Biology Reference
In-Depth Information
In summary (
Section 2.1
), several markers and several isolation protocols
have been advocated, which result in different cell types that are isolated. If a
cell population is termed EPC, the isolation process including the origin of
the cells (human (h) or mouse (m); BM, PB or cord blood (CB)) should be
made clear as well as the further identification of the cells.
Without a cultivation step, the cells termed EPCs should be termed as
circulating EPCs (CEPCs). If cells are cultured before further processing,
then the term “early EPC”/CAC or “late EPC”/ECFC should be applied.
For all other side population cells, the term “progenitor-like cells” is used till
date. For a short overview of the different cell types, see
Table 2.1
. Further,
it has been proved that in some isolation protocols, parts of platelet-derived
micromolecules can also be included and therefore mimic an endothelial
phenotype in culture. Therefore, the isolation protocol as suggested by
Urbich et al. (2011)
should be used for genetic research.
2.2. Phenotypical characterization
According to the initial discovery, EPCs or CEPCs were defined as cells pos-
itive for both HSCmarkers such as
CD34
and an endothelial marker protein
such as vascular endothelial growth factor receptor 2 (
VEGFR
2
). Because
CD34 is exclusively expressed not only on HSC but, albeit at a lower level,
Table 2.1 Overview of the different cell types that are associated with the term
endothelial progenitor cells
Name
EPC (CEPC)
CAC
ECFC
CFU-Hill
Definition Found by flow
cytometry
using positive
markers
Derived from
plating PBMC on
fibronectin. Appear
after 4-7 days
Appear after
>
Colonies
forming
according to
the Hill-assay
7 days in
culture
High
proliferative
potential
Origin
Hematopoietic
lineage
Myeloid origin
Unclear, not
hematopoietic
Myeloid and
hematopoietic
origin
Positive
markers
CD34
KDR
CD133
CD14
CD45
Bind UEA
Take up LDL
CD31
CD34
CD105
No uniform
markers, but
mostly:
CD31
Tie-2
KDR
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