This BCCMA entitled “Cardiovascular Remodeling following Arteriovenous Fistula Creation” brings together three VA investigators to elucidate the mechanisms of arteriovenous fistula (AVF) maturation failure in the setting of chronic kidney disease (CKD). In this specific Project 2, entitled “Type VIII Collagen Contributes to Adverse Arteriovenous Fistula Remodeling,” we plan to advance our understanding of the molecular mechanism determining venous maturation after arteriovenous anastomosis with the hope of developing personalized interventions to prevent early failure. Vascular access failure is the most important cause of morbidity and hospitalization among veterans and the general population receiving hemodialysis (HD). This highlights a clear need for in-depth research initiatives that apply state-of-the-art research technology to clinically relevant tissues to dissect the cellular and molecular mechanisms leading to failure. This retro- translational research (from clinical to basic science) finds support in preliminary premises that reveal the association between alterations in extracellular matrix (ECM) composition and failure. We have recently discovered that embryogenic type VIII collagen in the human AVF is associated with non-maturation. This collagen promotes further matrix deposition during vascular development and fibrotic diseases. Our fundamental hypothesis is that postoperative activation of the non-canonical TGF-b / MAPK / ELK-1 signaling axis in venous SMC upregulates COL8A1 expression and protein accumulation to exacerbate fibrosis and inward remodeling of the fistula wall. To test the hypothesis, we will use an integrated molecular/cellular approach, encompassing in vivo and in vitro models. In Aim 1, we will demonstrate the causality of SMC-derived Type VIII collagen in AVF remodeling. In Aim 2, we will dissect the molecular and cellular mechanisms by which type VIII collagen increases the risk of AVF failure. Finally in Aim 3, we will demonstrate the relationship between the number of COL8A1+ SMCs and the increased risk of maturation failure in patients undergoing AVF creation in two stages. We will reveal the first cellular atlas of mature and failed human AVF fistulas obtained at transposition. We will further confirm the association between this type of cells and AVF outcomes using a propensity score-matched retrospective cohort of 100 human AVF samples. We expect to demonstrate the causality of type VIII collagen to the improperly remodeled AVF wall.