| The need for the development of a functional small diameter vascular graft is great. In order to meet this pressing need, we have pursued the development of a completely biological tissue engineered artery, termed a "bioartificial artery" (BAA), which will incorporate both arterial tissue cells and a natural biopolymer matrix to form a living tissue that can be fully integrated into the recipient following implantation. The goal of this thesis was to examine the roles that certain mechanical signaling mechanisms play in the development of a functional BAA, as these mechanisms have been shown to dramatically influence the development of native arteries. To this end, we have developed two bioreactor systems that were capable of subjecting our engineered tissues to a wide range of physiologically relevant mechanical stimuli.; The first system was designed for the purpose of isolating the effects of cyclic distension (CD) on media-equivalents (MEs). MEs were formed by entrapping smooth muscle cells (SMCs) in a type I collagen or fibrin gel that was subsequently compacted around a rigid, non-adhesive mandrel by cell-generated traction on the surrounding fibrils resulting in strong circumferential alignment. Using this system, we were able to show that it was possible to enhance the mechanical properties and matrix composition of collagen-based MEs by subjecting them to 5 weeks of CD in a manner that was dependent upon loading parameters such as strain, stretch time, and relaxation time. Furthermore, CD induced a partial reversion of the SMCs to the contractile phenotype as evidence by increased expression contractile phenotype markers and enhanced sensitivity to vasoactive drugs.; The second system developed for this project was a pulsatile flow loop system capable of mimicking the hemodynamic environment of the arterial system. A robust method of seeding endothelial cells (ECs) onto the lumen of fibrin-based MEs was developed that allowed us to achieve near complete EC surface coverage. We were able to show that ECs elongated and aligned in the direction of flow when endothelialized MEs were exposed to physiological flows. EC surface coverage remained high in response to flow indicating that ECs were highly adherent to the MEs. |
