Chinese scientists have bred the world's purest inbred line of pigs that may prove ideal organ donors for human beings.
A team of zoologists headed by Prof. Zeng Yangzhi of Yunnan Agricultural University has bred, for 21 successive generations, pigs born of sows that mated with their own sons or siblings.
International geneticists define "inbred line" of mammals as those that have had at least 20 generations of full-sibling or parent-offspring inbreeding and all of them trace back to the same pair of ancestors.
Though Prof. Zeng's research finding is still subject to an appraisal by the Ministry of Science and Technology in October, a latest gene testing with state-of-the-art micro-satellite devices suggests at least 98.6 percent homogeneity in the inbred line of pigs.
"This highly homogeneous pig species will provide a technological platform to tackle various diseases and improve human health," said Dr. Liu Yinong, a renowned Chinese American zoologist.
Pigs are ideal lab animals in biomedicine because they are similar to human beings in anatomy, physiology and metaboly. Inbred line of pigs, like precision equipment in physics and pure reagents in chemical reactions, provide highly sensitive and reproductive lab materials for biomedicine and life sciences.
Over the past century worldwide scientists conducted at least 200 massive experiments to breed inbred line of pigs, all futile because of severe devolution of the species.
The inbreeding of mammals is therefore widely deemed as a "mission impossible," until the recent success of Prof. Zeng's team.
Their success story started in 1980, when the team found in a mountain village in Xishuang Banna, southwest China's Yunnan Province, an ideal brood of piglets for their inbreeding program.
"We adopted new technologies to ensure even the earlier generations that were more susceptible to deformations survived and produced offspring," said Zeng. "Today the homogeneous pigs have overcome many problems and the survival rate is nearly 80 percent."
According to Prof. Zeng, at least one new generation of inbred pig is being born each year, and the family has expanded to nearly 900 members in 18 sub-lines.
His inbred Banna pigs project is now sponsored by the Natural Science Fund as a key scientific research program.
This unique pig species is smaller than ordinary pigs. Some of them are hairless, while others are very much like wild boars with mane on in the neck and on the head. The family also includes the world's smallest pig that is most suitable for biomedical tests: One weighs less than 30 kilograms at 18 months old, while an average pig weighs at least 90 kilos at five months.
"The mini, inbred Banna pigs are very likely to become the optimal organ donors to human beings," said Li Youping, a Sichuan University professor who has been dedicated to researches on animal-to-human organ transplants. "In fact, scientists are already carrying out experiments to transplant genetically modified pig organs to human."
A comparative test on the liver functions of pigs and humans indicates the inbred Banna pigs resemble human beings in many ways. "Once the transplant experiments turn out successful, the pigs will provide ideal organs to human patients," said Prof. Li.
The scientist expects new technological breakthrough in five years.
(Xinhua News Agency September 17, 2005)
