The Great Cell Debate

By Andrew Goldstein

WHAT ARE STEM CELLS?

Some call them magic seeds, for their ability to replicate indefinitely and morph into any kind of tissue. Taken from human embryos only days old, stem cells are nature's blank slates, capable of developing into any of nearly 220 cell types that make up the human body. Scientists believe they will lead to cures for diseases once thought untreatable.

1 EMBRYO An egg is fertilized or cloned to form an embryo. The embryo begins to divide.

2 1 TO 5 DAYS The embryo divides again and again and takes shape as a sphere called a blastocyst

3 5 TO 7 DAYS By this time embryonic stem cells are visible and are capable of developing into any tissue in the body

4 STEM LINE The cells are removed and grown in a Petri dish. As they divided, they create a line of stem cells

5 TISSUE PRODUCTION Using various recipes of nutrients and other factors, scientists hope to turn stem cells into any of the body's more than 200 tissues, such as:

--Pancreatic islet cells Could provide a cure for diabetes

--Nerve cells Could be used to treat Alzheimer's and Parkinson's diseases and spinal-cord injuries

--Muscle cells Could repair or replace a damaged heart

FOUR WAYS TO GET EMBRYOS

The controversy begins at the source--the human embryos that must be destroyed to retrieve stem cells. Scientists can obtain these embryos in four ways, each with its own ethical challenges. The least morally problematic--using embryos left over from fertility treatments--is the only method Bush is considering supporting. Private groups are already attempting the others.

--FERTILITY CLINICS During in-vitro fertilization, clinics routinely fuse more than one egg with sperm. That way, if implanting a fertilized egg doesn't work the first time, they can try again. This practice has left thousands of unwanted embryos stored in clinic freezers. James Thomson, left, the first scientist to establish a human stem-cell line, used such embryos.

--ABORTED FETUSES John Gearhart, above right, the Johns Hopkins biologist credited, along with Thomson, with first culturing stem cells, extracted his from fetuses donated by women at a nearby abortion clinic.

--CLONING Advanced Cell Technology of Worcester, Mass., acknowledged last week that it is trying to create cloned human embryos (euphemistically referred to as "entities") as sources for stem cells. The company has considered selling its stem cells to other researchers.

--MADE TO ORDER The Jones Institute in Virginia, where the first U.S. test-tube baby was conceived, has mixed sperm and eggs expressly to create embryos as sources for stem cells.

WHY DOES FEDERAL FUNDING MATTER?

Since a lab in Virginia has already created made-to-order embryos for stem-cell research, and another in Massachusetts is cloning embryos for the same purpose, it's hard not to wonder: Is federal money really necessary? No matter what Bush decides, stem-cell research is sure to continue. But federal funding would dramatically change the scope of this research, widening the circle of scientists involved and most likely accelerating the rate at which cures are found.

IF PRESIDENT BUSH SAYS...

YES

The floodgates would open. Right now most scientists steer clear of stem-cell research because they have to: if any part of their lab receives federal money (and most do), they can't touch this research. If that changes, hundreds of labs across the country, including medical powerhouses like those at Harvard and M.I.T., would probably begin work on stem cells. Scientists would be able to share findings freely and review one another's conclusions. The government could choose to regulate how embryos are cultivated, handled and ultimately destroyed. Treatments would probably come sooner. Of course, there are no guarantees: it's been 18 years since the government said an AIDS vaccine would soon be in hand.

NO

Research would proceed but only in the handful of labs willing to fund it on their own. These labs are subject to minimal oversight. They rarely consult with one another, research doesn't get peer-reviewed, and studies may be unknowingly (and unnecessarily) duplicated. Many of the nation's top scientists who would otherwise lead the research effort would remain on the sidelines. And commercial pressures could make private labs focus more on research that might turn a profit than on studies that advance general knowledge. Says James Thomson, the stem-cell pioneer: "Industry and other countries will go forward. The field will progress without federal funding, but very, very slowly."

WHY NOT JUST USE EXISTING STEM LINES?

Last week, before both sides in this debate had fully dug in their heels, there was talk of a compromise. Since some colonies of stem cells already exist, why not permit funding of research on these cells only? (After all, the embryos had already been destroyed.) Bush adviser Karl Rove, below left, was searching for a way to satisfy Catholics without putting a lid on research. But religious conservatives quickly countered that such a compromise would still mean profiting from the killing of human embryos--and thus propagating a "culture of death." And scientists weren't satisfied either. They say the dozen or so existing cell lines (essentially self-replenishing colonies of stem cells) offer too little genetic diversity. Each cell line is subtly different, and researchers have yet to determine which ones will be best. The most robust cell lines may not yet exist. Only when there are a few hundred cell lines, say scientists, will we truly know what stem cells are capable of doing.

WHY NOT JUST USE ADULT STEM CELLS?

Republican Senator Sam Brownback, below left, believes a "wonderful" compromise for Bush would be to increase greatly funding for research on adult stem cells, which are harvested from bone marrow and brain tissue and have begun to show some of the same potential as those derived from embryos. But scientists aren't so sure. It's not yet clear whether adult stem cells will prove as versatile as embryonic ones, particularly in developing cures for Parkinson's disease and diabetes. Researchers also note that it is more difficult to produce large quantities of adult stem cells, and fear they may lose their potency over time.

IF NOT FOR RESEARCH, THEN FOR WHAT?

What motivates many of the most vocal advocates of embryonic stem-cell research, including those who are staunchly pro-life, is that most of the embryos used in the research would otherwise be discarded. What else should we do with the approximately 100,000 embryos currently in fertility-clinic freezers? Research opponents want them put up for adoption. This week three children who were adopted as frozen embryos are scheduled to appear before Congress. The conservative Family Research Council says every frozen embryo deserves "an opportunity to be born."