JIM LEHRER: Finally tonight, the first of two reports on stem cells. The subject of stem cells generates headlines, both for scientific breakthroughs in the lab and controversies over surrounding political issues.

Tom Bearden, with our science unit, has been looking at the scientific questions about adult stem cells, which were also the subject of a committee hearing today in the U.S. Senate. Here is his report.

TOM BEARDEN: They are almost magical: Stem cells -- immature, unformed cells taken from human embryos usually less than a week old. They have the ability to become any kind of tissue. They can also replicate themselves indefinitely in the laboratory.

Research is underway to see if embryonic stems cells can be used to treat a host of deadly diseases. But the process of obtaining embryonic stem cells means destroying the embryo, and some have raised serious questions about the ethics of such research.

Adults have stem cells, too, but in recent years scientists have discovered that they can be found in many more places in the bodies of adults and children than previously believed. They're in bone marrow, skin, brain, blood, and muscle, among others.

Cutting edge research
TOM BEARDEN: This is the cutting edge of adult stem cell research -- an operating room in Brazil, where doctors recently tried to use the stem cells of human patients to repair their damaged hearts. Studies like this were undertaken after research using mice indicated that adult stem cells might be coaxed into behaving more like embryonic cells.

They extracted bone marrow tissue and used a sophisticated machine to separate out relatively scarce stem cells from the larger mass of mature cells. Then they inserted a catheter through a small incision, and using a 3-D video map of the heart, injected the purified cells into places where a heart attack had killed muscle cells.

The work was done by a team of Brazilian and American doctors, including Emerson Perin and James Willerson of the Texas Heart Institute in Houston.

DR. JAMES WILLERSON, University of Texas Health Science Center: The patients that were treated had better blood flow to their hearts and better local function of their heart where we'd injected the cells and better overall function of their heart. And they'd also improved symptomatically, so much so that at least two or three of the original 14 not only could do more, but they were now jogging on the beach.

TOM BEARDEN: Dr. Willerson recently got the government's okay for a larger American-based follow up to the Brazilian study, using heart patients in the Houston area. He believes the stem cells used in his research did their work by promoting the growth of new blood vessels in their human patients.

Some animal studies have shown that adult stem cells can actually transform themselves into new heart muscle. But other scientists, working with mice, say they've been unable to repeat those results, and that's led to an unusually pointed controversy in the scientific community.

Dr. Helen Blau and her associates at Stanford University were among several scientific teams who transplanted bone marrow stem cells in mice to see if they could do more than just make blood cells.

Healing damaged muscles
HELEN BLAU, Stanford University School of Medicine: Adult stem cells, until recently, were thought to be tissue-specific. That is the skin had its own stem cells, and the liver had its own stem cells, and muscle. And now stem cells have been considered something broader in the adult, and this was quite unexpected.

HELEN BLAU: This cell is a muscle stem cell, and it's green because the...

TOM BEARDEN: Blau's group found that the bone marrow cells were converted into a specific muscle cells called satellite cells, which helped re-grow and repair damaged muscle cells -- the ones in green. But when Charles Murry at the University of Washington tried to use stem cells from one mouse to grow new muscle in the damaged heart of a second mouse, nothing happened.

CHARLES MURRY, University of Washington School of Medicine: We had a very sensitive readout system that could essentially find the needle in the haystack. We could find even one cell in an entire heart that was derived from the bone marrow that had turned into a muscle cell. And yet despite that, out of the 145 experimental animals that we studied, we found zero cells that were turned into heart cardiac muscle.

TOM BEARDEN: The mystery of the contradictory results is more baffling because both scientists used the same advanced research techniques. Both Blau and Murry used stem cells from mice that had been genetically modified to glow green under ultraviolet light, that way they could easily see the progress of the stem cells. If they turned into new muscle cells, those cells would also glow green.

Blau's team saw green muscle cells in their mice, but Murry's team examined cross-sections of mouse hearts under a microscope and did not see green cells. Why the contradictory results?

Conflicting research results
HELEN BLAU: One of the problems in the stem cell field is that there are all kinds of stem cells that are being claimed-- my cell, your cell-- and many people are not working on the same cells. So then it's hard to compare. You're looking at apples, oranges, and pears and trying to conclude something.

So because they don't see it in the heart, doesn't mean it isn't true for parts of the brain and for muscle. So I wouldn't say that Chuck Murry differs with us. He's looking at a different system.

TOM BEARDEN: Other scientists couldn't replicate the early results either, leading to a flurry of point-counterpoint articles in scientific journals. Writing in Science Magazine, Blau said "non-seeing is not the same as non-being." Another group of scientists replied, "In stem cell science, seeing may not always establish being." Charles Murry says there's a very good reason for the intensity of the arguments.

CHARLES MURRY: The thing that makes this somewhat different, perhaps, from a usual academic sort of argument -- does the cell turn green or not-- is the fact that the initial report had prompted clinical trials. And that makes it a bit more serious when you're starting to change the way patients are treated.

TOM BEARDEN: Ironically, even though her experiments showed promise, Blau thinks any human experimentation is premature.

Human trials
HELEN BLAU: People have come to me and said, "Please use my daughter as one of your experiments." No, we won't. We don't understand what's happening yet, we don't know whether this will be useful, we want to understand it better.

And I think it's well worth going slowly with clinical trials in a measured way so that we don't do harm and do succeed in making this a useful field, because a few mistakes and we can really set the whole field back.

TOM BEARDEN: James Willerson of the Texas Heart Institute disagrees.

DR. JAMES WILLERSON: Professor Blau is one of the foremost investigators in cardiovascular science in the world, and I am very familiar with her work and I have deep respect for her. I would say that in the studies that have been done so far in humans, one has not found discouragement.

And so one could argue, and I shall, that the human is the very best model for testing as long as it's safe, and I think it's pretty clear that what we've done is safe.

TOM BEARDEN: For Nancy Sizemore the debate is more than just academic.

NANCY SIZEMORE: Does it sound like it's going fast?

TOM BEARDEN: Last spring, at the age of 46, a massive heart attack destroyed her quality of life. She hopes to participate in the new Houston-area stem cell study.

NANCY SIZEMORE: On a good day, I can go to the store and get groceries and push my cart. Some days, I can't go all the way through the store. I can just do three rows or whatever, but I'm just limited. I have to lay down then. And then there's some days where I'm so sick I can't get out of the house.

TOM BEARDEN: What are your prospects if you don't get in the study?

NANCY SIZEMORE: My prospects probably aren't good because the disease is progressive.

TOM BEARDEN: Sizemore's doctor, Reynolds Delgado, says the Houston trial and several others around the world are vital. With 100,000 new cases of heart failure each year in the U.S. alone, he says there's a tremendous need for new treatments.

DR. REYNOLDS DELGADO, Cardiologist, Texas Heart Institute: Heart failure is becoming a disease that we're making more of, but we're falling behind in making new treatments for. We're still grappling with old treatments that are 20, 30 years old, such as heart transplant. We're under 2,000 transplants per year in this country, and current estimates are that there are over 100,000 people who need them per year.

TOM BEARDEN: If the human heart trials succeed, researchers hope to get federal approval to use adult stem cells as a standard treatment for severely damaged hearts within two years. But the argument over what adult stem cells can or can't do doesn't exist in a vacuum.

Ever since 2001, when the Bush administration restricted federal funding of embryonic stem cell research, an added layer of emotion has complicated every argument about how the scientific investigation should proceed.

Citing ethical concerns about embryos being destroyed to obtain stem cells for research, the president banned the use of federal funds for research on any stem cells taken from new embryos. Only those stem cell lines already in existence could be used.

PRESIDENT GEORGE W. BUSH: (2001) I have concluded that we should allow federal funds to be used for research on these existing stem cell lines, where the life-and-death decision has already been made.

TOM BEARDEN: Of the 78 stem cells lines which qualified, fewer than 20 can be used in research because of difficulty in developing them, and some of those aren't suitable for use in humans.

Many scientists worry that any success with adult stem cells will be used by opponents of embryonic stem cell research as an argument to cut off further studies. None of the scientists we spoke to want that to happen, since nobody knows whether adult stems will be as useful as embryonic ones.

DR. CHARLES MURRY: I think at the moment, our knowledge of both adult stem cells and embryonic stem cells is so limited that there's no rational way to say "the adult stem cell is better," "the embryonic stem cell is better." I think what we're -- what we need to do, and what I'm doing in my own laboratory, is pursue both tracks in parallel.

HELEN BLAU: There's too much emotion in the field. People need to be more objective about the findings and be more open to the excitement of what we're seeing in terms of plasticity. And they really do have very strong views, almost sometimes irrational.

TOM BEARDEN: Researchers hope that stem cells will eventually become a routine medical procedure for diseases like Parkinson's, diabetes, and spinal-cord repair. But it may take a lot longer to understand the underlying science of how stem cells work.

JIM LEHRER: Today the National Institutes of Health said it would create a center to help scientists find and work with existing embryonic stem cells but the ban on funding new stem cell research remains in place. Embryonic stem cells will be the focus of our second report, which will air very soon.


"We have lost so much time already" - Nancy Reagan