Embryonic stem-cell research: what is it?

The Government has remained strongly in favour of proposals put before yesterday's council of ministers meeting in Brussels.

The Government has remained strongly in favour of proposals put before yesterday's council of ministers meeting in Brussels.

It related to whether EU funding should be used to support research that involves the destruction of embryos as a source of embryonic stem cells. It also included a number of restrictions on the conduct of that research.

There is a wide range of scientific opinion about whether stem cells might offer new treatments for intractable medical conditions. The following are explanations for the terms being used in stem-cell research.

Stem cells: These are the source cells from which the body's specialised tissues grow. They change from a non-specific, undifferentiated state into a differentiated "adult" state, taking on one of the body's more than 200 different cell types.

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Embryonic stem cells: These are the most "plastic" or changeable stem cells, apparently able to differentiate into any of the body's various tissues. Their use is controversial because they are recovered from a dividing embryo, but their plasticity means they may be the most valuable form of stem cell for medical treatments.

Adult stem cells: Adults also produce stem cells but they are much less changeable than embryonic cells. They have been found in liver, marrow and brain tissue, and tend to convert into cells appropriate to these locations.

Umbilical and placental stem cells: Stem cells have also been recovered from the placenta and umbilical cord, although they act more like adult stem cells than embryonic stem cells. Their value is still being assessed.

Stem cell lines: These are cultured stem cells originally taken from embryos but which now divide perpetually. Many countries accept research using cultured stem cells including Germany, which is strongly opposed to, and has legislated against, embryo research, but readily imports stem cell lines from other countries, including Israel.

Embryonic cloning: Ethically fraught, being able to clone embryos would produce an endless supply of embryos, but also an endless supply of stem cells.