Scientists at Yale University have recently collaborated with Duke University researchers as well as Poland and United States surgeons in order to build bioengineered blood vessels that assist patients on dialysis that are suffering from kidney disease. So far studies show the man-made vessels are safe and even more durable than synthetic versions currently used.
Patients with kidney failure require dialysis, which is generally administered via a synthetic graft that is implanted within the arm. Unfortunately, the grafts are extremely prone to infection and clotting, along with many other serious complications. Studies regarding alternative grafting methods (taken from patients, donors or even the tissue of animals) have been shown to not perform any better than their synthetic counterparts.
Nicholas Greene Professor of Anesthesiology and biomedical engineering at Yale, Laura Niklason, M.D. along with her co-authors built innovative bioengineering vessels as a way to offer dialysis to 60 patients at 6 different research locations. The vessels were created by Humacyte, Inc, which Niklason is co-founder of. The vessels are called human acellular vessels (or HAVs).
In order to create such vessels, researchers isolated vascular cells and grew them in tissue cultures. The cells were then put on a scaffold in the shape of a blood vessel that is completely degradable. As the tissue became larger, it was given a bath in nutrients and pulled to achieve the physical properties that match naturally created blood vessels.
Niklason says the process took eight weeks in total. Upon completion, the scaffold deteriorates and what remains is an engineered tissue that has been built from scratch. Finally, the team washed the cellular components away with a unique solution, leaving behind only a protein structure that the cells created during the culture process. The protein is made mainly of collagen and non-living segments. The decellularized tissue maintains its vessel structure, minus components that lead to tissue rejection.
Jeffrey Lawson, M.D., a professor of surgery and pathology at Duke and chief medical officer at Humacyte has been a collaborator of Niklason’s for a long time. Lawson says the bioengineered blood vessel represents a very crucial step in tissue engineering technology because the vessels do not have any living cells within them. This will mean no waiting periods for patients who require vessels, as well as patient-specific creations.
Niklason says after being implanted, the new blood vessels do not appear to cause any adverse side effects on a large scale and maintain full functionality. They keep their mechanical integrity and show no signs of being rejected by the body. While there were minor instances of blood clotting, the rates at which these occurred were very similar to those that occur in today’s treatment methods already. Synthetic grafts have a durability of about 60% after about a year, while the bioengineered vessels show 90% staying power after the same amount of time.
Researchers also noticed that after implantation, the bioengineered vessels begin to repopulate within the patient’s living cells. Niklason explained that the non-living tissue starts to turn into living tissue over time, calling this an example of regenerative medicine in its truest sense.
A large number of new vessels can be created from samples provided by a single donor. This could completely change the care patients with kidney failure receive, and sufferers of other diseases down the road. Niklason says the finding that acellular tissue has the ability to turn itself into human tissue provides many new and exciting possibilities in the world of regenerative medicine.
The latest findings were published on May 12th in The Lancet journal.