EMBRYO RESEARCH

What is the human embryo?

The human embryo is formed when a sperm penetrates an egg, fertilising it and forming a unique genetic identity. After four days the embryo gains an outer layer of cells which become the placenta, and an inner cell mass which will become the fetus. That minute, growing thing becomes itself and its environment! Over the next 14 days the embryo travels up the fallopian tube to the womb, where it settles in the womb wall and starts to grow. In that time it might divide and become two or even three identical twins/triplets. Normally, about 70% of all embryos never reach the womb.

When does life begin?

The legal status of the embryo

The Human Fertilisation and Embryology Act of 1990, and subsequent regulations passed by Parliament in 2001, permit under strict controls the use of the embryo for research purposes up to 14 days. Then it must be destroyed. These embryos will have been created by in vitro (literally ‘in glass’) fertilisation (IVF), that is, outside the woman’s body.

IVF treatment is offered to parents who for various reasons cannot have children in the ordinary way. The mother has to take drugs so that she produces more eggs than normal. Those eggs are then removed from her body and fertilised by her partner’s sperm. As many as twelve eggs will be fertilised in vitro. Then up to two embryos will be replaced in the mother’s womb. These embryos can be tested for genetic conditions (see Designer Babies) before they are implanted.

That leaves ten spare embryos. They may be frozen for future pregnancies, but, with the parents’ permission, they may also be used for research. If they are, they must be destroyed within 14 days.

Should those embryos only be used to create human life or can they be used for research, if the research is aimed at helping other humans to live?

UK law also permits the creation of human embryos by means of cell nuclear transfer, more popularly known as therapeutic cloning. This technique could be used to create cloned human beings. It involves taking a cell from an adult human, removing the cell’s nucleus, which contains all of that person’s DNA or genome, and putting it into an enucleated human egg. The egg with the replacement nucleus is ‘tricked’ into thinking it is fertilised and starts to grow as an embryo. Were it to be placed in a woman’s womb it could develop as any other embryo could, and a cloned human being could result. The law does not permit this (Human Reproductive Cloning Act of 2001). These cloned embryos must also be destroyed after 14 days.

Why is the embryo of interest to medical researchers?

The inner mass of the embryo consists of stem cells. These cells are what ultimately become all the different cells of the human body, from fingernails to lungs. If they are removed from the early embryo (which destroys the embryo) they can be channelled to grow into whichever cells are needed for treatment. Currently incurable diseases, such as Parkinsonism, Alzheimer’s Disease, liver and heart disease, are all potentially curable by the creation and transplantation of healthy cells specific to the diseased area: neural cells for Parkinson’s or Alzheimer’s, and heart and liver cells for heart and liver disease.

Is it right to use embryos as a means to an end and then destroy them? What if they are being used to cure lots of very sick people?

If the stem cells are genetically identical to the patient needing the cell transplant, then there is no rejection of the donated cells. This is the advantage of cell nuclear transfer or therapeutic cloning. The patient gives a cell of his or her own body, the nucleus of which replaces the nucleus in the egg, thereby creating an embryo which is a clone of the patient. Stem cells harvested from such an embryo will be genetically identical to the patient needing the transplant.

Will someone use the technique of therapeutic cloning to create a human clone? Should the technique therefore not be developed at all?

Cells have the capacity to divide and proliferate. This means that once stem cells have been harvested from embryos, they can continue growing on their own as stem cell lines. A bank for stem cell lines has been established by the UK Government, overseen by an ethics committee. This bank will provide a continuous source of stem cells for future research and treatment. So there is no need to think that embryo factories will be needed for stem cells in the future.

But there is a long way to go before embryonic stem cells can be used for treatment. Stem cells can be found in other parts of the body, and these are also being researched for possible treatment. Such sources of stem cells, which do not involve using embryos at all, are showing great therapeutic potential. The consensus amongst scientists, however, is that more understanding is needed of the development of stem cells in embryos before other sources of stem cells can be usefully and safely adopted.