Integrin-Mediated Cell-Matrix Interaction in Physiological and Pathological Blood Vessel Formation

Figure 2

Diverse types of vessel formation. Tumor neovascularization can take place by distinct types of vessel formation, which can proceed simultaneously and also merge seamlessly. (A) Neovessel formation by recruitment of bone-marrow-derived endothelial progenitor cells. (B) Sprouting angiogenesis is initiated by the differentiation of an EC into a migratory but nonproliferating tip cell. (C) Intussusceptive angiogenesis starts with the insertion of a connective tissue pillar into a preexisting vessel, and the vessel is displaced as the pillar extends in size. (D) In glomeruloid angiogenesis, complex vascular aggregates of several closely associated vessels are formed. (E) Vessel co-option is the acquisition of host capillaries by the tumor. (F) In vascular mimicry, tumor cells can partly assume EC function and form vessel-like hollow structures. Arrows denote consecutive stages of vessel formation. Tumor tissue is depicted dark gray. See text for details.