The Multiple Roles of Lysyl Oxidase in Arteriovenous Fistula Failure

超过14000名退伍军人依靠动静脉(A-V)瘘或其他类型的血管 获得接受血液透析和延长生命的机会。静脉转化为瘘管是一种 最耐人寻味的血管生物学过程。理想的情况是瘘管成熟后成为 较大的血管，管腔面积增大，壁厚。不幸的是，动静脉瘘经常失败(~40%) 因为静脉狭窄会影响血液流动。我们最近发现，狭窄是由于 过度的中层纤维化，并因内膜增生(IH)而加重。我们的具体目标是证明 动静脉瘘静脉肢体中赖氨酰氧化酶(LOX)的上调介导了不正确的细胞外 基质(ECM)内膜重塑和病理性扩张，导致狭窄和衰竭。这 建议建立LOX和瘘管结局之间的因果关系，以便设计 有针对性的治疗。我们的提案建立在强大的科学前提之上(手稿和独特的初步 数据)表明，在自然瘘管术后LOX上调之间存在机制关系 以及导致瘘管失败的不适当的重塑。具体地说，我们假设LOX破坏了 表观遗传标记确保了平滑肌细胞(SMC)收缩基因的表达，从而促进了 新生动静脉瘘的表型转换、新生内膜形成和纤维化。我们也 假设细胞外LOX同时增加僵硬和改变胶原蛋白的构型 血管通路的类型。我们将在三个具体目标和五个实验布局中测试我们的假设 这将证明：1)血管LOX在术后动静脉瘘狭窄中的作用；2)LOX在 瘘管形成后SMC表型的表观遗传控制；3)前两者之间的关系。 人类队列中现有的LOX和动静脉瘘的结果。我们将使用精细的显微外科技术在 新型条件性基因敲除小鼠和体外和原位模型成功实现了我们的目标。我们会 也询问人类生物库中的300名患者，这些患者正在进行两阶段臂旁路手术 转位瘘管以寻找LOX水平和成熟失败之间的联系。在……里面 最后，随着这项提案的成功完成，我们正在为设计 有效靶向动静脉瘘纤维化和减少血管病变的新药和针对细胞类型的干预 进入并发症。

More than 14 000 enrolled veterans depend on an arteriovenous (A-V) fistula or other type of vascular access to receive hemodialysis and prolong their lives. The transformation of a vein to a fistula is one of the most intriguing processes in vascular biology. The desired scenario is that the fistula matures becoming a larger vessel with increased luminal area and a thicker wall. Unfortunately, A-V fistulas frequently fail (~40%) because venous stenosis compromises blood flow. We recently discovered that stenosis occurs due to excessive medial fibrosis, and is aggravated by intimal hyperplasia (IH). Our specific goal is to demonstrate that up-regulated lysyl oxidase (LOX) in the venous limb of the A-V fistula mediates improper extracellular matrix (ECM) remodeling and pathological expansion of the intima, which causes stenosis and failure. This proposal establishes the cause- effect relationship among LOX and fistula outcomes in order to design targeted therapies. Our proposal is built on strong scientific premises (manuscripts and unique preliminary data) that suggest a mechanistic relationship between postoperative upregulation of LOX in native fistulas and the improper remodeling that causes fistula failure. Specifically, we hypothesize that LOX disrupts the epigenetic marks that secure contractile gene expression in smooth muscle cells (SMC), thereby facilitating the phenotypic switch of SMCs, neointima formation, and fibrosis of newly created A-V fistulas. We also postulate that extracellular LOX simultaneously increases stiffness and altered collagen configuration in this type of vascular access. We will test our hypothesis in three specific aims and five experimental layouts that will prove: 1) the contribution of vascular LOX to postoperative A-V fistula stenosis; 2) the role of LOX in the epigenetic control of the SMC phenotype after fistula creation; and 3) the relationship between pre- existing LOX and A-V fistula outcomes in a human cohort. We will use fine microsurgical techniques in a novel conditional knockout mice and in vitro and in situ models to successfully achieve our goals. We will also interrogate a human biorepository of >300 patients undergoing creation of a two- stage brachiobasilic transposition fistula to search for associations between the levels of LOX and maturation failure. In conclusion, with the successful accomplishment of this proposal, we are paving the way for the design of new drugs and cell type-specific interventions to effectively target A-V fistula fibrosis and reduce vascular access complications.