Growing living-tissue heart valves a reality in 3-5 years
- Growing living-tissue heart valves a reality in 3-5 years
Surgeons will soon be able to literally mend a broken heart using
live tissue grown from a patient's very own stem cells, top
cardiologists said Monday.
The whole procedure -- harvesting cells from bone marrow, growing
tissue, and surgically implanting the heart muscle or valve -- could
take as little as six weeks and could become routine within three-to-
five years, they reported.
Their findings were published in a special issue of the Philosophical
Transactions of The Royal Society B in Britain.
One reason heart attacks are so debilitating, even when they are not
fatal, is because the human heart -- a massive muscle surrounding
four valves controlling the body's blood flow -- does not regenerate.
Damaged tissue stays damaged.
Most problems occur with age, when the old ticker simply begins to
"But the highest medical need for tissue-engineered heart valves is
in the treatment of congenital heart malformation," which affects
nearly one percent of all newborns, Simon Hoeurstrup, lead author of
one of the studies, told AFP.
Artificial heart valves currently available must be periodically
children grow, leading to great suffering and higher death rates than
Bio-engineered heart muscle that could be grafted onto a patient's
living tissue without fear of rejection by the immune system has long
been a holy grail of cardiovascular medicine.
Artificial replacements "do the job and save people's lives," said
celebrated heart surgeon Magdi Yacoub, who coordinated the 20-odd
"But they cannot match the elegant, sophisticated functions of living
While durable, mechanical hardware increases the risk of bacterial
infection in the heart's inner lining, as well as abnormalities in
blood flow. Recipients must also take medication to prevent blood
clots, boosting the chances of internal bleeding and embolisms.
Cardiovascular disease, the number one killer worldwide, claimed some
17.5 million lives in 2005, according to the World Health
Organisation. Many of these deaths might have been avoided by timely
surgery to implant replacement valves and heart muscle.
There are currently two broad techniques for making bio-prosthetic
heart valves, and both have serious drawbacks.
Animal grafts, especially from pigs, are readily available, but
differ in structure and tend to wear out. Human valves from donors
work much better, but are in chronically short supply and can easily
provoke immune reactions.
In the tissue engineering approach favored by Yacoub and Hoerstrup,
the patient's own stem cells -- taken from bone marrow -- are
isolated and expanded in the laboratory using standard cell culture
They are then "seeded" onto a special matrix in the shape of a heart
valve that is positioned in a device called a "bioreactor" that
tricks the cells into growing in the right shape.
Once mature, the living-tissue heart valves can be implanted in the
patient. The whole process unfolds in a matter of weeks.
This procedure has already been extensively tested in sheep, but
several years of follow up are required before it can be deemed
effective and safe, said Hoerstrup.
Another hurdle, he said, is that the capacity of some patients to
yield suitable stem cells may be compromised by diseases such as
© 2007 AFP