Chapter 7: Biology of the Vessel Wall
Which of the following is true about vascular development?
A. A bipotent hemangioblast is capable of giving rise to endothelial cells and blood cells
B. The primitive vasculature arises from coalesced blood islands
C. Postnatal vasculogenesis requires angioblasts that are active in the adult
D. Collateral arteries that form in the presence of obstructive coronary artery disease are the result of bone-marrow-derived progenitor cells
E. VEGF is a potent inhibitor of angiogenesis
The answer is B. (Hurst’s The Heart, 14th Edition, Chap. 7). The notion that a bipotent hemangioblast gives rise to endothelial cells and blood cells has recently been challenged. Instead, blood cells probably develop from hemogenic endothelial cells residing in specialized vascular niches (option A).1 Early blood vessels are derived from blood islands, which are clusters of mesodermal progenitor cells. These islands are marked by central hematopoietic progenitor cells and peripheral angioblasts (option B). Unlike during development, postnatal vasculogenesis does not rely on angioblasts, but instead occurs by the sprouting of new vessels from preexisting vessels. In the adult, vasculogenesis may be limited. However, in scenarios such as the development of collateral vasculature with obstructive coronary artery disease, arteriogenesis occurs. Arteriogenesis occurs by the sprouting of new vessels from preexisting capillaries or arterio-arterio anastomoses (option C).2 Much work has gone into understanding cytokines that stimulate vasculogenesis. The prototypical angiokine is VEGF.3 In fact, VEGF inhibitors are used clinically as anticancer agents to inhibit tumor-related angiogenesis (option E).
Which of the following is incorrect regarding the role of endothelial cells?
A. The endothelium serves as a prothrombotic surface
B. The endothelium regulates the inflammatory response by affecting leukocyte recruitment and margination
C. The endothelium helps to regulate vascular tone
D. The endothelium regulates signaling by allowing for the selective passage of molecules across the barrier
E. The endothelium serves as a barrier to circulating blood constituents
The answer is A. (Hurst’s The Heart, 14th Edition, Chap. 7). Among its many functions, the endothelium is of particular importance for maintaining and protecting the integrity and function of the vascular wall, with specific roles. These include (1) functioning as a metabolic tissue that actively secretes vasoactive factors governing vascular tone (option C); (2) acting as an anticoagulant and antithrombotic surface (option A); (3) serving as a barrier to most circulating blood constituents (option E); (4) regulating the transendothelial passage of specific ...