Blood Outgrowth Endothelial Cells Reduce Hypoxia-Mediated Fibroblast to Myofibroblast Conversion by Decreasing Proangiogenic Cytokines

Abstract

Purpose: Hypoxic conditions cause fibroblasts to differentiate into alpha smooth-muscle cell actin (α -SMA)-positive cells, i.e. myofibroblasts. This process is a hallmark of venous neointimal hyperplasia (VNH) associated with hemodialysis vascular access. The purpose of this study was to determine if blood outgrowth endothelial cells (BOEC) may reduce the conversion of fibroblasts into myofibroblasts under hypoxic conditions, and to determine the potential mechanisms involved. Methods: An experimental model was used, in which fibroblasts and BOEC were subjected to hypoxia under contact and transwell conditions to determine if BOEC reduce the conversion of fibroblasts into myofibroblasts under hypoxic conditions. Gene expression under different conditions was performed. In addition, functional assays including cell proliferation and migration were determined. Results: This study demonstrates that contact needs to occur between BOEC and fibroblasts for the reduction of the hypoxia-driven conversion of fibroblasts into α-SMA. This is associated with a decrease in several proangiogenic genes including vascular endothelial growth factor A, platelet-derived growth factor, fibroblast growth factor and matrix metalloproteinase 2 in fibroblasts in contact with BOEC when compared to fibroblasts alone. In addition, migration is significantly reduced while proliferation remains unchanged. Conclusion: This study helps provide rationale for using BOEC delivered to the adventitia of the outflow vein of hemodialysis vascular access to reduce VNH.

Rationale and Trial Design of MesEnchymal Stem Cell Trial in Preventing Venous Stenosis of Hemodialysis Vascular Access Arteriovenous Fistula (MEST AVF Trial)

“…Our laboratory reported that autologous late outgrowth endothelial cells delivered to the anastomosis after placement of a hemodialysis polytetrafluoroethylene grafts could reduce VS in a porcine model (9). We showed in cell culture that endothelial progenitor cells cocultured with fibroblasts reduced phenotypic conversion of fibroblasts to myofibroblasts under hypoxic injury (53). In a rat model, MSCs were shown to reduce carotid artery stenosis after arteriotomy (54).…”

The Vascular Involvement in Soft Tissue Fibrosis—Lessons Learned from Pathological Scarring

“…Nieves Torres et al showed by in vitro experiments that when blood outgrowth endothelial cells (BOEC, a subset of circulating progenitor cells with an endothelial cell phenotype), were in contact with fibroblasts, they decreased the conversion of the fibroblasts into myofibroblasts. This associated with reduced fibroblast migration and size and down-regulation of fibroblast expression of pro-angiogenic genes, including VEGFA, PDGF, fibroblast growth factor-1, and matrix metalloproteinase-2 [111].…”

Endothelial Cells Inhibit the Angiotensin II Induced Phenotypic Modulation of Rat Vascular Adventitial Fibroblasts

“…The decrease of α‐SMA expression in hypoxia‐stimulated fibroblasts when they come in contact with cultured BOEC, meant that the conversion of fibroblasts to myoblasts was decreased. Several proangiogenic genes including vascular endothelial growth factor A( VEGFA ), platelet‐derived growth factor ( PDGF ), fibroblast growth factor ( FGF ), and matrix metalloproteinase 2 ( MMP2 ) are involved in this process [Nieves et al, ]. Angiotensin II (Ang II) can stimulate adventitial fibroblasts to produce collagen I and differentiate into myofibroblasts [Wang et al, ; Yuan et al, ; Poduri et al, ; He et al, ].…”