Tissue engineering in blood vessels

Abstract: Severely occluded coronary- and peripheral arteries, caused by atherosclerotic plaques, are treated with bypass surgery. Autologous veins are the most commonly used replacement graft. Among the patients that need a vascular bypass, 5-10% lack appropriate replacement veins due to previous surgery of bad quality of the vessels. Available synthetic grafts fail due to high thrombogenicity and compliance mismatch. Considering the huge number of patients in need of a vascular bypass, there is a tremendous need for a replacement graft with similar properties to those of native blood vessels.The major aim of this thesis was to develop a tissue engineered blood vessel that can be used as a vascular graft in bypass surgery. The specific aims were to investigate the interactions between endothelial- and smooth muscle cells during static and dynamic conditions, the production of extracellular matrix proteins in a tissue engineered blood vessel and if bacterial cellulose has the potential to be used as a scaffold for tissue engineered blood vessels.Endothelial- and smooth muscle cells in co-culture affected each other and this interaction resulted in an altered expression of coagulation- and fibrinolytic factors. When the co-culture was exposed to shear stress, both endothelial- and smooth muscle cells responded to the stimulation, which also lead to an altered gene- and protein expression of coagulation- and fibrinolytic factors. These results are important to consider for tissue engineered blood vessels.Blood vessels engineered by combining human smooth muscle cells and a scaffold of poly (glycolic acid), produced qualitatively the same extracellular matrix proteins as native blood vessels, although quantitatively there were large differences. The results in this thesis show that it is feasible to construct a tissue engineered blood vessel in vitro.Bacterial cellulose was very well integrated into the host tissue and did not trigger any chronic inflammatory reactions. Thus, the biocompatible properties of bacterial cellulose make it a promising scaffold alternative for tissue engineered blood vessels.