New experimental observations often require fresh concepts for their interpretation, and at times even changes of paradigms. This is the situation with the recent realization that circulating endothelial progenitor cells may have an important contribution to the maintenance and formation of new endothelium in adult organisms, in a surprisingly wide variety of situations. The classical paradigm of angiogenesis, centered on the notion of "sprouting" can hardly accommodate them. It was previously realized that it needs to be "stretched out" to include alternative mechanisms of microvascular...

New experimental observations often require fresh concepts for their interpretation, and at times even changes of paradigms. This is the situation with the recent realization that circulating endothelial progenitor cells may have an important contribution to the maintenance and formation of new endothelium in adult organisms, in a surprisingly wide variety of situations. The classical paradigm of angiogenesis, centered on the notion of "sprouting" can hardly accommodate them. It was previously realized that it needs to be "stretched out" to include alternative mechanisms of microvascular...