Cholesterol-rich conditions lead to an activated synovium, rather than synovial thickening. Thickening of the synovial lining layer was determined in hematoxylin and eosine stained sections, using an arbitrary score between 0 and 3. All mice showed moderate synovial thickening with no significant differences between various groups (A). Immunohistochemistry, however, showed an increase in S100A8 expression in WT mice after receiving a cholesterol rich diet, suggesting enhanced macrophage activation (B). *P<0.05. n = 10 mice per group.WT, wild type.