Monocytes, Macrophages and Other Inflammatory Mediators of Abdominal Aortic Aneurysm

Macrophages early invade the forming abdominal aortic aneurysm (AAA) and greatly contribute to its pathogenesis. Recent findings have shown that Ly-6Chigh and Ly-6Clow monocytes are rapidly mobilized from the splenic reservoir in response to angiotensin II infusion and sequentially infiltrate the abdominal aorta. The first wave of Ly-6Chigh monocytes prevails in the aorta and promotes the accumulation of inflammatory macrophages, which most likely cause irreversible changes in the abdominal aorta. In this review, we discuss the current knowledge on the cellular mechanisms that initiate AAA in mice. We particularly focus on the role of monocyte and macrophage subsets during the early steps of the aneurysmal process.