Nearly 25 years ago, University of Minnesota researcher Robert Tranquillo began studying ways to engineer a biological human blood vessel for use in dialysis patients.
Published this month, Tranquillo’s research is awaiting Food and Drug Administration review and, if approved, will move to a human clinical trial. Experts hope the completely biological vascular grafts will eventually be used in place of synthetic blood vessels, which are known to cause adverse reactions in patients.
The 400,000 U.S. patients undergoing dialysis must have blood drawn and re-entered into their bodies multiple times each week to prevent kidney failure. Doctors use a number of methods to establish dialysis access, including implanting a synthetic graft.
These synthetic grafts can’t heal from the needle pricks and are prone to infection, Tranquillo said.
“[Synthetic grafts are like] putting a Band-Aid on an injury, but if the wound doesn’t heal below it, you can keep changing the Band-Aid but it doesn’t cure the problem. What we hope to do with a living vessel is to actually cure the problem,” said Zeeshan Syedain, senior research associate at the University.
Many in the medical community have sought to provide dialysis patients with access similar to real tissue as opposed to a plastic tube, since “durable vascular access is extremely important for patients who require dialysis for survival,” said Ty Dunn, associate professor in the Department of Surgery.
The tissue-engineered blood vessel made by University researchers could provide this ongoing access and limit the risk of adverse reactions, if approved by the FDA.
To create the blood vessels, researchers take a small skin biopsy and isolate the skin cells. Next, they expand and culture additional cells from the biopsy, which are used to grow thousands of vessels.
The final step is to decellularize the blood vessels, which lets researchers implant them into any person without causing an immune response. This also means the body’s own cells can repopulate the blood vessels, Tranquillo said.
“We tried to create an artery, and we failed, but we succeeded in creating an excellent regenerative medicine tool,” he said.
The grafts also have the potential for use in coronary bypass procedures, where blood flow is diverted around blocked arteries. These procedures use the patient’s veins, so those who require a second bypass surgery are in a dire situation, as there are no more spare veins and synthetic grafts can’t be used, Tranquillo said.
Additionally, the surgery to find veins for a coronary bypass poses many risks to the patient, which would be mitigated by using the new blood vessels developed by the University. These can be easily stored in a refrigerated, airtight, saline-filled container, said Tranquillo.
This allows doctors to easily “pick up a graft from the shelf and use it,” Syedain said, “which has the potential to save many lives.”
Tranquillo said the material could also be used in children born with heart defects. Currently, these children are faced with multiple open heart surgeries from the time they are born through adulthood, as the vein or valve implanted can’t maintain the correct blood flow rate.
Researchers have shown this material is capable of growing with the body, eliminating the need for multiple surgeries.
“[This material] could transform the whole realm of pediatric cardiovascular surgery,” Tranquillo said.