Novel Functions of Fibulin-4 in the Vasculature

项目摘要 细胞外基质（ECM）成分，包括fibulin-4，在主动脉瘤中起关键作用 直接通过基因突变或间接通过非ECM中的突变， 分子，导致ECM破坏。纤维蛋白-4对于弹性纤维组装是必不可少的：然而， 还没有研究纤蛋白-4在脉管系统中的其它功能。纤维蛋白-4缺乏 动脉瘤在动脉瘤形成之前和形成期间显示细胞增殖增加，但这些细胞的起源与动脉瘤的形成有关。 细胞和驱动其活化的机制是未知的。此外，观察到的增殖 如果弹性纤维完整性的损失是驱动 增殖这表明ECM微环境中的额外局部变化是 必要我们的长期目标是更好地了解导致 主动脉瘤和夹层，以便开发治疗方法。具体来说，我们的目标是 确定增殖细胞的亚群和胶原蛋白中的特定分子缺陷， 结果是fibulin-4缺乏。我们的初步数据显示缺乏胶原交联和改变 fibulin-4敲除小鼠中胶原类型的表达。成熟的纤维状胶原抑制细胞 体外增殖：因此，是否由fibulin-4损失诱导的胶原蛋白缺陷促进了这一点， 扩散的增加值得调查。我们正在检验的假设是， 创造了一个微环境，促进主动脉壁中的局部细胞增殖，部分通过 破坏胶原蛋白的合成和成熟。我们将使用三个单独的fibulin-4缺陷小鼠 模型来表征身份并确定增殖细胞的来源。胶原 将在小鼠体外分析前胶原合成、前胶原加工和胶原成熟 胚胎成纤维细胞（MEF）模型系统，并在整个主动脉组织。MEF模型还将 用于确定胶原缺陷和观察到的增殖之间的因果关系。完成 这些研究将使我们能够确定fibulin-4以前未描述的功能， 了解ECM的变化如何为血管壁的增殖创造一个允许的环境， 导致动脉瘤形成。此外，具有祖细胞样特性的细胞已被鉴定 这就提出了一个问题，即增殖的细胞是否是祖细胞。最后， 确定fibulin-4的新作用可能会导致识别新的药物靶点， 可能用于延迟或预防动脉瘤进展。

PROJECT SUMMARY Extracellular matrix (ECM) components, including fibulin-4, play critical roles in aortic aneurysm formation, either directly through genetic mutation or indirectly through mutations in non-ECM molecules, resulting in ECM disruption. Fibulin-4 is essential for elastic fiber assembly: however, additional functions of fibulin-4 in the vasculature have not been investigated. Fibulin-4 deficient aortas show increased cell proliferation prior to and during aneurysm formation, but the origin of these cells and mechanism(s) driving their activation are unknown. Furthermore, the observed proliferation is not as widespread as expected if loss of elastic fiber integrity were the sole factor driving proliferation. This suggests that additional localized changes in the ECM microenvironment are necessary. Our long-term objective is to better understand the molecular mechanisms leading to aortic aneurysms and dissections so that treatments can be developed. Specifically, our goal is to identify the subpopulations of proliferative cells and the specific molecular defects in collagen that result from fibulin-4 deficiency. Our preliminary data show deficient collagen cross-linking and altered expression of collagen types in fibulin-4 knockout mice. Mature fibrillar collagen inhibits cell proliferation in vitro: therefore, whether defects in collagen induced by fibulin-4 loss promote this increase in proliferation warrants investigation. The hypothesis we are testing is that fibulin-4 loss creates a microenvironment that promotes localized cell proliferation in the aortic wall, in part through disruption of collagen synthesis and maturation. We will use three separate fibulin-4 deficient mouse models to characterize the identity and determine the origin of the proliferating cells. Collagen synthesis, procollagen processing, and collagen maturation will be analyzed both in vitro in a mouse embryonic fibroblast (MEF) model system, and in whole aortic tissue. The MEF model will also be used to determine a causal link between collagen defects and the observed proliferation. Completion of these studies will allow us to define previously undescribed functions of fibulin-4 and better understand how changes in ECM create a permissive environment for proliferation in the vessel wall, leading to aneurysm formation. Additionally, cells with progenitor-like properties have been identified in the aorta, raising the question of whether the proliferating cells are progenitor cells. Finally, determining novel roles for fibulin-4 may lead to identification of new drug targets, which could potentially be used to delay or prevent aneurysm progression.