Adult stem cells or embryonic? Scientists differ

Blau says embryonic research is crucial for a better understanding of adult stem cells

(CNN) -- The controversy over embryonic stem cell research centers on the source of the research material: human embryos, which are destroyed in the process of harvesting the stem cells.

The research, say many opponents to stem cell research, is unethical and immoral -- and unnecessary. Working with adult stem cells, they say, may yield the same results.

But is adult stem cell research a realistic substitute for research based on the use of cells that are a biological blank slate?

The answer is not yet clear, according to Professor Helen Blau of Stanford University, who conducts research with adult stem cells.

What President Bush's decision means Bush will allow federal funding for research on 60 lines of embryonic stem cells. These lines of cells have the ability to regenerate themselves indefinitely but not all have been approved by the National Institutes of Health, which sets federal standards for research. Embryonic stem cells have the potential to turn into any other kind of cell in the body, and have been looked to as possible treatments for Alzheimer's disease and Type I diabetes. VIDEO Watch President Bush's speech on federal funding for stem cell research (Part 1) (August 9) Play video (QuickTime, Real or Windows Media) Bush's speech (Part 2) Play video (QuickTime, Real or Windows Media) More video     MORE STORIES Bush to allow limited stem cell funding   U.S. to create registry of stem cell lines   Reaction mixed to stem cell decision   More stories     EXTRA INFORMATION In-depth: The stem cell debate     RESOURCES CNN Access: Bioethicist on implications of Bush's decision

"The whole field of (adult stem cell) research is in its infancy; it's only two years old," she said. "We don't know the potential of those cells, we don't know how to enlist that potential. ... We hope that it will solve our dreams, but it may not do everything we want even in the best chances."

Stem cells are essentially "blank" cells that have the potential to develop into any tissue in the body -- muscle cells, nerve cells, blood cells. Scientists hope the cells can help develop therapies for diseases like diabetes, Parkinson's or Alzheimer's. Typically, scientists harvest the stem cells from embryos (usually those left over from fertility treatments) that are a few days old. The process destroys the embryo.

Embryonic stem cell research, Blau explained, has been conducted for decades, and scientists have learned a great deal -- things like what factors induce the cells to grow and differentiate and migrate to different parts of the body -- about these early master cells.

Those findings, Blau said, are important to the field of adult stem cell research.

"We don't know at this point which will be better for what," she said. "We need to learn from both. We need to learn the differences, the relative advantages, and we learn a tremendous amount by comparing the two cells."

Some other scientists disagree.

"Those adult stem cells … , this alternative, are actually much more effective at reaching these goals of therapeutic treatment," said Dr. David Prentice, a professor of life sciences at Indiana State University and a founder of Do No Harm, The Coalition of Americans for Research Ethics.

Adult stem cells could provide certain benefits over embryonic stem cells, according to the National Institutes of Health.

Foremost, adult stem cells do not present the ethical dilemma that embryonic stem cells do because harvesting them does not destroy the donor. And because adult stem cells could be taken directly from the person receiving treatment, immune rejection of the cells would not be an issue.

But the technique also has limitations, NIH said.

"Adult stem cells are often present only in minute quantities, are difficult to isolate and purify, and their numbers may decrease with age," the agency writes in its stem cell primer.

Prentice says adult stem cell research is a viable alternative to embryonic stem cell study

Further, adult stem cells have not yet been found in all tissues of the body. Those that do exist may not be useable if a patient has a genetic defect, since the defect would probably be present in the stem cells as well as other cells. Or the cells may contain DNA errors caused by replication or exposure to toxins.

A recent report from the NIH called for research into both adult and embryonic stem cells to continue.

Blau agrees. "I feel strongly we need embryonic stem cells. The answers are not just going to come from the adult stem cells and it would be extremely short-sighted to shift completely to just adult stem cells."

Federal funding of embryonic stem cell research is needed, she added, because it provides for peer review and regulation and often is more experimental than industrial research designed to develop a specific product.

Prentice has a different view.

"The root of the debate really comes down to the ethical question of what's the moral status of a human embryo," he said. "Is it a person or is it a piece of property? And obviously we have no consensus on that in this country and I think that means we should not use taxpayer funds to fund this type of research."

CNN Medical Correspondent Elizabeth Cohen contributed to this report.