Title

Stressed and strung out : the development and testing of an in vivo like bench-top bioreactor for the observation of cells under shear stress

Date of Award

2015

Degree Name

M.S. in Bioengineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Advisor: Robert Joseph Wilkens

Abstract

Bioreactor systems used for tissue engineering applications are an essential component of understanding the development of new tissues and studying the biochemical interactions between cells and their environment. A bioreactor is typically designed to mimic physiological, environmental, and mechanical stimuli that occur in vivo, and bioreactors are generally created for a specific application, such as for studying 3-dimensional tissues or dynamic fluid flow in 1-dimensional cell monolayers. The leading cause of death in the United States is coronary artery disease, which is treated with bypass graft surgery using a left internal mammary artery or human saphenous vein as the graft. Since human saphenous vein grafts often fail, investigating vascular function as a whole will help to understand more about the method of graft failure. A bioreactor system to study vascular function was successfully developed using the application of endothelial cells under shear stress in a microfluidic slide. The temperature control and diffusion rate of CO2 were recorded inside the bioreactor to confirm the system could stay within a temperature range of 37±0.5°C and a CO2 concentration between 56,000 ppm and 45,000 ppm. Also, a physiological level of shear stress was determined to be feasible with the peristaltic pump. The performance characteristics of the bioreactor were analyzed, and the apparatus was determined to be successful in generating physiological relevant conditions. Then, human umbilical vein endothelial cells were exposed to both static conditions and venous shear stress conditions for up to four days in an IBIDI® microfluidic chamber. The cell morphology, alignment, and elongation were also evaluated. The cells stayed viable during the duration of all of the dynamic flow experiments, and the cells showed evidence of cell division. The cells were also more aligned and elongated towards the direction of flow for the 48 and 72 hour flow experiments compared to the 48 and 72 hour static experiments (P-value < 0.05). The 96 hour flow experiment cells were also more aligned than the cells exposed to static conditions (P-value < 0.05). The 48 hour, 72 hour, and 96 hour dynamic flow experiments had a statistically significant difference in cell alignment compared to the 24 hour flow test, and the 72 hour dynamic flow experiment also had a statistically significant difference in cell alignment compared to the 48 and 96 hour flow experiments (P-value < 0.05). The 72 hour flow experiment was more elongated than the 24, 48, and 96 hour flow experiments (P-value < 0.05). Overall, the lab setup and bioreactor system yielded desirable results and provided a system that was fully capable of studying endothelial cells under venous shear stress conditions for studies up to 4 days.

Keywords

Bioreactors Design and construction, Endothelial cells Effect of stress on, Vascular grafts, Biology, Biomedical Engineering, Biomedical Research, Chemical Engineering, Engineering, Bioengineering, Bioreactors, Monolayers of cells under shear stress, Perfusion Systems, Fluid Mechanics, Human umbilical vein endothelial cells, Venous shear stress, Microfluidic chambers, Coronary artery disease, Endothelial cells

Rights Statement

Copyright 2015, author

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