VEGF Gradients in Porous Hydrogels for Therapeutic Angiogenesis

 描述(申请人提供)：我们这项建议的直接目标是研究血管内皮细胞(血管网络的主要细胞)中血管内皮生长因子(VEGF)梯度强度和TIP细胞表型激活之间的关系。我们理解这种关系的最终目标是最大限度地增加体内血管的渗透和生物材料植入物的吻合。天然细胞外基质(ECM)包含生物分子的异质组成(不是均匀的浓度或分布)。这种异质性在胚胎维管系统的发育过程中尤为重要。试图概括天然ECM的工程ECM(EECM)通常缺乏这种异质性。我们认为，这种缺失是一个重大的疏忽。特别是，我们对专注于控制细胞行为的指导性化学梯度感到兴奋。我们认为，水凝胶缺乏异质性是基于水凝胶的体内疗法未能治疗复杂疾病的原因，例如慢性和缺血性皮肤伤口。在这项建议中，我们将重点放在TIP细胞表型的激活上，这是血管生成芽的主要内皮细胞所呈现的表型。我们推测，通过激活这种表型，我们随后将提高血管生成芽的渗透速度和方向性(例如，进入水凝胶植入物的中心)。具体地说，在这项提议中，我们将使用我们已经发表的光化学和酶化学的混合平台(混合光催化反应或HYPER)来空间控制在透明质酸(HA)水凝胶支架中共价固定VEGF的过程。在我们以前的工作中，我们已经证明，HYPER允许在水凝胶中创建梯度和固定大的生长因子。在这项提议中，我们将结合这些能力来产生受控的血管内皮生长因子梯度。拟议的培训计划是一项综合研究，包括材料合成、体外生化和细胞行为分析以及体内研究。我们还将在体内研究中包括糖尿病小鼠群体，以分析我们的方法作为一种潜在的治疗方法。除了扩大受训者和广大科学界的知识之外，我们相信这个项目将提供一条治疗伤口愈合能力减弱的患者的途径。

 DESCRIPTION (provided by applicant): Our immediate goal of this proposal is to investigate the relationship between vascular endothelial growth factor (VEGF) gradient strength and activation of the tip cell phenotype in endothelial cells (the primary cell of the vascular network. Our ultimate goal of understanding this relationship is to maximize in vivo vascular infiltration and anastomosis within a biomaterial implant. The natural extracellular matrix (ECM) contains a heterogeneous composition of biomolecules (not a homogeneous concentration or distribution). This heterogeneity is of particular importance during development of the vascular system in embryos. Engineered ECMs (eECMs) that attempt to recapitulate the natural ECM generally lack this heterogeneity. We believe that this lack is a significant oversight. In particular, we ar excited to focus on instructional chemical gradients to control cell behavior. We believe that the lack of heterogeneity in hydrogels is the reason hydrogel-based in vivo therapies have failed to treat complex maladies, such as chronic and ischemic skin wounds. In this proposal we intend to focus on the activation of the tip cell phenotype, which is the phenotype presented by the leading endothelial cell of an angiogenic sprout. We hypothesize that by activating this phenotype we will subsequently enhance angiogenic sprout infiltration speed and directionality (e.g. into the center of a hydrogel implant). Specifically, in this proposal we will use a hybrid platform of photochemistry and enzymatic chemistry (Hybrid Photopatterned Enzymatic Reaction or HyPER) that we have published to spatially control the covalent immobilization of VEGF within a hyaluronic acid (HA) hydrogel scaffold. In our previous work, we have shown that HyPER allows for both the creation of gradients and immobilization of large growth factors within hydrogels. For this proposal, we will combine these abilities to produce controlled gradients of VEGF. The proposed training plan is a comprehensive study that includes material synthesis, in vitro biochemical and cell behavior analysis, and in vivo studies. We will also include a diabetic mouse colony in our in vivo studies to analyze our approach as a potential therapy. Beyond expanding the knowledge of the trainee and the scientific community-at-large, we believe that this project will provide a route to treating patients with diminished wound healing ability.