Bioengineered blood vessels that replace pulmonary arteries in three young lambs are capable of growth within their recipients, reports a new study in Nature Communications. If confirmed in humans, these new vessel grafts would overcome the need for repeated surgeries in young patients.

One of the greatest challenges in vessel bioengineering is that of designing a vessel that will remodel upon its implantation and grow with its new owner without being rejected by the immune system. Scientists have been developing strategies to generate such vessels, but they involve lengthy and meticulous preparation of vessels made with patients’ own cells and grown in the lab before implantation.

Robert Tranquillo and colleagues have generated vessels that can be stored and implanted when they are needed, without the need for customized vessel growth in the lab. They generated artificial blood vessels by placing sheep skin cells into a specialized tube and rhythmically pumping the nutrients necessary for cell growth. The rhythmical stretching helped cells deposit proteins into their surroundings that confer the right mechanical properties to the vessel. The sheep cells were finally washed away, leaving behind an “acellular”, protein scaffold that does not cause immune reaction.

In fact, when these newly generated, acellular vessel grafts replaced a part of the pulmonary artery in three lambs, the implanted vessels were soon populated by the lambs’ own cells, causing the vessel to bend its shape and grow together with the recipient until adulthood. No adverse effects such as clotting, vessel narrowing or calcification were observed.

Although the results of this proof-of-concept study are encouraging, future studies might include higher number of animals to ascertain that the procedure is effective and safe for potential testing in humans.