이번 회는 지난 4회에서 다루었던 21세기 생명공학 최고의 화두인 줄기세포 (Stem Cell)의 후편을 다루어 보고자 한다.
영어에 관심있는 사람이라면 누구나 한번쯤 읽고 싶어하는 영자주간지 Time사이트에 게재된 내용이다.
지난 5월 말 타임지는 황우석 박사의 줄기세포를 통한 배아 복제 성공에 관한 특집 기사를 실었다.
참고로 Time 영문사이트(www.time.com)는 자연과학뿐만 아니라 정치 경제 문화 예술 기술 등 다양한 분야의 깊이 있는 영문을 담고 있다.
Time지는 여타 영어 주간지에 비해 함축적인 표현이 많아 영어를 꽤 공부했다는 사람들도 읽으면서 막히는 부분이 자주 나오는 잡지이지만,이번 내용은 여러분이 신문이나 방송을 통해 충분한 배경지식(Schema)을 갖춘 상태이므로 그리 어렵게 느껴지지는 않을 것이다.
지난 4회에서는 줄기세포에 관한 '배경지식(Schema)의 활성화'를 다뤘다.
그때 익혔던 몇 가지 유용한 생명공학 용어와 표현이 떠오를 것이다.
적절한 Schema를 갖춘 여러분에게 오늘의 기사는 편안한 읽을거리가 될 것으로 기대한다.
This is the sixth-floor lab in Building No.85 at Seoul National University,the center of operations for Woo Suk Hwang, the South Korean scientist who made headlines last week when he announced that his team, using Dolly-the-sheep techniques, had created 11 human stem-cell lines perfectly matched to the DNA of human patients - a giant leap beyond anything any other lab has achieved.
The eggs hollowed out in Building No.85 were fused with skin cells taken from nearly a dozen patients-ages 2 to 56, suffering from a variety of injuries and disorders-and grown with unprecedented efficiency into early embryos lined with stem cells.
The development, published online by the journal Science, takes doctors an important step closer to creating custom stem-cell treatments for everything from Alzheimer's disease to severed spinal cords.
Scientists, for their part, were singing a different tune. "It's a tremendous advance," says Paul Berg, a Nobel laureate from Stanford University and a major backer of California's independent stem-cell initiative.
"The Koreans' work is incredibly impressive," says Stephen Minger, director of the stem-cell biology laboratory at King's College, London. "It is fantastic-a major,major breakthrough."
The crux of that breakthrough is this: each of the newly created stem-cell lines is genetically identical to one of Hwang's patients.
That means any new tissue derived from that patient's cell line can be injected into that individual without triggering an immune reaction.
If researchers can figure out how to fix the original defect, they may someday be able to generate replacement tissue that is custom designed to treat the patient's condition.
Or at least that's the dream.
No one knows yet whether those stem cells can be safely used in people.
Many scientists were astonished by how far the South Koreans had come.
Only 15 months ago, Hwang's group created a stir as the first-and so far the only-lab to generate human stem cells via SCNT(Somatic Cell Nuclear Transfer).
Back then it had to use 242 eggs before it was able to create a single, viable set of stem cells from a healthy woman.
This time it was able to create 11 stem-cell lines using an average 17 eggs each.
"The efficiency is exceptionally high-much higher than I would have thought possible," says Doug Melton, a stem-cell researcher at Harvard University and the Howard Hughes Medical Institute in Boston.
"It's about what has been achieved in mouse cells after decades of work."
A veterinary scientist by training, Hwang says his pioneering work with human stem cells would not have been possible without an extensive animal-research program.
Building on what he learned from his experiments on cows, pigs and ducks, Hwang developed his own assembly line of nearly two dozen steps to improve the efficiency of human stem-cell production.
"I wanted to develop a unique technique, not just mimic and modify what others had done," he says.
For example, whereas Hwang's assistants gently squeeze the nuclei from eggs donated by female volunteers, researchers at other labs use a microaspirator to suck out the contents,which Hwang believes may damage the eggs unnecessarily.
"Professor Hwang jokes that we're good at manipulating the egg this way because we can use chopsticks," says Okjae Koo, one of the graduate students in the lab.
After DNA from a human patient is inserted into a hollowed-out egg, the fused cell is stimulated electrically and chemically to get it to start dividing.
At that point, other researchers have used animal-based growth factors and feeder cells to sustain the growing egg, but that creates problems if the cells are going to be used to treat humans.
So Hwang has concocted a growth medium made of human-based nutrients, starting with human skin cells from one of the donor subjects.
When the stem cells inside start growing out onto the underlying feeder cells, the researchers don't try to hurry the process. Most scientists working with embryos left over from in-vitro-fertilization treatments will use chemicals at this stage to separate the cells.
"I think the less we manipulate the cells the better," Hwang says.
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