New bioveins open doors for surgery

Bioengineers have designed “off the shelf” veins out of human cells.

Yale researcher Laura Niklason led a study reported in the Feb. 2 issue of the journal of Science Translational Medicine that used tissue engineering techniques to create bioengineered veins to help patients suffering from renal failure and clogged arteries. The technique will be useful in dealing with the limitations of hemodialysis, a procedure used to filter blood, and bypass heart surgeries, which transport blood and oxygen in patients with clogged arteries, the study’s researchers said.

The project, which took place from 2005 to 2010, was a collaboration between Yale, Duke, East Carolina University and Humacyte, a regenerative medicine company.

“A large number of patients need bypass surgery but have no conduit veins of their own for grafting,” East Carolina University researcher Alan Kypson said. “In addition, the harvesting of leg vein from the patient for bypass is painful and fraught with complications, particularly as the population gets older and more overweight.”

In order to create the veins, human cells are put into a tubular mold which they grow in for two and a half months in a bioreactor. The process causes the cells to secrete proteins, which form the tissue and cause the the mold to degrade. The cells are then washed away, leaving a tissue tube or graft, that can be used like a vein, providing a passage for blood.

The bioengineered vein has been shown to be more effective than prosthetic or synthetic veins, with lower infection rates, better blood flow, and lower levels of calcium buildup, said co-author Roberto Manson, assistant surgery professor at Duke University Medical Center. The veins also facilitated hemodialysis, peripheral arterial bypass surgery and coronary artery bypass surgery by creating a connection to allow blood flow. The scientists created veins with different diameters for each of the procedures, said Shannon Dahl, a cofounder of Humactye who helped design the experiments.

Patients with kidney failure often require hemodialysis to filter waste products from the blood using a machine that connects to a vein. The bioengineered vein connects to a large artery to increase the rate of filtration with less clogging than in synthetic veins, the paper said.

Patients with clogged arteries require a new route to allow regular blood flow. In bypass heart surgery, a portion of a vein from another part of the body such as the leg is sewed and passed over the diseased artery.

Limitations of small vein size and disease create the need for an artificial connection between blood sources, Manson said. The bioengineered product demonstrated resistance to obstruction and clotting, he added.

This novel product can be supplied by any donor because the synthesized tissue does not react negatively with the immune systems of recipients because the cells themselves are washed away from the tissue product.

“The study showed that it is possible to engineer functional tissues from human cells, that can then be rendered acellular and therefore be available ‘off-the-shelf,’” Laura Niklason, Yale anesthesiology and biomedical engineering professor and founder of Humacyte said.

The non-patient specific engineered veins can be stored in a refrigerator for up to one year, and can therefore can be ready in a patients time of need, said Dahl.

“Wouldn’t it be amazing if you could tailor grown blood vessels?” said Kypson. “People would have less incisions in their legs and they would spend less time in the operating room.”

Manson said the next step is to test the veins in humans on hemodialysis.

Niklason said she hoped these “immunologically bland” tissues could be used for repair and replacement of other connective tissues besides arteries.

The study was funded by Humacyte, which was founded in 2004 and located in Durham, North Carolina.

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