China edges closer to animal-human organ transplant

16:07, March 24, 2011      

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A group of researchers in east China's Nanjing city have voiced confidence that genetically modified pigs would be born later this year to provide much-needed organs for transplant into human bodies.

Researchers with the Nanjing Medical University said Thursday that pig organs were expected to be put on clinical trials within two to three years, depending on the type of organs concerned.

"We expect to take pig cornea and skin to clinical test first, probably within two years. Major organs like heart, kidney and liver could take up to five years," Dai Yifan, lead researcher of the project, told Xinhua in an interview.

Dai said the pig organs would have been genetically altered to be compatible with human body, and strict hygiene supervision would make them free of bacteria or virus.

According to Dai, researchers first took out cells from ordinary pigs, modified the gene that causes immune rejection from human body, and then transfer the modified gene back into cells and replace the original ones.

For about a decade, Dai has studied gene knockout on pigs to avoid hyperacute rejection from human body. Several of his academic papers on this subject have been published on the Science and Nature Biotechnology journals.

He came back to China from the United States last year. At the beginning of this year, thousands of frozen cells taken from genetically modified pigs also arrived in Nanjing.

Dai said his team have started to make such pigs by cloning. "The piglets will have to be separated from their mothers immediately after cesarean birth and be raised by our staff in bacteria-free environment," Dai said.

"They will also have to pass a series of quarantine inspections to be qualified for organ transplant."

Allan Zhao, Dai's colleague on the team, said they expect to lower the cost of organ transplant with future pig substitutes.

"For example, one genetically-modified pig cornea would cost around 10,000 yuan (1,500 U.S. dollars), in addition to surgery expenses," Zhao said.

Lou Jinning, director of the Institute of Clinical Medicine at the Beijing-based China-Japan Friendship Hospital, cited the latest progress of Dai's team as "an obvious breakthrough" in China.

"We are now catching up with a few other countries that have made major breakthroughs in this field. Some have already bred such pigs for transplant research in non-human primates," he told Xinhua.

Lou believed transplanting animal organs into human bodies is a trend in bio-engineering and pigs are the best possible animal for this.

Long waiting lists and few donor responses have long been a disheartening picture when it comes to human organ transplant around the world, particularly in China.

Statistics show there are around 1.5 million patients in China on the waiting list each year for a transplant organ, but the number of donors is only about 10,000, less than one percent of the demand.

Lou said one major reason for this gap is the traditional Chinese culture that believes humans should die intact. "And this is not going to change anytime soon."

Researchers say a major challenge now is to make pig organs compatible with human bodies permanently or for a long time.

"They can now ensure there is no acute rejection from human body after transplants, so the key is to work on long-term compatibility," Lou said.

He also said before actual clinical trials, a breeding base needs to be built that can turn out several hundred such modified pigs a year.

In the meantime, some doctors have voiced worries that theoretical feasibility does not necessarily ensure a clinical success.

"Theoretically, knocking out relevant genes could be a solution for rejection from human body, but we have to admit animals are still different from human bodies and the success on monkeys does not necessarily mean success in humans," said Doctor Ding Yitao at the Nanjing Gulou Hospital.

"Besides, would they bring unknown viruses or diseases to human bodies?" Ding asked.

Source: Xinhua
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