Embryonic stem cells – what are they?

Embryonic stem cells are the cells that exist in an early stage embryo. The ultimate embryonic stem cell is a fertilised egg – one cell that is capable of dividing to give rise to every one of the billions of different cells in the human body. The stem cells in an embryo are very special – not only can they develop into a new and unique human being, they have recently been shown to have many useful applications in modern medicine.

Perhaps not surprisingly, the use of embryonic stem cells is fraught with controversy. Many people feel that it is morally wrong to use human embryos just to harvest cells, no matter how they will be used. They believe that life starts at the moment of fertilisation and taking cells from an embryo can never be justified. Others take the view that as long as the research is tightly controlled, doctors should be allowed to use early stage embryos to provide the stem cells that could help people with cancer or Parkinson’s disease.

This article on embryonic stem cells is by Kathryn Senior, a freelance journalist who writes health, medical, biological, and pharmaceutical articles for national and international journals, newsletters and web sites.  

How are embryonic stem cells obtained?

Embryonic stem cells for use in medicine and medical research are taken from very early stage embryos. These are embryos that have been created by in vitro fertilisation. During this process, quite a large number of ‘spare’ embryos are generated. The couple whose egg and sperm have been used are able to donate these spare embryos to medical research, which they do by giving their written consent. No embryos are created specifically for medical research.

The embryos used are about 5 days old and usually contain a hollow ball of cells. This is the blastocyst that eventually differentiates to form the baby and the placenta. The embryos used to obtain stem cells are never implanted into a woman’s body. They are created in the laboratory and are then used there. Individual cells are removed and then cultured in special conditions. Many of the cells don’t survive but some do and are used to create stable embryonic cell lines and can be cultured over a long period for research.

What’s special about embryonic stem cells?

Embryonic stem cells have a special property that makes them unique. They are pluripotent. This means that a single embryonic stem cell can divide and change into any of the specialised cells that occur in the human body. An intestine cell, a heart muscle cell, a skin cell, a nerve cell or a kidney cell. In the embryo, natural processes tell the cells how to change and become specialised but in the cell culture systems used in research, these signals aren’t there. Scientists are now only just beginning to find out how to push embryonic stem cells along to develop into the specific types of cells they want to use.

What other types of stem cell are there?

Not all stem cells are embryonic stem cells. Every adult has stem cells in their body. These are cells that are only partly specialised but are not fully differentiated into a particular cell type. But, when needed, they can provide the raw material for new cells to repair tissues. For example, the only type of nerve cell in the body that can divide are stem cells that occur in the tissues of the nose. These have great potential for research that is trying to help people with spinal cord injuries but they are very difficult to obtain. Adult stem cells are present in very low numbers and trying to get them is a bit like trying to find the proverbial needle in a haystack.

The potential of embryonic stem cells

A great deal of research is going on to find out how adult stem cells can be used but because embryonic stem cells can be harvested in much greater numbers, they provide more research opportunities at the moment. One of the great hopes is that using embryonic stem cells to generate replacement tissues and even organs (this isn’t possible yet) will help all of the people who desperately need a transplant but who can’t have one because donors are in short supply.

Some of the diseases that could see a new therapy based on stem cells in the future include diabetes, heart disease, Parkinson’s disease, spinal cord injury and arthritis. Clinical trials in which stem cells are being used to replace the lost dopamine-producing cells in people with Parkinson’s disease are currently in progress.

The safeguards in place for using embryonic stem cells

Countries such as the UK, the rest of Europe, the US, Australia and others have very strict regulations about the use of embryonic stem cells in medicine and medical research. In the UK the Human Fertilisation and Embryology Authority (HFEA) regulates all embryo research, which had to be approved by Parliament before it was able to go ahead. Every research group that uses embryos in research, or makes use of embryonic stem cells must follow very strict ethical guidelines.

The future of embryo research 

Using embryonic stem cells provides a lot of potential but also poses many challenges. As technology advances, new regulations must be put in place to protect the rights of the donors of embryos and also the rights of society in general to limit research so that it is acceptable to the majority.

Profile of the author

Dr Kathryn Senior is an acclaimed medical journalist who has written over 500 feature articles for leading international journals within The Lancet group. As Senior Writer at Freelance Copy she produces high quality scientific and medical content for websites and printed publications for companies and organisations in the health, medical and pharmaceutical sectors.

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