. Author manuscript; available in PMC: 2018 Oct 4.
Published in final edited form as: Stem Cell Res. 2018 Jul 6;31:31–41. doi: 10.1016/j.scr.2018.07.004
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).