Hiraki Harrison L, Matera Daniel L, Rose Michael J, Kent Robert N, Todd Connor W, Stout Mark E, Wank Anya E, Schiavone Maria C, DePalma Samuel J, Zarouk Alexander A, Baker Brendon M
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States.
Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, United States.
Front Bioeng Biotechnol. 2021 Jun 16;9:679165. doi: 10.3389/fbioe.2021.679165. eCollection 2021.
Fibrous extracellular matrix (ECM) proteins provide mechanical structure and adhesive scaffolding to resident cells within stromal tissues. Aligned ECM fibers play an important role in directing morphogenetic processes, supporting mechanical loads, and facilitating cell migration. Various methods have been developed to align matrix fibers in purified biopolymer hydrogels, such as type I collagen, including flow-induced alignment, uniaxial tensile deformation, and magnetic particles. However, purified biopolymers have limited orthogonal tunability of biophysical cues including stiffness, fiber density, and fiber alignment. Here, we generate synthetic, cell-adhesive fiber segments of the same length-scale as stromal fibrous proteins through electrospinning. Superparamagnetic iron oxide nanoparticles (SPIONs) embedded in synthetic fiber segments enable magnetic field induced alignment of fibers within an amorphous bulk hydrogel. We find that SPION density and magnetic field strength jointly influence fiber alignment and identify conditions to control the degree of alignment. Tuning fiber length allowed the alignment of dense fibrous hydrogel composites without fiber entanglement or regional variation in the degree of alignment. Functionalization of fiber segments with cell adhesive peptides induced tendon fibroblasts to adopt a uniaxial morphology akin to within native tendon. Furthermore, we demonstrate the utility of this hydrogel composite to direct multicellular migration from MCF10A spheroids and find that fiber alignment prompts invading multicellular strands to separate into disconnected single cells and multicellular clusters. These magnetic fiber segments can be readily incorporated into other natural and synthetic hydrogels and aligned with inexpensive and easily accessible rare earth magnets, without the need for specialized equipment. 3D hydrogel composites where stiffness/crosslinking, fiber density, and fiber alignment can be orthogonally tuned may provide insights into morphogenetic and pathogenic processes that involve matrix fiber alignment and can enable systematic investigation of the individual contribution of each biophysical cue to cell behavior.
纤维状细胞外基质（ECM）蛋白为基质组织中的驻留细胞提供机械结构和粘附支架。排列整齐的ECM纤维在引导形态发生过程、支撑机械负荷以及促进细胞迁移方面发挥着重要作用。已经开发出多种方法来使纯化的生物聚合物水凝胶（如I型胶原蛋白）中的基质纤维排列整齐，包括流动诱导排列、单轴拉伸变形和磁性颗粒法。然而，纯化的生物聚合物在生物物理线索的正交可调性方面存在局限，这些线索包括刚度、纤维密度和纤维排列。在此，我们通过静电纺丝生成了与基质纤维状蛋白具有相同长度尺度的合成细胞粘附纤维段。嵌入合成纤维段中的超顺磁性氧化铁纳米颗粒（SPIONs）能够使无定形块状水凝胶中的纤维在磁场作用下排列整齐。我们发现SPION密度和磁场强度共同影响纤维排列，并确定了控制排列程度的条件。调节纤维长度能够使致密的纤维状水凝胶复合材料排列整齐，而不会出现纤维缠结或排列程度的区域差异。用细胞粘附肽对纤维段进行功能化处理可诱导肌腱成纤维细胞呈现出类似于天然肌腱内的单轴形态。此外，我们证明了这种水凝胶复合材料在引导MCF10A球体进行多细胞迁移方面的实用性，并发现纤维排列促使侵入的多细胞链分离成不相连的单个细胞和多细胞簇。这些磁性纤维段能够很容易地整合到其他天然和合成水凝胶中，并通过廉价且易于获取的稀土磁体进行排列，无需专门设备。刚度/交联、纤维密度和纤维排列可进行正交调节的三维水凝胶复合材料，可能为涉及基质纤维排列的形态发生和致病过程提供见解，并能够系统地研究每种生物物理线索对细胞行为的个体贡献。
