每种特性对基因表达变化的相对贡献因细胞类型而异。受生物信息学分析的启发，发现包埋小鼠间充质干细胞的水凝胶的刚度调节了广泛的细胞因子的分泌，并相应地影响了 Transwell 共培养模型中的造血干细胞分化。这些结果深入了解了细胞如何在不同组织中整合生物物理特征，并为合成生物学家和生物工程师提供了设计对细胞生物物理环境响应的策略。
