Progression of foam-cell formation in vitro in elicited macrophages after incubation with ox-LDL

Abstract

Thioglycollate elicited mouse peritoneal macrophages incubated with copper-oxidized LDL(ox-LDL) developed foam cell morphology as observed by Nile red fluorescent staining for neutral lipids and by electron microscopic observations. Total cellular cholesterol content rose steadily over 168 hrs and esterified vs free cholesterol ratios also increased.Cultured macrophages were incubated with ox-LDL, fixed, and stained with Nile red or processed for electron microscopy. Macrophages stained with Nile red exhibited progressive accumulation of lipid over 24, 72 and 168 hrs (Fig. 1-3). The percentage of cells with lipid inclusions and the size and number of inclusions per cell increased progressively over 168 hrs. Control cells incubated without ox-LDL did not have staining indicative of foam cell formation.Transmission electron microscopy of cultured cells at 24, 72, and 168 hrs showed distinct ultrastructural changes (Fig. 4-6). Macrophages at 24 hrs possessed non-membrane bound lipid droplets. Following 72 hrs, lysosomes containing multilamellar lipoid structures were also present. Cells at 168 hrs had characteristics similar to those at 24 and 72 hrs with the addition of cholesterol crystal profiles.