Xanthoma tissue-extracted LDL density substances are the main inducer of myelin-like bodies and ceroid granules in foam cells.

Characteristic intracellular organelles of the foam cells in xanthoma are composed of membrane-bound lipid vacuoles, membrane-free lipid vacuoles, cholesterol crystals, multivesicular or multilocular lipid bodies, myelin-like bodies, and ceroid granules. We aimed to clarify the formation of myelin-like bodies and ceroid granules in the foam cells of xanthoma. We ultrastructurally examined mouse peritoneal macrophages incubated with human low-density lipoprotein (LDL) modified by incubation with xanthoma tissue, with xanthoma tissue-extracted LDL density substances, and with homogenized xanthoma tissue-derived crude material. A large number of membrane-bound and membrane-free lipid vacuoles were observed in macrophages incubated with xanthoma tissue-modified LDL. The macrophages incubated with the xanthoma tissue-extracted LDL density substances contained a large number of myelin-like bodies and ceroid granules. The macrophages incubated with the homogenized xanthoma tissue-derived crude material accumulated many vacuoles containing vesicular structures and a small number of myelin bodies and ceroid granules. Membrane-bound lipid vacuoles are derived from lysosomes that accumulate mostly extravasated modified LDL in xanthoma tissue. On the other hand, myelin-like bodies and ceroid granules are mostly derived from LDL density substances derived from xanthoma tissue homogenate.