Step-by-step En face O red oil method for aortic plaque staining and quantification in ApoE knockout mouse.

The en face Oil Red O (ORO) technique is an established method for quantifying experimental atherosclerotic plaque. However, interlaboratory reproducibility is influenced by procedural factors, including aorta dissection, image preparation, and analysis. This paper provides a detailed step-by-step procedure for en face ORO analysis of ApoE knockout mice, with comprehensive photographic guidance for each step, for plaque staining and quantification using a standard digital camera and Adobe Photoshop. The procedure includes harvesting and trimming the aorta, staining, mounting, imaging, and quantitative analysis. Images are captured using generic digital cameras and plaques are quantified in Adobe Photoshop. Each step is documented photographically, providing a visual reference to aid protocol implementation and enhance methodological transparency. The workflow offers a practical and reproducible method for standardized en face plaque evaluation and could be valuable for novice researchers performing preclinical atherosclerosis studies. This method: • Provides a standardized, photographically documented workflow for en face ORO staining and plaque quantification in ApoE knockout mice. • Enables accurate plaque measurement using a conventional digital camera and Adobe Photoshop. • Includes practical photo guidance from aorta dissection through image capture and lesion measurement.