ABSTRACT
Extracellular lipid accumulations are mixtures of the remnants (including the lipid droplets) of foam cells that have died. The component particles are of variable size but are much larger than plasma-derived low density lipoprotein. Extracellular lipid accumulations are not taken up and broken down by macrophages or other cells. Instead, very slow degradation, perhaps partly by mechanical means, takes place in the intercellular space. Studies of the sequence in which lesion components regress support this observation. When high blood cholesterol levels were drastically lowered in monkeys, macrophages and macrophage foam cells were first to disappear from the lesions; only subsequently did extracellular lipid accumulations slowly decrease in the absence of macrophages (see pages 37-40 for details of lesion regression).
