THURSDAY, June 16, 2005 (HealthDay News) -- A bio-engineering technique of making old cells young again could make it possible to grow made-to-order blood vessels for cardiac bypass surgery patients, a new study suggests.
Cells taken from leg veins of four men, ages 47 to 74 years old, have been induced to grow like cells from newborns, Duke University researchers report. That could be an important step toward making personalized blood vessels for people who need bypass surgery but whose own blood vessels are too fragile to be used in the operation, said Dr. Laura Niklason, leader of the research group.
The old cells were made to grow like young ones by interfering with the process by which the body eventually makes cells stop dividing, said Niklason, associate professor of anesthesiology and biomedical engineering at Duke.
Every time a cell divides, a bit of a structure called a telomere that sits at the end of the gene-carrying chromosomes is clipped off by an enzyme, she explained. When the telomere becomes too short, the cell can no longer divide.
The Duke researchers made cells feel young by adding a molecule, telomerase, that prevents telomere clipping. They used a technique developed by Carol Greider at Johns Hopkins University and Robert Weinberg at the Whitehead Institute in Boston. Christopher Counter, a member of the Duke research team, worked with Weinberg before coming to the university, Niklason said.
"We put the telomerase gene in a retrovirus that carries it into the cells," Niklason said. "The cells make a bunch of telomerase enzyme, which makes the telomeres nice and long again. They continue growing and dividing in the laboratory. Essentially, they live on forever."
The study results appear in the June 18 issue of The Lancet.
The cells used in the study came from the saphenous vein, a blood vessel in the leg that often is used for grafts for bypass surgery. But in many older people these veins are not strong enough to be used for bypass surgery. The eventual goal of the research project is to grow saphenous vein cells on a tube, then use the resulting vessels for bypass procedures, Niklason said.
Heart bypass surgery is used to create a detour around the blocked part of a coronary artery to restore blood supply to the heart. An estimated 100,000 of the 1.4 million Americans who need small vessel grafts are unable to get them because their own or prosthetic vessels are unsuitable, the Duke researchers said.
Several hurdles must be overcome before the new technique can be used on humans, Niklason stressed. First, the cells now being grown in the laboratory aren't strong enough because they do not produce enough collagen, a structural protein. "So we have to get the cells to make more collagen," she said.
A second challenge is to limit the growth of the cells. Because the unchecked growth of cells is the very definition of cancer, "we are looking at modification of the telomerase enzyme so that we can turn it off after a brief period of time," Niklason said.
She would also like to speed the growing process. "It now takes eight to 10 weeks," she said. "For some patients it would be a tolerable time period, for others it would not."
The cell-growing technique could be put to use in medical practice within a decade, Niklason predicted.
"I've been working in engineering blood vessels for the past decade," she said. "When I was first asked when it could be used in humans, I said 10 to 20 years. Now I'm saying five to 10 years."
Dr. Bruce Lytle, a cardiovascular surgeon at the Cleveland Clinic who has done many bypass operations, is more cautious. "These things always take longer than we think," he said. "This is an interesting concept and the hope is that it works out as planned."
Still, Lytle said, "this is another step along the way to make tissue engineering a real medical phenomenon."
More information
The National Library of Medicine has more about bypass surgery.
