The influence of hypertension on injury-induced myointimal thickening

Although hypertension has been identified as a risk factor in atherosclerosis, how hypertension enhances plaque growth is not clear. To study the influence of essential hypertension on injury-induced arterial intimal thickening, we employed a model of arterial endothelial injury (aortic balloon injury) in spontaneously hypertensive rats (SHR). SHR rendered normotensive with drugs served as controls. The injured vessels were fixed by perfusion at intervals between 2 weeks and 3 months and studied by light, transmission, and scanning electron microscopy. Endothelial regeneration at 2 weeks was assessed by the difference between total and blue-stained arterial surface area in rats receiving Evans blue by injection and was decreased in SHR. Intimal thickening was increased in SHR as compared with controls at all time intervals and appeared to be due to increased smooth muscle cell proliferation. Although neither SHR or controls injured arteries were stained by Evans blue at 3 months, the SHR (but not the control) injured arteries demonstrated subendothelial edema and focal necrosis in the intima. These data in a model of arterial endothelial injury support the concept that essential hypertension has a deleterious effect on arterial wound healing by enhancing arterial myointimal thickening. This effect can be reduced by adequate control of the hypertension with drugs.