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February 04, 2011

Bioengineered veins could help patients needing bypass surgery, dialysis

Vein drain: Using human cells, scientists have grown shelf-stable blood vessels, like this six-millimeter-diameter model, that they hope to eventually see used as grafts for heart surgeries and hemodialysis. Credit: Science/AAAS
New research published in the current issue of the journal Science Translational Medicine demonstrates the capability of tissue-engineered vascular grafts that are immediately available at the time of surgery and are less likely to become infected or obstructed. The bioengineering method of producing veins shows promise in large- and small-diameter applications, such as for coronary artery bypass surgery and for vascular access in hemodialysis.

Humacyte, a Morrisville biotechnology company, worked with East Carolina university researchers to develop the veins.


The researchers have grown vessels using human cells for the first time. They used the vessels
to link an artery and a vein in baboons, creating a structure called a fistula to mimic the setup required by hemodialysis patients, who have a needle injected into such a link two or three times a week to get their blood filtered. Also, while previous versions of the vessels required a wait of several weeks while the insides of the vessels were "personalized" with some of the patient's own cells, a process that makes them less likely to clog, these hemodialysis vessels did not need that treatment. They could potentially be immediately available to the patients



"This new type of bioengineered vein allows them to be easily stored in hospitals so they are readily available to surgeons at the time of need," said Dr. Alan P. Kypson, a cardiothoracic surgeon, associate professor at the Brody School of Medicine at ECU and an author of the paper. "Currently, grafting using the patient's own veins remains the gold standard. But, harvesting a vein from the patient’s leg can lead to complications, and for patients who don’t have suitable veins, the bioengineered veins could serve as an important new way to provide a coronary bypass."

Scientists generated bioengineered veins in a bioreactor -- a device designed to support a biological environment -- and then stored them up to 12 months in refrigerated conditions. The bioengineered veins, 3 millimeters to 6 millimeters in diameter, demonstrated excellent blood flow and resistance to blockage in large animal models for up to a year.

Science Translational Medicine - Readily Available Tissue-Engineered Vascular Grafts

Autologous or synthetic vascular grafts are used routinely for providing access in hemodialysis or for arterial bypass in patients with cardiovascular disease. However, some patients either lack suitable autologous tissue or cannot receive synthetic grafts. Such patients could benefit from a vascular graft produced by tissue engineering. Here, we engineer vascular grafts using human allogeneic or canine smooth muscle cells grown on a tubular polyglycolic acid scaffold. Cellular material was removed with detergents to render the grafts nonimmunogenic. Mechanical properties of the human vascular grafts were similar to native human blood vessels, and the grafts could withstand long-term storage at 4°C. Human engineered grafts were tested in a baboon model of arteriovenous access for hemodialysis. Canine grafts were tested in a dog model of peripheral and coronary artery bypass. Grafts demonstrated excellent patency and resisted dilatation, calcification, and intimal hyperplasia. Such tissue-engineered vascular grafts may provide a readily available option for patients without suitable autologous tissue or for those who are not candidates for synthetic grafts.

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