Womb Fluid Cells Used To Create Heart Valves

By Lindsey Tanner, Associated Press, November 15, 2006

Offering a revolutionary advance that may be used to repair defective hearts in the future, scientists have grown human heart valves for the first time using stem cells from the fluid that cushions babies in the womb.

In order to have them ready to implant in a baby with heart defects after it is born, the thought is to generate these new valves in the lab while the pregnancy progresses.

The Swiss experiment suggests that people may one day be able to grow their own replacement heart parts — in some cases, even before they're even born. Recent successes also include growing bladders and blood vessels.

The homegrown heart valves are more resilient and effective than artificial or cadaver valves; they are among several futuristic tissue engineering advances that could advance infant and adult heart treatment.

"This may open a whole new therapy concept to the treatment of congenital heart defects," said Dr. Simon, a University of Zurich scientist who led the work, which was presented Wednesday at an American Heart Association conference.

In another first, Japanese researchers stated that they have grown new heart valves in rabbits using cells from the animals' own tissue. It's the first time replacement heart valves have been created in this manner, said lead author Dr. Kyoko.

"It's very promising," University of Chicago cardiologist Dr. Ziyad said of the two studies. "I don't doubt" that it will be applied one day in humans, he said.

Killing more babies in the United States in the first year than any other birth defects, more than one percent, or 1 million babies, born worldwide each year have heart problems according to the National Institutes of Health.

Using ultrasound tests at about 20 weeks of pregnancy, the heart valve defects can be detected. And according to Simon, treatment with replacement valves would be feasible for at least one-third of afflicted infants have problems.

"It could be quite important if it turns out to work," said Dr. Robert, a Northwestern University heart valve specialist.

There are drawbacks to conventional procedures for repairing faulty heart valves. Patients with artificial valves must take anti-clotting drugs for life because the valves are prone to blood clots. Repeating open-heart surgeries to replace heart valves is a problem with human cadaver valves or animal valves due to deterioration. And since cadaver and animals valves don’t grow along with the body, this is especially true in children, said Dr. Ziyad.

Valves made from the patient's own cells are living tissue and might be able to grow with the patient, said Kyoko, a scientist at the National Cardiovascular Center Research Institute in Osaka.

The Swiss procedure has another advantage: Using cells the fetus sheds in amniotic fluid avoids controversy because it doesn't involve destroying embryos to get stem cells.

"This is an ethical advantage," Simon said at the meeting.

The experiment began with amniocentesis, which is a prenatal test for birth defects that is often offered to pregnant women aged 35 and older. The amniotic fluid was obtained this way by inserting a needle into the womb during this procedure.

Fetal stem cells were isolated from the fluid, cultured in a lab dish, then placed on a mold shaped like a small ink pen and made of biodegradable plastic. Growing each of the 12 valves created in the experiment took only four to six weeks.

The valves appeared to function normally during lab testes said researchers.

A new two-year experiment is underway involving valve transplants in sheep. Simon says it is the next step.

He and co-researcher Dorthe called their method "a promising, low-risk approach enabling the prenatal fabrication of heart valves ready to use at birth."

Simon said amniotic stem cells also can be frozen for years and could potentially be used to create replacement parts for aging or diseased valves in adults

Experts say implanting tissue-engineered human valves in human hearts is likely years away, but the research is only preliminary. Despite the experts, the treatment is not as far-fetched as it sounds.

Earlier this year, U.S. scientists used tissue grown from the patient’s own cells to re-engineer seven diseased bladders.

And last year, created from their own skin and vein tissue, two kidney dialysis patients from Argentina received the world's first tissue-engineered blood vessels.

Dr. John, a Children's Hospital Boston heart surgeon and tissue engineering pioneer, said scientists are optimistic that this area of research will revolutionize how people with valve disease will be cared for in the future.

According to John, each year more than 250,000 patients worldwide have surgery to replace heart parts.

In one of John’s experiments, sheep were implanted with heart valves fashioned from stem cells harvested from sheep bone marrow. The valves appeared to function normally. Cells harvested from sheep arteries were used in a similar experiment.

Amniotic fluid has the potential to be a richer supply of stem cells in contrast to other sources says Simon.

The real test will be to see whether or not valves created from amniotic fluid will be superior to those made from other cell types said John.

"I'm pretty sure the ball will continue to be advanced down the field," John said. "We'll get there one way or the other."