Assessing Atherosclerosis in the Aorta from AAV8-PCSK9-Injected Mice by Oil Red O Staining

Mouse models have long been fundamental tools in the study of atherosclerosis, providing critical insights into the molecular and cellular mechanisms underlying plaque formation, lipid metabolism, and cardiovascular inflammation. Beyond Apoe^-/- or Ldlr^-/- mice, AAV8-PCSK9^D377Y injection in normal C57BL/6J mice with concurrent western-type diet feeding emerges as a commonly used model for translational research in atherosclerosis. Oil Red O staining is a cornerstone technique for visualizing neutral lipid accumulation in vascular tissues. Its simplicity, cost-effectiveness, and high sensitivity for detecting lipid-laden lesions make it the gold standard for assessing atherosclerotic plaque burden in preclinical studies. In this study, we provide a detailed, reproducible protocol for the dissection, perfusion, longitudinal opening, Oil Red O staining, imaging, and semi-automated quantification of atherosclerotic burden in the en face aorta, without the need for pins or complex mounting steps. Our results demonstrate that the combination of AAV8-PCSK9^D377Y injection and western-type diet feeding effectively induces significant atherosclerotic lesion formation in mice, and that en face Oil Red O staining is a reliable and efficient technique for assessing lipid deposition and plaque burden. Furthermore, although this protocol is optimized for the AAV8-PCSK9-induced model in C57BL/6J mice, it can be readily adapted for use in other models and species, such as Apoe^-/- mice, Ldlr^-/- mice, and Ldlr^-/- golden Syrian hamsters.