189specifi c factors, but this requires better understanding of the events regulating cell
lineage commitment and differentiation. Even though in vitro differentiation can
generate multiple cell types, in vivo differentiation, such as following injection into
a host blastocyst, demonstrates the full developmental potential of undifferentiated
ES cell lines (Amit et al. 2000 ). In vivo many of the normal features of tissue archi-
tecture are replicated, for example, cell epithelium exhibits polarity, is enveloped by
a basement membrane and is surrounded by mesenchyme (Amit et al. 2000 ).
9.3 Challenges Faced
9.3.1 Ethical Dilemma
The use of human ES cells raises serious ethical, religious and political controver-
sies. The main ethical issue concerns the derivation of ES cells from embryos which
are then destroyed. Controversies arise due to varying views on the personhood of
an embryo. For those who believe that life begins at conception, destroying a human
embryo is wrong, while others argue that even though an embryo is potential for
life, it cannot be regarded as a person, and it is more unethical to stop research
(Buxton 2009 ). An intermediate position on the status accorded to the embryo attri-
butes a special status to the embryo that is less than human life but deserving of
respect that imposes limits on its ethical use (Chiu and Rao 2003 ). A second objec-
tion raised is that it is wrong to create blastocysts for research purposes, whether
through fertilisation or nuclear transfer, with the intention of destroying it. Some
fear that the use of nuclear transfer to derive human ES cells could eventually lead
to its use to produce a child. Further concerns are shown with regard to research
involving donor oocytes, which could result in the exploitation of women. In addi-
tion, some people are worried about the mixing of human and nonhuman cells for
research purposes (Medicine and Council 2005 ). Other methods of obtaining stem
cells such as induced pluripotent stem (iPS) cells avoid ethical problems specifi c to
embryonic stem cells raising fewer concerns. However, as with any human stem cell
research, there are diffi cult dilemmas, like consent to donate materials for research,
early clinical trials of therapies and oversight of research (Lo and Parham 2009 ).
9.3.2 Technical Challenges
Therapeutic use of ES cells is yet to become a successful reality for treating diseases
owing to the technical challenges that come with it. If these challenges are over-
come, stem cell therapy can revolutionise medicine. However, results have shown
that the approaches proposed so far do not permit clinically safe, reliable and cost-
effective procedures (Di Nardo et al. 2012 ).
9 Human Embryonic Stem Cells and Associated Clinical Concerns