Effect of Natural Vascular Scaffolding Therapy on Rat Arteriovenous Fistula Development

Abstract

BackgroundA mature arteriovenous fistula (AVF) has sufficient enlargement of vascular lumen (i.e. outward remodeling) and limited neointimal hyperplasia (i.e. inward remodeling) to allow increases in AVF blood flow for dialysis. The required vascular wall distention is likely affected by the integrity of vascular extracellular matrix (ECM). We hypothesized that preserving ECM integrity at the time of AVF creation surgery could improve AVF development. Collagen and elastin are the most abundant vascular ECM components and are key regulators of vascular remodeling. Natural Vascular Scaffolding (NVS) Therapy is known to interlink collagen and elastin by covalently linking these proteins via photoactivation. Thus, we investigated the effect of NVS treatment on AVF development.MethodsFemoral AVFs were created in young Wistar male rats by connecting the femoral artery (side) and femoral vein (end) in the same limb. Immediately after the blood flow was restored and dilatation of the femoral vein occurred, a 10 μl‐drop of the NVS compound (at 2 mg/ml diluted in phosphate buffered saline (PBS)) was placed at the anastomosis perivascularly and incubated for 5 minutes, giving the compound time to diffuse into the vascular wall. Next, the NVS compound was activated by a 1 minute illumination by 450nm light. The control group received a 10 μl‐drop of PBS and the same light activation. The skin was closed immediately after light activation. Rats were euthanized 1 week (early time point, 4 per group) and 4 weeks (later time point, 10 per group) post‐AVF creation for histology and morphometry. Verhoeff‐Van Gieson (VVG)‐stained thin cross‐sections were used to measure the area enclosed by internal elastic lamina (IEL), the area of open lumen, and the area of neointimal hyperplasia (NH) by Image J software. The percent open lumen area was calculated by “open lumen area/IEL‐enclosed area X 100%”. These analyses were done at three locations: the entire AVF, the AVF venous limb, and the AVF arterial limb.ResultsThe animals tolerated the treatment well in both experimental groups. At 1 week, the entire AVF’s lumen looked similar between treated and control groups. At 4 weeks, however, the entire AVF’s open lumen area and % open lumen area were trending larger in treated rats than in control rats, being 2.25 and 1.49‐folds larger, respectively (p=0.062, p=0.052). When the venous and arterial sides of the AVF were considered, the difference in open lumen area occurred in the venous side, where the AVF venous limb’s open lumen area and % open lumen area in treated rats were 4.18 and 1.98‐folds larger than in control rats, respectively (p=0.014, p=0.009). The AVF arterial limb’s open lumen area was similar in both groups. Importantly, the NH area was similar in both groups, regardless of the locations.ConclusionOur studies showed that rats tolerated NVS treatment well and the NVS treatment significantly increased the AVF open lumen area, without significantly affecting the NH area, suggesting that NVS treatment may have therapeutic potential by facilitating outward remodeling to enhance AVF maturation in patients.Support or Funding InformationAlucent Biomedical Inc.