One possibility is that mature endothelial cells are present in the circulation and can participate in neovascularization. In 1970, Gaynor and colleagues identified endothelial cells in the circulation of rabbits after exposure to endotoxin. A body of evidence has since accumulated, demonstrating the presence of mature endothelial cells in the circulation after various types of vascular injury. However, it is unlikely that these cells contribute significantly to vas-culogenesis. Two pieces of data that argue against mature ECs participating in vasculogenesis are their extremely low prevalence in the blood (1 to 3 per milliliter of blood) and their limited proliferative capacity based on in vitro assays.
The prevailing evidence indicates that these circulating mature ECs are not the cells responsible for vasculogenesis in the adult. Nevertheless, the presence of increased mature ECs in the circulation may be useful as a marker for vascular injury.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.