Aug. 18, 2000 -- As the human embryo grows, the early cells start dividing and forming different kinds of cells like heart cells, bone cells, muscle cells, and so on. These early cells, called "stem cells," theoretically could be used to form a variety of cells which doctors could then use to repair diseased cells virtually anywhere in the body. A series of recent reports show that research into this area of medicine is moving at an incredible pace.
In May, researchers showed that brain stem cells could be used to form cells that could treat multiple sclerosis and a variety of serious nerve diseases. In June, they turned brain stem cells into heart, gut, and liver cells. This week, researchers turned human bone marrow stem cells into nerve cells.
Encouraged by this research, the British government is proposing to change the ban on human cloning to allow scientists to perform research on embryonic stem cells. Currently, these cells are derived from either very early embryos discarded at in vitro fertilization clinics or from tissue from aborted fetuses.
However, experts say treatments derived from embryonic stem cells are at a much earlier stage of the game, not to mention that such research also is extremely controversial.
Till then, studies on the much less disputed stem cells from adult humans have raised hopes of new treatments to regrow or replace diseased tissue. But when, if ever, will patients benefit from this research?
"Not for a while," says Mark Frankel, PhD, director of the prominent stem-cell panel at the American Association for the Advancement of Science.
"These are all one-time studies. They're exciting, but they don't prove anything. Much more work needs to be done," he tells WebMD. But other researchers say that the first stem cell-derived therapies could show up in the clinic within five years.
The recent studies also show that adult stem cells present many more options than anyone had previously thought, says Ira Black, MD, professor of neuroscience and cell Biology at the Robert Wood Johnson Medical School in Piscataway, N.J.
Some kinds of stem cells already have been an accepted medical treatment for years. Physicians transplant bone marrow because it contains stem cells that can form blood cells to replenish depleted blood in patients with cancer and other diseases.
Although researchers had known that bone marrow contained stem cells, until recently they thought that other adult cells could not alter their destinies, Black says. "These cells are far more flexible than anyone suspected just a few short years ago," he tells WebMD.
This week, Black and his colleagues provided an important new example of this flexibility: They took bone marrow stem cells and, using precise laboratory techniques, coaxed them to form nerve cells.
Because the stem cells can grow quickly and almost indefinitely in the lab, "they constitute a virtually limitless supply [of nerve cells]." The New Jersey team is now testing these nerve cells in rat models of Parkinson's disease, Alzheimer's disease, stroke, and spinal cord injury, but "we don't have any answers yet," Black says.
Annemarie Moseley, MD, PhD, president and chief executive officer of Osiris Therapeutics in Baltimore, says her company is working on ways to make bone marrow stem cells more effective as well.
Researchers there are trying to use stem cells for bone formation, cartilage formation, as well as therapies targeting heart and kidney conditions. She tells WebMD that clinical trials are already underway using bone marrow stem cells to regrow and replace bone that had to be removed from bone cancer patients.
But Moseley agrees treatments using embryonic stem cells have a long road ahead of them. Because these cells can in theory form any cell in the body, researchers believe they can eventually even be used to create replacement organs like the heart, liver, or kidney. But even though for some researchers the ideal continues to be embryonic stem cells, such research faces considerable opposition in the U.S. Congress.
Federal funding for research on these cell lines has been blocked for several years. However, earlier this week, the Los Angeles Times reported that the National Institutes of Health would for the first time allow limited research on these types of cells.
Nevertheless, "There are a number of things standing in the way," says Ronald M. Green, PhD, director of the Ethics Institute at Dartmouth College. Before human embryonic stem cell research can move forward, ethical, political, and scientific obstacles have to be overcome, he says.
From a scientific point of view, researchers still need to learn how to reliably transform embryonic stem cells to specific cell types.
On the ethical side, however, Green argues that there's a strong reason to allow such research. Replacement tissues from stem cells -- derived from either adult tissues or embryos -- could one day be widely used in the clinic.
"It could be a while, but I believe this research is going to transform medicine," he says.