Politics obscure science of the stem-cell debate
This article first appeared in the St. Louis Beacon, Jan. 31, 2012 - When a reporter tells Michael Howard that he wants to write an article that clears away the politics of the stem cell debate and just talks about the science, the UMSL assistant teaching professor of biology is quick with a response.
"Good luck with that," he said, a good-natured tone in his voice.
As Howard well knows, the politics and rhetoric of the emotionally charged issue can sometimes prove difficult to separate from the facts and the studies. The use of human stem cells in medical treatments and research has long been controversial, resting astride an ideological fault line that splits those who feel life-saving cures are being ignored from those who believe that the use of discarded embryos in medicine is ethically impermissible.
One part of that rift making news in recent years has been the use of so-called adult stem cells. These are cells taken from fully grown humans, a process that steers clear of the moral controversies associated with embryonic stem cells. Many who oppose using embryonic cells say the adult versions hold more promise while proponents maintain that valuable research remains to be done on cells from fertilized human eggs.
Who is right?
'A Pool of Potential'
While anti-abortion activists may have spearheaded the campaign against stem-cell research, abortion clinics aren't the source of embryonic stem cells. Most come from in vitro fertilization facilities where unused embryos are slated for removal as medical waste. Researchers have found these undifferentiated cells to be of use due to their pluripotent nature, that is, their ability to become any type of cell in a human being.
Other stem cells are produced through somatic cell nuclear transfer (SCNT), a process that implants a cell nucleus from a patient into an unfertilized human egg.
"The whole purpose of a stem cell is that it represents a pool of potential," said Howard. "When a normal cell divides, it just becomes two new cells. What a stem cell does when it divides is that it produces a cell that is more differentiated, that is becoming something new, something more specific, at the same time regenerating itself."
That holds out tantalizing possibilities for researchers who would like a window on how organs and other bodily tissues develop, a study tool that could lead to a better understanding of the dysfunctions that can make them go awry.
Dr. Steven Teitelbaum, Messing professor of pathology and immunology at Washington University School of Medicine, said embryonic stem cell research holds many possibilities.
"Hopefully, we'll be able to use it for identifying new drugs and regenerative medicine, the replacement of old tissues with new, but we won't know that until the science is done," he said.
And the science is far from done. In fact, Teitelbaum said that, to this point, there are no proven therapeutic treatments involving embryonic stem cells. As much potential as they hold, the future of what they might produce continues to be a question mark that excites researchers and inflames activists.
A couple of hurdles remain before the controversial cells might be of use in everyday treatments. For one thing, given their active, fast-dividing nature, such cells tend to produce tumors in laboratory mice. For another, since embryonic stem cells don't originate from the patient being treated, rejection becomes an issue, just as with organ transplants. SCNT is designed to alleviate this problem since it uses genetic material from the person receiving the treatment.
Despite the challenges, Teitelbaum said he thinks research holds promise and should be allowed to continue. Uncertainty about what that research may uncover is precisely why it is necessary.
"That's true of anything in science," he said. "Unless you do the experiments, you don't know. Science is unpredictable by its very nature."
It's a point that was emphasized just last week when scientists at UCLA and Advanced Cell Technology, an American biotech firm, announced preliminary findings that show possible improvement for two women suffering from blindness due to eye ailments. According to the Associated Press, researchers report that the treatment, which employed embryonic stem cells, has shown no abnormal growth or signs of rejection so far, although it is still very early in the process.
UMSL's Howard said the development was an exciting one, noting that the eye has long been a target of embryonic stem cell work. Other problems such as Parkinson's disease, in which the set of cells showing dysfunction is known, limited and definable, are possible candidates for improvement.
"Ideally, you want to have only one kind of tissue that needs to be repaired," Howard said. "You can't repair a complex tissue because there are too many different types of tissue. It's asking too much of the stem cells at this stage."
Reinventing the Wheel
By contrast, the nature of adult stem cells is better known than that of their embryonic cousins. And they do have at least one accepted therapeutic use -- the treatment of leukemia.
"We can basically wipe out the leukemic bone marrow because we can replace it with adult stem cells, which will then differentiate into bone marrow," said Teitelbaum.
Adult stem cells can be extracted from various parts of a patient's anatomy. Although they have not fully differentiated, they don't share the full pluripotency of their embryonic cousins, instead remaining tied to specific biological systems such as the skin, blood or kidneys. They aren't as flexible, but they aren't hampered by the same problems of rejection and tumors as embryonic stem cells. They also don't come attached to the same political minefield.
"If you can use a stem cell from a mature source then you don't have to deal with all the baggage" that goes with embryonic cells, said Howard. "Nobody would choose to use embryonic stem cells for anything if there was an alternative. All other things being equal, we'd certainly prefer to use a non-controversial source."
But Howard also points out that all things are not equal.
"There are certain aspects of research today that make embryonic stem cells more potentially useful in a lot of ways than the adult stem cells are right now," he said. "That may change radically any time but today embryonic stem cells can do things that adult stem cells cannot."
Teitelbaum believes the advent of adult stem cell technology has brought about some significant advancements. However, some have oversold the phenomenon, claiming cures for many diseases when use is still limited to leukemia, a cancer of the blood or bone marrow.
"They have not been successful in helping with the treatment of solid tumors, such as breast cancer," he said.
Other experimental options are showing promise as well, including induced pluripotent stem cells (IPS cells). These are ordinary cells that have their DNA altered to make them devolve into a state much like an embryonic stem cell.
"The question is whether or not these induced pluripotent stem cells are the mirror of embryonic stem cells," Teitelbaum said. "The data are that they are probably not, but they have many of the characteristics that are important."
Howard said that while IPS cell technology shows promise both in reducing the threat of rejection and avoiding the political dimension of the debate, he is wary of artificially introducing new constructs into the cell that could have unknown repercussions on its effectiveness.
"People are going to incredible lengths to take a cell and turn it into an embryonic stem cell, going through all these manipulations to try to produce something that already exists naturally," he said. "All of the research that's done to change one cell back into a stem cell is trying to reinvent the wheel."
'A Hot Topic'
There is no question where Dena Ladd falls on the issue.
"We support all types of stem cell research so we are a proponent of adult stem cell research as much as we are for embryonic stem cell research," said Ladd, the executive director of Missouri Cures, a pro-stem cell advocacy group.
Ladd's organization played a key role in boosting Amendment 2, the initiative narrowly passed by the state's voters in 2006 protecting all stem cell research allowed by federal law.
"We think both types of research are very important to find cures for some of these diseases," she said.
But Patty Skain, executive director of Missouri Right to Life, feels differently. She said that while her group supports the effort to find cures, any research using embryonic stem cells is wrong.
"We cannot support the use of embryonic stem cells because harvesting them destroys the embryo," she said. "We are very much in favor of helping people through the use of adult stem cells, which seems to be where most, if not all, of the therapies are coming from."
David Prentice agrees with Skain. A cell biologist by trade, Prentice is now a senior fellow for life sciences with the Washington, D.C.-based Family Research Council, which opposes the use of stem cells derived from embryos. He was involved in advocacy on Missouri's Amendment 2 as well.
While he agreed that leukemia was the primary therapeutic use for adult stem cells today, he said many future potential applications are already in the pipeline even if they are not in general use at the moment.
He said promising research involving hundreds or even thousands of patients and numerous published papers show that adult stem cells could have applications in treating a wide range of ailments from sickle cell anemia to lupus to Crohn's disease to juvenile diabetes. Other research has shown promise for helping with spinal cord injuries, repairing damage to the heart and restoring circulation in limbs.
He said that both IPS cells and adult stem cells may prove a better choice than embryonic because they don't present the same problems with tumors and rejection.
"The potential is out there in terms of their flexibility, but the real danger is out there because of that same flexibility," he said of embryonic cells. "That wildness in the growth of the embryonic stem cells makes them a less attractive candidate to go into the clinic and treat patients with."
He said that while researchers often like to use embryonic stem cells to examine problems, interactions between different cells and tissues during development may not always be accounted for.
"You might be able to get some simple answers, but I'm not so sure you can get a total model of how normal or disease development occurs just from these cells," Prentice said.
He said that the emergence of IPS cells and adult stem cells make their embryonic counterparts "dated science."
Still, there's one thing everyone can agree on.
"This debate comes and goes, but I think it's going to be a hot topic for years to come," he said.
David Baugher is a freelance writer in St. Louis.