Nodal Points in Marfan Syndrome Progression

该PPG已经表明，马凡氏综合征（MFS）的某些临床表现，引起的突变，在1，是由高水平的活性TGF-β介导的，并选定的表型的进展是由血管紧张素1型（ATI）受体拮抗剂氯沙坦阻断。来自项目2（Rifkin）的工作已经表明，潜伏的TGF-β在MFS血管平滑肌细胞（VSMC）的培养物中被激活，潜伏的TGF-β的激活剂是MMP，最可能是MMP-9，并且TGF-β刺激AT 1受体表达。我们提出了一个模型，其中有缺陷的基质产生异常的潜伏性TGF-B螯合随后激活，活性TGF-B刺激增强ATI受体和MMP-9的表达，MMP-9激活潜伏性TGF-B，ATI受体信号传导促进持续TGF-B的表达。因此，建立了激活、增强表达和激活的循环。然而，这个周期的起始事件是未知的，一些相互关系也是未知的。 该基金解决了MFS中有关TGF-B、ATI受体和MMPs的三个问题。在目的1中，我们将测试是否扰动矩阵的结果在TGF-β形成，ATI受体表达上调，MMP介导的潜在TGF-β激活的周期，如果这些变化是相互关联的。在目标2中，我们将使用流式细胞术分离和表征有助于主动脉根VSMC群体的不同谱系的细胞。细胞包括心神经嵴、次级心野、中胚层和内皮。因此，我们将确定MFS中的异常细胞是否来自特定的谱系，其中细胞通常激活潜伏的TGF-β，并具有高水平的ATI受体和MMPs。将这些结果与Aim 1的结果进行比较，其中细胞由于基质失效而产生这些分子。在目标3中，我们将产生缺失MMP-9的MFS小鼠，以确定体外激活剂MMP-9是否是体内激活剂。这些目标的完成将使我们了解潜伏性TGF-β激活的起始物、激活的细胞以及体内激活物的性质

This PPG has shown that certain clinical manifestations of Marfan Syndrome (MFS), caused by mutations in fibrillin-1, are mediated by high levels of active TGF-B and that progression of selected phenotypes is blocked by the angiotensin type 1 (ATI) receptor antagonist losartan. Work from Project 2 (Rifkin) has shown that latent TGF-S is activated in cultures of MFS vascular smooth muscle cells (VSMCs), that the activator of latent TGF-B is an MMP, most likely MMP-9, and that TGF-B stimulates AT1 receptor expression. We propose a model in which defective matrix yields abnormal latent TGF-B sequestration followed by activation, the active TGF-B stimulates enhanced ATI receptor and MMP-9 expression, MMP-9 activates latent TGF-B, and ATI receptor signaling promotes continued TGF-B expression. Thus, a cycle of activation, enhanced expression, and activation is established. However, the initiating event in this cycle is unknown, as are some ofthe interrelationships. This grant addresses three questions concerning TGF-B, ATI receptor, and MMPs in MFS. In Aim 1, we will test whether perturbing the matrix results in the cycle of TGF-B formation, ATI receptor expression up-regulation, and MMP-mediated latent TGF-B activation and if these changes are interrelated. In Aim 2, we will use FACS to isolate and characterize cells of different lineages that contribute to aortic root VSMC populations. Cells include cardiac nural crest, secondary heart field, mesoderm, and endothelium. Thus, we will determine whether or not abnormal cells in MFS arise from specific lineages, in which cells normally activate latent TGF-B, and have high levels of ATI receptor and MMPs. These results will be compared to those of Aim 1 in which cells generate these molecules because of failed matrix. In Aim 3, we will generate MFS mice that are missing MMP-9 to establish if the in vitro activator MMP-9 is an in vivo activator. The completion of these aims will inform us as to the initiator of latent TGF-B activation, the cell that activates, and the nature ofthe in vivo activator