Fig. 3.

Mouse liver sections obtained 6 months after a high-cholesterol (1%) and high-fat (15%) diet. Osmium tetroxide staining (stains triglycerides and cholesterol esters black) with methylene blue counterstaining (A–D) shows early cholesterol crystallization under polarized light (B) in the periphery of an intact LD in a normal hepatocyte (A), and advanced cholesterol crystallization (D) with cholesterol crystals as large as 10 µm, in a remnant LD of a dead hepatocyte surrounded by KCs forming a CLS (C). KCs processing remnant LDs of hepatocytes in a CLS transform into characteristic lipid-laden foam cells containing multiple small LDs (E–F). The KCs in CLSs also stain strongly positive for NLRP3 (G) and activated caspase 1 (I) by immunohistochemistry, suggesting activation of the NLRP3 inflammasome. CLSs also stain strongly for acid phosphatase (J), suggesting activation of lysosomal enzymes in the processing of the LD.