Measurements from light and polarised light microscopy of human coronary arteries fixed at distending pressure

Abstract

With the long term goal of improving our understanding of the mechanisms involved in coronary artery spasm, we have undertaken a two part study of the artery structure. We have made a comparison of the relative proportions of the different layers in proximal and distal regions of the main coronary arteries, and have quantitatively assessed their three dimensional structural fabric. Major coronary arteries from nine hearts were prepared for histological examination after fixation at a transmural pressure of 120 mm Hg. Measurements from 14 proximal and distal pairs of the cross sectioned arteries showed a dominant subendothelial layer, which diminished in thickness distally, with a small fraction of muscle cells interspersed with collagen. Three dimensional orientation measurements of the collagen and muscle components, which are birefringent, were obtained from one pair of segments from each of the left anterior descending, circumflex and right coronary arteries, using the polarising light microscope and Universal stage. Findings showed (1) a single circumferential order of adventitial collagen, with a mean circular standard deviation (CSD) of 22.3 degrees; (2) very highly ordered medial smooth muscle, mean CSD of 5.0 degrees (both findings are quantitatively similar between proximal and distal segments of artery, and between arteries); and (3) a multilayered fabric of collagen in the subendothelium in all vessel segments. The principal contributor to functional differences between proximal and distal regions may be the prominent and structurally varied subendothelial layer of the coronary arteries.

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

“…Adjacent or nearby sections to those used for measurements were stained with Gomori's one-step trichrome and were used to assess the relative concentrations of smooth muscle fibers. The subendothelial layer of brain arteries was found to contain a higher proportion of smooth muscle than that in our assessment of coronary arteries, 5 with the exception of the areas of localized intimal thickening where the smooth muscle was less concentrated, and in some areas, very sparse.…”

“…1 -3 Quantitative alignment studies by polarized-light microscopy have substantiated those early findings. 4 - 5 A similar morphometric study applied to the subendothelium might establish if that layer, which with time becomes a characteristic component of the larger brain arteries, also has the potential to be a contributor to the mechanical behavior of those arteries. Research that concerns mechanical function of arteries has focused on the tunica media, the layer considered to be the most significant mechanically, 6 and there the role of smooth muscle cells is well documented.…”

Microstructural quantification of collagen fiber orientations and its integration in constitutive modeling of the porcine carotid artery

“…Then the segments were further dehydrated, embedded in paraffin, and tangentially sectioned at 7.0 [µm] thickness. In order to enhance the birefringent properties of collagen, which also improves the precision of subsequent collagen orientation measurements, histological sections were stained with Picrosirius red [6]. According to this histological preparation the collagen in the vessel wall appeared bright orange-yellow-red when viewed with polarized light, see Fig.…”

“…The ability to get detailed fiber orientation [6,8,27] and recruitment [7] data makes structural SEFs all the more relevant, such that structural and mechanical model parameters can be separately identified by histological and mechanical experiments, respectively. Specifically, inflation [35,38], planar biaxial [20,24] and uniaxial [11,32] testing are preferable in-vitro mechanical test protocols for vascular tissue.…”

Experimental investigation of collagen waviness and orientation in the arterial adventitia using confocal laser scanning microscopy

“…Different techniques such as polarized light microscopy (PLM) (Hilbert et al 1996;Canham et al 1991;Smith et al 1981;Finlay et al 1995;Braga-Vilela et al 2008;Rieppo et al 2008;Whittaker and Canham 1991), small angle light scattering (SALS) (Ferdman and Yannas 1993;Sacks et al 1997;Billiar and Sacks 1997), transmitted light microscopy (TLM) (Elbischger et al 2005;Canham et al 1989), fluorescence microscopy (FM) (Axer et al 2001;Young et al 1998), micro coherence tomography (Micro-CT) (Xia and Elder 2001), optical coherence tomography (OCT) (Hansen et al 2002), small angle X-ray scattering (SAXS), second harmonic generation (SHG) (Boerboom et al 2007;Wicker et al 2008;Bayan et al 2009) and electron microscopy (EM) (Franchi et al 2007;Magnusson et al 2002;Xia and Elder 2001;Wolinsky and Glagov 1964) have been used to characterize collagen bundle orientation and/or crimp properties in soft tissue. Fewer studies have focused on quantifying the organization of collagen fibers within the arterial wall Smith et al 1981;Finlay et al 1995;Canham et al 1989;Dingemans et al 2000).…”