United Press International- July 19, 2001
WASHINGTON, Jul 18, 2001 (United Press International via COMTEX) -- More research is needed on both adult stem cells and embryonic stem cells to determine their potential in the development of treatments for disease, according to a National Institutes of Health report released Wednesday.
Dr. Lana Skirboll, of NIH's Office of Science Policy, told a news briefing the report "tries to lay out in a very balanced manner what we know about both sources."
The report, which Skirboll said was prepared after reviewing 1,200 scientific articles and reports and interviewing some 50 scientists and experts, was requested by President Bush shortly after he took office. The report, "Stem Cells: Scientific Progress and Future Research Directions", concluded the future of stem cell applications is "impossible" to predict and that "the answers clearly lie in conducting more research." Bush currently is considering whether to approve the use of federal funding for embryonic stem cell research, which some pro-life groups oppose because it requires the death of an embryo.
The promise of stem cells is in their unique potential to grow into different types of tissue. "Stem cells may hold the key to replacing cells lost in many devastating diseases," the report said. Scientists might someday be able to replace liver cells lost to disease or mend damage from spinal cord injuries, research supporters say. Stem cell research is considered by many to be the path to new treatments for multiple sclerosis, Parkinson's disease, Alzheimer's and diabetes.
There are at least three types of such versatile cells -- each of which has a different potential to "differentiate" or grow into various tissue. Adult stem cells are rare and are taken from adult tissue, a sample of muscle perhaps.
Embryonic stem cells are found in the handful of cells that make up a four- to five-day old embryo and embryonic germ cells are found in five to 10-week old fetuses -- specifically they are the cells that would eventually develop into testes or ovaries.
Of these, the embryonic stem and germ cells have the greatest ability to differentiate though their abilities are not quite the same, NIH said. "Stem cells in adult tissues do not appear to have the same capacity to differentiate as do embryonic stem cells or embryonic germ cells," the report's executive summary said.
Skirboll said embryonic cells are more of a blank slate, not committed to producing cells of any one type of tissue. Adult stem cells produce cells specific to the kind of tissue in which they are found rather than having the versatility of their embryonic counterparts.
"No matter what you say, an adult stem cell is in an undifferentiated state but it's hard to say that it's not committed." The question is, she added, is if they can be turned back so they "don't remember their commitment."
Another challenge facing the scientific community is that of plasticity. The report said in experimental conditions adult stem cells from bone marrow have apparently generated cells that resembled other cell types in the brain, leaving open the possibility adult stem cells could be reprogrammed to generate the specialized cells of different tissues. Clonality, in which a single cell divides into genetically identical cells, also is elusive in adult stem cells, Skirboll said.
"Clonality is an extremely important issue to treatment," Skirboll said. "Can you get a single cell line that is identical that you can grow and know what you have."
Skirboll said a major problem is that there are not any good markers for undifferentiated adult stem cells.
In 1999 NIH banned studies using stem cells from aborted fetuses or human embryos. President Clinton in August 2000 said stem cells from frozen embryos that were to be destroyed by fertility clinics could be used in research.
The new administration blocked the move shortly after Bush took office. Consideration of federal grant requests for stem cell research has been frozen pending a decision by Bush on which direction, if any, the research would take. The issue has split the Republican Party with vocal factions on both side of the issue.
In 2000, NIH spent $256 million on stem cell research, the vast majority on adult stem cells, Skirboll said.
William Haseltine, chief executive office for Human Genome Sciences Inc. in Rockville, Md., told UPI the evidence from NIH is convincing and that federal funding is the only route for stem cell research "It is clear that there is great promise in stem cell research but the work itself is in a very early stage," Haseltine said. "It is for the most part conceptual and needs a great deal of further explanation before we can understand how it can best be used for medicine." Haseltine said only the government can fund that research because there is no profit in it at this point for the private sector.
"The potential utility is too far in the future and unpredictable," he said. "Most biotech companies and pharmaceutical companies will not make the appropriate investment."
Copyright 2001 by United Press International