Oil Red O staining and foam cell formation rate

According to the aforementioned method, THP-1 macrophages were adjusted to a cell density of 4x10⁵ cells/ml and 1x10⁶ cells/well were seeded into 6-well plates containing pre-implanted sterile coverslips in an incubator at 37˚C and 5% CO₂. Subsequently, cells on the coverslips were washed with PBS 3 times, 5 min each time, and then fixed with 4% paraformaldehyde for 30 min at room temperature. Oil red O staining was performed for 10 min and the cells were counterstained for 5 min with hematoxylin at room temperature. Under the optical microscope, the number of larger red dye particles in the cell >5 can be used as the standard for foam cell formation. Ten fields were randomly observed to calculate the number of foam cells and the total number of cells at magnification, x200. The ratio of foam cells to total cells was deemed the foam cell formation rate.