Foamcellen

Foamcellen, also known as foam cells, are lipid-laden cells commonly found in atherosclerotic lesions. They arise predominantly from macrophages that have ingested large amounts of modified low-density lipoprotein (LDL), particularly oxidized LDL (oxLDL), through scavenger receptors such as SR-A and CD36. Vascular smooth muscle cells (VSMCs) can also acquire lipids and dedifferentiate into foam cells, contributing to the plaque’s cellular makeup.

Inside foam cells, stored cholesterol is mainly in esterified form within cytoplasmic lipid droplets, giving a foamy appearance on histology and staining with Oil Red O. Uptake of modified LDL is not downregulated by cholesterol levels, unlike the LDL receptor pathway, allowing progressive lipid accumulation. Foam cells are typically detected by histology and immunohistochemistry, with macrophage-derived cells often expressing CD68 and/or MAC-2, while VSMC-derived foam cells may retain some smooth muscle markers.

Foam cells are central to the development of atherosclerotic plaques. They contribute to early fatty streaks and to ongoing plaque inflammation by secreting cytokines and matrix-degrading enzymes. When foam cells die, they can form a necrotic core that destabilizes plaques and increases the risk of rupture.

Lipid efflux pathways counterbalance accumulation, notably via ATP-binding cassette transporters ABCA1/ABCG1 and apolipoprotein A-I, promoting cholesterol removal to HDL. Impairment of efflux or excessive lipid uptake promotes foam cell formation. Clinically, therapies that lower LDL cholesterol, enhance cholesterol efflux, or reduce inflammation aim to reduce foam cell burden and plaque progression.