Nodal Points in Marfan Syndrome Progression

这篇PPG显示了马凡综合征(MFS)的某些临床表现，由 纤维蛋白-1的突变是由高水平的活性转化生长因子-β和选定的 血管紧张素1型(ATI)受体拮抗剂氯沙坦可阻断其表型。项目2(Rifkin)的研究表明，潜伏的转化生长因子-S在MFS血管平滑肌细胞(VSMCs)的培养中被激活，潜伏的转化生长因子-β的激活剂是基质金属蛋白酶，很可能是基质金属蛋白酶-9，转化生长因子-β刺激AT1受体的表达。我们提出了一种模型，在该模型中，基质缺陷导致潜在的转化生长因子-β异常滞留，随后激活转化生长因子-β，转化生长因子-β激活ATI受体和基质金属蛋白酶-9的表达，基质金属蛋白酶-9激活潜在的转化生长因子-S，转化生长因子受体信号转导促进限制性转化生长因子-β的表达。这样，就形成了一个激活、增强表达和激活的循环。然而，这个周期中的启动事件是未知的，一些相互关系也是未知的。 这项资助解决了关于MFS中转化生长因子-β、ATI受体和MMPs的三个问题。在目标1中， 我们将测试干扰基质是否导致转化生长因子-B形成周期、ATI受体表达上调和基质金属蛋白酶介导的潜在转化生长因子-β激活，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来分离和鉴定不同谱系的细胞，这些细胞有助于主动脉根部VSMC的普及。细胞包括心神经沟、次级心野、中胚层和内皮细胞。因此，我们将确定MFS中的异常细胞是否来自特定的谱系，在这些谱系中，细胞正常激活潜伏的转化生长因子-β，并具有高水平的ATI受体和MMPs。这些结果将与目标1的结果进行比较，在目标1中，细胞由于基质失败而产生这些分子。在目标3中，我们将产生缺失基质金属蛋白酶-9的MFS小鼠，以确定体外激活物基质金属蛋白酶-9是否是体内的激活物。这些目标的完成将使我们了解潜在的转化生长因子-β激活的启动者，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.