Scientific progress or science-fiction nightmare?
May 13, 2002
That's the shape of an upcoming Senate debate over therapeutic cloning, a type of medical research in which scientists trigger the earliest stages in the formation of a human embryo.
By cloning human reproductive cells in a laboratory, researchers hope to grow microscopic clumps of highly adaptive stem cells, the biological raw material capable of developing into virtually every type of tissue, bone and fluid in the human body.
The hope, proponents say, is that this sort of "therapeutic cloning" will yield genetically tailored treatments for patients suffering such ailments as diabetes, Parkinson's disease, cancer and spinal cord injuries.
The danger, President Bush and a broad coalition of critics argue, is that the research amounts to the establishment of "embryo farms" devoted to creating, and then destroying, human life.
"No human life should be exploited or extinguished for the benefit of another," Bush said earlier this year.
Therein lies the basic moral and scientific judgment that lawmakers face as they head into a Senate debate over an effort to outlaw therapeutic cloning. While some see the research as nothing short of miraculous, others call it immoral and unnecessary.
The outcome of the Senate debate is likely to shape American biomedical research for years, perhaps decades, to come.
Unraveling the moral, religious and political complexities of the Senate debate requires an understanding of how the research works, its promise and its problems.
The nexus of the Senate debate revolves around embryonic stem cells, the starter material of human development.
Stem cells begin to form during the first, microscopic cell divisions in the growth of a human embryo. The sperm fertilizes the egg. The egg divides, and divides again.
Within five to seven days, the egg cells, or oocyte, have transformed into a sphere of around 100 to 300 cells, called a blastocyst. Inside the blastocyst's outer layer of cells are 20 to 30 stem cells, a mass about the size of the tip of a pencil lead.
Within the womb, these stem cells continue to divide, each one morphing into all of the specialized sorts of tissue required for human development.
But within a lab, scientists are breaking apart blastocysts taken from animals to extract the stem cells, allowing them to replicate in a petri dish. They hope one day to train those stem cells to regenerate damaged or degenerating tissue.
The next step, already under way, will be to replicate the results in human stem cells and then develop medical treatments.
Under an executive order signed last year, Bush allowed federal funding for some types of stem-cell research. His order limited funding to research using existing stem cells obtained from excess embryos at fertility clinics.
The president banned research funding to obtain additional stem cells.
But one problem with transplanting stem cells emanates from the patient's own body. The human immune system tends to reject foreign tissues.
Enter therapeutic cloning.
Many scientists believe that patients would be less likely to reject stem cells if those cells contained the genetic coding of the patient or a close relative.
Here is how it might work.
Rather than fertilizing the female egg cell with sperm, scientists would remove the egg cell's nucleus, which contains almost all its genetic material. Scientists would transplant the nucleus of a mature cell from a patient or relative into the emptied egg.
Among researchers, this process is called somatic cell nuclear transfer. Within the political debate, it's known as therapeutic cloning.
During the process, the egg cell with a transplanted nucleus is allowed to grow into a blastocyst containing stem cells with the donor patient's genetic information.
At this point, critics argue, the blastocyst could be transplanted into a uterus, allowing it to grow into a self- sufficient human being. Almost every member of Congress favors banning this sort of "reproductive cloning," a procedure almost universally denounced among researchers.
But in therapeutic cloning, the blastocyst is not transplanted into a womb. Rather, researchers pull apart the outer layer of cells to obtain embryonic stem cells inside.
Sen. Sam Brownback, R-Kan., and a coalition of supporters that includes Bush argue that therapeutic cloning amounts to the creation and destruction of a human life in order to pursue unproven science.
Brownback's main argument is that this blastocyst, even outside the womb, amounts to a human life, and should never be destroyed. He argues further that allowing therapeutic cloning will make it impossible to stop unethical scientists from creating a cloned baby.
And if a blastocyst can be created and destroyed, critics contend, why not allow fetal development to continue a bit further, perhaps to extract other sorts of fetal tissue?
"Where do you draw the line?" said Erik Hotmire, Brownback's spokesman.
Research advocates emphasize that the egg cell is never fertilized and doesn't grow beyond a tiny "clump" of cells. They point out that this clump can't grow into a human being unless it is implanted into a womb.
"It's just a bundle of cells," said Larry Goldstein, a stem-cell researcher at the University of California at San Diego. "And they have special abilities."
Lawmakers supporting Brownback's push to outlaw therapeutic cloning include Nebraska Sens. Chuck Hagel, a Republican, and Ben Nelson, a Democrat. Brownback also enlisted support from Tennessee Sen. Bill Frist, the Senate's only physician and an important proponent of Bush's plan to fund stem-cell research.
Frist, a Republican and a heart surgeon, argues that treatments from therapeutic cloning are years away, if they happen at all. And like Brownback and Bush, Frist contends that scientists should first pursue research using stem cells drawn from adults.
Research advocates from both political parties argue that the federal government has no business banning research that could save millions of lives.
"It's a way of trying to help humankind," said Utah Sen. Orrin Hatch, a Republican and a staunch abortion opponent.
In announcing his support for therapeutic cloning, Hatch said he was swayed by the promise that research might bring about treatments for patients such as diabetic children.
Hatch and Sen. Tom Harkin, D-Iowa, are supporting a bill sponsored by Sens. Arlen Specter, R-Pa., and Dianne Feinstein, D- Calif., that would allow therapeutic cloning while outlawing any effort to create a baby through cloning.
Hatch said he doesn't believe that a blastocyst in a petri dish constitutes human life. He added that each of his colleagues will have to come to a decision.
"Each of us much search our own souls," he said.
1 Needle removes genetic materials from unfertilized egg
2 Cumulus cell (cell that nurtures developing eggs in the ovaryand is found clinging to eggs after ovulation) is taken intoneedle. Nuclei from other cells, e.g. a sick donor's skin cells,can also be used in this step
3 Cumulus cell injected into empty egg
4 Injected egg exposed to chemicals designed to cause it todivide; after 24 hours, egg beings to divide; cells containgenetic material only from injected cumulus cell
5 Division progressed to six cells before growth stopped
GOAL (not yet accomplished in humans)
6 By fourth or fifth day, 100 cells form, including inner cellmass containing stem cells
7 Inner cell mass removed and grown to yield stem cells; in turnstem cells are coaxed to grow into a variety of cells to beinjected into patients
Source: Advanced Cell Technology, Scientific American Graphic:Elsebeth Nielsen, Morten Lyhne, Todd Lindeman
Stem cells - Highly adaptable cells able to transform intovirtually every tissue within the human body.
Blastocyst - A microscopic ball of cells formed during theearliest stages of embryonic development. Contains embryonicstem cells used in therapeutic cloning.
Therapeutic cloning - A method of obtaining genetically tailoredstem cells in a laboratory by growing a human egg cell with atransplanted nucleus and genetic information.
Reproductive cloning - A widely denounced form of research inwhich a cloned human egg is transplanted into a womb in order toproduce a cloned human being.
Brownback bill - Senate measure sponsored by Sen. Sam Brownback,R- Kan., to outlaw reproductive and therapeutic cloning.
Specter-Feinstein bill - Senate measure sponsored by Sens. ArlenSpecter, R-Pa., and Dianne Feinstein, D-Calif., to banreproductive cloning but allow therapeutic cloning.
(C) 2002 Omaha World-Herald.