Vascular Endothelium - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 467

Circulating endothelial progenitor cells can be incorporated into ischemic tissues
as well as at the border of infarcted regions and facilitate neovascularization, as they
secrete paracrine factors [ 868 ]. They release growth factors and chemokines that
stimulate endothelial regeneration by resident endothelial cells. They also contribute
to the endothelial lining of microvessels during wound healing.
Circulating endothelial progenitor cells may be involved in re-endothelialization
after mechanical vascular injury that prevents intimal hyperplasia. Mobilization of
endothelial progenitor cells EPCs may contribute to endothelial regeneration pro-
moted by estrogen, exercise, heme oxygenase-1, and statins [ 868 ]. However,
homing of circulating endothelial progenitor cells is a minor factor with respect
to endothelium growth from the edges of the injured region.
Mobilization, circulation, homing, and local differentiation of bone marrow-
derived leukocytes intervene in evolution of most arterial diseases characterized by
inflammation.
In adults, the name “endothelial progenitor cell” applied to different cell types.
Early endothelial progenitor cells , or endothelial-like cells, have a myelomonocytic
origin. They have paracrine effects in neovascularization in vivo. Late endothe-
lial progenitor cells , blood-outgrowth endothelial cells, or endothelial colony
forming cells, are highly proliferative. They also participate in neovasculariza-
tion. Few circulating late endothelial progenitors are CD31

+ ,CD34 + , CD146 + ,

18 cells similar to mature circulating and resident endothelial

PTPRc − , prominin-1 −

cells [ 868 ].
Endothelial progenitor cells or angioblasts can be isolated from blood [ 869 ].
Circulating endothelial progenitor cells (CEPC) differ from mature circulating
endothelial cells (CEC) by their markers (Table 9.4 ). Endothelial progenitors and
hematopoietic stem cells share numerous surface markers, but the former also
express VEGFR2 receptor.
Bone marrow is a reservoir of stem cells that can regenerate the bone marrow
as well as other tissues. Bone marrow is constituted by different types of stem and
progenitor cells, such as multipotent adult progenitor cells that can, at least in vitro,
generate many cell types as well as mesenchymal stem cells, and hemangioblasts.
However, the contribution of bone marrow-derived progenitor cells to repair of
vascular damages is rather limited.

9.3.1 Hemangioblast

Hemangioblast is a common precursor for hematopoietic and endothelial cells under
the influence of growth factors. Hematopoietic stem cells give birth to lymphoid

18 Pentaspan transmembrane glycoprotein prominin-1 is also called macular dystrophy, retinal
protein McDR2, Stargardt disease protein StgD4, hematopoietic stem cell antigen CD133, and
AC133.