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24-10-2011 | Article

Elastin-rich fibers play crucial role in resistance vessels

Abstract

Free abstract

MedWire News: Elastin in the arteriolar wall plays a crucial role in stress-bearing and constraining vascular smooth muscle cells, study findings indicate.

The team that conducted the study says that studying the biomechanics of the extracellular matrix (ECM) will aid our understanding of how these elements are affected in aging and disease.

Researchers led by Michael Hill (University of Missouri, Columbia, USA) tested the hypothesis that an adventitial population of elastin-rich fibers exist in the vessel wall and are predominantly arranged in a longitudinal fashion - and thereby bear and exert longitudinal mechanical stress.

To investigate, they isolated arterioles from the cremaster muscle of rats and exposed the adventitial surfaces to elastase.

Using 3D confocal microscopy to visualize the ECM within the vessel wall, the team found that elastin exposure led to a significant and irreversible lengthening of the vessel segment.

By contrast, repeating this process on isolated rat cerebral arteries had no such lengthening effect.

The team then attempted to identify the precise involvement of different matrix proteins. Staining with a specific elastin antibody confirmed the presence of elastin in cremaster vessels, as well as in small mesenteric arteries, but not in cerebral vessels.

Further staining studies showed that elastin-containing fibers were distinct from type I collagen fibers. Similarly, cleaving of the fibers with elastase led to a leftward shift in the passive pressure-diameter relationship at low pressures, consistent with the contribution of elastic to vascular mechanics as compared with that of collagen.

"This, however, does not indicate that the stained adventitial fibers are composed of elastin alone and presumably contain other proteins, such as fibrillin," write the authors in the journal Arteriosclerosis, Thrombosis and Vascular Biology.

They say their observations support a significant role for elastin-containing fibers in the mechanical properties of resistance vessels, although the precise structures and functions remain to be elucidated.

"Despite consisting of only a few cell layers in thickness, the walls of small arteries and arterioles present a complex biomechanical structure," they conclude.

"Knowledge of the 3D architecture of the ECM components of the vessel wall is also of importance to our understanding of how these elements are affected in aging and disease states, particularly where matrix proteins are damaged, degraded, or posttranslationally modified."

By Joanna Lyford