Investigation of histological response by manipulating mechanical fields of rat abdominal aorta

Abstract

Formation and progression of cerebral aneurysms are associated with vascular wall thinning, but the cause is still unclarified. We hypothesize that the cause is (1) microscopic change of vascular-wall mechanical fields, (2) erosion of elastic lamina (EL) by smooth muscle cells (SMCs), (3) elongational amplification and collective death of SMCs and (4) internal collapse of vascular structure associated with cell death, in order. We have validated it for a few years. When manipulating vascular-wall mechanical fields of rat abdominal aorta, disorder of the EL, collective death of SMCs and vascular wall thinning was observed. On the other hand, the formation of aneurysms couldn’t be found in this experiment. This result suggests that the cause is that the repair response is fast. Therefore, the same experiment was conducted in an aged rat. The study focused on 76 weeks old male SD rat abdominal aorta. Manipulating the mechanical field of the vascular wall by stenosing the artery by 35% and elongating the artery axis resulted in EL tears and EL structures resembling intimal thickening, which were not observed in both young and old control groups. These results suggested that the mobility of SMCs has been increased by changes in the vascular tissue structure due to aging and making it easier for them to migrate in response to mechanical stimuli.