Akademik Veri Yönetim Sistemi
Tezin Türü: Doktora
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye
Tezin Onay Tarihi: 2009
Öğrenci: PINAR ZORLUTUNA
Danışman: VASIF NEJAT HASIRCI
Özet:One of the major causes of death in developed countries is cardiovascular disease that affects small and medium sized blood vessels. In most cases autologous grafts have to be used which have limited availability. A functional tissue engineered vessel can be the ultimate solution for vascular reconstruction. Tissue engineered constructs with cells growing in an organized manner have been shown to have improved mechanical properties. In the present study collagen scaffolds with 650 nm, 500 nm and 332.5 nm wide channels and ridges were seeded with human vascular smooth muscle cells (VSMC) and human endothelial cells seperately and then co-cultured on tubular scaffolds. When the films were seeded with endothelial cells it was observed that nanopatterns do not affect cell proliferation or initial cell alignment; however, they significantly influenced cell retention under shear (fluid flow). While 35 ± 10 % of the cells were retained on unpatterned films, 75 ± 4 % was retained on 332.5 nm patterned films and even higher, 91 ± 5 % was retained on 650 nm patterned films. It was shown that nanopatterns as small as 332.5 nm could align the vascular smooth muscle cells (VSMC) and that alignment significantly improved mechanical properties. Presence of nanopatterns increased the ultimate tensile strength (UTS) from 0.55 ± 0.11 on Day 0 to as much as 1.63 ± 0.46 MPa on Day 75, a value within the range of natural arteries and veins. Similarly, Young’s Modulus values were ca. 4 MPa, again in the range of the natural vessels. Since the films would be ultimately rolled into tubes of collagen, nutrient transfer through the films is quite crucial. Diffusion coefficient for 4-acetaminophenol and oxygen through the collagen films were found to be 1.86 ± 0.39 x 10-7 cm2.s-1 and 5.41 ± 2.14 x 10-7 cm2.s-1, repectively in the unseeded form, and increased by 4 fold after cell seeding, which is comparable to that in natural tissues. When both cell types were co-cultured on the nanopatterned tubes (a both-side nanopatterned collagen tube), it was shown that on the outside of the tube VSMCs proliferated in an oriented manner and on the inside endothelial cells proliferated as a monolayer. Therefore, this study showed that cell guidance enhances the mechanical properties of engineered vessels, and help overcome the two most important challenges in vascular tissue engineering; the need for adequate mechanical properties and continuous lining of endothelial cells even under physiological shear stress.