Bypassing the patient: comparison of biocompatible models for the future of vascular tissue engineering

The objective of vascular tissue engineering is to develop tissue-engineered, biocompatible, small-diameter vessels suitable to withstand in vivo systolic pressures as well as be immunologically compatible with the patient, in order to minimize graft rejection. In this study, we present and compare two models of biocompatible, tissue-engineered vascular grafts (TEVG), using chitosan and acellularized rat aortas as options for scaffolds. Human aortic adventitial smooth muscle cells and fibroblasts were seeded onto a fibrin gel and subsequently wrapped around either of the two scaffolds. After several weeks of maturation in standard culturing conditions, the graft models were analyzed and compared by mechanical testing, cell viability, and histology. Histological and viability data showed that both models were viable and developed similarly, with a scaffold surrounded by two layers of cells, the fibroblasts lying on top of the smooth muscle cells. Both models responded to 200 mM potassium chloride (KCl) (tensions of 38 ± 3, 78 ± 13, and 52 ± 7 μN) and 25 mM 8-bromo-cyclic AMP (tensions of -23 ± 4, -39 ± 10, and -31 ± 12 μN) stimulation by vasoconstriction and vasorelaxation (n = 3), respectively; however, the chitosan model was unable to maintain the contracted and relaxed tension. Because the acellularized aorta TEVGs were able to maintain stimulated tension better than chitosan TEVGs, we concluded that the acellularized aorta model was better suited for further development.