CAREER: Determining the structure and properties of cell re-engineered microenvironments using rheology in synthetic wound healing scaffolds

人间充质干细胞（hMSCs）在迁移到创面后通过调节炎症在创面愈合中发挥关键作用。一种帮助伤口愈合的策略是将含有分离hMSCs的水凝胶直接植入伤口部位。水凝胶为周围组织提供结构完整性。然而，在伤口愈合过程中，随着时间的推移，hMSCs会重塑和降解水凝胶。为了设计具有最佳伤口愈合性能的水凝胶，必须更好地了解这些过程。这个CAREER项目将结合新的和现有的方法来描述细胞重塑和合成水凝胶材料降解过程中细胞周围区域的特征。联合研究和教育工作的目标是：(1)使用新颖的跨学科方法提供新技术来回答生物材料和细胞生物学中的关键问题；(2)招募和培训多样化的工作人员；(3)在生物材料，材料表征和伤口愈合方面教育广大受众。这项研究将对生物材料设计产生重大影响。这些新材料具有提高伤口愈合速度和防止慢性伤口发展的潜力。此外，首席研究员将招募、培训和教育广泛的受众。这将通过以下方式完成：(i)在宾夕法尼亚州Allentown的达芬奇科学中心向公众宣传；（ii）对中学生和高中生进行指导；（iii）对本科生和研究生进行指导和培训。这项工作的总体目标是表征合成水凝胶在细胞介导降解过程中的空间和时间流变演变，以确定其作为植入式伤口愈合支架的可行性。假设物理微环境可以控制细胞迁移过程中hMSC的降解策略，从而有效地将hMSC输送到伤口并控制材料降解。为了验证这一点，研究包括a)表征模拟天然组织刚度的均相水凝胶中的hMSC降解策略，b)确定响应界面刚度的变化，以及c)确定支架刚度梯度如何改变hMSC介导的降解和直接运动，以增加细胞传递和材料完整性。hMSCs将被封装在一个完善的光聚合聚（乙二醇）肽水凝胶三维。这种材料中的肽交联剂被细胞分泌的酶降解。动态支架性能将用体流变学和微流变学来测量。多粒子跟踪微流变学（MPT）将测量被封装的hMSCs在支架中产生的时空降解谱。这些测量将确定hMSCs在响应其微环境变化时使用的独特降解策略。体积流变学将量化hMSCs永久降解合成支架时材料完整性的变化。利用这些知识，这些材料作为植入式伤口愈合支架的可行性和微环境的可行性将被确定，这些微环境最有效地将hMSCs输送到损伤处，同时为周围组织提供结构。研究结果将是：1)识别微环境细胞工程在运动过程中响应支架中的同质和异质环境；2)确定增加细胞传递和材料完整性的微环境。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Human mesenchymal stem cells (hMSCs) play a critical role in wound healing by regulating inflammation after migrating to the wound site. One strategy to help wound healing is to implant a hydrogel containing isolated hMSCs directly into the wound site. The hydrogel provides structural integrity to the surrounding tissue. However, during wound healing, hMSCs remodel and degrade the hydrogel over time. These processes must be better understood to design hydrogels with the optimal properties for wound healing. This CAREER project will apply a combination of new and existing methods to characterize the region around cells during cell remodeling and degradation of the synthetic hydrogel material. The goal of the combined research and education effort is to: (1) use a novel interdisciplinary approach to provide new techniques to answer a critical problem in biomaterials and cell biology, (2) recruit and train a diverse work force and (3) educate a broad audience in biomaterials, materials characterization, and wound healing. The research will have a major impact on biomaterials design. These new materials have the potential to increase the rate of wound healing and prevent development of chronic wounds. In addition, the principle investigator will recruit, train and educate a broad audience. This will be done by: (i) outreach to the public at the Da Vinci Science Center in Allentown, PA, (ii) mentoring of middle and high school students and (iii) mentoring and training of undergraduate and graduate students.The overall goal of this work is to characterize the spatial and temporal rheological evolution of a synthetic hydrogel during cell-mediated degradation to determine viability as an implantable wound healing scaffold. The physical microenvironment is hypothesized to control hMSC degradation strategies during cell migration to efficiently deliver hMSCs to the wound and control material degradation. To test this, the research includes a) characterizing hMSC degradation strategies in homogenous hydrogels that mimic the stiffness of native tissues, b) determining the change in response to an interface in stiffness, and c) determining how gradients in scaffold stiffness change hMSC-mediated degradation and direct motility to increase cell delivery and material integrity. hMSCs will be encapsulated in 3D in a well-established photopolymerizable poly(ethylene glycol)-peptide hydrogel. The peptide cross-linker in this material is degraded by cell-secreted enzymes. Dynamic scaffold properties will be measured with bulk rheology and microrheology. Multiple particle tracking microrheology (MPT) will measure the spatio-temporal degradation profile created in the scaffold by encapsulated hMSCs. These measurements will determine the unique degradation strategies hMSCs use in response to changes in their microenvironment. Bulk rheology will quantify the change in material integrity as hMSCs permanently degrade the synthetic scaffold. Using this knowledge, the viability of these materials as implantable wound healing scaffolds and the microenvironments that most efficiently deliver hMSCs to an injury while providing structure to the surrounding tissue will be determined. The research outcomes will be: i) identification of the microenvironment cells engineer during motility in response to homogeneous and heterogeneous environments in the scaffold and ii) determination of microenvironments that increase cell delivery and material integrity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.