Click here for an animated explainer about what stem cells are and how they are used.

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Stem Cell Research

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University of Wisconsin's stem cell research.

Graphics of embryonic stem cells.

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National Bioethics Advisory Commission

NIH Stem Cell Primer

Nature Medicine

Political Science
July 25, 2001

When does human life begin? Despite thousands of years of debate, we are still trying to answer that question.

Today, the question has a new twist in the form of a very unique material called the stem cell. Scientists are making medical breakthroughs with human stem cells and it is causing quite an uproar.

What are human stem cells and how is science using them?

Masters of the Body

There are stem cells inside your body right now. Each human life needs stem cells to get started.

Stem cells are pluripotent cells that can develop into any kind of tissue. Pluripotent means something with plural uses and the potential to develop into something else. Adult stem cells are found in bone marrow (the stuff inside your bones) and the brain.

Stem cells have been on the news a lot recently because scientists have discovered that these cells have the potential to cure diseases. Although, doctors have found stem cells from embryos are more useful than stem cells from adults.

Embryonic Stem Cells

Doctors gather stem cells by extracting them from human embryos. Embryos are fertilized eggs. Think back to that picture in health class: a fertilized egg is the joining of an egg and sperm.

Stem cells are located in the inner cell mass of the human embryo. At this stage of embryonic development an embryo is only described as a blastocyst. A blastocyst is big mass of cells. That mass of cells would develop into a baby if it is implanted in a woman's uterus.

However, once doctors extract the stem cells from the blastocyst, the human embryo is destroyed. It can no longer continue to grow into a baby human being.

Because the stem cells have yet to develop into a specific kind of cell, like a skin cell or a liver cell, they are capable of reproducing themselves again and again. Doctors take the reproduced cells and mix them with hormones and signaling fluids found in the body that change them to specific type of cells.

Doctors could produce unlimited cells to help combat deadly diseases like leukemia, for example. Actor Michael J. Fox left his TV show "Spin City" because of Parkinson's disease. That disease is one among many doctors think they can cure with stem cells.

Making Organs

Besides finding a cure for diseases like Parkinson's and Leukemia, doctors believe they can take the cells and grow whole organs. There is a large need for "spare" organs in the U.S.

Thousands of people die each year waiting for organs to replace ones that fail in their own bodies. Although the body can reproduce some cells like skin and blood, doctors hope to use stem cells to reproduce organ cells and grow new organs.

This is why stem cells are attracting so much attention. They could assist in repairing and replacing human organs and find cures for many fatal diseases.

So if they can do so much good, why is the idea of using the cells in scientific research so controversial?

Is it Life?

Stem cells are taken from human embryos that are 3 to 5 days old. The stem cells doctors use in their research are leftover from couples using fertility methods to get pregnant. All stem cells used so far have come through fertility clinics, but that might change. A Virginia-based business harvested human embryos this month simply for stem cell extraction.

Although the human embryos used in stem cell research are created in fertility clinics, the fertilized egg is exactly the same as an embryo created inside the body.

That sameness is fueling a huge political debate.

Most people agree stem cell research has great potential. It is the process of getting the cells is what divides people, because a human embryo must be developed and destroyed to get the cells.

Opponents of stem cell research believe destroying a human embryo is murder. They argue the egg is fertilized and has the potential to become a fetus and that embryo is already a life.

They argue that their tax dollars should not go to an activity that is morally offensive and they want the government to stop funding this type of research. Doctors get the money to do their research from the government and those dollars come from taxes.

The pro-stem cell research side argues stem cells have unlimited potential. If research is allowed to continue, amazing medical breakthroughs could result. They also say these embryos are already destined to be destroyed, so they should be used for research. There are also people who believe that since the cells are created in labs and extracted within days, they are not human lives.

Will we or won't we?

Stem cells have not been used to treat or cure anything yet. More research is needed if doctors want to get stem cells to do what they think is possible.

And there is the possibility that more research will show problems with using stem cells. Stem cells that are introduced into a human body, either in a spare body part or a disease vaccine, could possibly also be harmful. The cells might travel to other parts of the body and become tumors.

It will probably be several years and hundreds of human embryos before stem cells are used regularly.

People, politicians, religious leaders and the scientific community have all gone to the president for an answer. Should this type of research receive federal funds? Should only frozen embryos be used for research? Is science on the verge of something big?

When Bill Clinton was president, he and the National Institutes of Health (NIH) created guidelines for stem cell research. The guidelines said federal money could only be used for stem cells obtained through fertility clinics. No federal money could pay for research on cells from abortions.

When President Bush came to the White House he declared a temporary ban on all stem cell research. Since then he has talked to scientists, members of Congress and even the Pope about stem cells. "This is an issue that speaks to morality and science and the juxtaposition of both, said President Bush.

"It's the kind of research that may offer the solution for some of our worst, most terrible diseases that we are unable to deal with today. But at the same time it raises questions about the sanctity of life, issues of cloning start to work into it," said Vice President Cheney in an interview with Jim Lehrer.

Not all religious leaders oppose the research, although most do. And not all scientists and doctors support doing research on human embryos. The political and social divide is real.

The president knows that any decision will anger some Americans-- but that's the price of having the power to make critical choices. He is expected to make a decision soon.

What do you think? Should federal tax dollars pay for embryonic stem cell research?