ANISOTROPY IN HEALING MYOCARDIAL SCAR TISSUE

心肌梗死后，正在愈合的梗塞的机械特性是决定心室功能、梗塞扩大、壁瘤形成和破裂以及心室重塑的关键因素。具体地说，最近的研究表明，心肌瘢痕组织是各向异性的(一个方向比其他方向更坚硬)，并表明这种各向异性有助于保护心功能。本研究的主要目的是建立胶原纤维结构、交联度、水肿和成纤维细胞张力决定机械各向异性的物理机制，并确定它们在整个过程中的相对重要性。 脑梗塞后康复的可能性。拟议的研究将从复制瘢痕各向异性生理水平的创新胶原凝胶模型系统，到体外组织测试，再到体内功能研究。具体目标1下的工作将利用最先进的双轴测试来确定交联性、水肿性和成纤维细胞力的产生改变成纤维细胞填充的胶原凝胶的机械各向异性的机制，测试假设：A)吡啶酚交联剂通过限制胶原纤维之间的剪切来改善各向异性；B)间质水肿通过对胶原基质施加各向同性的预应力来降低各向异性；以及C)成纤维细胞通过在胶原基质上产生各向同性的主动应力来降低各向异性。接下来，我们将在体外进行特定目标2的心肌瘢痕组织测试，以确定在大鼠梗死后愈合过程中，作为各向异性决定因素的交联性、水肿性和成纤维细胞力的相对重要性，测试假设：A)水肿性和成纤维细胞力是最初几天各向异性的主要决定因素；B)胶原纤维结构在1-2周是各向异性的主要决定因素；以及C)吡啶类交联物是随后时间点的各向异性的关键决定因素。最后，《特定目标3》将测试这一假说，即急性降低各向异性会在大鼠脑梗塞后愈合的中后期阶段损害心功能。由此产生的对心肌瘢痕组织结构-功能关系的基本定量理解将对未来试图了解和预测内科、外科和再生治疗的效果以及 尝试使用组织工程学方法修改或替换心肌疤痕组织。

Following myocardial infarction, the mechanical properties of the healing infarct are a critical determinant of ventricular performance, infarct expansion, aneurysm formation and rupture, and ventricular remodeling. Specifically, recent studies have shown that myocardial scar tissue is anisotropic (stiffer in one direction than in others) and suggested that this anisotropy helps to preserve ventricular function. The primary goal of this proposal is to establish the physical mechanisms by which collagen fiber structure, crosslinking, edema, and fibroblast tension determine mechanical anisotropy and to identify their relative importance over the course of postinfarction healing. The proposed studies will progress from an innovative collagen gel model system that reproduces physiologic levels of scar anisotropy to in vitro tissue testing to in vivo functional studies. Work under Specific Aim 1 will utilize state-of-the art biaxial testing to determine the mechanisms by which crosslinking, edema, and fibroblast force generation modify mechanical anisotropy in fibroblast-populated collagen gels, testing the hypotheses: A) Pyridinoline crosslinking modifies anisotropy by limiting shearing between collagen fibers; B) Interstitial edema reduces anisotropy by applying an isotropic prestress to the collagen matrix; and C) Fibroblasts reduce anisotropy by generating an isotropic active stress on the collagen matrix. Next, myocardial scar tissue will be tested in vitro in Specific Aim 2 to determine the relative importance of crosslinking, edema, and fibroblast force generation as determinants of anisotropy during postinfarction healing in the rat, testing the hypotheses: A) Edema and fibroblast force are the primary determinants of anisotropy in the first days; B) Collagen fiber structure is the primary determinant of anisotropy at 1-2 weeks; and C) Pyridinoline crosslinking is a critical determinant of anisotropy at later time points. Finally, Specific Aim 3 will test the hypothesis that acutely reducing anisotropy impairs ventricular function at intermediate and late stages of postinfarction healing in the rat. The resulting fundamental quantitative understanding of structure-function relationships in myocardial scar tissue will be critical to future attempts to understand and predict the effects of medical, surgical, and regenerative therapies as well as to attempts to modify or replace myocardial scar tissue using tissue engineering methods.