Reprogramming complicates stem cell debate

Alan Boyle Science editor • Profile • E-mail

Imagine being able to reprogram the cells of your own body to produce fresh heart cells, regenerated nerve cells to heal spinal cord injuries, pancreatic cells to stop diabetes — or any other type of tissue to cure what ails you.

This may sound like a widely exaggerated vision of the future, based on the politically controversial use of stem cells extracted from made-to-order human embryos. But that assessment would be wrong on two counts: First, somatic cell reprogramming avoids the political controversy. And second, it's sounding less and less like a wild exaggeration with each passing month.

In fact, experts on both sides of the stem cell debate say the scientific hopes for somatic cell reprogramming, also known as dedifferentiation, are rising sharply — although they caution that much more work remains to be done.

"Just a few years ago, it was beyond the reach of the existing science at the time ... almost like alchemy, where you're trying to turn lead into gold," said Dr. Robert Lanza, vice president of medical and scientific development at Massachusetts-based Advanced Cell Technology.

But today, new tools have changed the landscape: "Our group, and I know at least two or three others, are playing with different techniques, and it's very clear that something is going on here. We're definitely getting reprogramming," Lanza said.

Dr. Leon Kass, chairman of the President's Council on Bioethics, sees cell reprogramming as the "most exciting new development" in stem cell research.

"I think that's where the gold is buried," he told MSNBC.com.

The research is already having an effect on the political debate, even as Congress considers the Castle-DeGette bill, H.R. 810, to widen federal support for human embryonic stem cell research. On the political landscape, the science of cell reprogramming plays into the central controversy over stem cell research.

Science and politics
Stem cells are the master cells that replenish all the body's tissues, from skin and blood to the brain and heart. In children and adults, particular types of stem cells are distributed throughout the body, and are specialized to create particular types of tissues. But in the early embryo, all-purpose stem cells can make virtually any kind of tissue, a quality known as pluripotency.

Currently, the only sure way to get pluripotent stem cells is to extract them from surplus frozen embryos or from embryos created through nuclear transfer — a procedure also known as therapeutic cloning.

Either way, the process of extraction destroys the embryo — and critics of the procedure see that as tantamount to abortion. Thus, they emphasize alternate ways to take advantage of "stemness" — by using less versatile adult stem cells, or umbilical-cord blood, or cells from a newborn's placenta, or exploring different avenues of research.

One of the bills proposed as an alternative to the Castle-DeGette bill, H.R. 3144, would fund four different approaches cited by the President's Council on Bioethics:

• Harvesting stem cells from frozen embryos that are considered "dead" and thus unsuitable for implantation in the womb.
• Taking one cell from an embryo at the eight-cell or 16-cell stage, known as the blastomere stage, when the rest of the cells could still develop into a viable fetus. This procedure is already done for a type of test called preimplantation genetic diagnosis or PGD.
• Genetically or biochemically altering cells to create an embryo-like tissue that has no chance of developing into a fetus, but yet produces embryonic stem cells.
• Reprogramming garden-variety cells — somatic cells — so that they have the pluripotent characteristics of embryonic stem cells.

The first three approaches have raised questions from one side or the other in the stem cell debate. For example: How do you determine if an embryo is dead, and can useful cells really be harvested from such an embryo? What medical risks and moral issues are involved in taking one cell from an early embryo? Would genetically altering cells create a kind of "Franken-embryo," sparking a new set of ethical concerns, and would the stem cells taken from such an altered cell mass even be safe for medical use?

Reprogramming, however, would win support from all sides — if only it could be done.

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