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，由 高水平的活性TGF-B介导了TGF-β基因的突变， 表型被血管紧张素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，随后是acfivion，活性TGF-B刺激增强ATI受体和MMP-9表达，MMP-9激活潜伏性TGF-S，ATI受体信号传导促进限制性TGF-B表达。因此，建立了活化、增强的表达和活化的循环。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。 本基金主要研究TGF-β、ATI受体和MMPs在MFS中的作用。在目标1中， 我们将测试扰动基质是否导致TGF-β形成、ATI受体表达上调和MMP介导的潜在TGF-β激活的循环，以及这些变化是否相互关联。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剂的性质。

This PPG has shown that certain clinical manifestafions 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 acfivafion, the active TGF-B sfimulates enhanced ATI receptor and MMP-9 expression, MMP-9 activates latent TGF-S, and ATI receptor signaling promotes confinued TGF-B expression. Thus, a cycle of activafion, enhanced expression, and activafion is established. However, the initiating event in this cycle is unknown, as are some ofthe interrelationships. This grant addresses three quesfions 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 formafion, 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 populafions. 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 acfivate 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 acfivator. 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.