Very interesting. I wonder if stem cells can also encourage enhancement - e.g. if injected in normal mice, do they result in increased intelligence?

Eliezer addressed a similar idea a few days ago (the relation to your question will be clear about 11 paragraphs down): http://www.overcomingbias.com/2009/01/growing-up-is-hard.htm...

Probably not, given that they are just following the standard blueprint.

Also given the risks (tumors and immune-response), this seems to be the kind of thing only used in extreme cases.