Embryonic stem cells
are the parent cells of all other cells in the body. As an embryo develops, they become specialized and make all the different tissues -- muscle, bone, hair -- that make up a critter.
Images courtesy of Lexicon Genetics Inc.
Ian Wilmut, the Scotsman who manufactured the peculiar lamb, was trying to turn sheep into factories to make proteins with medicinal potential. The idea may sound far-fetched, but already animals -- well bacteria, really -- are used to make insulin, interferon and other drugs. Some companies have tried inserting genes for other drugs into soybeans with the idea of growing drugs by the acre.
Wilmut's idea is to put genes into sheep that would be expressed (defined) in the mammary cells, so the valuable protein would appear in the milk. The company that funded the research, PPL Therapeutics P.L.C., is interested in making sheep produce alpha-1 antitrypsin in their milk. This protein could be helpful in treating symptoms of cystic fibrosis. The Roslin Institute, where Wilmut did his work, has succeeded, using genetic engineering, in making sheep that produced some of the protein. If scientists could, using genetic engineering or conventional breeding, produce a single sheep that produced large amounts of the protein, that animal could be cloned to make an entire herd.
That would give animals another use: serving as hooved pharmaceutical factories.
The cloning technology might also be used to culture embryonic stem cells -- primitive cells that appear between six and 12 days after fertilization and can go on to form any body cell. Since the cells could be used to grow organs or even tissues for transplant, they have a lot of potential uses.
Brigid Hogan, a Howard Hughes Medical Institute biologist at Vanderbilt University, speculates that someone who needed a bone marrow transplant to treat cancer but who could not find a donor with the right kind of tissues might try producing a clone with the right genetics. This could be done by taking an egg cell from an informed, willing donor, removing the nucleus, and replacing it with genetic material from the future transplant recipient. Within a few days, the embryo should be producing stem cells suitable for use in the transplant.
Doing the right thing?
What about ethical objections to creating life solely for the purpose of exploitation? Hogan, who served on a national commission studying the ethics of using embryos for scientific research, isn't buying that argument. "There are important distinctions," she say. "This is not a fertilized egg, everything would be donated with consent, it's never being put back into another uterus."
Already, she points out, researchers are trying to identify stem cells in mouse embryos. Once that is possible, and assuming that cloning works with humans, "it would not be so difficult to do it with embyronic stem cells in humans."
The possibility of organ grafts also interests Norm Fost, a University of Wisconsin-Madison professor of ethics and pediatrics. Fost agrees that, in terms of the immune system, clones would make the perfect donor. But he raises another possibility: What if a parent or child who needed a kidney or bone marrow transplant formed a clone to get some spare body parts? That would be possible, he says, and it does have an ominous ring.
But in fact, this is already being done with an existing technique called sex. "There are dozens of examples of parents having children" so they can get a transplant for themselves, or for a child.
This might sound like exploitation, but Fost counters that the child is not suffering, indeed is benefiting from the arrangement. "In addition to being born into a loving family, they have the benefit of saving somebody they are very close to with a very low-risk procedure [a bone marrow transplant]. That doesn't turn out to be any kind of trauma -- they are much better off for it."
Protecting the children?
If the ethical goal is to prevent children from being brought into the world for selfish or exploitative purposes, he adds, then our attention should be focused not on the few children who might result from cloning, but on the thousands of children born to mothers with AIDS, or to parents with histories of child abuse or drug addiction.
Fost dismisses the Brave New World scenario -- creating clones and robbing them of vital organs like hearts or livers -- as almost inconceivable. "It would be a radical change in what is permissible to do to children -- nightmarish," he says. In any event, he adds, that could be done today, but it's not permissible. The existing regulation about shifting organs between people is quite restrictive, he says, perhaps overly so. "People are upset at the thought that a competent adult might donate their kidney to a non-relative. That's not legal, and that's an example of how protective we are about bodily integrity."
Ever wonder how DNA does its genetic magic?
