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Science Translational Medicine: Growing Blood Vessels to Save Lives
A 6-mm-diameter decellularized human TEVG before implant.
[Image courtesy of Science/AAAS]
Researchers have figured out a way to grow a ready-made supply of blood vessels for transplant into patients undergoing heart surgery, reports a new study in the journal Science Translational Medicine.
The blood vessels, or “vascular grafts,” can be made ahead of time, so surgeons can grab them off the shelf when patients need them. Until now, no other vascular graft engineered from human tissue has tolerated simple storage.
Moreover, the new grafts are non-immunogenic, meaning that grafts grown from the cells of one donor could likely be transplanted into any number of unrelated patients without triggering an immune response.
Engineered blood vessels can be grown from the patient’s own cells, but this process takes nine months or more and patients usually can’t wait that long for surgery.
Now, Shannon Dahl and colleagues at Humacyte, a biotechnology firm based in North Carolina, have demonstrated a new approach to grow readily available blood vessels that retain their strength and efficacy during long-term storage and function successfully once implanted into large animals.
The researchers grew the blood vessels by culturing smooth muscle cells from human donor tissues on tube-like scaffolds made from a biodegradable polymer.
A brief explanation of how engineered blood vessels are generated.
[Video © Science/AAAS]
The smooth muscle cells produced collagen and other molecules that formed an extracellular matrix. When the scaffold degraded, fully formed blood vessels were left behind. Using a detergent, Dahl and colleagues then stripped the smooth muscle cells from the vessels to make sure they would not elicit an immune response in recipients when transplanted.
These human blood vessels retained their strength and elasticity, and remained unclogged even after storage in a simple salt solution for a year.
The human vascular grafts were also tested in large animals that had arteriovenous bypass surgery, where the blood vessel acts like a pipe between an artery and a vein (an approach that allows human patients with kidney disease to undergo dialysis).
The team showed that the blood vessels in the animals restored blood flow and remained open and strong for up to six months.
When the grafts were removed and examined, they showed no evidence of fibrosis or thickening of the vessel walls. The results indicate that these durable vascular grafts derived from different donors and scrubbed of donor cells are suitable for surgical transplant.
2 February 2011