Science stirs fury and hopes of cures
CAROLYN ABRAHAM, MEDICAL REPORTER
Friday, August 10, 2001
From the moment they were first snatched out of the molecular machinery of a human embryo, stem cells have become a story of extremes -- inflaming wild hopes and intense outrage all the way to the White House.
In a University of Wisconsin lab in 1998, biologist James Thompson first isolated the powerful cells from an embryo in the fleeting window of time before they could grow into the different cellular parts of a human baby.
Days later, Johns Hopkins University scientists announced they too had grown and harvested elusive stem cells with tissue taken from an aborted fetus.
Scientists had long imagined the feat, the way they envisioned cracking the human genetic code or creating a weapon to slay bacteria. They believe stem cells, with the ability to grow into the various cell types that constitute the human body, can revolutionize medicine.
"This really is tremendous, it really does have the potential to cure diseases that are currently incurable," said Bob Casper, head of reproductive sciences at Mount Sinai Hospital and the University of Toronto.
Researchers describe stem cells as the essential tools of regenerative medicine.
The stem cells allow doctors to repair and replace damaged parts with lab-grown human tissues: new brain cells for Alzheimer's and Parkinson's patients; mint-condition hearts for those with coronary disease; new nerves for the paralyzed.
Editors of the prestigious medical journal Science dubbed stem-cell research the most significant breakthrough of 1999.
As soon as the advance captured headlines, so too it ignited passionate controversy.
Many scientists and patients trumpet stem cells as the basis of future life-saving therapies.
But those who believe life begins at conception see research into embryonic stem cells as the medically sanctioned destruction of life, since the embryo itself is destroyed to harvest them.
"There are those who believe that destroying an embryo at any stage of development is the equivalent of infanticide," said Seang Lin Tan, director of the McGill Reproductive Centre in Montreal.
"But it would be tragic to have such a categorical view against stem-cell research, something which could bring cures for millions of people."
U.S. President George Bush announced his long-deliberated decision last night on the issue -- concluding that the White House would place strict limits on funding embryonic stem-cell research.
Mr. Bush's decision -- which was sure to anger either anti-abortionists or scientists, some of whom have talked of leaving the country for more tolerant shores -- is based on the belief that other sources of stem cells will prove equally valuable as those from embryos.
Scientists once suspected that embryos or aborted fetuses were the only sources of stem cells versatile enough to grow into different types of human tissue.
But over the past two years, researchers have found stem cells in adult tissues and other unusual places that may carry the same chameleon capabilities. Mr. Bush is putting federal money behind that work.
Studies have found that stem cells exist in adult tissues, such as bone marrow, blood and even the brain; once chemically coaxed, they too can grow into different types of cells.
They are also present in umbilical-cord blood and placenta -- tissues that are usually discarded -- and even in the dreaded "spare tires" that line our abdomens.
In April, U.S. scientists reported they had discovered stem cells amid the fat tissue sucked out of the overweight during liposuction procedures.
Researchers were then able to manipulate these stem cells to become muscle, bone and cartilage.
In June, Pittsburgh researchers reported that they had used stem cells from the muscles of adult mice to grow a urethral sphincter muscle.
"I don't think it would be a disaster if Bush said there isn't going to be embryonic stem-cell research," said Dr. Casper, who added there are also practical medical reasons to forgo the use of embryonic stem cells.
"If you're going to try and regenerate a liver for somebody, you may have to find a match among an embryonic stem-cell line," Dr. Casper said. But if doctors were able to harvest a person's own stem cells to grow them replacement body parts, he explained, there would be no concerns that a transplant would be rejected.
While some say embryonic cells have less chance of causing rejection in transplant patients, Dr. Casper said that if the cells actually grow into mature organs, rejection could still be a problem.
But Dr. Tan, based at the Royal Victoria Hospital in Montreal, said that "until we actually do the research on embryonic stem cells we will never know and to close it off right now it would be a mistake."
He added that adult stem cells may have some versatility, but in the adult system they are already earmarked to become the tissue type that they were found in. Stem cells found in adult muscles, for example, are destined to become muscle if left to their own devices. Dr. Tan, like defiant researchers in the United States who reported last month that they had created human embryos for the sole purpose of harvesting stem cells, feels the draft legislation in Canada on the issue is too restrictive.
The three types of stem cells
These form as the fertilized egg starts to divide and can develop into a complete individual.
The totipotent cells group together into a blastocyst. The pluripotent cells inside can develop into any tissue in the body.
These are found in mature tissue, and have a limited ability to grow into different types of cells.