Flow cytometric quantification of cholesteryl ester-containing "foam" cells. II. Analysis of aortas from cholesterol-fed swine.

We have examined foam cell accumulation in abdominal and thoracic aortic segments of swine with experimentally induced atherosclerosis. Young (less than 1-year-old) male swine were divided into four groups that were fed control, lard (20%), lard (20%) plus cholesterol (1%), and regression (3 months cholesterol-lard followed by 3 months control) diets for 6 months. Aortas were removed from animals and enzymatically dissociated. Foam cells were detected by specifically staining their cholesteryl ester inclusions with the fluorescent dye filipin. Flow cytometry was used to quantify the number of foam cells in each aortic cell suspension. Cholesterol-lard feeding increased serum cholesterol levels 6-fold and induced a substantial increase in both abdominal and thoracic foam cell densities. Lesion development in cholesterol-lard-fed animals, as assessed by macroscopic evaluation of aortas, correlated with foam cell accumulation as determined by flow cytometry. Accumulation of foam cells was extremely variable from animal to animal and did correlate significantly with serum cholesterol but not with serum triglyceride levels. Interestingly, although serum cholesterol levels increased 1.5-fold in swine fed the lard diet, foam cells did not increase significantly as compared to control animals. Animals placed on a control diet following 3 months of the cholesterol-lard diet showed a trend toward lower foam cell densities as compared to animals fed the cholesterol-lard diet for the entire 6 months. Flow cytometric analysis of filipin-stained aortic foam cells provides a new means to evaluate atherosclerotic lesion development.