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Stem cells are master cells of the human body which can do one of two things. They can either simply make copies of themselves, or they can produce other types of specialised cells. The very early embryo contains stem cells which slowly specialise to produce all the cells of the body. Adult cells can now also be reprogrammed in the laboratory so that they return to an embryonic-like state and can be used to make all kinds of specialised cells.

Author / translator Andrea Bandelli


Stem cells are master cells of the human body which can do one of two things. They can either simply make copies of themselves, or they can produce other types of specialised cells. The very early embryo contains stem cells which slowly specialise to produce all the cells of the body. Adult cells can now also be reprogrammed in the laboratory so that they return to an embryonic-like state and can be used to make all kinds of specialised cells.

The medical importance of stem cells

Stem cells taken from embryos or created by reprogramming adult cells would not be injected directly into the adult body because of a risk that they might go on copying themselves and become cancerous. But they can be induced under special conditions in the laboratory to grow into (in principle) any type of cell in the human body. This would give a ready source of cells to replace ones that normally can’t be replaced once damaged, such as heart and nerve cells. Take a patient with a spinal cord injury. They might be helped to recover if nerve cells were injected into the spinal cord. Nerve cells might also be able to slow or even stop Parkinson’s disease. Pancreatic cells might bring diabetes under control, and so on. The potential is clearly enormous, but at this early stage in the research it is difficult to know how many of these hopes will indeed become viable therapies. To extract stem cells from embryos is very controversial and the techniques for reprogramming cells are very new. It is not yet known whether reprogrammed cells will be able to do everything that embryo-derived cells can.

Created 2 February 2010
Last edited 21 June 2018
Topics Ethics, Health, Science

Policy positions

Policy position 1

Stem cell research is only to be carried out on adult or cord blood stem cells.

Policy position 2

As well as adult or cord blood stem cells, stem cell research can also be carried out using ‘surplus’ embryos under 14 days old that would be destroyed otherwise.

Policy position 3

In addition to position 2, stem cell research can be carried out using embryos created specifically for research by IVF.

Policy position 4

In addition to position 3, embryos can be cloned for stem cell research.

Story cards


Anna Fitzgerald is a scientist working on induced pluripotent stem cells cells. She is optimistic about the potential of reprogramming cells and thinks stem cell therapies will be hugely important as a way to treat the underlying causes of many serious diseases. However, she knows such therapies are still a long way off and thinks we should not rush into clinical trials. She is also concerned that a lot of resources will be needed to make therapies available to a lot of people in a cost effective manner. She wants her research to provide benefits for everyone, not just a small group of rich patients who can afford specialist treatment.

Anna Fitzgerald

Liz Hopeful has been married for 5 years. She would really like to have children but it hasn’t happened. So she and her husband have started IVF treatment. The first cycle of treatment failed but they still have 6 embryos in cold storage. All of them have names. One of the forms asked if they were prepared to donate some of the embryos from the IVF treatment to stem cell research. The idea that embryos be experimented on horrifies Liz. However, if she does have a baby she might consider having her baby’s cord blood stored even though therapies using cord blood stem cells are a long way off.

Liz Hopeful

Father O’Reilly is a Catholic priest. He sees a lot of suffering around the world and in his own country and feels a deep compassion about this. But true to a stream of his church’s teaching, he believes that a human embryo is a sacred life from conception onwards. This means that it is impossible to accept any kind of research on embryos. Experiments should only be done on stem cells obtained from cord blood, or on iPS cells. He thinks scientists do not concern themselves with the spiritual laws and should be guided by those who do.

Father O’Reilly

My name is Áron Sárallyai. I am a 23 year old university student. I was born with an inherited primary immune deficiency, which caused many difficult illnesses during my whole life. My state of health was getting worse and worse during the last few years and finally it became serious. The only treatment that has helped has been stem cell therapy. I received the stem cells from a foreign adult donor, to whom I am so thankful. The process was painless for both of us. With the donated stem cells my immune system can be the same as the donor’s immune system. I got a chance to be healthy. I support stem cell therapy, but only with adult volunteers, as it can cure serious diseases. However, I would urge everyone to be cautious, as it is not a miraculous solution, but with sufficient attention, it can help many people.

Áron Sárallyai

Sir Grant Cameron heads one of the leading research teams on embryonic stem cells. He is disturbed by what he sees as the blatant emotional appeal of those opposed to embryo research. It is irrational to ascribe human moral status to what is just a ball of cells at this very early stage of its development. In media appearances he appeals for an intelligent, rational debate. How can others deny a cure to so many? He thinks it’s immoral to stand in the way of this research which could find cures for these debilitating diseases. Even now that iPS cells can be created, he believes embryonic stem cell research is vital to help scientists understand how stem cells work.

Sir Grant Cameron

Janice Fortune has been an entrepreneur all her life. She has set up a company to create human stem cells for research and eventual clinical practice. She cares about sick people and is aware of ethical issues, but her primary concern is how to run a viable company when it could still take 10 years or more to fulfil the huge promise of stem cells. If embryos look to be able to deliver the fastest results, she will use them; if adult or iPS cells look best, she will opt for that route.

Janice Fortune

Ted Murdoch is 50 years old and has a good career. He is close to his family and looking forward to eventual retirement. But he has been diagnosed with Parkinson’s Disease and is already losing some functional ability. This disease scares him. He will die slowly and probably give much pain to his family on the way. He doesn’t want to be a burden. He has heard about stem cells as a possible cure and feels it could save people like him. He has become a strong supporter of all kinds of stem cell research, including the use of embryonic stem cells. Together, scientists using all these different approaches must surely beat the disease.

Ted Murdoch

Amanda is a young cell biologist at a leading stem cell research institute. Recently, government regulators licensed her boss to use cloned embryos, made using a blood sample from a patient with motor neurone disease. Stem cells would be taken from the patient to create a supply of cells which exhibit the disease. Amanda has misgivings about creating embryos just for research. She is worried that maverick scientists could use the results to try to make cloned babies. The project is speculative, but might achieve real breakthroughs in understanding an awful disease. She struggles to work out where she stands.

Amanda Prentice

Zed is a transhumanist. For him, regenerative medicine with stem cells is only a short term goal. He anticipates a convergence of reprogramming, genetic, stem cell, cybernetic and nanotechnology research which will open up techniques for creating permanent human genetic changes and much else. These would not only eliminate genetic diseases but would also enable enhancements. We could expand our intelligence, extend our sensory capacities, increase our endurance and overcome ageing. He scorns our current religious and ethical short-sightedness. We should grasp our human destiny in our own hands. All regulation risks denying us that destiny.

Zed Omega

Dr. Sharon Taylor is a neurosurgeon and often sees patients who are paralysed as a result of a serious injury to their spinal cord. She keeps up to date with the latest developments and is keen to try the latest technologies, but she is worried that stem cells are often presented as a magical cure. She feels under pressure from patients and their families to perform stem cell transplants whatever the risk. However, she knows that such therapies have not been thoroughly tested and clinical trials are only just beginning. She is not prepared to use stem cells until a safe and effective therapy is available, but she worries that desperate patients will turn to unscrupulous people who might exploit them to make money, despite health risks.

Dr. Sharon Taylor


A big potential

If the power of embryonic stem cells can be harnessed and we are not prevented by opponents, we have the potential to treat a wide range of currently untreatable fatal diseases.


When does human life begin?

What is an embryo?

What status should we give to a 14 day old embryo:
• a cluster of cells;
• a potential human being;
• a form of life;
• fully human life, with all the rights a human baby has?

Justification for research

Is the prospect of treating currently terminal illnesses justification enough for stem cell research using human embryos?

An ethical trade-off

In embryonic stem cell research, embryos under 14 days old are destroyed. Some people argue it is unacceptable to destroy a new life, even to save the life of an ill person. Where does the balance lie?

Whose moral values?

How important are moral values of the past? Should we still be bound by them or should we adjust our moral values as times change?

Science and human values

Are deeply rooted human values being sacrificed under pressure from scientific innovations? Or can we find a good balance?

What use of embryos is justified?

Is it wrong to create embryos just for stem cell research? What about using surplus embryos from IVF or embryo selection that will be destroyed otherwise?

Spare parts machines?

If we create embryos simply to use them as a source of stem cells is it treating embryos like a resource for getting spare parts? If so, is this okay or not?

Other issues related to pregnancy

Should we be allowing IVF (in vitro fertilisation or ‘test tube’ babies) and/or PGD (selecting embryos to avoid serious genetic diseases)?

A slippery slope?

Does the creation and use of cloned embryos and reprogrammed cells bring us nearer to creating cloned human babies?

One step at a time?

Should we do research with cloned embryos now? Or should we wait until we have thoroughly explored the potential of stem cells taken from spare IVF embryos or from adult tissue? Should the ability to reprogram cells change our view on using embryonic stem cells?

Which moral limits should science have?

Should we place moral limits on science? For example, only allow non-embryonic stem cell research? How might that affect the progress of research? Does that make a difference to your moral standpoint?

The limits for embryo research and abortion

Are the 14 day limit on embryo research and the 24 week limit on abortion based on science or moral distinctions, or are they just arbitrary legal boundaries?

Limiting the use of science

A UN ban on human cloning is proposed. Should society seek to limit certain applications of science? Or will it always be done, if it can be done?

Who should be involved?

Who should be involved in developing stem cell technologies and therapies - government, private corporations, foundations or trusts, academic institutions?

Other uses for the money

Should the research money for all stem cell research be reallocated to the foreign aid budget, to increase basic healthcare in poor countries?

Effects on developing countries

Will these technologies make the global divide between rich and poor better or worse?

Stem cell research is not just about embryos

Adult stem cells are already used in treatments, e.g. in bone marrow transplants for leukaemia. All stem cell research can help improve understanding of how stem cells work. Does this affect your view of embryonic stem cell research?

Raising expectations

Are we falsely raising expectations of cures for people suffering from degenerative diseases?

Embryo research and quality of life

How far are we justified in doing controversial research with embryos to help an ageing population live longer? What if the quality of very old age cannot be improved much?

Accepting that we all die sometime

Is there eventually a limit to medical research? Is there a point where we have to accept our mortality and the reality of suffering?

A question of democracy

How democratic is policy making on these issues and how democratic should it be?

The role of society

Even in medicine, researchers must not just make up the rules to suit their aims. Society has a right to say what should or should not be researched. How far should this be taken? How much control over research should society have?

Who should pay?

Stem cell research has great potential for treating serious diseases. However, where should funding for important research come from? Who should pay for the expensive process of creating patient-specific stem cells and specialised cells for disease treatment?

What regulations do we need?

Induced pluripotent stem cells (iPS cells) could potentially be used to create many cloned babies from an adult’s cells. What regulations should be put in place to control how iPS cell research is developed and applied? How can we legislate for future developments?

Is it a question of politics?

If research is tightly controlled by regulation and legislation, is there a risk that science becomes too much of a political issue? How much influence should non-specialist political lobbyists have?

What are stem cells?

Stem cells are master cells of the human body which are able either to produce copies of themselves, or to produce other, specialised types of cells.

Stem cells in embryos and adults

In the embryo, stem cells gradually specialise to produce all the cells of the body.
In adult tissue, stem cells exist to keep regenerating particular body cells during the person’s life.

Where do stem cells come from?

extracted from:
• Embryos
• Some adult tissues (e.g. bone marrow)
• Placental cord blood
• Amniotic liquid

Storage and use of stem cells

Scientists are able to isolate stem cells and keep them indefinitely in the laboratory. They can induce some stem cells to turn into specialised cells, e.g. nerve, skin, blood cells.

The benefits of stem cells

Stem cells - or specialised cells derived from them - might be able to slow or even stop some degenerative diseases, repair damaged tissues, or cure burns.

What are degenerative diseases?

Degenerative diseases can affect people of any age, from childhood through to old age. They include:
• Parkinson’s
• diabetes
• cystic fibrosis
• multiple sclerosis
• muscular dystrophy
• hepatitis
• osteoporosis

The status of current research

Research in this field is at an early stage. One day, stem cells may lead to cell replacement therapies, but it is unknown how effective these would be.

Taking stem cells from embryos

Embryonic stem cells are usually taken from embryos created by in vitro fertilization. The cells are taken when the embryo is about a week old; it has 30 - 150 undifferentiated cells and measures 0.14 millimetres. The embryo is then destroyed.

Which embryos do stem cells come from?

Embryos used in research are mostly ‘surplus’ from clinical treatments like IVF. Some countries permit them to be created specifically for research.

Surplus embryos

In IVF, ‘surplus’ embryos arise when more embryos are created than a couple wants to implant. Currently there are hundreds of thousands of these embryos stored in Europe and destined to destruction.

Adult stem cells

Stem cells are found in adult tissues such as bone marrow and the brain. They are few in number and are often difficult to obtain.

Limits of adult stem cells

Adult stem cells usually produce only the few types of cells that are related to that particular part of the body (e.g. bone marrow producing different types of blood cells but not liver cells).

iPS cells

Induced pluripotent stem cells (iPS cells) are very similar to embryonic stem cells. They are made by reprogramming adult cells and can be used to grow all the different specialised cells of the body. A whole mouse can be grown from iPS cells combined with host embryo cells.

Stem cells from placental cord blood

Stem cells are found in placental cord blood at birth. They are more abundant than adult blood stem cells, easier to obtain, and may pose fewer rejection risks. However, recent research suggests they cause cancer when used to treat disease.

Banking’ cord blood

If placental cord blood cells could be turned into other cell types, cord blood could be frozen at birth and ‘banked’, to be available for cell therapy in later life. Therapies of this kind are still a long way off at the moment, and may prove not to be practicable because of technical hurdles and cost.

The 14 day limit

In human development the embryo implants into the womb about 7 days after fertilization at which time the first steps toward cell differentiation begin. The first stages of the nervous system appear after 14 days. This is the legal limit for research on embryos.

Reasons for the 14 day limit

Before the 14 day limit for research an embryo may split into twins. About half of all embryos, or perhaps even more, abort naturally because of spontaneous genetic abnormalities such as extra chromosomes in their DNA.

Different countries, different rules

Some EU countries permit no embryo stem cell research. Some allow it only with surplus IVF embryos. The UK allows embryos to be created for stem cell research, including creating cloned embryos.

Purpose and process of cloning

In the UK it is illegal to create a cloned human baby (reproductive cloning), but it is legal to make a cloned human embryo and allow it to grow up to the 14 day limit in order to make stem cells (therapeutic cloning). The difference is in the purpose not the process.

Hybrid embryos

Human-animal hybrid embryos can be created by removing the genetic material from an animal egg and replacing it with human DNA. In 2008 some researchers in the UK were given permission to create this kind of hybrid for research.

Preventing rejection by cloning

Therapeutic cloning aims to stop a patient’s body from rejecting stem cells as foreign tissue. Cells are taken from a cloned embryo, created from the patient’s own cells.

How therapeutic cloning works

In therapeutic cloning, cells would be taken from a patient’s body and fused with a human egg that has had its DNA removed. This creates a cloned embryo of the patient.

Abortion for social or medical reasons

Week 24 is the limit on abortions for social reasons. Abortion for medical reasons is legal until full term (weeks 38-40).

Cloning and the United Nations

In 2004 a United Nations ban on cloning collapsed. All nations support a ban on reproductive cloning (making a baby using cloning techniques), but some wanted to outlaw research with cloned embryos, which others allow.

Development of the foetus

The foetus develops its brain structure by week 10. The limit for abortion for social reasons is 24 weeks, when the foetus starts to respond to light, sound and other sensory stimuli. The legal limit for research on the embryo is however 14 days.

Preventing rejection by reprogramming

Scientists can now manipulate cells taken from adult skin cells to return them to an embryonic state in the laboratory. This is a much easier and more efficient procedure than cloning.

The Jewish mainstream position

Before 40 days after fertilisation, Jewish law does not consider the embryo as “human life”. Therefore, taking cells from an embryo is morally neutral.

The Roman Catholic position

- Against: human life begins from the one-cell stage.
- In favour: according to Saint Tomas d’Aquino’s developmental approach: God introduces the human soul progressively in the embryo: The vegetative soul, then the sensitive soul and, then the human soul.

The Protestant position

It covers a wide range of views from a total opposition to embryonic stem cell research to a position in favour of therapeutic cloning.

The Muslim position

According to Muslim law, the moment when an embryo receives a soul does not occur until the fourth month of pregnancy. Embryonic stem cell research is morally neutral according to mainstream Muslim Law.

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