Biomedical Engineering Reference
In-Depth Information
stem cell therapy). The Somatonuclear transfer as a part of therapeutic cloning is
a technique in which the patient's nucleus content (DNA) is injected into an
enucleated unfertilized egg and used to generate ESCs which are then cultured
and allowed to differentiate, following transplantation into the patient. The entire
procedure is called therapeutic cloning, since it does supply the source of ESC
with patient's HLA system (clones identical immunological features in the organ-
ism as the patient already possesses and therefore does not require immunosup-
pression). The use of such cells may bypass the ethical objections and
immunological issues of using ESC and is the future of stem-cell clinical appli-
cation. The leading scientist Woo Suk Hwang (of Seoul National University)
claimed to have created an ESC line from a cloned human embryo for the first
time. But there were doubts about the results. The technique requires an adult
cell and an egg, and because in Hwang's experiment both came from the same
person, it was difficult to prove that embryo really was cloned (
8
) . The process
was also very inefficient, taking 242 eggs to create just one ESC line. Then,
Hwang has created 11 more ESC lines from cloned embryos in an impressive
study that answered all the criticisms of his original study. He has also greatly
increased the efficiency of the process: the 11 lines came from just 185 fresh
eggs donated by 18 unpaid volunteers, meaning an average of only 17 eggs were
needed per ESC line (
9
). The donor “adult” cells came from patients aged 2-56,
with a variety of conditions ranging from spinal injuries to an inherited immune
condition. The work proved that matching ESCs can be derived via nuclear
transfer from donors of any age and sex. This was an enormous stride in the long
journey to determine whether nuclear-transfer-derived human ESC might be
eventually suitable for transplantation medicine. However, the chain of events
has happened very soon causing Korean group to withdraw their results.
Therapeutic cloning is much less controversial in South Korea than in the West.
More than 70% of South Koreans agree with therapeutic cloning, whereas a
recent poll in the USA suggests that 75% are opposed to it. Furthermore, South
Korean law allows the use of fresh eggs from young women who are prepared to
donate their eggs by undergoing ovarian stimulation, which can be a risky and
painful procedure. In the western countries by contrast and for example, scien-
tists are only allowed to use eggs rejected or left over from in vitro fertilization
(IVF) treatment. Apparently, the supply of the eggs is lacking in the West.
While ESCs show great promise for treating many diseases, such as heart
disease, diabetes, and Parkinson's, non-matching ESCs would be rejected by
patients' immune systems unless they take immunosuppressant drugs. This is
why many stem cell researchers are trying to create ESCs that are identical to
people's (recipient's) own cells. However, Yuri Verlinsky of the Reproductive
Genetics private Institute, in Chicago, claims to have produced patient-matched
ESC without resorting to therapeutic cloning. Unlike therapeutic cloning, it uses
existing ESCs instead of human eggs, the step much cheaper and easier.
Furthermore, because no embryos are destroyed, it would bypass many ethical
issues. In fact, if Verlinsky's claims stand up, there might be a much easier way
to create matching ESCs. Verlinsky has created 13 ESC lines using his new
