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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.
Such respect for the natural order of things might seem unusual in a scientist whose work seems anything but natural. But for Hwang, generating stem cells is more than just a scientific process. It's no accident that there are more people than machines in Hwang's lab. It's part of an effort on his part to keep the entire procedure as human as possible. He even makes sure that at least one of his researchers keeps the cells company all day and most of the night, as a way of nurturing respect for them. "In this kind of work, you need to insert the human spirit," explains Hwang, who always wears a gold Buddha medallion around his neck. "You need the heart and the spirit, the human touch."
Hwang also takes care to avoid off-putting words such as cloning or therapeutic cloning, preferring instead to call his process nuclear transfer. He doesn't want anyone to confuse his work with reproductive cloning, which he deems "unsafe and unethical." He thinks cloning fully grown humans may be biologically impossible, given the many miscarriages and genetic anomalies that have bedeviled attempts to clone animals, and he doesn't like giving people the impression that therapies or treatment will be available anytime soon.
Indeed, the most immediate benefit of Hwang's work, assuming it can be replicated, will be to better understand how diseases develop. "Rather than having to study the patient or freshly dissected tissues from that patient, we can have a cell line of stem cells that can grow virtually forever," says Hans Keirstead, a neurobiologist at the University of California, Irvine.
"I'm very excited about the possibility of being able to have large amounts of material--for instance, from juvenile diabetes patients--to do research on the complex genetic and nongenetic causes of the disease," says Anne McLaren, a developmental biologist at the Wellcome Trust/Cancer Research Campaign Institute in Cambridge, England. "[That's] going to be the future of cloned stem cells rather than therapeutic cloning."
Meanwhile, the question many researchers are asking is: What will the South Koreans do next? Hwang met last week with Scotland's Ian Wilmut, Dolly's cloner, who wants to work with the South Koreans on Lou Gehrig's disease. Similar collaborations are under way at Memorial Sloan-Kettering Cancer Center in New York City and at Johns Hopkins in Baltimore, Md. By the end of last week, however, Hwang was back at his lab in Seoul, putting even more distance between himself and the rest of the scientific world.
--With reporting by Helen Gibson/London and Laura A. Locke/San Francisco