Department of Chemical and Biomolecular Engineering, Lehigh University, 111 Research Dr., Iacocca Hall, Bethlehem, PA 18015, USA.
Soft Matter. 2018 Apr 25;14(16):3078-3089. doi: 10.1039/c8sm00408k.
Human mesenchymal stem cells (hMSCs) dynamically remodel their microenvironment during basic processes, such as migration and differentiation. Migration requires extracellular matrix invasion, necessitating dynamic cell-material interactions. Understanding these interactions is critical to advancing materials designs that harness and manipulate these processes for applications including wound healing and tissue regeneration. In this work, we encapsulate hMSCs in a cell-degradable poly(ethylene glycol)-peptide hydrogel to determine how cell-secreted enzymes, specifically matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), create unique pericellular microenvironments. Using multiple particle tracking microrheology (MPT), we characterize spatio-temporal rheological properties in the pericellular region during cell-mediated remodeling. In MPT, the thermal motion of probes embedded in the network is measured. A newly designed sample chamber that limits probe drift during degradation and minimizes high value antibody volumes required for cell treatments enables MPT characterization. Previous MPT measurements around hMSCs show that directly around the cell the scaffold remains intact with the cross-link density decreasing as distance from the cell increases. This degradation profile suggests that hMSCs are simultaneously secreting TIMPs, which are inactivating MMPs through MMP-TIMP complexes. By neutralizing TIMPs using antibodies, we characterize the changes in matrix degradation. TIMP inhibited hMSCs create a reaction-diffusion type degradation profile where MMPs are actively degrading the matrix immediately after secretion. In this profile, the cross-link density increases with increasing distance from the cell. This change in material properties also increases the speed of migration. This simple treatment could increase delivery of hMSCs to injuries to aid wound healing and tissue regeneration.
人骨髓间充质干细胞（hMSCs）在迁移和分化等基本过程中会动态重塑其微环境。迁移需要细胞外基质的入侵，这需要动态的细胞-材料相互作用。了解这些相互作用对于推进材料设计至关重要，这些材料设计可以利用和操纵这些过程，应用于伤口愈合和组织再生等领域。在这项工作中，我们将 hMSCs 包裹在可细胞降解的聚乙二醇-肽水凝胶中，以确定细胞分泌的酶，特别是基质金属蛋白酶（MMPs）和金属蛋白酶组织抑制剂（TIMPs），如何创造独特的细胞周微环境。我们使用多粒子跟踪微流变学（MPT）来表征细胞介导重塑过程中细胞周区域的时空流变性质。在 MPT 中，测量嵌入网络中的探针的热运动。我们设计了一种新的样品室，在降解过程中限制探针的漂移，并最大限度地减少细胞处理所需的高价值抗体体积，从而实现 MPT 特征。之前在 hMSCs 周围的 MPT 测量表明，在细胞直接周围，支架保持完整，交联密度随着与细胞距离的增加而减小。这种降解模式表明 hMSCs 同时分泌 TIMPs，通过 MMP-TIMP 复合物使 MMP 失活。通过使用抗体中和 TIMPs，我们对基质降解的变化进行了特征描述。抑制 TIMP 的 hMSCs 会产生一种反应-扩散型降解模式，其中 MMPs 在分泌后立即积极降解基质。在这种模式中，交联密度随与细胞距离的增加而增加。这种材料特性的变化也会增加迁移速度。这种简单的处理方法可以增加 hMSCs 对损伤的输送，以帮助伤口愈合和组织再生。
