The single-cell landscape of the human vein after arteriovenous fistula creation and implications for maturation failure.

introductionThe biological mechanisms underlying arteriovenous fistula (AVF) maturation in patients receiving hemodialysis remain poorly understood despite decades of research.

methodsTo address this gap, we first investigated the cellular changes in the venous wall after fistula creation in histological biopsies of longitudinal veins and AVF samples (23 patients). Using single-cell RNA sequencing of 70,281 cells from independent pre-access veins, early resections, mature, and failed AVFs (20 patients), we then created a complementary transcriptomic atlas of the human vein before and after anastomosis.

resultsAVFs had increased wall area and cell number but reduced cell density in histological sections, suggesting that postoperative wall thickening occurs predominantly through extracellular matrix (ECM) deposition. The early remodeling of the AVF was characterized by a loss of smooth muscle cells, increased monocyte infiltration, and the reprograming of myofibroblasts and fibroblasts toward reparative phenotypes. In contrast, later stages of remodeling were dominated by ECM-producing myofibroblasts and fibroblasts, occurring in the context of low cell proliferation. Failed AVFs displayed persistent inflammation and exaggerated healing responses as defining features. Specifically, these AVFs contained abundant proinflammatory and adhesive macrophages with upregulation of the Myddosome signaling complex, proinflammatory vasa vasorum endothelial cells, and hyperactivated fibroblasts and myofibroblasts. Macrophage-derived osteopontin emerged as a key paracrine signal driving vascular cell activation in failed AVFs. Additional signals derived from fibroblasts, myofibroblasts, and endothelial cells, including chemokines, semaphorins, fibroblast growth factors, angiopoietin-like proteins, periostin, and transforming growth factor-β, were also enriched within the inflammatory microenvironment sustaining AVF failure.

conclusionsOur findings uncover previously unrecognized cellular and molecular patterns in human veins following AVF creation, providing novel insights and potential therapeutic targets to improve AVF maturation outcomes.