ABSTRACT
Vasculogenesis is the differentiation of endothelial progenitor cells and their assembly into a primary capillary plexus (Li et al. 2006). Vessel formation has been defi ned in several ways (Carmeliet and Jain 2011). Vasculogenesis, the de novo formation of vessels from mesoderm-derived endothelial precursor cells (angioblasts), is responsible for the formation of the fi rst, primitive blood vessels in the embryo (Ferguson et al. 2005). The vascular tree develops early in embryogenesis to provide oxygen to the developing organism (Flamme et al. 1997, Hickey and Simon 2006, Robb and Elefanty 1998, Watson and Cross 2005). Physiological and pathological blood vessel growth in later life is predominantly achieved through angiogenesis. Unwanted angiogenesis has been associated with the expansion of atherosclerotic lesions, diabetic retinopathy, psoriasis, and cancer progression (Adams and Alitalo 2007, Carmeliet and Jain 2011). On the other hand, ischemic and cardiovascular diseases have been associated with insuffi cient angiogenesis (Adams and Alitalo 2007, Becker and D’Amato 2007, Fukumura and Jain 2007, Renault and Losordo 2007). Vessels fuel infl ammatory and malignant diseases to promote tumor neo-vascularization, growth and progression to metastasis
Associate Research Scientist, Division of Pulmonary, Allergy and Critical Care Medicine, Columbia University, Medical center, New York, NY, 10032. Email: Skq1@columbia.edu
in cancer (Folkman 2007). The blood vasculature surrounding and within the growing tumor not only delivers nutrients and oxygen required for sustained tumor growth but also provides access for macrophages to the tumor, which promotes further growth and metastasis (Condeelis and Pollard 2006). Blood vessels also provide the route for rapid tumor dissemination to distant organs (Wyckoff et al. 2007). The most important question in vascular developmental biology today is: what are the general mechanisms guiding angiogenesis?
