Development of a Semi-Automated, Bulk Seeding Device for Large Animal Model Implantation of Tissue Engineered Vascular Grafts.

David A Vorp,Samuel K Luketich,Timothy K Chung,Justin S Weinbaum,Lorenzo Soletti,Darren G Haskett,Katherine L Lorentz,Eoghan M Cunnane,William R Wagner,Edith Tzeng,Antonio D’Amore,Aneesh K Ramaswamy

doi:10.3389/fbioe.2020.597847

Abstract

Vascular tissue engineering is a field of regenerative medicine that restores tissue function to defective sections of the vascular network by bypass or replacement with a tubular, engineered graft. The tissue engineered vascular graft (TEVG) is comprised of a biodegradable scaffold, often combined with cells to prevent acute thrombosis and initiate scaffold remodeling. Cells are most effectively incorporated into scaffolds using bulk seeding techniques. While our group has been successful in uniform, rapid, bulk cell seeding of scaffolds for TEVG testing in small animals using our well-validated rotational vacuum technology, this approach was not directly translatable to large scaffolds, such as those required for large animal testing or human implants. The objective of this study was to develop and validate a semi-automated cell seeding device that allows for uniform, rapid, bulk seeding of large scaffolds for the fabrication of TEVGs appropriately sized for testing in large animals and eventual translation to humans. Validation of our device revealed successful seeding of cells throughout the length of our tubular scaffolds with homogenous longitudinal and circumferential cell distribution. To demonstrate the utility of this device, we implanted a cell seeded scaffold as a carotid interposition graft in a sheep model for 10 weeks. Graft remodeling was demonstrated upon explant analysis using histological staining and mechanical characterization. We conclude from this work that our semi-automated, rotational vacuum seeding device can successfully seed porous tubular scaffolds suitable for implantation in large animals and provides a platform that can be readily adapted for eventual human use.

Highlights

METHODSCardiovascular disease remains the primary cause of global death and encompasses disorders of the heart and blood vessels (Mendis et al, 2011; Benjamin et al, 2017)
The purpose of this work was to develop and validate a semi-automated, rapid, bulk seeding device that results in homogenous cell distribution within large scaffolds intended for use as “human-sized” tissue engineered vascular graft (TEVG)
Cell Source, Isolation, and Culture Sheep stromal vascular fraction was selected as the cell source be to seeded within the poly(ester urethane)urea (PEUU) scaffold intended for implant as we have previously demonstrated that the inclusion of such cells limits acute thrombosis and promotes positive vascular remodeling when incorporated into tubular PEUU scaffolds in a small animal model (Krawiec et al, 2017; Haskett et al, 2018). sSVF was obtained from the adipose tissue of a single donor sheep

Summary

Introduction

METHODSCardiovascular disease remains the primary cause of global death and encompasses disorders of the heart and blood vessels (Mendis et al, 2011; Benjamin et al, 2017). The vessels most frequently affected by cardiovascular disease are the coronary and peripheral arteries which require revascularization surgeries to treat occlusion and distal ischemia, respectively (Goodney et al, 2009; Alexander and Smith, 2016). Stent deployment is effective in the revascularization of localized obstructions; diffuse obstructions require bypass surgery. The saphenous vein and internal mammary artery are the gold standard bypass conduits for small diameter vessels (

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