Numerous factors have contributed to the failure to produce a successful small diameter vascular graft. It is clear that a working graft must include a cellular component since inert materials are unable to interact appropriately with the surrounding tissue. The body responds to implanted materials by initiating a complex series of biological reactions, broadly grouped as thrombotic, immunogenic and hyperplastic responses. In fact, even with grafts that include a cellular component, these negative biological responses occur leading to graft failure. It is our hypothesis that it is the inability of the cellular component of a tissue engineered vascular graft to respond appropriately that leads to graft failure. Therefore it is essential to define and measure specific aspects of endothelial and smooth muscle cell (SMC) function that are required to improve graft performance. Over the last several years, our laboratory has developed several innovative approaches for the development of a small diameter tissue engineered blood vessel. We use a decellurized human umbilical vein (HUV) as a remodelable scaffold. This scaffold is mechanically isolated from the tissue resulting in a long, tubular scaffold with uniform mechanical properties. We have developed a hydrogel 'shrink-wrapping'technique for rapidly seeding high densities of human SMC onto the ablumenal surface of the vessel. These preliminary investigations have shown the HUV scaffold to have an excellent capacity to remodel. Our goal with this project is to fully develop the HUV as a small diameter blood vessel, then characterize and define conditions leading to a cell phenotype that minimizes inappropriate responses to thrombogenic and inflammatory signals, including SMC hyperplasia.
Our specific aims are 1) Comprehensively assess the human umbilical vein (HUV) scaffold as an environment favorable for early regenerative events of smooth muscle cells. 2) Identify conditions promoting attachment, growth, and function (in vivo-like) of human endothelial cells on the lumen of the HUV scaffold. 3) Test the hypothesis that details of the fluid mechanical environment are critical in causing endothelial cells to adopt a phenotype that minimizes thrombosis and an inflammatory response. 4) Test the hypothesis that exposing the smooth muscle cells to hypoxic conditions does not severely impair the function of the fully oxygenated endothelial cells.
Our aim to develop functional blood vessels for cardiac and peripheral vascular reconstruction. A unique approach is taken using a bioscaffold derived from the human umbilical veins that have been machined from umbilical cords to yield a mechanically uniform, biologically compatible material. The investigations proposed herein aim to defined conditions that promote regeneration of the vascular wall to confer biological functionality. Further, we will investigate parameters that modulate undesirable cell function, such as negative aspects of wound healing. We believe, this unique approach using the human umbilical vein in concert with technologies described herein, a viable alternative can be developed to alleviate this clinical demand.
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