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Why human stem cells should concern us

What is special about stem cells?

THERE is nothing, it seems, quite like stem cells. They are capable of developing into any of the many cell types that make up the human body. This potential to be converted into a wide range of specialised cells is widely expected to pave the way for truly revolutionary future treatments for many human diseases, some of which are presently untreatable.

Doctors, scientists and biotechnology companies are keen to use stem cells to replace missing, dead or diseased cells and tissues. A few examples will serve to illustrate the considerable potential of stem cells to relieve suffering and cure disease.

Thus, it may be possible in future to cure Parkinson’s disease using new brain cells with the ability to produce the missing nerve chemical, dopamine; to provide diabetics with new insulin-secreting cells that will abolish the need for daily insulin injections while providing excellent blood glucose control; or to cure paralysis by repairing spinal cord injuries with new nerve cells that re-establish normal connections between brain, spinal cord and muscles. Little wonder then that the world can hardly wait for stem cell technology to become medical reality.

Stem cells are found naturally in the body, although not in great abundance. Embryonic stem cells are obtained from human embryos and foetuses, while adult stem cells are taken from blood and body tissues after birth (Diagram 1 — above).

First, an outline of how embryonic stem cells are obtained. The human body begins its development as a single cell formed by fusion of an egg cell (oocyte) and a sperm (Diagram 2 — facing page). Fertilisation occurs in the outer reaches of a fallopian tube, after which the single fertilised cell divides many times while simultaneously moving towards the cavity of the womb. Each division doubles the number of cells. In this manner, the embryo soon becomes a cluster of cells. After a few days, a central cavity appears inside the embryo which, at this stage, is known as a blastocyst. The blastocyst soon takes root (implants) in the lining of the womb where a fully-formed baby eventually develops. Embryonic stem cells are derived from cells that form the inner part of the blastocyst (known as the inner cell mass). The process of removing these inner cells destroys the blastocyst.

Embryonic germ cells are derived from the primitive gonads of foetuses, typically from abortions. Like stem cells, embryonic germ cells are capable of developing into many different cell types.

Stem cells can be obtained also from non-embryonic and non-foetal sources. Adult stem cells are found in blood (including umbilical cord blood of newborn babies) and several tissues such as bone marrow, liver and brain.

In order for stem cells to be medically useful, scientists need to devise ways to keep stem cells dividing in their “primitive” state (in which they have the greatest potential to form any type of cell), as well as develop reproducible and safe methods of changing — on demand — the growth environment of stem cells in order to produce the specific cell type required for treatment of individual patients.

The convergence of strong scientific and commercial interests in advancing stem cell technology has resulted in intense publicity. High expectations have been generated as a consequence, while media hype may be misleading the public into thinking that powerful new treatments from stem cells are imminent.

More research needed
In reality, the anticipated benefits are still years away because much remains unknown about stem cells. Much more research is essential before the dawn of cell replacement treatment. It is neither possible nor proper to offer stem cells as medical treatment as long as many uncertainties exist. There are, at present, no clear answers to many questions about stem cells and their behaviour.

For example, how are stem cells identified? How many different types of stem cells are there? Where are they all found? What causes stem cells to acquire specialised functions e.g. secretion of insulin or conversion into muscle cells? What occurs during the process of specialised conversion? Are there limits to what stem cells can be made to do? Are adult stem cells and embryonic stem cells equally versatile? How can stem cells be made to acquire different specialised functions in the laboratory? Is the specialised state permanent or reversible? How durable are engineered stem cells when introduced into the body? Could treatment with stem cells increase the risk of developing other diseases, such as autoimmunity and cancer? Can stem cells be customised to the immunological profile of individuals?

Society should study how scientific advances could and should be used

Stem cell research controversial
Despite the enormous potential of stem cell technology to relieve suffering and improve human health, recent advances in this field of research have raised issues that trouble people of faith, including Christians. The fundamental ethical and moral dilemmas can be distilled in a few questions. What constitutes human life? When is the embryo or foetus a living human being? Is it ever right to take one human life to benefit another?

Some take the view that humankind ought not to be denied the potential benefits of vastly superior treatment methods while maintaining some (diminished) respect for life. Several mental devices have been proposed to circumvent the moral dilemma and achieve the desired equipoise. Thus, it has been argued that the early embryo becomes a living human being only beyond certain stages of development such as after certain physical structures have formed, when the stage of potential individuation has passed or after the onset of sentience. These form the basis of the well-known 14-day rule. The natural corollary of this view is that the destructive use of early embryos (e.g. blastocysts) does not amount to killing.

Others hold that the single fertilised cell from which all human development starts is life, albeit at its very beginning. In this absolutist view, destruction of blastocysts (to say nothing of foetuses) to subserve the medical needs of other humans cannot be sanctioned. In the parlance of cloning, therapeutic cloning is the intentional production of embryos solely for purposes of treatment, not with the aim of producing a fully formed human. Those who hold that human life begins at conception also maintain that therapeutic cloning lies on the wrong side of the moral divide.

It may be possible in future to produce human blastocysts directly from single egg cells (oocytes) without fertilisation by sperms. (This unusual form of reproduction occurs naturally in some non-human species.) Some have suggested that this phenomenon, known as parthenogenesis, could be used to obtain stem cells for medical treatment. The use of parthenotes (embryos formed by parthenogenesis) could be morally more widely acceptable than conventional therapeutic cloning because parthenotes are believed to be incapable of completing the normal developmental pathway (i.e. cannot develop into a normal, fully formed human).

How should Christians respond?
Recent biomedical research has thrown up several difficult ethical and moral problems, of which those raised by stem cell technology are only one example. It is imperative that society as a whole should engage in knowledgeable and open discourse on how scientific advances could and should be used. While Christians do have sincere differences on these difficult issues, we need to recognise when intellectual and moral integrity is abandoned for utilitarian goals. The quest for sound foundational principles and values that should underpin the conduct of research and the application of scientific advances in the service of communities should be clothed in humility not hubris, be resolved by rational reflections unclouded by vested material interests and driven only by the desire to do what is right rather than what is expedient.

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‘The quest for sound foundational principles and values that should underpin the conduct
of research and the application of scientific advances in the service of communities should be clothed in humility not hubris, be resolved by rational reflections unclouded by vested material interests and driven only by the desire to do what is right rather than what is expedient.’

Dr Kon Oi Lian is Director, Division of Medical Sciences at the National Cancer Centre, and Associate Professor of Biochemistry at the National University of Singapore.