Understanding how MSCs controllably remodel their environment

 描述：细胞不是简单地驻留在材料中，它们主动地重新设计它们的微环境。细胞运动的开始是由于附着、牵引和酶分泌导致周围物质的急剧降解。就像细胞改变它们的微环境一样，细胞也接受来自材料的提示。合成生物材料支架的设计旨在总结和利用这种由外而内的信号来创造控制细胞运动的材料。了解这种现象将推动指导材料的设计，这种材料可以在空间上招募和增强被包裹的细胞的运动性，first 伤口愈合过程中的几个步骤。这项拟议的工作将使用高度工程化的基质金属蛋白酶(MMP)可降解的聚乙二醇多肽水凝胶微环境来包裹人骨髓间充质干细胞(HMSCs)，并使用高时空模数分辨率的微观流变特性来测量动态支架重建。这些结果将加强对细胞如何在运动之前和过程中与材料相互作用和重塑材料的理解。以前的工作使用微观流变特性来量化支架在重建过程中的微环境，确定支架的时间依赖和空间流变特性。在hMSC周围测量的降解梯度显示，离细胞最远的地方降解最大，僵硬的支架直接留在 手机。这表明细胞正在抑制基质金属蛋白酶支架的降解。我们假设细胞正在分泌金属蛋白酶的组织抑制物(TIMPs)来抑制支架的降解，以便在完全降解和加速运动之前进行附着和扩散。这项拟议的工作将调查TIMP在Well defiNed水凝胶支架环境的降解和重塑中的作用。SPECIfic Aim 1将确定TIMP在3DhMSC运动过程中的基质重塑中的作用。这将通过中和TIMP并测量由此产生的支架降解来实现。简单的模型将被用来描述细胞周围的降解PROfiLE，并精确地确定发生在 脚手架。SPECIfic Aim 2将确定物理微环境是否改变TIMP在支架降解和细胞运动中的作用。支架的刚度会有所不同，MPT将用来衡量hMSC的降解程度。预计随着材料变得更硬，细胞介导的降解将变得更具侵略性，对基质金属蛋白酶的抑制将会更少。总之，这项拟议的工作将确定TIMPs在支架降解和细胞运动性中的作用，确定TIMPs的中和是否会导致更积极的细胞介导的降解，从而产生可用于空间招募细胞和增强运动性的加速运动性。

 DESCRIPTION: Cells do not simply reside within materials, they actively reengineer their microenvironments. The onset of cellular motility is characterized by dramatic degradation of the surrounding material due to attachment, traction and enzyme secretion. Just as cells modify their microenvironment, cells also receive cues from the material. The design of synthetic biomaterial scaffolds has aimed to recapitulate and harness this outside-in signaling to create materials that control cell motility. Understanding this phenomenon will advance the design of instructive materials that can spatially recruit and enhance encapsulated cell motility, the first steps in the wound healing process. The proposed work will use highly engineered matrix metalloproteinase (MMP) degradable poly(ethylene glycol)-peptide hydrogel microenvironments to encapsulate human mesenchymal stem cells (hMSCs) and high spatio-temporal-modulus resolution microrheological characterization to measure dynamic scaffold remodeling. These results will enhance the understanding of how cells interact with and remodel materials prior to and during motility. Previous work used microrheological characterization to quantify the scaffold microenvironment during remodeling, identifying the time-dependent and spatial rheological properties of the scaffold. The degradation gradient measured around the hMSC shows greatest degradation furthest from the cell with stiff scaffold remaining directly around the cell. This suggests that the cell is inhibiting MMP scaffold degradation. We hypothesize that cells are secreting tissue inhibitors of metalloproteinase (TIMPs) to inhibit scaffold degradation to allow for attachment and spreading prior to complete degradation and accelerated motility. The proposed work will investigate the role of TIMPs in the degradation and remodeling of a well defined hydrogel scaffold environment. Specific Aim 1 will determine the role of TIMPs in matrix remodeling during 3D hMSC motility. This will be done by neutralizing TIMPs and measuring the resulting scaffold degradation. Simple models will be used to describe the degradation profile around the cell and pinpoint the type of degradation reaction occurring in the scaffold. Specific Aim 2 will determine if the physical microenvironment changes the role of TIMPs in scaffold degradation and cellular motility. The scaffold stiffness will be varied and MPT will be used to measure hMSC degradation. It is expected that as the material becomes stiffer cell-mediated degradation will become more aggressive and less MMP inhibition will occur. Collectively, the proposed work will identify the role of TIMPs in scaffold degradation and cellular motility determining whether the neutralization of TIMPs will lead to more aggressive cell-mediated degradation, resulting in accelerated motility that can be harnessed to spatially recruit cells and enhance motility.