Fetal Tissue Transplants:
Mastering the Master Cell
Fetal Tissue is Source of Stem Cells
Fetal Tissue Used to Treat Disease and Defect
Fetal tissue transplants are being investigated as treatments for a wide range of debilitating human conditions. Researchers hope to cure diabetes by regenerating insulin-producing pancreatic cells in diabetics, and blindness by regrowing retinal tissue in the eye. Scientists hope to develop better treatments for heart attack victims with fetal tissue used to regrow damaged heart muscle. Fetal tissue transplants also look promising for a variety of problems caused by destroyed nerve cells, such as Parkinson’s disease, Huntington’s Chorea, and even spinal cord injuries. And the benefits of such transplants may not only extend to adults. Healthy fetal tissue is also being investigated as a treatment for fetuses with identified genetic defects such as Sickle Cell Anemia. In one astounding case, a little boy with Hurler’s Syndrome, a fatal genetic disease in which a critical liver enzyme is missing, was born free of the disease after receiving a fetal tissue transplant in his liver while still in the womb.
The crux of the method is the use of fetal stem cells to replace damaged tissue that the body itself cannot repair. For instance, paralysis is currently incurable because, once destroyed, the nerve cells of the spinal cord are not able to grow back. Researchers hope that stem cells can be used bridge a spinal cord injury in much the same way as skin cells grow back to cover a cut. Although not ready to be tried in people, procedures that inject fetal tissue cells at spinal cord breaks have shown encouraging results in small animals, as in one study where scientists were able to get partially paralyzed cats to walk again. Similar experiments to regenerate nerve cells of the brain are also being investigated as cures for Huntingon’s Chorea and Parkinson’s Disease, two diseases caused when specialized nerve cells in the brain begin to die off.
The most advanced research on the use of human fetal tissue has been done in Parkinson’s disease, which affects about 1.5 million people in the U.S. In this progressive, debilitating illness, the cells in a small part of the brain called the substantia nigra are destroyed, depriving the striatum (the part of the brain that controls movement) of a critical molecule called dopamine. Patients with Parkinson’s disease experience tremors, slurred speed and slowness of movement that eventually progresses to total paralysis. Despite devastating loss of motor control, mental faculties in Parkinson’s patients remain intact, and while the disease is in itself not fatal, patients often succumb to complications such as injuries from falls or pneumonia.
The first line of treatment for Parkinson’s disease is durg therapy. Unfortunately, L-dopa, a precursor of dopamine able to be absorbed by the brain, helps only as long as there are some substania nigra cells still alive to absorb the drug. Once that area of the brain is destroyed, L-dopa becomes ineffective, which until recently left the patient without any available treatment for this disorder. Now pioneering fetal tissue transplants into the brain of Parkinson’s patients show promise in slowing or even reversing symptoms of the disease. In this treatment, cells from the pre-brain structures of 6-8 week old fetuses are injected into the patient’s striatum, where if all goes well they grow into a bundle of nerve cells that produce the needed dopamine. Patients with successful fetal tissue transplants have shown remarkable improvement in the severity of tremors and in their ability to move.
With such exciting results and millions of people in this country alone suffering from Parkinson’s and other diseases that may be helped by fetal tissue transplants, patients and their advocates are urging further research into the use of stem cells. However, currently the only reliable source of stem cells is electively aborted human fetuses, collected from abortion clinics with the permission of the mother. It is this controversial source of the tissue that caused the Reagan administration to ban Federal funding on research of fetal tissue transplantation. Tissue transplant research continued with private funding even during the Reagan/Bush years and the federal funding ban was reversed in the first days of the Clinton presidency.
Abortions and Human Embryo Cloning- a Hotbed of Controversy
As the body of evidence for successful fetal tissue transplant procedures continues to accumulate, the difficulty of procuring healthy fetal tissue remains an ongoing concern. Spontaneously aborted fetuses are not appropriate, because spontaneous abortions do not occur in controlled circumstances where the tissue can be collected before fetal cells die off, and also because spontaneous abortions are mostly due to genetic abnormalities that make the fetal cells unusable for transplantation. Similarly, cells cultured by scientists in the laboratory often are genetically abnormal.
Because of such concerns, the British House of Parliament, after fierce debate, approved the cloning of human embryos specifically for the production of fetal tissue for transplantation in January 2001, a worldwide first. In this process, a patient’s own cells would be fused to an enucleated donor egg to produce a growing embryo “clone” of the patient. After a few days, the embryo would be destroyed and the stem cells harvested for use in treating the patient’s disease. Human cloning to create living offspring is still banned under the new law, and therefore any unused embryos would have to be destroyed after 14 days, before specific tissues such as a heart and brain develop.
The green light for such research in Britain has rekindled worldwide debate as to whether it is ethical to create human embryos solely for body parts. Bioethicists agree that in the United States, the use of human embryos to obtain stem cells for disease treatments is too closely tied to the abortion issue. Federal funding for research involving human cloning is currently banned, and with the country polarized on the question of whether life begins at conception, the current political climate is such that congress is unlikely reverse its stance. Researchers note that without such funding, research will have to be sponsored through private efforts, making medical breakthroughs utilizing cloned fetal tissue in the U.S. improbable.
Although procedures utilizing fetal tissue appear to hold great promise for a wide variety of ailments, experts warn that such treatments are not a cure-all. For example, despite the flurry of excitement over success stories, only about one third of Parkinson’s patients that receive fetal tissue transplants have dramatic, life-transforming outcomes. Another third of patients see some modest improvement, while rest either see no lasting effects or end up worse than before. The evidence for most other uses of fetal tissue is still preliminary, and the procedures will need to be carefully evaluated in controlled studies before fetal tissue transplants become widely available as disease treatments or cures. Such research is ongoing, but the controversy over the source of fetal tissue appears only likely to escalate as fetal tissue research becomes embroiled in the arguments over the ethics of human cloning. Thus, the future of fetal tissue transplantation may lie as much with lawmakers pondering the ethics of such procedures as with the researchers developing the techniques to make it possible.
Fetal Tissue Web Site Links
National Institutes of Health - stem cell primer describing stem cells and their promise for science and medicine.
Tough Choices Project - television and print journalism articles on medical advancements and ethics
Focus on the Family Website - searchable Christian site with articles on fetal tissue research from a pro-life point of view.
Planned Parenthood - fetal tissue research fact sheet