"Yes" to adult stem cells.
An ethical alternative to the use of embryonic stem cells for therapeutic purposes is presented by adult stem cells, including umbilical cord-blood stem cells, which does not involve the destruction of a human embryo or human life.
Adult stem cell treatment has been around for some time. It was pioneered in the 1960s, with transplants of donated bone marrow. Bone marrow transplants, like peripheral blood transplants, are a type of adult stem cell treatment. They can be undertaken with donor stem cells (allogeneic transplants) or with the patients' own cells (autologous transplants). Autologous transplants of bone marrow were initially used to rescue bone marrow from patients due to undergo chemotherapy. Today, autologous peripheral blood stem cell transplants are used in treatment and in clinical trials involving patients with a variety of diseases, among them breast cancer, myeloma and leukemia. In fact, autologous stem cell treatments are now more common than allogeneic stem cell transplantation. However, allogeneic bone marrow transplants are still being used to treat congenital immune deficiencies, bone marrow failure and sometimes leukemia, while allogeneic peripheral blood stem cell transplants may be used to treat various blood disorders. (1,2)
The list of adult stem cell therapies is growing by the day. Only recently, Osiris Therapeutics, Inc., announced that the United States Food and Drug Administration had given the company permission to begin a Phase II clinical trial to evaluate IV mesenchymal stem cell treatment for Crohn disease. (3)
Given that numerous kinds of adult stem cell treatments already are firmly established, while many others are being assessed in advanced clinical trials, one may well ask why any scientist is keen to pursue human embryonic stem cell (hESC) research. The major reason why many researchers place their bet on therapeutic hESC research and therapeutic cloning is that embryonic stem cells are omnipotent; that is to say, embryonic stem cells are totally undifferentiated. This means that they may develop into any kind of tissue. The case is different with umbilical cord stem cells and other adult stem cells, as most kinds of adult stem cells are programmed to follow very specific differentiation paths, particular to each kind of tissue. Since the 1960s, it has been known that bone marrow, for example, contains at least two kinds of stem cells: hematopoietic stem cells, which normally form the different types of blood cells, and stromal cells, a mixed cell population that normally generates bone, cartilage and fibrous connective tissue.
However, today we know that some kinds of adult stem cells are more versatile than earlier thought: some kinds of adult stem cells are pluripotent and capable of developing into multiple types of tissue. In fact, hematopoietic cells may not only follow their normal differentiation paths and generate blood cells, but they may also transdifferentiate into other types of tissue, including brain neurons, skeletal muscle cells, cardiac muscle cells and liver cells. Likewise, bone marrow stromal cells may transdifferentiate into cardiac muscle cells (4) Moreover, today it is known that adult stem cells are not only found in blood and bone marrow, but can be found in many kinds of organ and tissue. (5)
A much-touted advantage of hESC and embryonic stem cell therapy is that it would make it possible to create stem cells identical with the recipient patient, which would overcome the risk of foreign tissue rejection. However, both embryonic stem cells and adult stem cells may be used for either autologous or allogeneic treatment, and as such, autologous adult stem cell transplants also present the possibility of avoiding transplant rejection.
Much hope, therefore, has been placed on autologous treatment using umbilical cord stem cells, and cord blood banks have sprung up all over the industrialized world. In Britain, the Rosie Hospital, which is part of Addenbrooke Hospital in Cambridge, is planning to setup a commercial umbilical cord stem cell bank where parents can store umbilical cord blood stem cells for their children. The bank will be run by the British Stem Cell Registry. The idea is to store cord blood taken at the birth of a child in case the child might need stem cell treatment in the future.
Of course, autologous stem cell therapy need not be restricted to stem cells obtained from umbilical cord blood or bone marrow. Professor Geoffrey Raisman, Director of the Spinal Repair Unit at University College Hospital, London, has announced that he and his team will start clinical trials using patients' own stem cells to treat spinal cord injuries. (6) The trials, which will start early in 2006 at the National Hospital for Neurology and Neurosurgery in London, are undertaken in the wake of 40 years of research on animals. In 1985, when he was working at the National Institute for Medical Research in Mill Hill, London, Professor Raisman discovered neural stem cells relating to olfactory ensheathing cells. Working with laboratory rats, he also found that these neural stem cells could be used to build a bridge across severed neural fibers. When receiving autologous treatment with olfactory ensheathing cells, rats whose nerves in the paws had been severed from the spinal cord regained paw movement and control. In addition, the animals regained the ability to breathe unaided. With this technique, there is hope that people who have suffered paralyzing spinal injuries will one day regain the ability to walk. The technique could also be used to restore bladder and bowel function, or other conditions involving damage to nerve fibers, such as some forms of deafness and blindness, as well as some forms of stroke.
Other adult stem cell treatments have already proved highly successful. One such treatment uses donated adult stem cells taken from the eye. This particular treatment is especially promising because there is no problem with foreign tissue rejection. The explanation for this amazing phenomenon is that the foreign stem cells act merely as catalysts triggering the regeneration of the patient's own cells. The technique in question has been pioneered at the Centre for Sight, at Queen Victoria Hospital, in East Grinstead, West Sussex, UK, where the sight of more than 20 people with damaged corneas has been restored. (7) The problem with this kind of patient is a shortage--or, as in the case of the treated patients, the complete loss--of limbal cells, the cells that protect the eye and keep the surface of the cornea clean and clear. Dr Sheraz Daya, the ophthalmic surgeon who carried out the treatment, has been working with his team on the new technique for five years. It involves taking limbal stem cells from the eyes of deceased donors and growing them into sheets of stem cells in the laboratory. These sheets are then transplanted to the surface of the injured eye. There they are kept in place by an amniotic membrane which dissolves as the sheet fuses with the cornea of the eye. The donated stem cells trigger the regeneration of the patient's own limbal cells. That this is the case is proved by the fact that when the patient is tested a year after treatment, there is no longer any trace of foreign DNA in the treated eye. Thus, not only is the repair of the injured eye permanent, but with this kind of treatment, there is no need to worry about tissue rejection and suppression of the patient's immune system.
If the biologic process could be unraveled, whereby donated adult stem cells act solely as a catalyst, triggering the regeneration of the patient's own cells, we might have a solution to the problem of foreign tissue rejection in connection with donated adult stem cells. Developments such as the ones illustrated here show that real progress is being made in the area of adult cell therapy. This is science, not fiction. More importantly, this is science which is respectful of human life and which shows that there is no need to go down the avenue of destruction, as in the case of therapeutic cloning, which necessitates the destruction of human embryos.
1. Lennard AL, Jackson GH. Stem cell transplantation. BMJ 2000;321:433-437.
2. Dainiak N, Ricks RC. The evolving role of haematopoietic cell transplantation in radiation injury: potentials and limitations. BJR Suppl 2005;27:169-174.
3. Osiris Therapeutics, Inc. Available at: http://www.osiristx.com.
4. Kuehnle I, Goodell MA. The therapeutic potential of stem cells from adults. BMJ 2002;325:372-376.
5. Rosenthal N. Prometheus's vulture and the stem-cell promise. N Engl J Med 2003;349:267-274.
6. University College London. New UCL Unit holds out hope of repair of spinal cord injuries. Available at: http://www.ucl.ac.uk/campaign/news/latest/newsitem.shtml?cnraisman.
7. The Queen Victoria Trust NHS, Annual Report 2001/2002.
This life that has been given to us as a gift, as such a precious gift. To really try to understand it, really try to recognize it, is the greatest meditation. Through the media of this knowledge we can tap into our inner sources that are so beautiful. --Prem Rawal
Agneta M. Sutton, PhD
From the Department of Theology, University of Chichester, Heythrop College, University of London, London, United Kingdom.
Reprint requests to Agneta M. Sutton, PhD, Department of Theology, University of Chichester, Heythrop College, University of London, London, United Kingdom. Email: firstname.lastname@example.org