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CB-EPC. These were epidermal growth factor (EGF), basic fibroblast
growth factor (FGF), fractalkine, GM-CSF, interleukin (IL)-6, IL-8,
platelet-derived growth factor-AA (PDGF-AA), and VEGF. Six cytokines
were evidently higher in hESC-EPC than in CB-EPC (fractakine,
GM-CSF, IL-6, IL-8, IL-9, and VEGF), whereas three cytokines were very
similar in both hESC-EPC and CB-EPC media (EGF, IP-10, and PDGF-
AA), and three cytokines were lower in hESC-EPC than in CB-EPC
(FGF-2, MCP-1, and PDGF-AA/BB; Lee et al., 2011 ).
In summary ( Section 2 ), EPC can arise from different sorts of tissue and
therefore also have different abilities. The term EPC does not identify one
single cell group. This rather heterogenic cell group can be subdivided into
CAC, which have a more monocytic lineage, whereas the late-outgrowth
ECFCs show a more endothelial lineage. CFUs are based on EPC as well as
monocytes and leukocytes. EPCs can also be found in vessel walls and even
as tissue resident endothelial progenitors.
Depending on which cell group is sought, different cell markers are
applicable. The most common markers for identifying EPC are CD34,
VEGF-receptor 2, CD133, and the uptake of acLDL. The cytokines that
are most relevant for mobilization of EPC are SDF-1a, MIF, G-CSF, and
VEGF. The cytokines that are mostly expressed by EPC are VEGF,
SDF-1a, and GM-CSF.
3. EPC IN HEALTH AND DISEASE
3.1. EPC in the healthy
The differences in EPC counts in the healthy seem to differ quite a bit. For
example, the amount of EPC in children is three times higher than in adults
( Jie et al., 2009 ). But these differences can be even higher. Physical training
can change the cell counts of EPC. Individuals who perform physical exer-
cise on a regular basis have higher amounts of EPC than individuals who do
not perform any type of physical exercise. Hence, the amount of EPC can be
increased in individuals by performing physical exercise ( Steiner et al., 2005;
Walther et al., 2008 ). Still, there has to be a certain amount of exercise to
increase the levels of EPC. As Laufs et al. proved, EPC counts are only
increased when at least 30 min of exercises are performed. Ten minutes
of exercise was not sufficient to increase the amount of circulating EPC
( Laufs et al., 2005 ).
Two other studies that demonstrated that the levels of EPC decrease
about an hour after the end of exercise have also showed this ( Adams
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