Human Embryos Cloned by U.S. Company, But Don't Survive
Bijal P. Trivedi
|November 26, 2001|
Scientists at a U.S. biotech company announced Sunday that they have
cloned the first human embryos. The company said it intends to use such
embryos to provide an endless source of stem cellswhich can
develop into any type of adult cell in the human bodyfor the
treatment of human diseases.
However, some experts consider the
research a complete failure because the cloned embryos all died very
early, long before reaching the multi-cell, or blastocyst, stage at
which stem cells could be harvested.
"This is not a breakthrough or even a scientific contribution," said Nobel laureate Paul Berg of Stanford University, a frequent consultant on federal policy regarding stem cell research, human cloning, and biotechnology. "The experiment was a failure and does not warrant the amount of press coverage it has received," he added.
The company, Advanced Cell Technologies (ACT), based in Worcester, Massachusetts, said the technique could ultimately produce a source of healthy new tissue for transplantation into patients whose own cells had been damaged or destroyed by disease or injury.
The research has generated intense controversy because if a cloned embryo were implanted into a woman's uterus, it could potentially grow into a human beinga human clone.
"Our intention is not to create cloned human beings," researcher Robert P. Lanza of ACT said in a press release. "But rather to make lifesaving therapies for a wide range of human disease conditions, including diabetes, stroke, cancer, AIDS, and neurodegenerative disorders such as Parkinson's and Alzheimer's disease."
A bill to ban human cloning is already under consideration in the Senate. If the bill becomes law, the penalty for engaging in such research would be a U.S. $1 million fine and a 10-year jail sentence.
Many people who oppose the research argue that creating and destroying embryos for the purpose of producing "spare parts" is unethical.
Currently, the only way to obtain embryonic stem cells is by creating embryos. Embryonic stem cells can be harvested only from embryos that are less than five days old. After that period, the cells begin to specialize.
"We're not talking about little embryos with hands and feet," Michael West, the president of ACT, told Tim Russert on the NBC News show Meet The Press. "We're talking about a cluster of cells, far smaller than the head of a pin with no body cells of any kind."
"Biologically, scientifically, the entities we're creating are not an individual," West said. "They're only cellular life, they're not a human life."
ACT scientists cloned the human embryo using a technique known as "somatic cell nuclear transfer." It's the same method that was used to successfully clone the first large animal, a sheep named Dolly, and is now the standard procedure used for cloning cattle, sheep, pigs, and mice.
ACT scientists created the cloned embryo by taking an unfertilized human egg and removing the nucleusthe compartment that contains the chromosomes and genetic material. The original nucleus was replaced with the nucleus of an adult skin cell or cumulus cell, which is a non-reproductive cell from the ovary.
Because human reproduction requires a combination of genetic material from both the mother and the father, the nucleus of a human egg has only half the genetic material required to make an embryo.
In the cloning procedure, however, the replacement nucleus comes from a mature skin or cumulus cell, which carries a complete set of chromosomes. As a result, the modified egg is able to divide as though it had been fertilized by the father's sperm.
The embryothe small ball of cells that forms as the egg dividesis a clone of the cell that donated the nucleus.
In the ACT cloning procedures, 19 eggs were given a new nucleus. Three began dividing and producing embryo clones; each of the eggs divided two to three times. Two embryos grew to four cells, and one reached six cells before dying.
All the embryos died before reaching the 32- to 64-cell stage, when embryonic stem cells are usually collected.
Lanza and his colleagues published their research in the online journal e-Biomed: Journal of Regenerative Medicine. The journal article also reports a second method used to create an embryo directly from the egg itself. The researchers have also published an account of their work in Scientific American.
Scientists who favor cloning technology believe that in the future, people could have their own healthy cells cloned to create a genetically matched "fix-it kit" of cells that could be used to treat a number of diseases without the threat of immune rejection.
Many scientists are interested in using somatic cell nuclear transfer technology to produce stem cells. Berg said he is "one hundred percent in favor of the procedure." But the work done by ACT, he contended, does little to advance progress toward that goal.
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