Origins, ethics and embryos: the sources of human embryonic stem cells

Last updated:
5 Nov 2015
Origins, ethics and embryos: the sources of human embryonic stem cells

Where do researchers get embryonic stem cells? This is the question that gives rise to much of the controversy surrounding human stem cell research. Should scientists limit themselves to using embryos left over from fertility treatment? Why not create embryos especially for research and maximize our chances of success?

Did you know?

There are over 300 existing human embryonic stem cell lines available in the world; about two-thirds of these are in just five countries: UK, Sweden, France, Spain, USA

Human embryonic stem cells growing on feeder cells

Human embryonic stem cells growing on feeder cells

Human blastocyst at six days old

Human blastocyst at six days old

Nucleus being injected into an egg cell in somatic cell nuclear transfer

Nucleus being injected into an egg cell in somatic cell nuclear transfer

Dolly the sheep

Dolly the sheep

Embryonic stem cells in research

Embryonic stem cell research focuses on stem cell lines. These are populations of cells, all carrying the same genes, grown in the laboratory through many cycles of growth and division over many generations of cells. One cell line can supply lots of researchers with huge numbers of cells.

There are three main sources of human embryonic stem cell lines.

  1. Cell lines that already exist.
  2. Spare embryos left over from fertility treatment.
  3. Custom-made embryos created by somatic cell nuclear transfer (SCNT), the technique used to create the sheep, Dolly.

Existing embryonic stem cell lines

Some people oppose using human embryonic stem cells under any circumstances. However, the use of cell lines that already exist is the most widely accepted source of stem cells. This acceptance is based on the argument that what’s done is done. Even if harvesting the embryos in the first place could be considered morally controversial, nothing can now be done to save the original embryos from which the lines were created.

Using spare embryos from fertility treatment

People who oppose using this source of cells for research are concerned that it shows a lack of respect for the embryos and therefore for human life. Here is a summary of the arguments for and against using spare embryos.

Arguments for using spare embryosArguments against using spare embryos

There is no reason to believe that the destruction of embryos will undermine society’s values – for many years embryos have been created and used for IVF and no significant change has been observed in how we value human life.

If it is morally acceptable to use embryos for fertility treatment, it should not be immoral to sacrifice embryos for curing devastating diseases.

The spare embryos are going to be destroyed anyway, once the time limit for keeping them in the freezer has expired; it is better not to waste these embryos, but to use them in research that could benefit people.

If stem cell therapies become routine treatments, then human embryos could be exploited as a source of therapeutic materials, which might indicate a decreasing respect for human life.

This is the beginning of a slippery slope leading to dehumanizing scenarios like embryo farms, cloned babies and fetuses used for spare parts.

This could encourage society to tolerate the loss of life to save a life. Where could that lead?

Using embryos created in the lab for research

Some people argue that it is morally worse to create an embryo with the intention of destroying it in research, than it is to create spare embryos as a byproduct of fertility treatment, where there was at least a chance that human life could be created.

However, such embryos will have a better chance of meeting the needs of patients because they can be produced from a specific patient as a source of cells that are compatible with that patient.

Therapeutic cloning – condemn or condone?

Therapeutic cloning is a term used to describe the creation of stem cells for use in a medical treatment for a particular individual. In fact, these cells are not used for treatments yet and would certainly not be put into a patient at present.

In practice, therapeutic cloning currently means creating an embryonic stem cell line by a technique called somatic cell nuclear transfer (SCNT). In this process, the nucleus of an adult cell from an animal is transferred into an egg cell that has had its nucleus removed. The embryo can be allowed to grow to a very early stage of development, and then used as a source of stem cells. In the future this method could provide a source of cells for therapy.

Therapeutic cloning: Somatic cell nuclear transfer can be used to create new embyronic stem cell lines.Therapeutic cloning: Somatic cell nuclear transfer can be used to create new embyronic stem cell lines.

There is no consensus on the ethical implications of therapeutic cloning.

Arguments for allowing therapeutic cloning
Arguments against allowing therapeutic cloning

The potential for huge benefits to human kind in the future outweighs any wrong-doing.

Even if destroying embryos is classed as killing, sometimes society may  justify killing to save the lives of others: eg if Hitler had been assassinated, millions of lifes would probably have been saved.

Embryonic stem cell lines could be created from the cells of patients suffering from rare, complex diseases, creating a vast resource that can be used by many scientists.

Misguided individuals could attempt to implant cloned human embryos in a woman’s uterus to create a cloned person (known as reproductive cloning). There are laws against this in many countries, but not all.

Commercial pressures and international competition could drive scientists to conduct more and more research on embryos, which would just become a resource for researchers.

The eggs used to create embryos in this way have to be donated by women, who could be exploited for their eggs, especially in poorer countries or places with fewer legal restrictions.

Does the end justify the means?

The source of human embryonic stem cells is not the only ethical issue to consider. It is uncertain who will benefit from stem-cell-based therapies, but it seems unlikely that the poorer countries in the world will reap the rewards, at least to begin with. Many other ethical questions are raised by the prospect of new therapies, and by discoveries such as induced pluripotent stem cells.

Find out more

Extended factsheet with a fuller discussion of the issues by Kristina Hug (pdf)
EuroStemCell factsheet on the ethical debate about use of embryos in research
EuroStemCell factsheet on the science of embryonic stem cells
Video of the SCNT process being carried out
EuroStemCell factsheet explaining induced pluripotent stem cell technology
EuroStemCell summaries of stem cell regulations in Europe
Research paper on the ethical issues relating to sources of embryonic stem cells

Acknowledgements and references

This factsheet was created by Kristina Hug and reviewed by Göran Hermerén.

Human blastocyst and human embryonic stem cell images by Jenny Nichols. Injection of nucleus in SCNT and Dolly the sheep by the MRC Centre for Regenerative Medicine at the University of Edinburgh.