On a somewhat related note, my dad (a dentist and scientist) recently discovered that there are stem cells that are almost as easy to manipulate as embryonic ones .. in our mouthes [1][2]. He always wondered why our gums heal so quickly, even as we age.

[1] Sorry for the PR-ish link (I'll ask him for the actual paper) - http://singularityhub.com/2012/05/10/toothless-no-more-resea...

[Edit 2] Here's the original publication (free) from Stem Cells Journal http://onlinelibrary.wiley.com/doi/10.1002/stem.425/abstract