vasculogenesis

Vasculogenesis is the process of blood vessel formation occurring by a de novo production of endothelial cells. Though similar to angiogenesis, the two are different in one aspect: the term angiogenesis denotes the formation of new blood vessels from pre-existing ones, while vasculogenesis is the term used for the formation of new blood vessels when there are no pre-existing ones. For example, if a monolayer of endothelial cells begin sprouting to form capillaries, angiogenesis is occurring. Vasculogenesis, in contrast, first believed to occur only during embryologic development, is the term for when endothelial precursor cells (angioblasts) migrate and differentiate in response to local cues (such as growth factors and extracellular matrix) to form new blood vessels. These vascular trees are then pruned and extended through angiogenesis. Recently, however, it was realized that vasculogenesis can also occur in the adult organism. Circulating endothelial progenitor cells (derivatives of stem cells) were identified and reportedly able to contribute, albeit to varying degrees, to neovascularization, such as during tumor growth, or to the revascularization process following trauma, e.g. after cardiac ischemia.
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