Patients' cells used for new heart valves
By JOHN FAUBER
November 16, 2003
Orlando, Fla. - Patients' own cells have been used to create new heart valves
that were surgically implanted in the heart, acting as viable replacements
for diseased valves, according to research presented here.
The research suggests that patients someday may become on-demand warehouses for their own spare parts.
"It's the first stage of a creation," said Niloo Edwards, chairman of cardiothoracic surgery at the University of Wisconsin-Madison, who was not involved in the study. "We are making parts of a human in a petri dish."
The breakthrough was accomplished by German researchers who took cells from blood vessels in the arms or legs of 23 patients, grew them on a scaffold in a laboratory and implanted the new valves in the hearts of the patients.
The research, presented last week at the American Heart Association annual meeting, suggests that so-called tissue-engineered valves soon may be a viable alternative to the mechanical, pig or cadaver valves now in use.
"We've had very good results," said Pascal Dohmen, head of tissue engineering research and a surgeon at Charite Hospital in Berlin.
"Using tissue-engineered valves overcomes many of the problems with mechanical or donor valves because it is a living structure from the patient's own tissue, and so it does not cause an immunological reaction."
Mechanical valves generally last a lifetime, but patients have to take blood thinners to prevent clots that can form around them.
Donor valves from pigs or cadavers eliminate the need for blood-thinning medicine but often break down in 10 or 15 years.
Immune-suppressing drugs are not used with donor valves because they are treated in a way that prevents an acute immune system rejection.
However, doctors think there may be some low-level rejection that causes donor valves to break down over time.
It is hoped that tissue-engineered valves can avoid both of those problems.
To create the new valves, researchers took cadaver valves and removed the human cells, leaving a scaffold of collagen and elastin, fibrous proteins found in connective tissue that provide elasticity. Pieces of vein from the patients were used to "seed" the structures with cells.
After a while, the cells not only grew around the structure, but also began producing their own collagen and elastin, Dohmen said.
The lab process took about four weeks.
All of the patients had disease in their aortic valve, a high-pressure valve connected to the left ventricle, the heart's main pumping chamber.
Because the engineered valves might not hold up under that pressure, surgeons swapped the valves, putting the existing pulmonary valve in the place of the aortic valve and using the engineered valve to replace the pulmonary valve.
The initial study was done with 23 patients with an average age of 44. It since has been expanded to 30 patients.
Three to five years after the valves were implanted, they were holding up well, Dohmen said. There was no calcification on the valves and no other signs of problems, he said. Imaging of the valves showed they were performing properly.
Three years is not enough follow-up, said Alfred Nicolosi, an associate professor of cardiothoracic surgery at the Medical College of Wisconsin.
"Very few valves fail within three years," he said. "You need at least 10 years of follow-up."
So far, the procedure has been used only with adults younger than 60 with diseased valves. But the researchers plan to try the valves in children with congenital valve problems, Dohmen said.
They also are working on developing a viable aortic valve from patients' own cells that would eliminate the need for swapping valves.
Those valves will come from horse or cow valves in which the cells have been removed and only a collagen scaffold remains, he said.
Edwards, the UW surgeon, said the engineered valves still must prove they will last over a lifetime.
But the German study is an exciting development with great potential, he said.
"It's completely novel," he said. "We have started to open the door to the body's own warehouse of parts that come from the individual himself."
From the Nov. 17, 2003 editions of the Milwaukee Journal Sentinel
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