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Heart Valves and Muscle Tissue Grown from Own Stem Cells Soon to be Reality

AFP, September 2, 2007

On Monday, top cardiologists all concurred that by using a patients own stem cell, surgeons will soon be able to literally mend a broken heart using live tissue grown from these cells.

The procedure could become routine within three-to-five years. In as little as six weeks, the entire process of harvesting cells from bone marrow, growing tissue, and surgically implanting the heart muscle or valve could be accomplished.

The Philosophical Transactions of The Royal Society B in Britain published these findings in a recent special issue.

A massive muscle surrounds the four valves of the heart, controlling the body's blood flow. One of the reasons heart attacks are so debilitating, even when they are not fatal, is that this muscle does not regenerate. Once tissue is damaged, it remains that way.

The muscle begins to wear out as it ages, and this is when most problems occur.

"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.

Leading to great suffering and higher death rates than in adults, artificial heart valves currently available must be periodically replaced as children grow.

Long considered the "holy grail" of cardiovascular medicine, bio-engineered heart muscle that could be grafted onto a patient's living tissue without fear of rejection by the immune system could soon become a reality.

Artificial replacements "do the job and save people's lives," said celebrated heart surgeon Magdi Yacoub, who coordinated the 20-odd studies.

"But they cannot match the elegant, sophisticated functions of living tissues."

Abnormalities in blood flow and an increased risk of bacterial infection in the hearts inner lining come along with the durability of mechanical hardware. Boosting the chances of internal bleeding and embolisms, patients must also take medication to prevent blood clots.

According to the World Health Organization, 17.5 million people were victim to cardiovascular disease in 2005, making it the number one killer in the world. Timely surgery to implant heart muscle or replacement valves could have potentially saved many of these individuals.

Serious drawbacks accompany the two mainstream techniques for making bio-prosthetic heart valves.

A tendency to wear out and differing structure are the main short coming of animal grafts; negative factors that outweigh their high level of availability. The short supply and susceptibility to immune rejection are drawbacks that comes with human valves from donors, despite the fact that they work better than animal grafts.

The patient's own stem cells -- taken from bone marrow -- are isolated and expanded in the laboratory using standard cell culture techniques in the tissue engineering approach favored by Yacoub and Hoerstrup.

A special matrix is created in the shape of a heart valve, and the cells are "seeded" onto this. The matrix is placed in a "bioreactor" that coerces the cells to grow into the proper shape.

The patient is implanted with the living-tissue heart valves once they reach maturity. In only a matter of week, a patient can have a "real" heart valve.

Several years of follow up are required before it can be deemed effective and safe, but the procedure has provided powerful results in animal models using sheep.

Other hurdles include the scenario of concurrent conditions such as diabetes, which could compromise the suitability of harvested stem cells.


 

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