Fabric organization of the subendothelium of the human brain artery by polarized-light microscopy.

Abstract

The thickened subendothelium of brain arteries that is characteristic of atherosclerosis was assessed for the directional organization of the two main birefringent components, smooth muscle cells and collagen. Thirty-three arteries from 16 autopsy cases were pressure fixed at 30, 60,110, and 200 mm Hg, sectioned at a thickness of 7 pm, and stained with silver impregnation to enhance tissue birefringence. The intended focus of the study was on muscle organization, but it also included the collagen among the cells because of the coalignment of the two tissues and their similar staining properties for polarized-light microscopy. The birefringent medial fabric at all pressures was circumferentially oriented, with a mean deviation of the 33 sections of 1.4° from circumferential with an average circular standard deviation of 3.5°, thereby showing remarkable coherence. In contrast, the subendothelium showed great variability both in thickness and in organization. Many arteries had no measurable subendothelium, and others had as much as 100%, with some atherosclerotic lesions as much as 300% of the medial width. Measurements from the subendothelium revealed a helical arrangement of tissue, often divided into separate regions, with a balance of left-and right-handed helical components and generally with lower pitch angles in the layers adjacent to the lumen. The average circular standard deviation within individual subendothelial layers was 14.5°. (Arteriosclerosis and Thrombosis 1991;ll:681-690)

Determination of the layer-specific distributed collagen fibre orientations in human thoracic and abdominal aortas and common iliac arteries

“…Our finding of two prominent helically organized fibre families in the intima (symmetrically arranged with respect to the cylindrical axis) was also documented for the subendothelium of human brain arteries in Finlay et al [52]. As depicted in figure 5, there is generally a much wider range of fibre orientations present in the intima than in the media and adventitia.…”

The layered fabric of cerebral artery fenestrations.

“…All layers of the subendothelium are helically oriented, with the more longitudinally oriented fibers adjacent to the media and more circumferentially oriented fibers next to the lumen, as in brain arteries. 23 Tissue sections cut longitudinally through the fenestration (the fenestration appearing as an island in the flow stream) reveal the full spectrum of microstructure from the leading to trailing edges, with the midsection appearing like normal artery wall. The media is completely absent locally at both edges, corresponding, for the leading edge, to the medial gap of brain artery bifurcations, 27 but the trailing edge medial gap occurs despite the substantial buildup of subendothelium.…”

A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

“…Most bifurcations of the cerebral vasculature are structurally stable, but a small number develop a weakness that causes the wall to expand outwardly in the region near the flow divider of the branching artery (Austin et al, 1993;MacDonald et al, 2000;Rowe et al, 2003). Some measurements of the macroscopic mechanical properties of cerebral arteries and aneurysms exist (Coulson et al, 2004;Monson et al, 2003Monson et al, , 2005Scott et al, 1972;Steiger, 1990;Tóth et al, 1998Tóth et al, , 2005 and the structural organisation of these tissues is fairly well documented (Canham et al, 1991b(Canham et al, ,a, 1992(Canham et al, , 1996(Canham et al, , 1999Finlay et al, 1991Finlay et al, , 1995Finlay et al, , 1998Hassler, 1972;MacDonald et al, 2000;Rowe et al, 2003;Smith et al, 1981;Whittaker et al, 1988). In the aneurysmal wall, the tunica media and the internal elastic lamina have often disappeared or are severely fragmented (Abruzzo et al, 1998;Sakaki et al, 1997;Stehbens, 1963;Suzuki and Ohara, 1978;Tóth et al, 1998).…”