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Unformatted text preview: tudies are missing. A number Conditioned medium from feeder cells or a medium with
animal components (such as the widely used Invitrogen
SR) is not optimal when we think of pathogens and possible
immunoreactions as well as batch-to-batch variation of
culture media. Very recently, important work has been
carried out by replacing animal components in SR-containing medium with more deﬁned media and supplements. Genbacev et al. (2005) and Li et al. (2005) used
X-VIVO 10 with bFGF, Vallier et al. (2005) used chemically
deﬁned medium with activin A, nodal and bFGF, and
Ludwig et al. (2006) used deﬁned culture medium with
bFGF, LiCl, GABA, TGF-b, and pipeolic acid. Deﬁned quality cells also needed for research
purposes Figure 2 Key features of human embryonic stem cell
line culture conditions which need to be optimized.
www.reproduction-online.org Reproduction (2006) 132 691–698 696 H Skottman and O Hovatta of karyotypic abnormalities have been identiﬁed in
cultured hESC (Allegrucci & Young 2006). Human ESC
is also epigenetically sensitive (Steele et al. 2005).
In feeder-free culture of hESC, new gently passaging
methods without dissociation of hESC for single cells
might enable preventing abnormalities caused by
selective pressure in long-term cultures of hESC.
If the cells are cultured only for research purposes, we
need not consider so much the immunoreactions caused
by animal substances in culture medium, but pathogens
may change the properties of the cells. The current
culture methods are by no means perfect, and they need
optimization also to gain high efﬁciency for the
production of sufﬁcient amounts of hESC for research
purposes. The use of feeder cells sets limitations for
research, since experimental data might result from a
combination of hESC and feeder cells (Klimanskaya et al.
2005). The variation in culture protocols may also affect
the ability to differentiate hESC with standard differentiation protocols or to provide standard systems for
developmental studies, disease modeling, drug discovery, and toxicology applications. Recently established
culture methods with high concentration of growth
factors and use of human matrix components are very
expensive for research purposes. Understanding the
mechanisms of hESC self-renewal and proliferation as
non-differentiated cells would greatly facilitate the
establishment of deﬁned derivation and culture conditions for hESC (Vallier et al. 2005, Wang et al. 2005a,
Armstrong et al. 2006, Rho et al. 2006, Stewart et al.
2006). Recent advantages in the use of biomaterials
(Anderson et al. 2004) and perfusion culture systems
(Fong et al. 2005) for the culture of hESC suggest that
large-scale culture of hESC in bioreactors under
controlled environment using deﬁned culture medium
and biomaterial substrates may be feasible in future.
International stem cell initiative (Andrews et al. 2005)
has been established by several organizations which
fund hESC research. It is an important atte...
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This document was uploaded on 09/21/2013.
- Spring '13