Tunica media remodeling in mesenteric arteries of hypertensive rats

Abstract

Background: The tunica media of the vascular wall is a composite material comprised of smooth muscle cells and fibrous and non-fibrous matrix proteins. Methods: Using morphometric techniques, this study quantifies the cell and matrix composition of normotensive (Wistar-Kyoto) and spontaneously hypertensive rat mesenteric arteries. Results: The data show that the superior mesenteric artery (SMA) and small mesenteric arteries are different in matrix composition, cell-to-matrix ratio, and cellular dense body content. Compared with normotensive arteries, hypertensive arteries have less basement membrane but more collagen and extracellular matrix ground substance. SMA from hypertensive rats has about 30% less elastin than does normotensive artery. In contrast, the elastin content of small arteries of both strains was about the same and was less than 4% of the matrix area. Except in hypertensive SMA, membrane dense bodies occupy 7-10% of the cell area and more than 10 times the area occupied by cytoplasmic dense bodies. In contrast, cells from hypertensive SMA have about half the membrane dense body area of the normotensive cells. A decreased proportion of dense bodies in the hypertensive SMA is consistent with the 'partial detachment' of these cells from the matrix. Conclusions: These results are consistent with both cellular and matrix 'remodeling' in diseased vessels in response to continuous, long- term elevated blood pressure.