ABSTRACT
In the adult, the endothelial cells of normal vessels maintain tight associations
with each other and have a low mitotic index. This state of quiescence depends in
part on cues from the extracellular matrix (ECM). However, signals are generated
during the normal host response to injury, or from pathological processes, that
activate the endothelia of preexisting microvessels to give rise to a new
vasculature, with bone marrow-derived endothelial progenitor cells contributing
to the cellular repertoire of the forming vessels. During this process of
angiogenesis, the ECM, through interactions with cell surface integrins, plays
critical roles in regulating functions of endothelial cells, including proliferation,
migration, resistance to apoptosis, and tube morphogenesis, that are essential to
formation of new vessels.
