Histopathological and duplex characteristics of deep venous stents: A novel microsurgical small animal model

Venous stent preclinical testing typically uses large animal models. We created two models of infrarenal inferior vena cava (IVC) stenting to study patency, flow rate, wall shear stress, and endothelial coverage over the stents in a microsurgery rodent model.

In Group 1, Sprague-Dawley rats underwent IVC stenting. Patency was measured by ultrasonography immediately postoperatively (POD-0) and at postoperative day 1 (POD-1). Stents underwent histological analysis up to 21 days postimplantation. Group 2 stented rats received periprocedural anticoagulation (enoxaparin 6 mg/kg SC) and were harvested to evaluate stent coverage using scanning electron microscopy (SEM). En face immunofluorescence (IF) staining was performed in Group 3. Human samples from stent occlusions were collected in the endovascular suite and compared with the animal histological findings.

In Group 1, 65% of the stented animals (13/20) were patent POD-0, increasing to 85% (17/20) by POD-1. Histologically, in-stent restenosis (ISR) was 6.2 ± 3.8%, and residual thrombosis (RT) was 32.01 ± 23.12% of the IVC total luminal stent area (LSA). These animals' pathological processes are similar to those in humans. The mean IVC vein wall thickness (VWT) was 80.18 ± 13.14 μm. In Group 2, all animals were patent (21/21) postimplantation and remained patent in POD-1. IF demonstrated stent coverage with CD31⁺ endothelial cells. Total stent endothelialization by SEM reached 69.53 ± 14.84% at 7 days and increased to 91.51 ± 11.23% at 21 days.

Quantifying rat venous stent patency and endothelialization via histology and microscopy revealed complete patency with anticoagulation and pathological occlusions (RT, ISR) when withholding anticoagulation. This rodent model will facilitate the preclinical testing of future venous stents.