Lemieux, Alaura

Key Points This study reveals the temporal development and progression of senescence in an arteriovenous fistula of uremic mice. Senescent genes including p21 increased 7 days after arteriovenous fistula placement, and p16 and phosphorylated p53 cells accumulate between days 14 and 28. Transcriptomic analyses confirm established genes in arteriovenous fistula failure and suggest a collection of novel genes of interest. Background Hemodialysis therapy for ESKD requires suitable vascular access, most commonly the arteriovenous fistula (AVF). Forty percent of AVFs fail within 1 year, leading to morbidity and care costs. Failure mechanisms remain unclear, and current therapies are inadequate. Cellular senescence may be critical in AVF failure, and ESKD itself may accelerate senescence and subsequent vascular dysfunction. Senescence follows AVF placement in rodents with normal kidney function, but the temporal and spatial features in uremic conditions are unknown. This study aimed to characterize AVF changes in uremic mice over time and versus control vessels. Methods Six- to eight-week-old male C57BL6/J mice underwent five/six nephrectomy. Twenty-eight days later, an AVF was created by cuff anastomosis (right carotid artery to the right jugular vein). Transcriptomic analysis was performed 7 days post-AVF, and further samples were collected at 14 and 28 days post-AVF creation for histologic assessment. Results AVF outflow vein morphometry showed reduced neointimal cell density. Whole transcriptomic analysis of outflow versus control veins at 7 days post-AVF placement revealed 1187 upregulated and 3256 downregulated genes. Differentially expressed genes were significantly enriched in two established senescence-related gene sets, SenMayo (a curated panel of approximately 125 genes validated across species to capture senescence and associated proteins) and SenSig (a broader panel assessed to represent fibrotic and stress-induced cell response). Histologically, senescence markers p16, p21, and phospho53 increased between days 14 and 28. Genes common to our dataset, SenMayo, and SenSig were validated with quantitative reverse transcription PCR. Conclusions These data support established markers of AVF failure, such as matrix-metalloproteinases and monocyte chemokines, and identify potential novel modulators of AVF survival that may inform senolytic strategies to improve patency. In summary, this study reveals for the first time the chronologic progression of vascular senescence in the AVF of uremic mice.

Chronic kidney disease (CKD) affects more than 10% of the world’s population. Hemodialysis, along with peritoneal dialysis and renal transplant, is one of the renal replacement therapies offered to patients with CKD/end-stage renal disease (ESRD). To proceed with hemodialysis, vascular access is required. The two means of long-term access are arteriovenous fistula (AVF) and arteriovenous graft (AVG). Multiple therapies have been created to help the long-term patency of AVFs. These therapies are needed as 40% of AVFs fail within the first year and additional intervention is required. Much of the existing research has focused on biomarkers, immune cells, hypoxia, and cell-based therapies. Regeneration therapy using mesenchymal stem cells seeks to investigate other ways that we can treat AVF failure. Mesenchymal stem cells are harvested as two main types, fetal and adult. Fetal cells are harvested at different times in fetal gestation and from multiple sources, placental blood, Whartons jelly, and amniotic stem cell fluid. Taken together, this review summarizes the different preclinical/clinical studies conducted using different types of MSCs towards vascular regenerative medicine and further highlights its potential to be a suitable alternative approach to enhance AVF patency.

Vascular access is an indispensable component of haemodialysis therapy for end-stage kidney disease patients. The arteriovenous fistula (AVF) is most common, but importantly, two-year failure rates are greater than fifty percent. AVF failure can occur due to a lack of suitable vascular remodelling, and inappropriate inflammation preventing maturation, or alternatively neointimal hyperplasia and vascular stenosis preventing long-term use. A comprehensive mechanistic understanding of these processes is still lacking, but recent studies highlight an essential role for inflammation from uraemia and the AVF itself. Inflammation affects each cell in the cascade of AVF failure, the endothelium, the infiltrating immune cells, and the vascular smooth muscle cells. This review examines the role of inflammation in each cell step by step and the influence on AVF failure. Inflammation resulting in AVF failure occurs initially via changes in endothelial cell activation, permeability, and vasoprotective chemokine secretion. Resultingly, immune cells can extravasate into the subendothelial space to release inflammatory cytokines and cause other deleterious changes to the microenvironment. Finally, all these changes modify vascular smooth muscle cell function, resulting in excessive and unchecked hyperplasia and proliferation, eventually leading to stenosis and the failure of the AVF. Finally, the emerging therapeutic options based off these findings are discussed, including mesenchymal stem cells, small-molecule inhibitors, and far-infrared therapies. Recent years have clearly demonstrated a vital role for inflammation in deciding the fate of the AVF, and future works must be centred on this to develop therapies for a hitherto unacceptably underserved patient population.