The fatty streak and transition to more advanced lesion

Non-progression or regression of foam cells and fatty streaks may result from a decrease in plasma and intimal LDL levels. 

In the progressing lesion, a number of additional processes come into play, the most important of which are cellular necrosis with the release of foam-cell lipids to the interstitium, and the mitogen-stimulated proliferation of myointimal cells (smooth muscle cells), with the subsequent synthesis of collagens, elastin and proteoglycans. 

Then begins the adherence of platelets and release of platelet-derived growth factor (PDGF) (55). 

In an extracellular location in the arterial intima the lipids must be regarded as comprising a largely inert metabolic pool. Its subsequent removal or clearance from the intima can be accomplished only after the phagocytotic uptake by macrophages, a process which will convert the cholesterol to a metabolically active intracellular pool, thus permitting the HDL-mediated reverse cholesterol transport. 

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