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Acute Aortic Disease.. - Index of

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310 Hackmann et al.<br />

treatment. New treatments are needed to stop aneurysm expansion and prevent rupture.<br />

Recent experimental work has focused on improving our understanding <strong>of</strong> the<br />

pathobiology <strong>of</strong> aortic aneurysms in hope <strong>of</strong> identifying new strategies for long-term<br />

suppressive therapy.<br />

PATHOBIOLOGY OF AORTIC ANEURYSMS<br />

Over the last two decades, research on the pathobiology <strong>of</strong> aortic aneurysms has<br />

greatly improved our understanding <strong>of</strong> the cellular and molecular mechanisms<br />

involved in progressive aortic dilatation. Most studies have focused on abdominal<br />

aortic aneurysm (AAA) formation. Until recently, most <strong>of</strong> the research regarding<br />

thoracic aortic aneurysms (TAAs) has concentrated on those related to connective<br />

tissue disorders, particularly Marfan syndrome (MFS). Relatively little is known<br />

about the pathobiology <strong>of</strong> TAAs related to chronic medial degeneration or dissection<br />

in patients without MFS. Studies in animals and human aortic tissue have shown<br />

that the development <strong>of</strong> aneurysms results from a cascade <strong>of</strong> interacting cellular<br />

and molecular processes, including matrix degeneration by elastin- and collagendegrading<br />

proteases, chronic inflammation, cytokine activity, and loss <strong>of</strong> smooth<br />

muscle cells (SMCs) (Fig. 1) (1). Together, these processes undermine the mechanical<br />

properties <strong>of</strong> the aortic wall, and lead to aneurysm expansion and rupture (2).<br />

Matrix Proteolysis<br />

The two proteins responsible for maintaining structural integrity <strong>of</strong> the aortic wall<br />

are elastin and collagen, which respectively confer elasticity and tensile strength.<br />

Figure 1 Diagram illustrating the overlapping cellular and molecular processes that<br />

contribute to aortic aneurysm formation.

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