Using gold nanorods to modify the extracellular matrix and mechanical properties

描述(申请人提供)：房室瓣(AV)将哺乳动物的心脏分成四个腔室，与肺动脉瓣和主动脉瓣相结合，确保单向血流。房室瓣叶由瓣膜间质细胞和细胞外基质(ECM)蛋白组成的三层结构组成。在目前存在的细胞外基质蛋白中，I型胶原尤其重要，因为它负责瓣膜的结构支撑和机械耐久性。当胶原周转平衡改变时，二尖瓣叶的机械性能也会改变。如果叶变得太硬，如在适应进行性心脏病期间可能发生的情况，或太软，如退行性瓣膜疾病，叶不完全关闭，从而发生返流。虽然有许多手术方法可以修复或完全替换病变的瓣膜，但针对导致瓣膜功能障碍的生化变化的治疗策略有限。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。我们团队最近的工作表明，带负电荷的金纳米棒可以改变心脏成纤维细胞的表型，阻止其转化为肌成纤维细胞，并影响I型胶原的产生。本文提供的初步数据表明，表面修饰的金纳米棒可以改变I型胶原纤维的组装，这与三维胶原凝胶的机械性能的变化有关。这项拟议的研究将检验表面修饰的金纳米棒可以通过改变胶原的机械性能来调节瓣膜间质细胞行为的假设。此外，还提出通过操纵纳米棒上的表面电荷，可以定制二尖瓣叶的机械性能以获得所需的功能特性。为了验证这一假说，人们提出了两个具体的目标：1)确定表面修饰的金纳米棒对体外房室瓣膜力学性能的影响；2)确定表面修饰的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的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治疗二尖瓣反流的微创疗法。如果成功，这些研究将证明利用金纳米棒提供的表面电荷来调节细胞行为、基质组装和组织机械性能的有效性。这些结果不仅将影响心血管领域，该领域对与基质重塑相关的机制和控制方法非常感兴趣，而且还将影响其他医学领域，在这些领域，控制纤维化对于保护器官功能至关重要。 与公众健康相关：胶原蛋白是一种在瓣膜叶中发现的结构蛋白，它在很大程度上决定了瓣膜的机械性能和正常功能。为了应对心脏负荷的增加或由于遗传缺陷，由瓣膜叶内的细胞维持的胶原生成和降解之间的平衡发生变化，这些瓣叶不再能正常发挥作用。本文提出的工作将采用一种新的方法，使用金纳米棒来调节细胞行为、胶原蛋白组装和心脏瓣膜的机械性能。

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.