The artificial vessels made by Humacyte do not totally mimic nature, that is to say, they are missing an important ingredient of natural vessels. That is, the protein elastin.
Bioengineers at the University of Pittsburgh coaxed engineered vessels to create elastin. This rubber-band material facilitates arteries and veins to snap into shape after each and every pulse. Actually, elastin has long been one of the great challenges in any attempt to make artificial blood vessels. Without elastin, a vessel could eventually become stretched out like an old rubber band; in turn, a stretched-out blood vessel can mean a dangerous aneurysm.
The study leader, Yadong Wang, said “Elastin has been very elusive.” Scientists can increase the protein’s levels by adding artificial genes, but treatments like these could turn out to be risky. Wang and colleagues made grafts with 20% of the elastin found in normal vessels, the highest amount yet reported. Wang also said the body’s cells can add more elastin once the graft is implanted.
Wang’s group convinced cells to manufacture elastin by growing baboon smooth-muscle cells in an elastic, biodegradable scaffold. The process took just three weeks and now the scientists are testing their grafts in rats.
While Wang’s vessels have only one-fifth of the natural amount of elastin, this is more than other researchers can boast. For instance, Robert Tranquillo, of the University of Minnesota, estimates that he gets 1% to 10% in his own artificial grafts.
Wang’s artificial vessels may withstand some 200 millimeters of mercury pressure; a healthy blood pressure maxes out at one-hundred and twenty.