Using gold nanorods to modify the extracellular matrix and mechanical properties

描述（由申请人提供）：房室瓣膜（AV）将哺乳动物的心脏分为四个腔室，并与肺动脉瓣和主动脉瓣结合，确保单向血液流动。房室瓣小叶由瓣膜间质细胞和细胞外基质（ECM）蛋白层组成的三层结构。在现有的ECM蛋白中，I型胶原蛋白尤为重要，因为它负责瓣膜的结构支撑和机械耐久性。当胶原蛋白转换的平衡被改变时，二尖瓣小叶的力学特性也会发生变化。如果小叶变得过于僵硬，如在适应进行性心脏病时可能发生，或过于松弛，如在退行性瓣膜疾病中，小叶不能完全关闭，导致反流发生。虽然有许多手术方法可以修复或完全替换病变瓣膜，但针对导致瓣膜功能障碍的生化变化的治疗策略是有限的。纳米材料因其治疗潜力而受到越来越多的关注，主要是在药物输送和成像领域。我们小组最近的研究表明，带负电荷的金纳米棒可以改变心脏成纤维细胞的表型，阻止它们转化为肌成纤维细胞，并影响I型胶原蛋白的产生。本文的初步数据表明，表面修饰的金纳米棒可以改变I型胶原原纤维的组装，这与三维胶原凝胶的力学性能变化有关。该研究将验证表面修饰金纳米棒可以通过改变胶原蛋白的力学特性来调节瓣膜间质细胞行为的假设。此外，还提出了通过控制纳米棒的表面电荷，可以定制二尖瓣叶的机械性能以获得所需的功能性能。为了验证这一假设，我们提出了两个具体的目标：1)确定表面修饰金纳米棒对房室瓣膜离体力学性能的影响；2)确定表面修饰金纳米棒改变胶原纤维形成的机制。本文提出的工作代表了一种多学科方法来研究金纳米棒在生物医学中的潜在用途，最终目标是开发一种微创治疗二尖瓣反流的方法。如果成功，这些研究将证明利用金纳米棒呈现的表面电荷来调节细胞行为、基质组装和组织力学性能的有效性。这些结果不仅会影响心血管领域，对与基质重塑相关的机制及其控制方法非常感兴趣，而且还会影响其他医学领域，其中控制纤维化对保持器官功能至关重要。

DESCRIPTION (provided by applicant): The atrioventricular valves (AV) divide the mammalian heart into four chambers and, combined with the pulmonary and aortic valves, ensure unidirectional blood flow. AV valve leaflets are composed of a trilaminar structure consisting of both valvular interstitial cells and layers of extracellular matrix (ECM) proteins. Of the ECM proteins present, collagen type I is particularly important because it is responsible for the structural support and mechanical durability of the valves. When the balance of collagen turnover is altered, the mechanical properties of the mitral valve leaflets change. If the leaflets become too stiff, as can occur during adaptation to progressive heart disease, or too floppy, as in degenerative valve diseases, the leaflets do not completely close allowing regurgitation to occur. While there are a number of surgical approaches which can repair or completely replace diseased valves, therapeutic strategies aimed at the biochemical changes leading to valvular dysfunction are limited. Nanomaterials are receiving increased attention for their therapeutic potential, largely in the areas of drug delivery and imaging. Recent work from our group has demonstrated that negatively charged gold nanorods can alter cardiac fibroblast phenotype, preventing their transformation into myofibroblasts, and affecting the production of type I collagen. Preliminary data presented herein demonstrates that surface-modified gold nanorods can alter the assembly of type I collagen fibrils which correlates with changes in the mechanical properties of three-dimensional collagen gels. The proposed study will test the hypothesis that surface-modified gold nanorods can modulate valvular interstitial cell behavior by altering the mechanical properties of collagen. Furthermore, it is proposed that by manipulating the surface charge on the nanorods, the mechanical properties of mitral valve leaflets can be tailored to obtain desired functional properties. Two specific aims are proposed to test this hypothesis: 1) To determine the effect of surface-modified gold nanorods on the mechanical properties of atrioventricular valves ex vivo and 2) To determine the mechanism by which surface-modified gold nanorods alter collagen fibrillogenesis. The work proposed herein represents a multidisciplinary approach to investigating the potential uses of gold nanorods in biomedicine, targeted ultimately at developing a minimally invasive therapy for mitral valve regurgitation. If successful, these studies will demonstrate the efficacy of using surface charges presented by gold nanorods to modulate cell behavior, matrix assembly and tissue mechanical properties. These results will not only impact the cardiovascular field, which is greatly interested in mechanisms associated with matrix remodeling and ways to control it, but also other areas of medicine where the control of fibrosis is essential to preserve organ function. PUBLIC HEALTH RELEVANCE: Collagen is a structural protein found within valve leaflets which is largely responsible for the mechanical properties and proper function of the valves. In response to increased load on the heart or due to genetic defects, the balance between collagen production and degradation, which is maintained by cells within the valve leaflets, becomes shifted and these leaflets can no longer function properly. The work proposed herein will take a novel approach using gold nanorods to regulate cell behavior, collagen assembly and the mechanical properties of heart valves.