Tissue engineering of small diameter vascular grafts by using pcl/collagen based scaffolds

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2013
Öncü, Sepren
Cardiovascular system is composed of the heart, blood vessels and blood. This system consists of five types of blood vessels: arteries, arterioles, veins, venules and capillaries. Cardiovascular diseases (CVDs) including diseases of coronary arteries and blood vessels of the brain are responsible for 17.3 million deaths a year in the world. Atherosclerosis is the main reason for CVDs which is the hardening and thickening of arterial walls with lipid molecules and affects especially the walls of medium and large sized arteries. For the treatment of this disease autologous vessels availabity of which is limited are used. Synthetic blood vessels are successfully used in large diameter vessels ( > 6mm). However they are not successful in small diameter vessels ( < 6mm) due to early thrombosis formation. Tissue engineering is an interdisciplinary approach which applies the fundamentals of engineering to life sciences to replace, repair, maintain or exchange of damaged tissues or organs. Tissue engineered blood vessels are promising for the treatment of CVDs. The aim of this study was the production of a tissue engineered blood vessel as a small diameter vascular graft and testing in vitro. For this purpose polycaprolactone-collagen based tubular scaffolds were fabricated by electrospinning. These scaffolds were crosslinked by treatment with glutaraldehyde. They were characterized microscopically by using stereomicroscope, and SEM. Thicknesses of scaffolds and fiber dimensions of scaffolds were calculated from the micrographs. Stability was tested in both PBS and collagenase type II. Their mechanical strength was determined by uniaxial tensile testing either in tubular form or in mat form. vi Fiber diameter was found to be 289±89 nm in the inner surface of the scaffold while it was 641±206 nm on the outer surface of the scaffold. Thickness of the scaffolds was found 117±23μm. Glutaraldehyde treatment did not change the stability or the mechanical strength of the scaffolds. In vitro studies were carried out by using human vascular smooth muscle cells (VSMC) on the one side of the mat and human internal thoracic artery endothelial cells (HITAECs) on the other side of the mat. Three types of constructs were tested: single VSMC seeded, single HITAEC seeded and cocultured of VSMC and HITAEC. VSMC seeded scaffolds were cultured for 21 days and it was shown that they supported cell attachment and proliferation. HITAEC seeded scaffolds were cultured for 14 days and it was shown that in the first week there was an increase but in the second week there was a plateau or a decrease in their proliferation. With the 12 days co-cultured scaffold it was observed that the optical density (OD) observed was higher than the individual cells combined indicating synergistic effect. These results were supported by the SEM micrographs. Single VSMC and HITAEC seeded mats and cocultered of VSMC and HITAEC mats increased the mechanical properties of these scaffolds. Suturability of the tubular scaffolds was tested on these scaffolds without any tear. This study showed that scaffolds made of electrospun PCL/Collagen supported cell proliferation and had appropriate mechanical properties. It can be said that they have a potential for use as a small vascular substitute.

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Citation Formats
S. Öncü, “Tissue engineering of small diameter vascular grafts by using pcl/collagen based scaffolds,” M.S. - Master of Science, Middle East Technical University, 2013.