<<返回上一页

Fake veins deliver the heart's desire

发布时间:2019-03-07 06:07:07来源:未知点击:

By Ian Sample CLOGGED coronary arteries could be replaced by artificial vessels if a technique being pioneered by a Massachusetts company proves successful. Grown on a scaffolding of collagen, the vessels expand and contract like the real thing, allowing them to regulate blood flow to the heart. When arteries become blocked, surgeons replace them by cutting out a vein—usually from the leg—and sewing it in to bypass the obstruction. Unfortunately, around a third of patients who need bypass surgery do not have veins that are healthy enough to transplant. Researchers have already shown that blood vessels can be made from cellulose, but these are poor substitutes for transplanted veins because they don’t expand and contract as the heart’s demand for blood changes. Now an alternative approach, reported in Nature Biotechnology (vol 17, p 1083), promises to remedy this. Sue Sullivan from Organogenesis, a biomedical company in Canton, Massachusetts, took collagen from a pig’s intestine and removed all the attached cells. This left a porous protein sheet that she wound around a rod to make a tube. After coating the inside of the tube with heparin, which stops blood clots forming, it was implanted into a rabbit’s artery. But even with the heparin coating, more than half of the 18 tubes she implanted into rabbits became blocked. Next, Sullivan used an inner layer of heparin-coated bovine collagen, which is smoother than collagen from pigs but mechanically weaker (see Diagram). When a further 18 of these twin-layered tubes were implanted, they became lined with the same endothelial cells that prevent clotting in natural blood vessels, and remained clot-free. What’s more, new capillaries and smooth muscle cells began growing into the tubes. After three months, Sullivan found the tubes contracted in response to the same chemical signals that make real blood vessels contract (see p 24,