In the Injury Theory, it's damage to the arterial endothelium, followed by platelet activation, then smooth muscle cell migration to injury, then macrophages, with resulting "foam cells." Engorged foam cells burst, starting the injury cycle all over again
A. Malijevský, S. Yuste, A. Santos, and M. Haro. Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)