The nonlinear elasticity of many tissue-specific extracellular matrices is difficult to recapitulate without the use of fibrous architectures, which couple strain-stiffening with stress relaxation. Herein, bottlebrush polymers are synthesized and crosslinked to form poly(ethylene glycol)-based hydrogels and used to study how strain-stiffening behavior affects human mesenchymal stromal cells (hMSCs). By tailoring the bottlebrush polymer length, the critical stress associated with the onset of network stiffening is systematically varied, and a unique protrusion-rich hMSC morphology emerges only at critical stresses within a biologically accessible stress regime. Local cell-matrix interactions are quantified using 3D traction force microscopy and small molecule inhibitors are used to identify cellular machinery that plays a critical role in hMSC mechanosensing of the engineered, strain-stiffening microenvironment. Collectively, this study demonstrates how covalently crosslinked bottlebrush polymer hydrogels can recapitulate strain-stiffening biomechanical cues at biologically relevant stresses and be used to probe how nonlinear elastic matrix properties regulate cellular processes.

中文翻译：

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非线性弹性洗瓶刷聚合物水凝胶调节间充质基质细胞中肌动球蛋白介导的突起形成

许多组织特异性细胞外基质的非线性弹性在不使用纤维结构的情况下很难重现，纤维结构将应变硬化与应力松弛结合起来。在此，合成并交联瓶刷聚合物以形成基于聚乙二醇的水凝胶，并用于研究应变硬化行为如何影响人间充质基质细胞（hMSC）。通过定制瓶刷聚合物长度，与网络硬化开始相关的临界应力会系统地变化，并且仅在生物可及的应力范围内的临界应力下才会出现独特的富含突起的 hMSC 形态。使用 3D 牵引力显微镜对局部细胞-基质相互作用进行量化，并使用小分子抑制剂来识别在工程应变硬化微环境的 hMSC 机械传感中发挥关键作用的细胞机制。总的来说，这项研究证明了共价交联的洗瓶刷聚合物水凝胶如何在生物相关应力下重现应变硬化生物力学线索，并用于探索非线性弹性基质特性如何调节细胞过程。