THE ROLE OF THE MONOCYTE IN ATHEROGENESIS .2. MIGRATION OF FOAM CELLS FROM ATHEROSCLEROTIC LESIONS

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  • 1 January 1981
    • journal article
    • research article
    • Vol. 103  (2) , 191-200
Abstract
A defined role in the atherogenic sequence is proposed for the circulating monocyte. A monocyte clearance system in which large numbers of circulating monocytes invade the intima of lesion-prone areas in arteries, become phagocytic and accumulate lipid is shown. A fatty cell lesion results. Once lipid-laden, foam cells migrate back into the bloodstream by crossing the arterial endothelium. The ratio of penetrating monocytes to emerging foam cells decreases as fatty cell lesions develop until a 1-to-1 ratio is achieved in late fatty cell lesions, which do not progress further. Advanced fibroatherosclerotic plaques in Yorkshire pigs do not show the same characteristics and have smooth muscle cell involvement. Advancement of the lesion apparently is at least partially a result of failure of the monocyte clearance system to remove sufficient lipid. The invasion of monocytes and endothelial damage caused by foam cell clearance may, in late fatty lesions, contribute to plaque evolution by introducing growth factors from macrophages and platelets and allowing greater lipid influx. Elucidation of this system was facilitated by the examination of vessels from diet initiation onwards and by the observation of late nonprogressing fatty cell lesions.