Stem cells: FAQs
Scientists have been all abuzz in the last few years over stem cells — cellular magicians that promise to dazzle and amaze.
In December 1999, the editors of Science, the journal devoted to scientific and medical matters, called stem cell research the "Breakthrough of the Year."
Since then, there has been a flurry of announcements about developments in stem cell research and hints of promising treatments for diseases such as Alzheimer's, Parkinson's and cancer. In May 2007, Ontario and California announced a $30-million stem cell research deal aimed at finding new therapies for those diseases.
A year later, the Ontario government announced it would contribute $1 million to the Gladstone Institute of Cardiovascular Disease in San Francisco. Researchers there are working on technology that induces human skin cells to change into the kind of stem cells that have been created by embryos. That process has been called "cellular reprogramming" and was recognized as the breakthrough of the year for 2008 by Science.
Ontario and California together account for about 70 per cent of the stem cell research currently conducted in North America. On June 16, 2008, Massachusetts Gov. Deval Patrick signed legislation that would set aside $1 billion toward biotechnology over 10 years. Some of that money would be aimed at turning the state into the second-largest stem cell research region in the United States.
The first clinical trials involving a patient receiving human embryonic stem cells began in October 2010 at the Shepard Center, a spinal cord injury hospital in Atlanta. The tests are being conducted by Geron Corp., a company based in California's Silicon Valley.
But there has been intense debate over the use of stem cells. Scientists say embryonic stem cells are the most useful type because they have the potential to become any type of cell within the body. However, they are harvested from embryos grown in the lab.
Opponents argue that any embryo has the potential to develop into a mature human. Some argue that the possibility of mimicking stem cells without acquiring them from embryos, side-steps that moral dilemma. However, researchers at the Harvard Stem Cell Institute say reprogrammed cells won't eliminate the need or value of studying embryonic stem cells.
What are stem cells?
Stem cells can be thought of as blank slates or cells that have yet to become specialized. They are in an early stage of development and have the ability to become any type of cell to form skin, bones, organs or other body parts.
Are there different kinds of stems cells?
Yes. Stem cells come in three forms: embryonic stem cells, embryonic germ cells and adult stem cells. Embryonic stem cells come from embryos, embryonic germ cells from testes, and adult stem cells can come from bone marrow.
Embryonic stem cells are pluripotent — they have the ability to become virtually any type of cell within the body. Adult stem cells are more limited. They are found in adult organs. They are still developing and they have the potential to become any of the major specialized cell types within that organ. But recent evidence suggests it may be possible to reprogram adult stems to repair tissues.
In a study published in the online journal Nature on March 1, 2009, Canadian researches described a new method for generating stem cells from adult human tissue. The researchers, at Mount Sinai Hospital in Toronto, say the development could bring personalized regenerative medicine a step closer to reality.
"This new method of generating stem cells does not require embryos as starting points and could be used to generate cells from many adult tissues, such as a patient's own skin cells," said principal author Andras Nagy, senior investigator at Mount Sinai's Samuel Lunenfeld Research Institute.
The ability to transform skin cells into stem cells isn't new. But previous approaches required the use of viruses to deliver the four genes needed to activate the cell and accomplish that task. Using viruses increases the risk of damaging the cell's DNA.
What could stem cells be used for?
Scientists are fascinated by the ability of stem cells to become any type of cell. This makes them perfect for a wide range of medical uses, from repairing tissue to treating diseases such as Parkinson's and Alzheimer's.
Doctors can already transplant tissue and organ cells but they are limited by a lack of donors. Stem cells could allow them to grow the tissue they need, when they need it.
The first human trials using embryonic stem cells were on patients with spinal cord injuries. The first phase of the trial — like any new drug or treatment trial — is only to determine whether such treatments are safe, not whether they are effective.
In animal trials of the spinal cord treatment, paralyzed rats regained some movement.
The company behind the trials, Geron Corp., says the details of the clinical trial are confidential. The first patient to receive human embroynic stem cells is at the Shepard Center, a 132-bed spinal cord and brain injury rehabilitation hospital and clinical research centre in Atlanta. Geron says it is one of seven U.S. research centres that can enrol patients in their trial.
The study's participants must be "newly injured," Geron said, receiving the treatment within 14 days of the injury.
What do stem cells have to do with cloning?
When people think of cloning they usually think of copying people from head to toe. But human cloning also includes making copies of just cells.
Researchers don't necessarily need to clone stem cells, but cloning would make their work a whole lot easier. Instead of having to collect the millions of stem cells needed to grow a patch of skin for a patient who suffered a severe burn, for example, doctors could collect only a few stem cells and make millions of copies.
What are the ethical issues involved?
Currently, the best source for stem cells is a human embryo. But using human material, such as aborted fetuses, in research is a contentious issue because it can be construed as the sacrifice of human life for scientific progress.
Former U.S. President George W. Bush struck down proposed legislation to expand embryonic stem cell research in July 2006. The Stem Cell Research Enhancement Act, which passed in the Senate, would have eased limits on human embryonic stem cell research. It had been restricted to cell lines, or colonies, that were derived on or before Aug. 9, 2001, the day the policy was announced.
On March 9, 2009, U.S. President Barack Obama reversed Bush's restrictions when he signed an executive order clearing the way for federal funding of research using embryonic stem cells.
On July 7, 2009, new rules came into effect governing what types of stem cells would be eligible for funding. The guidelines, which were drafted by the National Institutes of Health, say that only science that uses cells culled from leftover fertility clinic embryos — ones that otherwise would be thrown away — would be eligible.
The guidelines expand the number of stem cell lines available to researchers from 20 to about 700. The agency will also create a registry of qualified stem cells so scientists don't have to second-guess if they're applying to use the right ones.
In August 2006, researchers at Advanced Cell Technology, a biotechnology firm in Alameda, Calif., published a paper in the journal Nature, saying they had found a way to spare embryos by growing lines of stem cells from a single embryonic cell. The team said they hoped the findings would bypass U.S. legislation.
Other scientists noted the success rate, while opponents of the research said the study does not put an end to the ethical debate because spare embryos created through in vitro fertilization for the stem cells lines still would be destroyed.
Members of the medical community are debating what should and shouldn't be allowed, but the overall consensus seems to be that stem cell research should go ahead, but with strict limitations.
One of the most contentious issues in the stem cell debate is the use of hybrid embryos. These embryos are created by taking nuclei containing DNA from human cells and transferring them into animal eggs that have had almost all of their genetic information removed. The embryos are grown in a lab for a few days and then harvested for stem cells. The embryos are close to 99.9 per cent human.
The creation of hybrid embryos — or chimeras — was first raised as a way of dealing with the shortage of human embryos for research.
On Sept. 5, 2007, Britain's Human Fertilisation and Embryology Authority agreed in principle to allow human-animal embryos to be created and used for research. Scientists wanting to use hybrids to grow stem cells would have to apply to the authority for approval.
Britain becomes the first country in the world to allow the creation of hybrid embryos. In Canada, the Assisted Human Reproduction Act — enacted in March 2004 — made it illegal to create hybrid embryos.
In March 2001, the Canadian Institutes of Health Research released its first set of guidelines for the use of stem cells. The guidelines have been updated several times, with the latest revision published on June 30, 2010. They limit scientists to using embryos created for reproductive purposes that are no longer required, and then only if the people for whom the embryos were created agree. The CIHR guidelines include:
- Research can only use embryos created by in vitro fertilization that are no longer wanted for reproductive purposes. This means the creation of human embryos solely for research purposes is prohibited. Also, cloning human embryos is not allowed.
- The use of stem cells in reproduction is not allowed.
- Combining non-human stem cells with a human embryo or fetus is not allowed.
- Embryos used in research must not exceed 14 days old (two weeks post-fertilization).
- There must be free and informed consent from the donors of the stem cells or other reproductive material. This consent must be renewed when the time of the actual research comes so donors have a clear opportunity to change their minds.
- No commercial transactions or financial incentives are allowed when it comes to the donation or creation of reproductive material.
- Research on stem cell lines created outside of Canada and imported for research purposes will only be permitted if the stem cells were created in accordance with CIHR's guidelines.