3D printed bioreactor enabling the physiological culture and the study of pathological processes in large vessels.

Abstract

Routine cardiovascular interventions such as balloon angioplasty, result in vascular activation and remodeling, often requiring re-intervention. 2D in vitro culture models and small animal experiments have enabled the discovery of important molecular and cellular pathways involved in this process, however the clinical translation of these results is often underwhelming. There is a critical need for an ex vivo model representative of the human vascular physiology and encompassing the complexity of the vascular wall and the physical forces regulating its function. Vascular bioreactors for ex vivo culture of large vessels are viable alternatives, but their custom-made design and insufficient characterization often hinders the reproducibility of the experiments. The objective of the study was to design and validate a novel 3D printed cost-efficient and versatile perfusion system, capable of sustaining the viability and functionality of large porcine arteries for 7 days and enabling monitoring of post-injury remodeling. MultiJet Fusion 3D printing technology was used to engineer the EasyFlow insert, converting a conventional 50 ml centrifuge tube into a mini bioreactor. Porcine carotid arteries either left untreated or injured with a conventional angioplasty balloon, were cultured under pulsatile flow for up to 7 days. Pressure, heart rate, medium viscosity and shear conditions were adjusted to represent the typical arterial physiology. Tissue viability, cell activation and matrix remodeling were analyzed by immunohistochemistry, and vascular function was monitored by duplex ultrasound. Physiological blood flow conditions in the EasyFlow bioreactor preserved endothelial coverage and smooth muscle organization and extracellular matrix structure in the vessel wall, as compared to static culture. Injured arteries presented hallmarks of early remodeling, such as intimal denudation, smooth muscle cell disarray and media/adventitia activation in flow culture. Duplex ultrasound confirmed physiological hemodynamic conditions, dose-dependent vasodilator response to nitroglycerin in untreated vessels and impaired dilator response in angioplastied vessels. We here validate a low-cost, robust and reproducible system to study vascular physiopathology, laying the basis for future investigations into the pathological remodeling of blood vessels and creating a platform to test novel therapies and devices ex vivo, in a patient relevant system.