Now researchers have tested a new type of lab-grown blood vessel implant. The results are encouraging, with the bioengineered vessels proving more durable and just as safe as commonly used synthetic grafts when implanted into patients undergoing kidney dialysis.
Due to the frequent needles involved, ongoing dialysis can damage a patient’s blood vessels, and grafts are often necessary. The problem is that existing techniques, including synthetic and other bioengineered grafts, are often prone to infection or being rejected by the body. And there is also a waiting period for bioengineered vessels tailor made using a patient’s own cells.
A team, made up of researchers at Duke University, Yale University and the tissue engineering company Humacyte, grew bioengineered vessels in the lab that contain no living cells, then implanted them into 60 patients who require dialysis due to kidney failure, with results suggesting they perform better than synthetic alternatives.
The key is that these lab-grown vessels are acellular, which means they contain no living cells and therefore don’t contain the components that can cause tissue rejection. As a result, a supply of these acellular blood vessels can be kept on hand and implanted on short notice, reducing time patients spend on the waiting list.
"The bioengineered blood vessel represents a critical step in tissue engineering," says Jeffrey Lawson, professor of surgery and pathology at Duke and the chief medical officer of Humacyte. "Because these vessels contain no living cells, patients have access to off-the-shelf engineered grafts that can be used without any waiting period associated with tailor-made products."
The vessels are created from human vascular cells grown in tissue culture and placed over a blood vessel-shaped scaffold. Under the right conditions, the tissue grows and acquires the properties of real blood vessels. After eight weeks, the scaffold degrades away, and what’s left is lab-grown tissue with the structure of the blood vessel, ready to be washed with a special solution to remove the last of the cells, and then implanted.
And the results of this first trial have been positive. Patients showed no signs of rejection a year after implantation, and although there were cases of adverse effects, such as clotting, these were at rate comparable to other dialysis grafts. The bioengineered vessels held up better over the course of the year, too, with the scientists measuring their durability at 89 percent, compared to around 60 percent reported in previous studies for synthetic grafts.
Interestingly, the patient’s own cells began to replace the bioengineered ones, which similar tests have shown previously.