Scientists grow heart valves from stem cells
Scientists for the first time have grown human heart valves using stem cells from the fluid that cushions babies in the womb - a revolutionary approach that may be used to repair defective hearts in the future.
The idea is to create these new valves in the lab while the pregnancy progresses and have them ready to implant in a baby with heart defects after birth.
The Swiss experiment follows successes at growing bladders and blood vessels and suggests that people may one day be able to grow their own replacement heart parts - in some cases before they are born. And it is one of several radical tissue engineering advances that could lead to homegrown heart valves for infants and adults that are more durable and effective than artificial or cadaver valves.
"This may open a whole new therapy concept to the treatment of congenital heart defects," said Simon Hoerstrup, a University of Zurich scientist who led the work. It was presented yesterday at an American Heart Association meeting.
Also at the conference, Japanese researchers said they had created new heart valves in rabbits using cells from the animals' own tissue. It was the first time replacement valves had been grown in this manner, said the study's lead author, Kyoko Hayashida.
"Very promising," University of Chicago cardiologist Ziyad Hijazi said.
Heart-valve defects can be detected during pregnancy with ultrasound tests at 20 weeks. At least one-third of afflicted infants have problems that could be treated with replacement valves, Hoerstrup said.
"It could be quite important if it turns out to work," said Robert Bonow, a Northwestern University heart-valve specialist.
Conventional procedures to fix faulty heart valves have drawbacks. Artificial valves are prone to blood clots and patients must take anti-clotting drugs for life. Valves from human cadavers or animals can deteriorate, requiring repeated open-heart surgeries to replace them. That is especially true in children, because these valves do not grow along with the body.
Valves made from the patient's own cells are living tissue and might be able to grow with the patient, said Hayashida, 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 does not involve destroying embryos to get stem cells.
"This is an ethical advantage," Hoerstrup said.
Here is how it worked:
Amniotic fluid was obtained through a needle inserted into the womb during amniocentesis, a common prenatal test.
Fetal stem cells were isolated from the fluid, cultured in a lab dish, then placed on a mold shaped like a small pen and made of biodegradable plastic. It took only four to six weeks to grow each of the 12 valves created in the experiment.
Lab tests showed they appeared to function normally.
The next step is to see if they work in sheep, a two-year test Hoerstrup said is under way.
He and co-researcher Dorthe Schmidt called their method "a promising, low-risk approach enabling the prenatal fabrication of heart valves ready to use at birth."
