טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentPreis Meir
SubjectPhenotypic Changes of Endothelial and Smooth Muscle
Cells Mediated Bio-Synthetic Vascular Grafts
Patency, Expansion, and Stabilization of
Collateral Circulation
DepartmentDepartment of Medicine
Supervisor Professor Moshe Flugelman


Abstract

Cardiovascular related syndromes are the leading cause of morbidity and mortality in the developed countries. Arterial narrowing and occlusion due to atherosclerosis in leg arteries lead to peripheral arterial disease (PAD) and affects 16 million patients worldwide. Available treatments for PAD include exercise protocols, drug therapy, angioplasty, and bypass surgery. In some of these patients those treatments are not effective. Lack of adequate treatment emphasizes the need for novel therapeutic approaches.

In this work, two integrative approaches of cells and gene therapy were evaluated; both are based on autologous vascular cells that are phenotypically modified by gene transfer.

The first approach was to use bio-synthetic grafts as arterial bypass conduits using autologous endothelial cells (EC) lining graft luminal surface. More than 50% of the currently used synthetic grafts are occluded in 4-5 years after implantation due to blood clotting and scar formation within the graft. Covering graft surface with EC can prevent clotting and scar formation. The hypothesis of this doctoral thesis was that phenotypic modulation of EC by selectively over-expressing fibulin-5 (protein facilitating EC adhesion) and VEGF165 (protein facilitating EC survival) will improve our capacity to cover vascular grafts with EC and improve their patency. In this work it was demonstrated that fibulin-5 expression increased EC retention following exposure to shear-stress tested in vitro. Fibulin-5 expression increased EC retention on synthetic grafts. Both Fibulin-5 and VEGF165 expression were required in order to support EC proliferation. In vivo experiments demonstrated that fibulin-5 and VEGF165 improved short and long term patency of synthetic grafts by improving EC coverage and therefore reduced thrombosis. Fibulin-5 expression was found to inhibit smooth muscle cells (SMC) proliferation in-vitro and therefore formation of scar tissue.

The second therapeutic approach that was derived from the hypothesis is therapeutic angiogenesis.  Based on in-vitro data, we tested the hypothesis that intra-arterial injection of genetically modified endothelial and smooth muscle cells can facilitate angiogenesis, expand and stabilized collateral arteries in the ischemic region. Autologous genetically modified EC (over-expressing Angiopoietin-1) and SMC (over-expressing VEGF165) were injected intra-arterially in a hind limb ischemia model. Injection of autologous genetically modified vascular cells improved blood flow, improved blood perfusion in the ischemic muscles, and resulted in visible collateral arteries. The physiological and anatomical effect was maintained up to 24 weeks following cells injection.

In summary, by phenotypic modulation it was shown that EC and SMC can serve for therapeutic purposes of cardiovascular syndromes.