Vascular Endothelium - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 469

Tabl e 9. 5. Factors of endothelial progenitor cell (EPC) mobilization (Source: [ 870 ]).

Factor Effect

Age ↓ EPC mobilization, survival, activity

Estrogen ↑ EPC concentration

Exercise ↑ EPC concentration

↑

Growth factors EPC mobilization

↓

Hypercholesterolemia EPC proliferation, migration, survival

Hypertension ↑ EPC proliferation

↓ EPC survival

Smoking ↓ EPC density

9.3.2 Endothelial Progenitor Cell - Circulating Angiogenic

Cell

Endothelial progenitor cells, or circulating angiogenic cells, 20 can reside in the bone
marrow and blood as well as adventitia and endothelium [ 868 ].
Endothelial progenitor cells are activated by stimuli for tissue regeneration,
such as vascular endothelial growth factor, placental growth factor, granulocyte-
monocyte colony-stimulating factor (CSF2), granulocyte colony-stimulating factor
(CSF3), erythropoietin, 21 angiopoietin-1, and CXCL12 chemokine, are recruited
from the bone marrow into blood flow to be convected toward angiogenesis sites
(Table 9.5 )[ 870 , 871 ]. 22 Circulating endothelial progenitor cells yield protection by
their innate ability to replace dysfunctional or damaged endothelium.
However, during angiogenesis, slight recruitment of bone marrow-derived cells,
in particular VEGFR2

+

precursors, does not contribute to vascular endothe-
lium [ 872 ]. Bone marrow-derived cells that express platelet-endothelial cell adhe-
sion molecule PECAM1, VEGFR1, and VEGFR2 are always stromal or perivascu-
lar cells. Perivascular hematopoietic cell populations that can produce endothelial
markers are not bone marrow-derived endothelial cells.

20 The term “endothelial progenitor cell” initially designated immature precursor cells capable of
differentiating into mature endothelial cells in vivo. However, endothelial progenitor cells can
comprise circulating angiogenic cells without an endothelial fate. Blood-derived pro-angiogenic
cells with paracrine activity boosting local endothelial cells can be an adequate, although long
term that avoids confusion with immature progenitor and precursor cells that differentiate into a
given mature cell type [ 868 ].
21 Receptor EpoR that stimulates proliferation of early erythroid precursors and differentiation of
late precursors of the erythroid lineage localizes to endothelial cells.
22 After endothelial injury, platelet adhesion to the vascular wall causes a cytokine-mediated
release of CXCL12 chemokine, or stromal cell-derived factor SDF1, that, in turn, recruits and
provokes proliferation of CD34 + , CXCR4 + ,VEGFR1 + endothelial progenitor cells for re-
endothelization [ 870 ]. Chemokine CXCL12 that targets receptor CXCR4 is a major actor of tissue
engraftment of endothelial progenitor cells.