Endothelial Progenitor Cells—Potential New Avenues to Improve Neoangiogenesis and Reendothelialization - International Review of Cell and Molecular Biology - page 49

endothelial media after preplating and washing. The colonies that arise after
these steps are commonly termed CFU-Hill. They consist of different types
of cells such as monocytes, leukocytes, and endothelial-like progenitor cells.
The number of colonies in patients is known to be inversely correlated with
the Framingham risk score ( Hill et al., 2003 ). CFU-Hill are therefore not
specific for one cell-line. But they can be used as an indicator for impaired
or improved angiogenesis.
2.1.5 MC, which differentiate into ECs under the influence
of cultivation factors
An endothelial-like cell type can also be harvested from BM. By cultivating
murine BM-derived MNCs (BM-MNCs) in preconditioned endothelial
medium, the BM-derived cells differentiated into EPC ( Asahara et al.,
1999a; Wang et al., 2011 ). These BM-derived EPCs (BM-EPCs) have a high
proliferative potential and are able to form tubular structures in vitro ( Wang
et al., 2011 ). Asahara et al. (1999a) proved that these cells were able to home
to ischemic tissue and therefore improve myocardial function after ischemia.
2.1.6 Other CPCs, termed “ side population cells ” or tissue resident
progenitor cells
The other source of nonhematopoietic EPC was described for the first time
by Aicher et al. (2007) . They investigated the contribution of circulating
cells from BM and non-BM sources to the vasculature. Doing so they dis-
closed the evidence for the mobilization of tissue resident c-Kit þ /CD45
progenitor cells, such as from the liver and small intestine. Based on these
findings, it seems possible that there are various resources from which EPCs
can be mobilized. Cells mobilized from peripheral tissue are termed tissue
resident progenitor cells (TPCs).
2.1.7 Circulating mature ECs that are sheared off from vessel walls
The concept of CECs is based upon work by Alessandri et al. (2001) who
described endothelial progenitor-like cells that could be harvested from
human embryonic aorta.
Ingram et al. expanded this concept by stating that EPCs could also be
isolated from the vessel walls in a mature organism. Even a hierarchy of dif-
ferent types of EPCs could be isolated from a vessel wall. Therefore, the con-
cept of ECs or EPCs that are sheared off from a vessel wall is plausible
( Ingram et al., 2005b ). In a further study, these resident progenitor cells were
shown to be involved in postnatal vasculogenesis ( Zengin et al., 2006 ). The
potential and function of these cells remain unclear.