Abstract 498: The Transcription Factor TWIST-1 is Specifically Expressed in Macrophage Derived Foam Cells
Lipid-laden macrophage derived foam cells are an early component of atherosclerotic lesions and likely to play a key role in disease progression. Therefore, macrophage derived foam cells may have a unique, macrophage and atherosclerotic-plaque specific gene expression profile. We used genome-wide microarray analysis to identify genes that are significantly higher expressed in atherosclerotic than in non-atherosclerotic macrophages. We isolated macrophages from advanced atherosclerotic lesions of the carotid artery and non-atherosclerotic tissues lung, liver, spleen from two human donors during autopsy. Atherosclerotic macrophages were isolated by laser capture microdissection on frozen sections using CD68-immuno-positivity on parallel sections as navigator. Non-atherosclerotic macrophages were isolated using CD68-coated immunomagnetic beads on cell suspensions. 42 genes were significantly higher expressed (p<0.01) in atherosclerotic macrophages from both patients, including 5 genes involved in transcription regulation. Microarray data and QPCR on 3 separate individuals indicated a 13.2 and 34.3 fold higher expression of TWIST1, a basic helix loop helix transcription factor, which has not been linked to atherosclerosis before, in atherosclerotic than in non-atherosclerotic macrophages. Immunohistochemistry showed strong TWIST1 staining in atherosclerotic macrophages in the subendothelial layer and faint staining surrounding the necrotic core. Immunoreactivity was also detected in endothelial and in some medial and neointimal vascular smooth muscle cells. Both nuclear and cytoplasm localization were observed. Conversely, none of the macrophages in 8 inflamed non-atherosclerotic tissues and 3 control tissues (3–5 samples per tissue) showed TWIST1 signal. In contrast foamy cells in the gall bladder and xanthelasma’s showed positive staining. Furthermore, acLDL and oxLDL loading increased TWIST1 expression in PMA-induced THP-1 macrophages 2.0 and 3.3 fold respectively. Our data indicate that TWIST1 is a transcription factor specifically expressed in foamy macrophages, suggesting a regulating role of TWIST1 during lipid-loading.