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Cellular Division

The field of stem cell research promises to continue provoking both political and scientific debate.

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For both sides of the controversy, it is a matter of life or death. Supporters of embryonic stem cell research (ESC) say that it has the potential to save millions of lives from the catastrophic consequences of a wide range of diseases, including diabetes, Parkinson's and Alzheimer's, and spinal cord injury. Opponents call it immoral and unethical to destroy an embryo under any circumstances, and argue that adult stem cells could be just as effective in battling those diseases.

Embryonic stem cell research has emerged as a major issue during this year's presidential campaign. Sen. John Kerry favors ESC research and has called on President George Bush to end the federal funding ban on using embryos made in in vitro fertilization clinics to create new ESC lines. Additionally, Kerry is one of 11 co-sponsors of Senate Bill 303, which bans cloning embryos for reproductive purposes but allows federal funding for therapeutic cloning under strict federal guidelines. Now in committee, the bill, sponsored by conservative Utah Republican Sen. Orrin Hatch, demonstrates how this issue can cross party lines.

In August 2001, Bush announced a long-awaited decision that federal funds could not be used for the development of new ESC lines, but could be used for research on ESC lines created before Aug. 9, 2001. In order to make these pre-existing lines available, the National Institutes of Health (NIH) Human Embryonic Stem Cell Registry was created. There is a dispute over how many ESC lines will be on the registry, with the number falling between 64 and 78. Currently, 28 lines on the registry can be used. However, of those 28 lines, five aren't available for shipping, and, according to the registry, one of the lines "failed to expand into undifferentiated cell cultures."

Bush opposes cloning embryos for either reproductive or therapeutic purposes. Aligned with the administration's stance is Senate Bill 1899, sponsored by Republican Sen. Sam Brownback of Kansas, which completely bans cloning. This bill also crosses party lines: Sen. Mary Landrieu is one of 30 co-sponsors of the Brownback bill. Like its counterpart, the bill is currently in committee.

Behind the politics is a new arena of medical science that still confuses many voters. What makes stem cells so unique -- and intriguing to researchers -- is that they are capable of replicating themselves. Blood cells, muscle cells or nerve cells, for example, can't normally replicate themselves, but stem cells, under certain circumstances can -- and the result is millions of new cells. Unlike blood cells and other cells that have specialized functions in the body, stem cells do not. However, stem cells can differentiate, which means they can become another type of cell. Due to these features -- replication and differentiation -- stem cells can be used in cell therapy to repair damaged adult cell populations. An example of this would be using stem cells to help repair damaged heart tissue.

According to the NIH, there are both adult and embryonic stem cells. Adult stem cells (ASC) are found in many of the human body's organs and tissues such as the brain, bone marrow, skin and liver. These cells are thought to remain non-dividing until activated by a disease or injury. After an injury or disease, the stem cells begin dividing and specializing in order to maintain or repair tissue. Until recently, researchers thought that adult stem cells only differentiated into the specialized cell types of the tissue in which they resided. For bone marrow stem cells, this would mean differentiating into cell types such as bone cells, cartilage cells, fat cells and other kinds of connective tissue. More recent experiments suggest that certain adult stem cells might be pluripotent, or able to develop into many different cell types of the body. It has been reported that bone marrow cells may differentiate into cardiac muscle cells and skeletal muscle cells.

Stem cells from embryos have the ability to become all cell types of the body, so they are considered totipotent. Currently, researchers are studying ways in which to stimulate ESC into becoming specific cell types. If this occurs, then researchers see ESC being used in gene therapy to counteract diseases such as Parkinson's, diabetes and Alzheimer's.

For opponents of ESC research, the main difference between ASCs and ESCs is that ESCs have to come from an embryo, and during the process of removing the stem cells, the embryo is destroyed. One possibile source for obtaining embryos for ESC research is from in vitro fertilization clinics. Doctors create more than one embryo, in case the fertilized egg doesn't survive when it is implanted in a woman's body. Leftover embryos are frozen, and there are currently an estimated 300,000 to 400,000 such embryos in existence. The ultimate fate of this growing number of embryos is unclear, with laws varying from state to state.

The other possibility for ESC research is somatic transfer, or cloning, in which scientists take a nucleus from an adult cell and transfer it to a woman's egg cell that has had its nucleus removed. From there, this combination is stimulated to form an embryo. The embryo is allowed to grow in the lab until the undifferentiated stem cells have formed. The cells are then removed from the embryo.

Whichever method is employed, it still amounts to destroying one life to benefit another, say Dorinda Bordlee, a lawyer for the anti-abortion group Americans United For Life, and state Sen. Arthur Lentini (R-Kenner). In June 2004, the two teamed up to attempt to pass a bill in the state Legislature banning cloning for either therapeutic or reproductive purposes. The bill failed. However, according to a Louisiana law passed in 1986, "the use of a human ovum fertilized in vitro is solely for the support and contribution of the complete development of human in utero implantation." In other words, it is illegal to use an in vitro embryo in Louisiana for stem cell research, but it is still legal to clone an embryo.

At one point during the state Legislature's battle over cloning, a compromise was proposed that would have made the practice of cloning illegal, but would have allowed the import of ESC lines created by cloning into Louisiana. Lentini didn't think much of this idea. "I'm just not going to compromise this in any way that doesn't make sense -- that isn't consistent with the ethical and moral concerns that caused me to file the bill," he says. "I'd rather not have a bill then have a bill that makes that type of concession."

Bordlee, who modeled the legislation after the Brownback/Landrieu bill, says it would have furthered research, not limited it. "Our stance would have actually promoted research in Louisiana because right now we have stem cell repositories in Baton Rouge. They get adult stem cells from the human placenta and those are being used to develop treatments for adults. These are pluripotent stem cells. Back in the mid 1990s, ESC were considered the only form of pluripotency, but since 1998 the adult stem cell research has far surpassed that."

Dr. Darwin Prockop, director of the Gene Therapy Center at Tulane, which does research only on adult stem cells, agrees that strides have been made in adult stem cell research. However, Prockop questions whether adult stem cells will ever have the same abilities as ESCs.

"ESCs have properties the adult stem cells don't have," Prockop says. "We're trying to make our adult stem cells do everything that ESCs do, but we're not there yet, and we're not certain we can get there. You learn more about how stem cells work with ESCs. You need that information."

Mac DeVaughn, the executive director of the state chapter of the Juvenile Diabetes Research Foundation, favors both therapeutic cloning and research on in vitro embryos. The decision to use an embryo is difficult, he says, but one that can be rationally made. "All of our somatic cells are life, but I cannot attach the same importance to 100 cells in a blastocyst as I can to a living, breathing human being," DeVaughn says. "Human potential, yes, but is that an actual living, breathing human being to me? It is not, and that's where I draw the distinction."

The political debate is not likely to end soon. At this point, about the only issue that everyone can agree about is that cloning for reproductive purposes should be outlawed. Compared to the debate over abortion, however, more nuanced views are emerging. Some, like Landrieu, are against therapeutic cloning but support the use of in vitro embryos to create new ESC lines. Landrieu, along with 57 other senators, recently signed a letter asking the president to ease the current restrictions against using frozen in vitro embryos for research that uses federal funding. The more we learn about stem cells, the more likely it is that the life-and-death debate will continue. Locally, at least, both sides are remaining civil. "I understand how the other side feels," Lentini acknowledges. "I don't accuse them of any ill motives."

Dr. Darwin Prockop directs the Gene Therapy Center at Tulane University. "We're trying to make our adult stem cells do everything that ESCs do, but we're not there yet, and we're not certain we can get there," he says.
  • Dr. Darwin Prockop directs the Gene Therapy Center at Tulane University. "We're trying to make our adult stem cells do everything that ESCs do, but we're not there yet, and we're not certain we can get there," he says.

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