September 08, 2007

Growing living-tissue heart valves-a reality

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 reported to have said.

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 is a massive muscle surrounding four valves controlling the body’s blood flow which does not regenerate. Damaged tissue stays damaged.

Most problems occur with age, when the old ticker simply begins to wear out.

“But the highest medical need for tissue-engineered heart valves is in the treatment of congenital heart malformation,” which affects nearly one per cent of all newborns, Simon Hoeurstrup, lead author of one of the studies, told to the agency.Artificial heart valves currently available must be periodically replaced as children grow, leading to great suffering and higher death rates than in adults.

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 studies. “But they cannot match the elegant, sophisticated functions of living tissues.” 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 favoured by Yacoub and Hoerstrup, the patient’s own stem cells that are taken from bone marrow are isolated and expanded in the laboratory using standard cell culture techniques.

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 diabetes.—AFP

Breakthrough drug for schizophrenia

THE first new class of drugs in more than a decade for treating schizophrenia worked at least as well in a clinical trial as standard medications, a study showed.

Unlike current anti-psychotic drugs, which block the uptake of a naturally occurring chemical called dopamine, the new drug acts on a different neurotransmitter, glutamate.

The new treatment also reduced certain undesirable side-effects, according to the study, published in the British journal Nature Science.

Imbalances in the brain of these chemicals are largely responsible for schizophrenia's disabling symptoms, which range from hallucinations and delusions to a severely impaired ability to express emotion. Environmental factors are thought to play a role too.

Sufferers often hear voices and may believe that other people are reading their minds or controlling their thoughts. These frightening experiences can cause withdrawal and extreme agitation.

There is no known cure for the chronic disease, which affects approximately one in 250 people, emerging in men in their late teens and early 20s, and a decade later in women, according to the World Health Organisation.

Until now, the only drugs able to keep the most severe symptoms in check without debilitating side-effects acted on dopamine receptors.

Dopamine is the chemical messenger in the brain mainly involved with thinking, emotions, behaviour and perception.

In a double blind clinical trial, a team led by Sandeep Patil, a researcher at Eli Lilly, which funded the study, administered the new drug known as LY2140023 -- to 97 patients alongside smaller groups given placebos or olanzipine, a commonly prescribed anti-psychotic medication.

LY2140023 matched the effectiveness of olanzipine for both ‘positive’ symptoms such as hallucinations as well as “negative” ones, including withdrawal.

As important, it avoided some of the adverse effects associated with dopamine-targeting drugs: weight gain, increases in blood fat called triglycerides, periodontitis, and inflammation of the gums.

Scientists have suspected for decades that improper neurotransmission of glutamate was linked to schizophrenia, but up to now the precise mechanism was not understood.

The researchers cautioned that this was only a ‘proof-of-concept’ study to see whether the drug held promise in the treatment of schizophrenia, and that more trials to test LY2140023 against other drugs and over long time periods were needed.—AFP

Chinese airline to launch in-flight cell phone

SHENZHEN Airlines reported to have said that the passengers will soon be able to use their mobile phones and connect to the Internet during flights.

Swiss-based technology firm OnAir, which is providing the service, said the move will allow travellers to call and send text messages from their mobile phones and can access the Internet on laptops during flights. The company aimed to set up the service on the airline, which is based in the southern Chinese province of Guangdong, by mid-2009.

They also hope three demonstrator aircraft will be in use by the Beijing Olympics next year. Shenzhen will be the first Chinese airline to offer the service. OnAir has previously signed deals with various European and Asian airlines that want to carry the technology, the firm said. Benoit Debains, chief executive officer of OnAir, said in a statement that China was a significant and fast growing aviation market. Airlines have previously provided onboard air-to-ground fixed telephones on some seats at a premium charge. But until now they have banned the use of mobiles.—AFP

China vows to clean up toxins amid food scares

CHINA will clamp down on foods tainted with illegal and excessive chemicals as it seeks to quell domestic and foreign alarm about toxins in meat, seafood and vegetables, the country’s top agriculture official reported to have said.

hina is battling a torrent of warnings and recalls abroad that have shaken international markets’ confidence in the ‘made in China’ label on products ranging from toothpaste and toys to food and tyres. Minister of Agriculture Sun Zhengcai said consumers had no reason to fear eating most of the nation’s farm produce.

“Judging from monitoring, the acceptability rate of China’s agricultural products is higher than it’s ever been,” he said in an interview published by the official People’s Daily.

The government has responded to the scandals with frequent news conferences and policy announcements -- including the farm minister’s vows of stringent controls.

While defending his government’s food safety record, Sun promised a stiff action against farmers and producers who used banned chemicals to boost yields and profits.

Among targeted practices are the use of chloramphenicol, malachite green and other potentially toxic banned chemicals in raising seafood. The United States in June reported to have said that it would not allow imports of Chinese farm-raised catfish, shrimp and other seafood unless suppliers proved shipments were free from harmful residues, including malachite green that is a potential carcinogen illegally used to kill fungus and bacteria in fish tanks. Earlier this year, Chinese-made melamine, that is a chemical used in plastics and fertilisers, surfaced in US pet food, killing animals and prompting wide recalls.

China’s quality watchdog has introduced a recall system for unsafe food products and toys to improve product safety. The regulations require manufacturers to stop production and sales, notify vendors and customers, and report to quality control authorities when product defects are found, and can bring fines of up to 50,000 Yuan ($6,600) for failure to do so. — Reuters