IT HAS BEEN REPEATED so often that it is now a mantra: "Embryonic stem cells offer the most promise for finding cures" for degenerative diseases and conditions such as Parkinson's disease and spinal cord injury. But saying something ten thousand times doesn't make it true. Indeed, the embryonic stem cell mantra has yet to be demonstrated scientifically.
More than that, the actual data published to date in peer-reviewed science journals tell a far different story. While there have certainly been successes in embryonic stem cell experiments in animal studies--many of them hyped to the hilt in mainstream media reports--the numbers pale in comparison with the many research advances being made with adult and umbilical cord blood stem cells, which are already being used in human patients.
Based on the published science, there are 72 maladies for which human patients have received some benefit (which is not the same as being "cured") from adult stem cell or umbilical cord blood interventions. Meanwhile, embryonic stem cells have yet to demonstrate any human therapeutic use.
This is not to say that embryonic stem cells don't have genuine scientific value. Researchers are excited about the prospect of gaining a more fundamental understanding of developmental biology by experimenting on embryonic stem cells, for example. And embryonic stem cells may well have the capacity to treat human diseases. But to win the current political debate over federal funding of embryo-destructive research, many supporters have made extravagant claims about pending cures. In their zeal, they forget to mention that
embryonic stem cells cannot be used safely in human beings at present because of worries over tissue rejection and their demonstrated propensity in animal studies to cause deadly tumors--problems not associated with adult stem cell therapies.
Some adult/umbilical cord stem cell treatments are now deployed in routine clinical practice. But most remain experimental. For example, as reported in the March 2005 edition of the science journal Blood, Stage 2 trials are currently underway in human patients with "severe" multiple sclerosis using the patients' own blood stem cells. After three years, the study reported, adult stem cells were "able to induce a prolonged clinical stabilization in severe progressive MS patients," meaning the disease stopped advancing, "resulting in both sustained treatment-free periods and quality-of-life improvements."
Another area of great hope for adult stem cell therapy comes from using a patient's olfactory tissues, found in the nasal cavity, to treat paralysis caused by spinal cord injury. Peer-reviewed animal studies previously highlighted great potential for this technique. For example, olfactory tissues have "promoted partial resto r ation of function" in paralyzed rats.
Human studies in this area have been ongoing for several years. In June, Dr. Carlos Lima from Portugal published his first findings in the Journal of Spinal Cord Medicine. Of the first seven paralyzed people he treated, "two patients reported return to sensation of their bladders and one of these regained voluntary contraction of anal sphincter." Most "recovered sensation below the initial level of injury." Moreover, "patients exhibited a modest amount of improvement in function that is not normally observed in complete SCIs [spinal cord injuries]," leading to the conclusion that olfactory mucosa "may possibly promote functional recovery in chronic, severe SCI in humans." (Further human trials have now commenced using olfactory tissue in Britain, Italy, and Japan, among other countries.)
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