Novel Functions of Fibulin-4 in the Vasculature

项目总结 细胞外基质(ECM)成分，包括纤维蛋白-4，在主动脉瘤中起关键作用 形成，直接通过基因突变或间接通过非ECM的突变 分子，导致细胞外基质的破坏。纤维蛋白-4对于弹性纤维组装是必不可少的：然而， 纤维蛋白-4在血管系统中的其他功能尚未被研究。纤维蛋白-4缺乏 在动脉瘤形成之前和期间，主动脉显示细胞增殖增加，但这些细胞的起源 推动其激活的细胞和机制(S)尚不清楚。此外，观察到的核扩散 如果弹性纤维完整性的丧失是唯一的驱动因素，则不会像预期的那样普遍 扩散。这表明ECM微环境的其他局部性变化是 这是必要的。我们的长期目标是更好地了解导致 主动脉瘤和夹层，从而可以开发治疗方法。具体地说，我们的目标是 确定增殖细胞亚群和胶原蛋白中特定的分子缺陷 由纤维蛋白-4缺乏所致。我们的初步数据显示缺乏胶原蛋白的交联和改变 纤维蛋白4基因敲除小鼠不同类型胶原蛋白的表达。成熟的纤维状胶原蛋白抑制细胞 体外增殖：因此，纤维蛋白-4缺失引起的胶原缺陷是否促进了这一作用 核扩散的增加值得调查。我们正在测试的假设是纤维蛋白-4的丢失 在主动脉壁创造促进局部细胞增殖的微环境，部分通过 胶原蛋白合成和成熟受阻。我们将使用三只单独的菲布林-4缺陷小鼠 用于确定增殖细胞的特征和来源的模型。胶原蛋白 合成、前胶原加工和胶原成熟都将在小鼠的体外进行分析。 胚胎成纤维细胞(MEF)模型系统，以及整个主动脉组织。MEF模式也将是 用于确定胶原缺陷和观察到的增殖之间的因果联系。完成 这些研究将使我们能够定义以前未曾描述过的纤维蛋白-4的功能 了解细胞外基质的变化如何为血管壁上的增殖创造一个允许的环境， 导致了动脉瘤的形成。此外，还鉴定了具有祖细胞样属性的细胞 在主动脉中，提出了增殖细胞是否是祖细胞的问题。最后， 确定纤维蛋白-4的新作用可能会导致识别新的药物靶点，这可能 可能被用来延缓或防止动脉瘤的进展。

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.