Conversation on what is Stem Cell

What is Stem Cell

Research on stem cells is advancing knowledge about how an organism develops from a single cell and how healthy cells replace damaged cells in adult organisms. This promising area of science is also leading scientists to investigate the possibility of cell-based therapies to treat disease, which is often referred to as regenerative or reparative medicine.

Stem cells have two important characteristics that distinguish them from other types of cells. First, they are unspecialized cells that renew themselves for long periods through cell division. The second is that under certain physiologic or experimental conditions, they can be induced to become cells with special functions such as the beating cells of the heart muscle or the insulin-producing cells of the pancreas.

Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells and adult stem cells, which have different functions and characteristics. Scientists discovered ways to obtain or derive stem cells from early mouse embryos more than 20 years ago. Many years of detailed study of the biology of mouse stem cells led to the discovery, in 1998, of how to isolate stem cells from human embryos and grow the cells in the laboratory. These are called human embryonic stem cells. The embryos used in these studies were created for infertility purposes through in vitro fertilization procedures and when they were no longer needed for that purpose, they were donated for research with the informed consent of the donor.

Stem cells are important for living organisms for many reasons. In the 3- to 5-day-old embryo, called a blastocyst, stem cells in developing tissues give rise to the multiple specialized cell types that make up the heart, lung, skin, and other tissues. In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.

Scientists want to study stem cells in the laboratory so they can learn about their essential properties and what makes them different from specialized cell types. As scientists learn more about stem cells, it may become possible to use the cells not just in cell-based therapies, but also for screening new drugs and toxins and understanding birth defects. However, as mentioned above, human embryonic stem cells have only been studied since 1998.

Stem cells differ from other kinds of cells in the body. All stem cells—regardless of their source—have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types.
Politics In Stem Cell

What's in a name? When it comes to controversial science, a lot.
South Korean scientists recently announced they had used cloning to produce 11 human embryos and destroyed them to harvest their embryonic stem cells. Actually, they said they had used "somatic cell nuclear transfer" to produce "human NT blastocysts," from which they extracted "hESC" (for human embryonic stem-cell lines).
In fact, nowhere in their paper did they use the word "clone."
"Everybody is terrified of the word, 'cloning' " said Dr. David Shaywitz, a stem-cell researcher at Harvard University. "It conjures up so many frightening images.
"Both sides are trying to manipulate language. People who are opposed to the research go out of their way to use that word, and people who support the research are trying to find other ways to explain what they are doing."
But cloning opponents are disturbed by the way stem-cell scientists these days almost always speak of "somatic cell nuclear transfer" rather than "cloning."
"The most important thing to be said is that the language is changing, and it seems to have an agenda behind it to make things more acceptable," said Dr. John Kilner, the president for the Center for Bioethics and Human Dignity, which opposes cloning and destroying human embryos to extract their stem cells.
"I'm concerned," he added. "People ought to debate the scientific issues on the merits."
The word "embryo" presents similar problems. The South Korean scientists, for example, did not get their cloned embryos by fertilizing human eggs. Rather, they removed the genetic material from donated eggs and replaced it with genetic material from the cells of patients. Those new genes took over and directed the eggs to grow and divide. So, they said, the resulting balls of cells should be called "nuclear-transfer constructs."
But avoiding the term "embryo" merely "avoids a moral question that is very much in the public consciousness," said Dr. Lisa Cahill, a theology professor at Boston College. After all, she said, those balls of cells, however created, can develop and, if implanted in a womb, could in theory become babies. Those who oppose such research say the embryos are human, and they object to destroying human life.
Early stages
Many scientists counter that embryos in their early stages, whatever their potential, are simply tiny clumps of undifferentiated cells — no budding organs or extremities, nothing remotely mammalian or babylike — and that they have no moral status.
Most Americans, Cahill said, occupy a position somewhere in between. They do not want to lose the promise of stem-cell research, but they also do not consider human embryos to be simply balls of cells.
This view, Cahill said, is "reflected in the fact that we've had the National Bioethics Council and the President's Council on Bioethics and a statement from the American Fertility Society all saying special respect was owed the embryo. But they didn't necessarily say that therefore it could never be used in research."
There is the further question of using cloning to create embryos. Should the word "clone" even be used if the embryos will never be allowed to develop into babies?
The International Society for Stem Cell Research wrestled with the issue and decided to use different words to distinguish between cloning to create embryos for their stem cells and to create babies.
The group decided that cloning to create embryos to the blastocyst stage, that critical time at about five days when stem cells can be obtained, and then destroying them to extract stem cells would be called "somatic cell nuclear transfer."
That term, said Gordon Keller, a stem-cell researcher at Mount Sinai School of Medicine in New York and the president-elect of the International Society for Stem Cell Research, accurately describes the process by which the blastocysts were made.
The other possible outcome for the blastocysts, something Keller said the society vehemently opposes, would be to implant them in a uterus to start a pregnancy. That would be called "cloning."
"The process is the same," Keller said. The important difference, he said, is "what you do with the blastocyst."
Council's conclusion
The president's Council on Bioethics unanimously came to a different conclusion about what to call the process of creating these blastocysts. "Although as a scientific matter 'somatic cell nuclear transfer' or 'nuclear transplantation' may accurately describe the technique that is used to produce the embryonic clone, these terms fail to convey the nature of the deed itself, and they hide its human significance," the council wrote.
Dr. Leon Kass, the council's chairman, said last week that the South Koreans' feat should not be disguised by jargon.
"The initial product of their cloning technique is without doubt a living cloned human embryo, the functional equivalent of a fertilized egg," Kass wrote in an e-mail message.
"If we are properly to evaluate the ethics of this research and where it might lead," he continued, "we must call things by their right names and not disguise what is going on with euphemism or misleading nomenclature."