Heterogeneity of atherosclerosis in mesenteric arteries and outgrowth remodeling

Abstract Background In patients with acute mesenteric ischemia by occlusive thrombo-embolism, the superior mesenteric artery (SMA) is more affected than the inferior mesenteric artery (IMA). Methods This study investigated postmortem mesenteric arteries from aged subjects ( n =21). Four atherosclerotic stages were defined by signs of degeneration and inflammation in sections stained with Elastica-van-Gieson and immunohistology, respectively. Results In females and males, Stages 3 and 4 were found in 62% of the SMA and 24% of the IMA. Lumenal areas based on diameter measurements remained essentially unchanged between Stages 1 and 4. Compared to a Stage 1 reference, remodeling was associated with thinning of the media below the plaque base and with pronounced thickening below the shoulder in the IMA. In Stages 3 and 4, the adventitia of the IMA had more vasa vasorum and a higher number of CD45-positive leukocytes than the adventitia of the SMA. During atherosclerotic progression, a stable fraction of leukocytes represented mast cells (6%) and CD117-positive cells as potential progenitor cells (1%). Conclusions Outgrowth remodeling occurred in both the SMA and the IMA. Less severe atherosclerosis in the IMA than in the SMA was associated with stronger signs of inflammation.