Tuesday, March 25, 2008

The alternative to using embryonic stem cells

Until recently it was taught in all medical schools that cells in the embryo were multipotent - able to give rise to every tissue - but by birth, this capacity was permanently lost. That has been the reason why almost all research effort focused on embryonic stem cells until just a few years ago.

However a moment's thought tells us how illogical such a view was, and indeed we are now finding that many cells in children and adults have extraordinary capacity to generate or stimulate growth of a wide variety of tissues, if encouraged in the right way.

Take for example the work of Professor Jonathan Slack at Bath University who has shown how adult human liver cells can be transformed relatively easily into insulin producing cells such as those found in the pancreas, or the work of others using bone marrow cells to repair brain and spinal cord injuries in mice and rats, and now doing the same to repair heart muscle in humans.

Why should this surprise us? We know that almost all cells in your body contain your entire genome or book of life: enough information to make an entire copy of you, which is the basis of cloning technology. So in theory just about every cell can make any tissue you need. However the reality is that in most cells almost every gene you have is turned off - but as it turns out, not as permanently as we thought.

If we take one of your skin cells and fuse it with an unfertilized human egg, the chemical bath inside a human egg activates all the silenced genes, and the combined cell becomes so totipotent that it starts to make a new human being.

What then if we could find a way to reactivate just a few silenced genes, and perhaps at the same time silence some of the others? Could we find a chemical that would mimic what happens in the embryo, with the power to transform cells from one type into another? Yes we can. Jonathan Slack and others have done just that. What was considered impossible five years ago is already history.

Could we take adult cells and force them back into a more general, undetermined embryonic state? Yes we can. It is now possible to create cells with a wide range of plasticity, all from adult tissue. The secret is to get the right gene activators into the nucleus, not so hard as we thought.


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