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Scientists coax a bit of stretch into artificial blood vessels

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The artificial vessels created by Humacyte do not perfectly mimic nature’s recipe. They lack a major component of natural vessels: the protein elastin.

Scientists at the University of Pittsburgh have now coaxed engineered vessels to make elastin, they reported Feb. 3 in the online edition of the journal Proceedings of the National Academy of Sciences.

The rubber-band material that allows veins and arteries to snap back into shape after every pulse, elastin has long been one of the greatest challenges in any attempt to make artificial blood vessels. Without it, a vessel might eventually become stretched out like an old rubber band — and a stretched-out blood vessel can mean a dangerous aneurysm.

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“Elastin has been very elusive” among blood vessel engineers, says Yadong Wang, an associate professor of bioengineering, who led the study. Scientists can boost the protein’s levels by adding artificial genes or growth factors, he explains, but such complicated treatments could be risky in people. Wang and colleagues created grafts that had 20% of the elastin found in normal vessels, the highest amount yet reported. Plus, Wang says, the body’s cells will add more elastin once the graft is implanted.

Wang’s group persuaded cells to manufacture elastin simply by growing baboon smooth-muscle cells in a stretchy, elastic, biodegradable scaffold. The process only took three weeks; the scientists are now testing their grafts in rats.

Although Wang’s vessels have just one-fifth of the natural amount of elastin, that’s more than other researchers can boast. Robert Tranquillo, a biomedical engineer at the University of Minnesota, Twin Cities, estimates that he gets 1% to 10% in his own artificial grafts.

Wang’s artificial vessels can withstand about 200 millimeters of mercury of pressure; healthy blood pressure maxes out at 120. Wang calls it “a reasonable safety margin,” but Tranquillo says it is insufficient for clinical use.

Amber Dance

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