Engineering a Physiologically Relevant Blood Vessel In Vitro

Abstract

Cardiovascular disease is a leading cause of death worldwide. There is a major unmet need to develop effective small diameter (<6 mm) conduits, suitable for vessel grafting. Bioreactors are emerging to be an important technology in conduit development, by providing a 3D environment and mechanical stimulation, including radial and circumferential strain, pressure and shear stress. Here, a new bioreactor to support vascular cell survival within a graft with physiologically relevant forces was created.

Different manufacturing production methods, including computer numerical control milling, fused deposition modelling and stereolithography (SLA) 3D printing, were used in the development and optimisation of a chamber to house the graft. SLA 3D printing was more capable of printing complex parts and allowed for the creation of the best chamber, capable of easy installation and housing the graft.

To better evaluate candidate vascular grafts, physiologically relevant conditions were reproduced. Surgical expanded polytetrafluoroethylene was used as the graft material due to its high water entry pressure. Initial seeding techniques were successful in attaching a uniform layer of human coronary artery endothelial cells. A peristaltic pump produced physiological flow and heart rate. To achieve shear stress, xanthan gum was used to thicken cell media to maintain physiological flow rates. Lastly, a physiological pressure of 120/80 mmHg was generated using a Windkessel model with reservoirs and a flow resistor. Thus, bioreactor was created to house vascular grafts, which could also reproduce physiological pressures.

A bioreactor chamber was designed with physiologically relevant physical stimuli to cultivate cells growing on a 3D vascular graft. This thesis details the design, manufacture and optimisation of the chamber, its integration with additional elements to simulate physical conditions matched to those found in humans, and proof-of-concept cell attachment and viability.