Biomedical Engineering Reference
In-Depth Information
Fig. 16.1
Therapeutical cloning: Principles
The wind came from the other side when
Dr Stojkovic
(
13,
14
) from Serbia
(after Dr. Hwang has withdrawn his discovery as not having meritorious values),
working at New Castle, UK, then in Spain, and now again, in Serbia, Leskovac,
has shown that analysis of arrested embryos demonstrated that these embryos
express pluripotency marker genes such as OCT4, NANOG, and REX1. Derived
hESC lines also expressed specific pluripotency markers (TRA-1-60, TRA-1-81,
SSEA4, alkaline phosphatase, OCT4, NANOG, TERT, and REX1) and differen-
tiated under in vitro and in vivo conditions into derivates of all three germ layers
(
14
). All of the new lines, including lines derived from late arrested embryos,
have had normal karyotypes. The line of work of this researcher and his group is
actually the first one which has clearly and with no doubts demonstrated the pos-
sibility of establishing embryonic human cell line from arrested embryos. These
results demonstrated that arrested embryos are additional valuable resources to
surplus and donated developing embryos and should be used to study early
human development or derive pluripotent hESC (
14
) . The simpli fi ed scheme of
therapeutic cloning is given in Fig.
16.1
.
2 .
Fetal stem cells
As the embryo grows it accumulates additional embryonic stem cells in yolk
sack. From weeks eight to 12 “fetal stem cells” are accumulated in the liver. Both
embryonic and fetal stem cells generate the developing tissues and organs. At
this stage such stem cells are designed as “multipotent” and they are more tissue
specific rather than generating all of the body's 200 different cell types. Such
stem cells are generally designated as “multipotent (
15
) . However, some research
suggests that at least some multipotent stem cells may be more plastic than first
thought and may, under the right circumstances, become pluripotent. Up until
