Vessel walls are comprised of several different cell populations residing in and on complex extracellular matrices. Each of the vascular cell types has diverse and sometimes unique functions and morphologies, and each has roles in repair processes following injury. Large vessel endothelial cells are known to respond to denudation injury by sheet migration and proliferation. This is in contrast to the migration through soft tissues with tube formation and subsequent lumen formation exhibited by microvascular endothelial cells in response to injury. Vascular smooth muscle cells of larger vessels respond to injury by migration from the arterial media into the intima, proliferation, and matrix biosynthesis, ultimately causing intimal thickening. Both these cell types exhibit "dysfunctional" phenotypes during their responses to injury. Microvascular cell responses to injury, while extremely variable, are less well documented. Specifically, responses to injury by microvascular endothelial vascular cells appear to be modulated, in part, by the composition and organization of the surrounding matrix as well as by the various soluble factors and cytokines found at sites of injury, suggesting that the extracellular matrix and soluble factors modulate each other's effects on local vascular cell populations following injury.