CAMBRIDGE, Mass. — Scientists are reporting progress in developing the first replacements for human arteries molded from human cells in the laboratory.
"It's very exciting. We're thrilled here," said Eugene Bell, president and chief scientific officer at Organogenesis Inc., a biotechnology company that is developing the arteries.
Although the arteries will not be ready for testing on humans for at least three years, Bell said the arteries could eventually offer a safe and readily available source of arteries for a variety of uses.
Extensive Need Seen
About 200,000 Americans undergo surgery each year to replace heart arteries that have become blocked by fatty buildups, while another 100,000 people in the United States undergo surgery to replace arteries elsewhere in the body.
Veins from the leg are usually used for such operations, but they are not always available. Synthetic arteries are also used, but they are prone to blood clots that can block the flow of blood, Bell said.
The laboratory-generated arteries could also be used to help treat about 10% of the 900,000 people who suffer strokes each year in the United States.
The arteries are made by first inserting a glass rod into a glass cylinder. Between the rod and the inside of the cylinder a mixture is poured containing proteins and cells taken from arteries from human umbilical cords. These cells form the smooth muscle layer of the artery.
Wrapper of Dacron Mesh
The mixture is then allowed to gel to form a thin layer around the rod. Next, a Dacron mesh is wrapped around this layer, offering added support for the artery.
Another mixture of cells and proteins is then poured on the outside of the mesh. This mixture contains cells that form connective tissue in normal arteries.
After this layer gels, the inner rod is removed and another mixture is poured into the interior of the newly formed cell cylinder. This mixture contains cells known as endothelial cells, which prevent clots in normal arteries.
"The cylinder is gently rotated so the cells adhere completely and cover it completely," Bell said. "Now what we have is a three-layered arterial equivalent."
The entire process takes about a month. The arteries can be made in various diameters by using rods of different sizes and various lengths.
In tests in the laboratory, Bell said, researchers have demonstrated that the interior lining of cells function properly to prevent clots and that the arteries can withstand high pressure. Short-term experiments with rabbits have shown that the arteries appear to function properly, he said.
The researchers now plan longer experiments using the arteries in sheep and hope to begin testing in humans within three years. The human tests are expected to take another three years to complete, Bell said.
"This will be the first living artery equivalent," Bell said. "This is a new kind of engineering. We feel we are creating a new industry. This is a new kind of biotechnology."
The company recently signed an agreement with Eli Lilly & Co. of Indianapolis to collaborate on the development, manufacture and marketing of the arteries.