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

人骨髓间充质干细胞（hMSCs）迁移到伤口部位后，通过调节炎症在伤口愈合中发挥关键作用。 帮助伤口愈合的一种策略是将含有分离的hMSC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，hMSC随着时间的推移重塑和降解水凝胶。 必须更好地理解这些过程，以设计具有最佳伤口愈合性能的水凝胶。该CAREER项目将采用新方法和现有方法的组合来表征合成水凝胶材料在细胞重塑和降解过程中细胞周围的区域。联合研究和教育工作的目标是：（1）使用新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劳动力，（3）教育广泛的受众生物材料，材料表征和伤口愈合。该研究将对生物材料设计产生重大影响。这些新材料有可能提高伤口愈合速度并防止慢性伤口的发展。此外，主要调查员将招募、培训和教育广大受众。这将通过以下方式实现：（i）在宾夕法尼亚州阿伦敦的达芬奇科学中心向公众推广，（ii）指导初中和高中学生，（iii）指导和培训本科生和研究生。这项工作的总体目标是表征合成水凝胶在细胞介导的降解过程中的时空流变学演变，以确定作为可植入伤口愈合支架的可行性。假设物理微环境在细胞迁移期间控制hMSC降解策略，以有效地将hMSC递送至伤口并控制材料降解。为了测试这一点，该研究包括a）表征模拟天然组织硬度的均质水凝胶中的hMSC降解策略，B）确定响应于硬度界面的变化，以及c）确定支架硬度梯度如何改变hMSC介导的降解和直接运动性以增加细胞递送和材料完整性。将hMSC以3D形式包封在公认的可光聚合的聚（乙二醇）-肽水凝胶中。该材料中的肽交联剂被细胞分泌的酶降解。动态支架性能将用本体流变学和微观流变学测量。多粒子跟踪微流变学（MPT）将测量由包封的hMSC在支架中产生的时空降解曲线。这些测量将确定hMSC响应其微环境变化所使用的独特降解策略。随着hMSC永久降解合成支架，本体流变学将量化材料完整性的变化。使用这些知识，将确定这些材料作为可植入伤口愈合支架的可行性以及最有效地将hMSC递送至损伤同时为周围组织提供结构的微环境。研究成果将是：i）识别在运动过程中响应支架中均匀和非均匀环境的微环境细胞工程和ii）确定增加细胞输送和材料完整性的微环境。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

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.