Endothelial Progenitor Cells—Potential New Avenues to Improve Neoangiogenesis and Reendothelialization - International Review of Cell and Molecular Biology - page 52

c-Kit , which is also known as CD117 , is the receptor for stem cell factor.
It can be found on early hematopoietic stem cells such as the angioblast. It
has been used to identify CEPC in an experimental model. Since c-kit seems
to be present in early forms of developing EPC, its use for the identification
of CEPC is questionable ( Balsam et al., 2004 ).
CD144 , which is also termed as vascular endothelial cadherin, is pre-
dominantly expressed on ECs. It has been reported to be found on ECFC
( Lin et al., 2000 ). When used for the isolation of EPC with fluorescence-
activated cell sorting, it is found predominantly on cells with monocyte scat-
ter characteristics. It should therefore not be used for primary identification
of EPC ( Hill et al., 2003; Mancuso et al., 2001 ).
Tie-2 or CD202 is known to be expressed by early hematopoietic cells. It
has been used in the identification of EPC and defines their origin from the
hemangioblast ( Asahara et al., 1999a ).

2.3. Genetic characterization
Medina et al. (2010) compared the transcriptomes of CAC and ECFC from
single donors with microvascular ECs and CD14 þ monocytes. They found
that CAC more closely resembled monocytes, whereas the expression pat-
tern of ECFC looked more like that of microvascular ECs. CAC expressed
significantly more of the genes involved in hematopoietic development,
such as RUNX1, WAS, and LYN, and genes involved in the immune
response, including TLRs, CD14, and HLAs. In contrast, genes involved
in angiogenesis, such as Tie2, eNOS, and Ephrins, were highly expressed
in ECFCs.
The explanation for this strong difference between these two cell groups
has been provided by Prokopi et al. (2009) . The authors used proteomics to
identify surface markers on CACs and compared these with genes expressed
in these cells. As a result, it was shown that many of the endothelial surface
markers are not expressed but are acquired from platelet microparticles
during isolation and culture. These findings indicate that the different
EPC phenotypes that arise in culture not only are functionally different
but also differ in their expression profiles and arise from distinct lineages,
which was confirmed by the comparison of transcriptome profiles

( Furuhata et al., 2007; Gremmels et al., 2011 ).
For good comparison of gene expression among human umbilical
vein endothelial cells

(HUVECs), CAC, and ECFC, please see also

Furuhata et al. (2007) .