Stem cell research
The potential to break bottlenecks in medicine
PUBLICITY IN the media portrays stem cell research as enabling the transplantation of healthy tissue to replace diseased or malfunctioning tissue. The promise is held out that those suffering from degenerative conditions such as diabetes and Parkinson’s disease, could be cured.
Roy Farrar looks into these possibilities, and the controversies around them.
DIFFERENT COUNTRIES have adopted varied and inconsistent legislation to regulate stem cell research. However, the battle lines are sharpest in the USA. There, the plight of certain celebrities (eg Christopher Reeve and Michael J Fox) has been used by politicians and others to protest against the Bush administration’s restrictive policy on stem cell research.
Bush’s decision to restrict US federal funding to investigating only embryonic stem cell lines created before August 2001 (as they were created from embryos that had already been destroyed), was claimed as no restriction at all!
Leon Kass, chair of the President’s Council on Bioethics, claimed that Bush’s policy, “provides an effective way to vigorously promote embryonic stem cell research and seek cures for disease without violating respect for nascent human life” (Washington Post October 2004).
Bush and his supporters lied in their claim that over 60 embryonic stem cell lines created pre-August 2001 were viable. Scientists prior to Bush’s 2001 decision had already found that most of the so-called existing lines were not viable in some way. The Bush administration stonewalled, then eventually admitted this.
The embryonic stem cells in question are from ‘in vitro’ sperm, and because they are the frozen ‘left-overs’, many scientists already doubted their usefulness. These cells mainly originate from affluent, middle class, white males who have fertility problems. Hardly a representative cross section of human populations in the USA, never mind the world. Any lines from these would lack the diversity of tissue type to provide cells for transplantation therapy. The nature of any stem cell lines derived from them would inevitably distort research conclusions that are intended to apply to the population as a whole.
Scientists recognise the need to spread the ‘genetic net’ to include the whole range of human diversity. Stem cells are required from individuals who have tissues containing the specific diseases to be studied. That is, embryonic cells that carry the genes of those suffering from diabetes, Alzheimer’s, cystic fibrosis, all the many kinds of cancer, and so on and so forth.
Research implications
AT SOME time in the future, transplantation may be a widespread therapy. But this is not the whole, nor probably the main outcome of the research. Laurence S B Goldstein’s notable speech (Rice University, November 2004) clearly delineated how stem cell research could break four major bottlenecks in medicine.
Firstly, an insufficient amount of cell tissues available for transplantation. Therefore, the answer would be to grow all different types as needed from embryonic stem cells.
Secondly, research and development of new drugs is expensive and not always conclusive. Animal trials are controversial and the results can be misleading. Testing drugs on embryonic stem cells could greatly assist in determining which therapies are more effective.
Thirdly, many areas of how diseases actually develop are not fully understood. But having stem cells with the genetic signature for a specific disease could allow a more comprehensive observation and study of diseases. ‘Somatic cell nuclear transfer’, known more commonly as ‘therapeutic cloning’, involves extracting the nucleus from a cell of an individual suffering from a specific disease.
The nucleus is then implanted into an unfertilised egg which is encouraged to divide and thus start a new stem cell line. We can learn how diseases develop. This research is likely to suggest new ideas on how to treat various diseases.
Finally, medical drugs presently in use are usually manufactured on the basis of ‘one size fits all’. The variations amongst individual patients mean that responses to drugs, and any potentially harmful side-effects, are not fully predictable. Human drug trials have their own disadvantages; often even large groups of individuals cannot reflect the fuller spectrum of the human population for whom the drugs are being targeted. Embryonic stem cell research opens up the possibility of creating a future medical arsenal of tailor-made therapies to suit the individual patient.
What is the controversy?
THE CONTROVERSY to a large extent exists only in the fevered minds of the anti-stem cell research campaigners, the religious right, the ‘pro-lifers’, and so on, who have found vocal allies in US president Bush and other right-wing politicians globally. Those who wish to generate opposition to certain areas of knowledge and research have learnt that faith based objections are not enough on their own to gather support for a moratorium on science.
This controversy has parallels with other so-called controversies. The creationists and the ‘intelligent designers’ realised that just denouncing evolution would not carry enough weight on its own. Their thinly disguised religious beliefs are posed as alternative or equal theories to that of evolution – a false even-handedness used as a Trojan horse to get their views publicity.
The tobacco companies, unable to deny outright that smoking was harmful, publicised ‘alternative’ scientific research to obscure that whole debate. A similar sorry story is still playing over climate change as vested interests try to sow doubts about what should be done, their aim being to protect the profits of the energy industry.
The opponents of stem cell research have learnt how to muddy the waters. ‘Bad science’ arguments are pushed forward. The so-called debate is artificially portrayed as adult versus embryonic stem cell research. In fact advances in stem cell research are more a question of how the two can complement each other.
The ‘pro-lifers’ and their allies allege that everything could be done using only adult cells. But the evidence mounted that adult cells are not sufficient. They are limited in supply, as only tiny amounts are found in any human tissue and hence they are described as ‘evanescent’. They also lack the robust growth of embryonic cells.
Then claims were made that adult stem cells have the ‘surprising ability for transformation into other tissue and cell types’. It has long been known however that once our primordial embryonic cells have differentiated or specialised into the various cell tissues they don’t ‘evolve’ back! “Surprising” is hardly the word!
Even if adult cells (with a mighty big “if”) could somehow be made to ‘un-specialise’ into all the many types of body cells, that would still not be sufficient to sustain research into the understanding of processes of early cell development required to break the above-mentioned bottlenecks in medicine.
Properties of stem cells
EMBRYONIC STEM cells have the ability to be pluripotent – to become every different kind of body cell. They were named ’embryonic’ because they were first noted in embryos, though adult laboratory mice have long been recognised as having both adult and embryonic stem cells.
Adult (or ‘mature’) stem cell tissue is specialised tissue that has the characteristics for cells in specific body organs: the cells in the blood, the heart, etc. Bone marrow transplants are now known to work through the ability of adult stem cells to renew blood cells.
Self-renewal is the key property of stem cells. Other cells divide into two daughter cells, but a stem cell divides unevenly: into a new stem cell and a progenitor cell. The progenitor cell loses the power of self-renewal, but gains the ability to change into the mature cell types of the specific tissue served by the stem cell.
After division, the number of stem cells in the tissue remains unchanged because one stem cell has been lost and one created. The stem cell population thus renews itself as it generates new body tissue. This self-renewal means that stem cells are sometimes referred to as being immortal.
The stem cells responsible for maintaining a tissue or an organ seem to have some way to regulate their own numbers, perhaps by sensing through an exchange of chemicals amongst themselves. It is thought that the key to successful cancer research may lie through exploring the idea that tumours could be the result of unrestrained stem cell growth.
