Pluripotent Stem Cells from the Postnatal Testis: Unlocking the Potential of Spermatogonial Stem Cells - Male Germline Stem Cells Developmental and Regenerative Potential - page 31

concluded that, for certain key pluripotency genes, post-transcriptional mechanisms
could be very important in controlling the phenotype. Thus, the extent to which the
preexisting epigenetic profile of germ cells contributes to the observed acquisition
of pluripotency is a matter of speculation.

2.5 Culture-Induced Pluripotency in Mice

While multiple laboratories have demonstrated the acquisition of pluripotency by
germ cells in vitro , the procedures and conditions used are remarkably different
(see Figs. 2.2 and 2.3 and Table 2.1 ). In 2004, it was discovered that SSCs derived
from the neonatal testis could reproducibly give rise to pluripotent embryonic-like
stem cells within 4-7 weeks of initiation of the stem cell culture in ~20% of experi-
ments but at a very low rate relative to the number of cells plated (Kanatsu-
Shinohara et al. 2004 ). These ES-like cells not only physically resembled ES cells
but also bore a similar gene expression profile, marked by the presence of mRNA
for Nanog , Rex1 , Utf1 , Esg1 , and Cripto , among others. When wild-type testes

Fig. 2.2 Variations in experimental approaches for obtaining pluripotent stem cells from post-
natal testis. Left panel : Some laboratories have employed long-term culture of SSCs prior to
obtaining pluripotent stem cells that were then separated from the parental cells by selection
(Kanatsu-Shinohara et al. 2004 ; Seandel et al. 2007 ; Ko et al. 2009 ; Yu et al. 2000 ). Right panel :
Other groups have employed short-term culture without parallel propagation of the precursor
(parental) cell population (Guan et al. 2006 ; Ko et al. 2009 ; Mizrak et al. 2010 )