Establishment and Identification for Different Stages of Foam Cells

Objective To establish and identify different stages of foam cell models. Methods THP-1 cell derived macrophage(THP-M) was induced with ox-LDL(80μg/ml) into different stages of foam cells models. Total cholesterol and cholesterol ester content in foam cells were detected by ELISA; Transmission electron microscopy(SEM) and oil red O staining were used to observe accumulated lipid in cells, MTT staining was used to determine foam cells viability at different stages. Results A lot of oil red O positive cells was observed in ox-LDL group since 24 h; Total cholesterol and cholesterol ester significantly increased in 24h-THP-M than control group. Cholesterol ester content is more than 50% of the total cholesterol, indicating that foam cells have been formed. MTT staining results showed that the survival rate of foam cells were respectively 93.21±3.66%, 72.15±2.23% and 63.06±1.83% after THP-M cells have cocultured with ox-LDL for 48 h, 60 h and 72 h; SEM results showed that intracellular lipid drops gathered apparently, cytoplasmic autophagosome increased gradually within 24 h. when incubated with ox-LDL for 36 h or 48 h, intracellular lipid droplets are different from each other both in size and shape. Autophagolysosome with half-digested lipid drops were visible. Some foam cells burst; when cocultured for 60 h and 72 h, the number of autophagosomes decreased significantly in the cell and more cells disrupted. Western blot test results showed that LC3II protein expression level was consistent with the results from SEM at different stages. Conclusion When cocultured with ox-LDL for 24h, or 36 h-48 h, or 60h-72h, THP-M cell morphology and lipid content were in line with the characteristics of foam cells at early stage, middle stage or late stage, respectively. So, we obtained different stages of foam cell models successfully. And cell vitality changes during those courses may be linked to type II apoptosis(autophagy death).