Sperm from stem cells:
If and when there is a serious attempt to restore the fertility of countries that now are below replacement levels, sperm will be a critical element.  Some men don’t make many, so if they could be produced in the lab from patients, it might prove to be a very good thing some day.  Now a team in Kyoto, Japan, has published online in CELL as of August 4, 2011 what may be a step in that direction.  The team was led by Mitinon Saiton.  Their report was reviewed in the News section of SCIENCE (Lab-grown sperm make mice SCIENCE vol. 333 no. 6044 page 807)

What they managed to do was extract some stem cells from mice, coax them into differentiating into sperm, use these sperm to fertilize mouse ova, which produced embryos that were then placed in surrogate mothers and emerged as normal mice. 

In theory that means you could extract cells from an adult male, coax them into changing into stem cells, then get them to change again into sperm and use those sperm to produce embryos with a potential future. 

The review points out that there are technical as well as esthetic hurdles.  I am not one to judge the ethics of others.  All right, at some level I scream under my breath, but I really have no business telling people what I think of them.  So far as I can tell everybody does their best.  But some of the technical hurdles seem clear.

For one thing, a mouse is not a human.  A technique proven in one may not translate into a viable procedure in the other.

For a second thing, the cells were derived from embryos.  We already have a way of getting people from embryos.  That’s were we all came from in the first place, and embryos can indeed be implanted with some success. 

There has been some success in getting mature cells, called somatic cells, to revert to stem cell status.  And the way that is proven is to have them differentiate.  But a sperm is kind of a highly specialized and one senses rather temperamental cell.  Getting an adult cell to make the double change would indeed be a tour de force.  But this is a step in that direction, and some day may be part of an answer.  Of course the issue of ova remains.

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