Soon artificial blood vessels could be available ‘off the shelf’. This would mean that heart bypass patients would not have to be subjected to a minor operation to graft veins from other parts of their body. This would also make life easier for surgeons as well.
The search for this type of blood vessels was on for three decades. Now researchers from Humacyte Inc., in Durham, N.C., have discovered how to recruit cells to build the vessel, then washing them away so the non-living tissue is storable and works for anyone. The team reported their findings in the Feb. 2 issue of the journal Science Translational Medicine. They have consequently made the first ready-to-use vessels that could be suitable for emergency surgery. The company estimates that, annually, 100,000 Americans who need bypass surgery do not get it because they have no suitable replacement veins.
Gordana Vunjak-Novakovic, a biomedical engineer at Columbia University in New York who was not involved in the study called this a “universal blood vessel” and said, “This is very practical and convenient for clinical applications.” Other approaches, customized with a patient’s own cells, take several months to prepare.
The next step is human clinical trials. It is yet unknown when these vessels would be available for human use. Dr. Alan Kypson, a heart surgeon at the East Carolina Heart Institute in Greenville, N.C., who co-authored the Humacyte report, said most self-to-self transplants perform quite well but the body’s own vessels may not be sufficient, he adds. Yadong Wang, an associate professor of bioengineering at the University of Pittsburgh who also works on artificial vessels added that these transplants are a case of “robbing Peter to pay Paul”. Removing the vessels lengthens time in the operating room and causes pain and swelling that can last up to six months he added. A new blood vessel also has to withstand the heart’s constant pumping. In a healthy person, blood pressure tops out at approximately 120 millimeters of mercury. In tests, Humacyte’s vessels could withstand a burst of more than 2,000 millimeters of mercury.
Apart from bypass operations these vessels could also be useful for people on kidney dialysis machines. To get easy access to fast-moving blood, doctors typically link an artery and vein, making an artificial shunt. But that structure can withstand only so much and eventually a replacement is necessary. Once a person runs out of his or her own vessels, artificial options exist, but they typically last for less than a year. Kypson tested artery-vein shunts in nine baboons; the shunts lasted for at least six months. The scientists have not yet tested the vessels for longer periods.
Humacyte’s protocol is a major advance, says Robert Tranquillo, a biomedical engineer at the University of Minnesota, Twin Cities, who was not involved in the study. However, he adds, it is not yet known if the cell-free vessels will eventually degenerate or get destroyed in the body. He notes that a company called Cytograft is also trying grafts made from patients’ own rolled-up skin cells. There is plenty of testing left to do, in terms of safety and effectiveness of the transplants.
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