Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a key mediator of
inflammation and plays an important role in the pathogenesis of
atherosclerosis. Conversely, LOX-1 deficiency has been shown to decrease
inflammation and
atherosclerosis, both of which have been proposed to contribute to
abdominal aortic aneurysm (AAA) pathogenesis. However, the role of LOX-1 in AAA pathogenesis remains unknown. Here, we investigated the effects of Olr1 (which encodes LOX-1) deletion on
angiotensin II (Ang II)-induced AAA in
apolipoprotein E knockout (
ApoE KO) mice to determine whether LOX-1 deficiency mitigates AAA development. To accomplish this, we used serial, non-invasive ultrasound assessment, which revealed that the incidence and expansion rate of AAA were similar regardless of Olr1 deletion. However, Olr1 deletion significantly increased severe AAAs, including ruptured AAAs resulting in death.
Oil Red O staining of the harvested aortas showed that the extent of
atheroma burden localized in aneurysmal lesions did not differ between LOX-1-deficient and control mice, suggesting that Olr1 deletion did not decrease
atheroma burden in the aneurysmal wall. Further histopathological analysis revealed that aneurysmal lesions in LOX-1-deficient mice had fewer fibroblasts and myofibroblasts, as well as thinner adventitial
collagen, although the degree of
elastin fragmentation or disruption was similar between LOX-1-deficient and control mice. An in vitro study confirmed that the proliferation of adventitial fibroblasts collected from LOX-1-deficient mice was significantly attenuated despite Ang II stimulation. In conclusion, Olr1 deletion may not mitigate
aneurysm development but rather increases the vulnerability of
rupture by suppressing adventitial fibroblast proliferation and
collagen synthesis.