While the newly grown blood vessels looked right, they weren't strong enough to be implanted into people. Much of the strength of blood vessels depends on elements around the cells, such as collagen and elastin. This will be the next major hurdle for researchers.

"The ability to grow new vessels from older cells represents a crucial initial step toward growing blood vessels from a patient's owns cells that can be used to treat that patient's vascular disease," said lead researcher Dr. Laura Niklason, an associate professor of anesthesiology and biomedical engineering at Duke University in North Carolina.

Currently, doctors bypass a coronary artery blockage by sewing in a new blood vessel, which usually comes from a vein in the patient's leg. However, in older people, the leg veins are often not good enough to be used in the chest, or the patient may have had previous bypass surgery and no longer has many suitable leg veins.

Important Advance in Tissue Engineering

Synthetic grafts are available, but they are not that effective for small blood vessels, said Eric Brey, a biomedical engineer from Chicago's Illinois Institute of Technology, who was not connected with the research. He agreed the study was an important advance in tissue engineering, but said there are major hurdles before it can be tried in treatment.

Scientists have grown human blood vessels before, but from young, healthy cells.

In this study, the blood vessels were engineered using cells taken from the leg veins of four elderly men with heart disease who were having bypass operations. Generally, cells from older people do not proliferate because they don't have enough life cycles left to be grown into functional arteries, experts say.

But this time, the scientists found a way to overcome that limitation by treating them with a chemical involved in cellular aging.

Could Be Perfected Within the Next 10 Years

To create the new arteries, the researchers made a tube from a sponge-like material and implanted smooth muscle cells along the tube, then pulsed a vitamin and nutrient solution through it until the cells filled the spaces in the dissolving scaffold. They then added cells of a different type to line the interior of the blood vessels to complete the artery.

While the vessels looked right, they weren't strong enough to be implanted into people, the researchers found.

Much of the strength of blood vessels is down to other elements around the cells, such as collagen and elastin, said Brey, who noted this will be the next major hurdle.

"Once you implant these vessels, if they are not strong enough, you are going to have serious problems. My gut is that it's not trivial to overcome," he said.

The researchers said the technique could be perfected within the next 10 years.