The Irish Times - Thursday, December 15, 2011
William Reville is a professor in the Biochemistry Department and public awareness of science officer at UCC. understandingscience.ucc.ie
Overcoming stem cell research difficulties
WILLIAM REVILLE
PROPONENTS OF human embryonic stem cell research (HESCR) pitched their case for support on the basis that it would lead to cures in the relatively near term for a wide range of devastating human diseases.
Many people who have serious ethical qualms about HESCR were persuaded to stay quiet and to pay a “relatively small ethical price” for this dazzling medical potential. But suddenly all has changed – HESCR has entered very stormy waters and prospects that this approach will achieve significant medical cures, even in the medium term, have dramatically diminished. The story is summarised by Andy Coghlan in New Scientis t on November 18th, 2011.
Embryonic stem cells are pluripotent – they can turn into any of the more than 200 cell types found in human tissues. These embryonic stem cells therefore have great theoretical potential to repair and regenerate failing human tissue, thereby curing a wide variety of human diseases. However, HESCR confronts ethical and technical difficulties.
Human embryos must be killed in order to obtain human embryonic stem cells, but many people believe that the human embryo has the inherent right not to be deliberately destroyed. Many others, of course, including many scientists, do not share this position.
Ethics aside, it has proven to be extremely difficult to reliably coax embryonic stem cells to develop along a chosen path. For example, if you introduce embryonic stem cells into ailing nervous tissue, hoping that the cells will develop into healthy nerves, there is a significant chance that the cells will instead develop into another tissue type or perhaps into a cancerous tumour.
As a result, progress with embryonic stem cells has been very slow. Not only have no medical cures come out of this research to date but almost no clinical trials of potential cures have resulted. The California-based Geron Corporation, the largest biotechnology company dealing with stem cells, launched a trial of human embryonic cell treatment of spinal cord injuries about a year ago, but pulled out of the trial in November in favour of continuing research on new cancer drugs. To my knowledge, there is only one remaining clinical trial worldwide involving HESCR.
Proponents of HESCR now emphasise the value of this research in the study of human development. This is fundamental or “blue skies” research, quite different to the applied medical research used before to sell HESCR to public and political audiences. However, exactly the same ethical objection applies as before – human embryos must be killed to obtain the embryonic stem cells.
The good news is that two other stem cell options are available to medicine. One approach uses induced pluripotent stem cells (IPSC) and the other approach uses adult stem cells (ASCs). In 2005 Shinya Yamanaka of Kyoto University discovered how to induce ordinary cells to change into embryonic-like stem cells with the pluripotent potential to generate a large range of body tissues. These IPSCs are acceptable to those who oppose HESCR on ethical grounds. However, just as in HESCR, much difficult work remains to be done to develop the medical potential of induced pluripotent stem cells.
Most adult tissues in the body have their ASCs, which are not pluripotent but multipotent – they have the capacity to change into a limited range of tissue types. However, they are relatively easy to prepare, they are predictable and unlikely to form tumours.
Research using ASCs has been underway for many years. Successful medical treatments have been developed and about 200 clinical trials using ASC treatments are underway worldwide. The Australian company Mesoblast is using injections of adult stem cells to develop treatments for diabetes, bone disease, heart attacks and eyes.
Adult stem cells are now clearly leading the way clinically in terms of success rate, trial numbers and commercial potential. Some medical success could still come from HESCR if companies decide to invest heavily and take the risk. Treatments based on the new IPSCs are the furthest from the clinic but a massive research effort is underway and we can expect rapid progress here.
William Reville is a professor in the Biochemistry Department and public awareness of science officer at UCC. understandingscience.ucc.ie
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