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Human Embryonic Stem Cells: Where Are They?

By Nancy Touchette

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Stem Cells

Colonies of human embryonic stem cells .
When President Bush enunciated his policy for research on human embryonic stem cells in 2001, many researchers felt duped. Citing the existence of “more than 60 genetically diverse stem cell lines,” he announced that federal funds could be used for research only on stem cell lines created before August 9, 2001, the date of his announcement.

Since the President's edict, stem cell researchers have disputed the number and quality of cell lines said to be available.

“The day after the President's speech, our phones were ringing off the hook,” says Kevin Wilson, a spokesperson for the American Society for Cell Biology in Rockville, Maryland. “We kept getting calls from scientists saying they were only aware of 10 available cell lines. Sixty sounded like a good number, but in reality these cells were dressed up as something they weren't.”

Now, two years later, as a result of efforts by the US National Institutes of Health (NIH), researchers are getting a clearer picture of what is and isn't available. NIH has created a Stem Cell Registry to document existing stem cell lines and their availability. And a Stem Cell Characterization Unit has just completed its initial tests to assess the quality of available cell lines.

Related Sites
NIH Human Embryonic Stem Cell Registry: available cell lines
Cells approved for U.S. Federal Funding
A total of 78 stem cell sources have now been catalogued and approved for what is known as the “Presidential List,” which includes all the derivations—cell lines or samples of cells frozen away—that can be studied using federal funds.

But of the 78 approved cells, only 12 are currently available for distribution. These cell lines, which have just been characterized, are listed in the NIH Human Embryonic Stem Cell Registry.

“Many of the lines sanctioned by the president are not available,” says Leonard Zon, president of the International Society of Stem Cell Research and a researcher at Harvard Medical School in Boston . “Some of these lines have patent issues and some were never cell lines to begin with.”

The Stem Cell Characterization Unit, under the direction of Ronald D. G. McKay of the National Institute of Neurological Diseases and Stroke has characterized the 12 stem cell lines on the NIH Registry and has posted its initial results on the NIH Stem Cell website.

The unit tested each cell line to learn whether it has been contaminated by pathogens or has any visible chromosome abnormalities. The cells have also been examined to see whether they express certain markers that indicate the cells' potential to become any type of specialized cell and for their ability to self-renew or replenish themselves.

The Stem Cell Characterization Unit and Stem Cell Registry are both part of the Stem Cell Task Force, a larger effort at NIH to support and encourage stem cell research. The task force, headed by James Battey, director of the National Institute on Deafness and Other Communication Disorders, aims to encourage the training of more stem cell researchers and to make more human embryonic stem cell lines available.

NIH provided funding in 2002 to all the institutions that currently make their cells available. In exchange for the funding these organizations agreed to distribute their available cell lines for a $5,000 fee. Researchers can now obtain a sample of human embryonic stem cells from any one of five organizations listed on the registry to receive one of the 12 available lines.

Researchers are not prohibited from studying human cells not on the list or from creating new cell lines but they cannot use federal money to do so. Not surprisingly, several companies and academic researchers in the U.S. and abroad have reportedly developed new embryonic stem cell lines without the use of U.S. funds.

For example, researchers at King's College London in the United Kingdom announced in August 2003 that they had created a new human embryonic stem cell line. And at the first meeting of the International Society for Stem Cell Research, held in Washington, D.C., this past June, Douglas Melton of Harvard University in Cambridge, Massachusetts, announced that he had derived several potential cell lines from human embryonic stem cells that he is now characterizing. Melton's work is funded by the Juvenile Diabetes Foundation.

There are several reasons why so few of the approved cells are available for distribution. Many of the cells approved for funding were not cell lines at all but were frozen, uncultured cells.

To be considered an embryonic stem cell line, researchers must be able to maintain the cells in culture in an undifferentiated, or unspecialized, state. The cells must be able to renew themselves, and they must be able to form all three of the basic cell types found in the early developing embryo. Many of the cells on the Presidential list do not satisfy these criteria and are of little use to stem cell researchers.

Many researchers had derived cells from fertilized embryos but had not tried to maintain them in culture. For example, nine cell lines on the approved list that were derived by the Karolinska Institute in Stockholm could not be cultured.

Other cell lines are unavailable for legal and political reasons. Ten cell lines were developed in India but the Indian government prohibits the export of human cells. One company in Korea has refused to make cells available to U.S. government-backed researchers.

And some companies refrain from sharing their cell lines due to their commercial interests.

Zon says that more cell lines were included on the original list to ensure that they would not be excluded from federal funding. Some of these cells had not been fully characterized and had not been maintained in culture, so their usefulness is uncertain.

Zon says this was not an attempt to mislead the public, but an effort to ensure that all possible cells were eligible for funding.

“There was this sense of wanting to be over-inclusive, to over-interpret what was really available, so we wouldn't miss out on potentially useful cells,” he says.

NIH has recently awarded grants totaling $6.3 million to the University of Washington in Seattle, the University of Michigan Medical School in Ann Arbor, and the WiCell Research Institute in Madison, Wisconsin, to develop the infrastructure to scale up production of the useful stem cell lines so that there will be more cells available to researchers.

NIH's actions to promote stem cell research are being received with cautious optimism by the stem cell research community. In May 2003, NIH Director Elias Zerhouni testified before a congressional subcommittee that 11 human embryonic stem cell lines are available to researchers and are listed on the Stem Cell Registry. Since that announcement another stem cell line has been added, bringing the total to 12. According to Wilson, Zerhouni's testimony went a long way in regaining the trust of scientists.

The scientific community will be forever grateful to Battey and Zerhouni,” says Wilson. “They injected a dose of reality by admitting that we are really working with far fewer cell lines than Bush had claimed. They are doing everything they can to get the most science out of a bad policy.”


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