Editing Embryonic stem cell (section)

===Derivation from humans===
[[In vitro fertilization]] generates multiple embryos. The surplus of embryos is not clinically used or is unsuitable for implantation into the patient, and therefore may be donated by the donor with consent. Human embryonic stem cells can be derived from these donated embryos or additionally they can also be extracted from cloned embryos created using a cell from a patient and a donated egg through the process of [[somatic cell nuclear transfer]].<ref>{{cite journal|last=Mountford|first=JC|title=Human embryonic stem cells: origins, characteristics and potential for regenerative therapy|journal=Transfus Med|year=2008|volume=18|pages=1–12|doi=10.1111/j.1365-3148.2007.00807.x|pmid=18279188|issue=1|s2cid=20874633}}</ref> The inner cell mass (cells of interest), from the blastocyst stage of the embryo, is separated from the trophectoderm, the cells that would differentiate into extra-embryonic tissue. [[Immunosurgery]], the process in which antibodies are bound to the trophectoderm and removed by another solution, and mechanical dissection are performed to achieve separation. The resulting inner cell mass cells are plated onto cells that will supply support. The inner cell mass cells attach and expand further to form a human embryonic cell line, which are undifferentiated. These cells are fed daily and are enzymatically or mechanically separated every four to seven days. For differentiation to occur, the human embryonic stem cell line is removed from the supporting cells to form embryoid bodies, is co-cultured with a serum containing necessary signals, or is grafted in a three-dimensional scaffold to result.<ref>{{cite journal|vauthors=Thomson JA, Itskovitz-Eldor J, Shapiro SS, Waknitz MA, Swiergiel JJ, Marshall VS, Jones JM |title=Embryonic stem cell lines derived from human blastocysts|journal=Science|year=1998|volume=282|pages=1145–1147|doi= 10.1126/science.282.5391.1145|pmid=9804556|issue=5391|bibcode=1998Sci...282.1145T|doi-access=free}}</ref>