Friday, 6 July 2007

Where do Stem Cells come from

A lot of the debate about the use of Embryonic Stem cells (ESC) in research comes from objections that are based about the murder of all those babies to get the ESC. You know the sort of thing where on The Simpsons, Mrs Lovejoy comes along and cries out "oh won't somebody please think of the children".

However this is a very unrealistic point. As anyone who has ever been a parent will know, how and when you find out you are going to be a parent is quite variable. Normally the first signs are morning sickness, or extreme tiredness, but neither of these are themselves a reliable test that you are pregnant. So how do we confirm pregnancy? Usually it involves a take-home pregnancy kit, some urine and human chorionic gonadotropin (hCG).

Well now that we know that what does it actually mean. hCG is produced during pregnancy to fulfill some role (that is unimportant to this discusion but can be found at the link above), and so once you are pregnant this hormone starts to be produced (by the embryo/placenta), and it takes some time for the levels to build up such that it is excreted from the mother's body.

For the test to be accurate you want it to cut down on the false readings. The way this is dealt with is by having a threshold concentration for the hCG, this at least cuts down on the false positives (where the test reads positive when you are not pregnant). However because it takes time for that concentration to build up it is possible to get false negatives (where the test reads negative when you are pregnant).

An example of this was with our first child, my wife got pregnant just before I left for Europe for a conference. Now she had her best friend's hens night several days after I left she was worried that she might be pregnant and didn't want to drink if she was. So she took the test and it came back negative. A week or so later the tiredness really kicked in and she went to the doctor and took another test there, it came back negative. Only another week of so later when the morning sickness was started up did a test finally come back positive (note that the timing of the morning sickness and the positive test are incidental).

So in this case my wife was pregnant for three weeks before actually knowing for sure that she was pregnant.

This delay is long enough such that the harvesting of ESC from a mother is not really an option.

So if this is not an option what is? Well as I see it there are two options either we specifically create embryos to take the stem cells from or we make use of the vast numbers of spare embryos that as we speak are sitting in freezers in IVF clinics all around the world. Spares that will most certainly never be anything more than they are now.

In fact since storage capabilities of any organistion are finite then eventually many of these will be destroyed. They clearly are surpluss to the parents IVF requirements and are unlikely to all be adopted. Since they can't be kept forever they will end up being destroyed, but why then can't they be put to a good cause, that of research in to finding cures to many debilitating diseases and conditions.

2 comments:

Rodrigo said...
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Anonymous said...
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