The failure of hemodialysis arteriovenous (A-V) fistulas, which are surgically created by anastomosing a vein to a nearby artery, remains an unmet medical problem in the field of vascular surgery. In fact, approximately four out of 10 newly created fistulas will require a surgical or intravascular salvage procedure to reach maturation and become suitable for hemodialysis. Arteriovenous fistulas fail because stenosis (vascular narrowing) prevents high blood flows through the venous limb and increases the risk for thrombosis. We recently discovered that stenosis occurs due to excessive medial fibrosis and increased extracellular protein crosslinking, and is aggravated by intimal hyperplasia (IH) in a human cohort of 165 patients. Therefore, our overall goals are, first, to establish the cause-and-effect relationship between LOX, the most important enzyme responsible for crosslinking, and A-V fistula failure and, second, to design new therapeutics to facilitate A-V fistula maturation through perivascular delivery of LOX inhibitors. 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 wall remodeling that causes fistula failure. Specifically, our overarching hypothesis is that LOX activity is a major contributor in A-V fistula maturation failure. Our primary hypothesis is that postsurgical upregulation of nuclear LOX deaminates lysine residues in histones to disrupt the epigenetic landscape that secures contractile gene expression in SMCs, thereby facilitating their maladaptive phenotypic switch, neointima formation, and fibrosis of newly created A-V fistulas. Our secondary hypothesis is that inhibition of LOX prevents inward remodeling in a preclinical A-V fistula model in swine. We will test our hypothesis in three specific aims that will: 1) identify the cellular source of LOX after A-V fistula creation, 2) demonstrate the impact of LOX mediated histone modifications on the SMC phenotype after fistula creation, and 3) demonstrate that LOX inhibitors attenuate inward remodeling, IH, and stenosis in preclinical A-V fistulas in swine. We will use fine microsurgical techniques in novel conditional knockout mice and in vitro and in situ models to successfully achieve our goals. We will also use a preclinical model in swine to demonstrate the efficacy and safety of perivascular delivery of LOX inhibitors in preventing A-V fistula 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.
Patients with end-stage renal disease require the creation of a vascular access to receive hemodialysis and despite all technological and surgical advances in hemodialysis access creation, postoperative narrowing of the blood vessels that form part of the access remains a major complication. It is estimated that over $2 billions are spent every year in the maintenance of hemodialysis accesses and their complications in the U.S. alone. This study aims at identifying a pathogenic molecule responsible for the failure of the most common vascular access, the arteriovenous fistula, and outcomes from these studies may represent a breakthrough that will provide new therapeutic targets and strategies to improve vascular access dysfunction, reduce medical complications, and ultimately, save lives.
