Extracellular matrix of the human aortic media: An ultrastructural histochemical and immunohistochemical study of the adult aortic media

Abstract

Aortic distensability is the key to normal aortic function and relates to the lamellar unit in the media. However, the organization of the extracellular matrix components in these lamellar units, which are largely responsible for the distensability, is insufficiently known, especially in the human. We therefore performed a detailed ultrastructural analysis of these components. Thoracic aortas of 56 individuals (age 45-74 years), none of whom suffered from aortic disease, were studied by immunoelectron microscopy of elastin, collagen types I, III, IV, V, and VI, fibronectin, and fibrillin-1, and by ultrastructural histochemistry of proteoglycans, which were further characterized by enzymatic digestion. The elastic lamellae were closely associated with thick collagen fibers containing types I, III, and V collagen. Between these collagen fibers, numerous complex, circumferentially oriented streaks of elastin protruded from the lamellae. In contrast to what is usually reported in the aortas of experimental animals, the smooth muscle cells preferentially adhered to these ill-defined streaks rather than directly to the solid lamellae. Fibrillin-1- and type VI collagen-containing bundles of microfibrils (oxytalan fibers) were also involved in the smooth muscle cell-elastin contact. The smooth muscle cells were invested by basal lamina-like layers connecting them to each other as well as to the oxytalan fibers. Unexpectedly, these layers were abundantly labeled by anti-fibronectin, whereas type IV collagen, a specific basement membrane component, was mainly found in larger, flocculent deposits. The proteoglycans present were collagen-associated dermatan sulfate proteoglycan, cell-associated heparan sulfate proteoglycan, and interstitial chondroitin sulfate proteoglycan. Our observations demonstrate that the extracellular matrix in the human aorta is extremely complex and therefore differs from most descriptions based on experimental animals. They serve as reference for future studies on aortic diseases, such as aneurysmas and dissections.

Female perineal membrane: a study using pelvic floor semiserial sections from elderly nulliparous and multiparous women

“…8). Therefore, these muscles are likely to modulate the tension of the PM elastic fibers, as is well known in arterial walls, where the elastic laminae are connected by smooth muscle [15]. The elastic plate associated with striated muscle seems to be a morphologic feature that would provide level III support.…”

Spindle-cell squamous carcinoma exhibiting myofibroblastic differentiation

“…As with so many diagnostically useful organelles, however, the fibronexus is not entirely specific for the myofibroblast: structures with varying similarity to welldeveloped fibronexus junctions have been seen in several mesenchymal cells and lesions [4,23,27,33,42,46,51,52,53,60]. The present paper provides evidence for the first unambiguously documented example of fibronexus junctions in an epithelial tissue in vivo and specifically a spindle-cell carcinoma, and discusses the significance of this wider distribution of the fibronexus.…”

“…Other well-developed fibronexuses have been observed in rat endothelium [23,53], while a structure resembling a fibronectin fibril has been observed in bovine arteriosclerotic aortic smooth muscle [27]. In a small number of other mesenchymal cells, less well defined structures, nevertheless reminiscent of the fibronexus, have been described: aortic smooth-muscle [4,5], scleral spur cell of the eye [60], mesenchymal stromal cells around the seminiferous tubule [20], and mesenchymal tumour cells of multicystic peritoneal mesothelioma [46]. Most of these cells, tissues or lesions can be seen to have an underlying, preexisting differentiation, for example, smooth-muscle or endothelial, and it seems appropriate, therefore, to regard the presence of fibronexus junctions in these cells as consistent with myofibroblastic metaplasia.…”

The Use of Immunofluorescent Array Tomography to Study the Three-Dimensional Microstructure of Murine Blood Vessels

“…Electron microscopy is a valuable tool capable of producing high resolution images of tissue and cellular ultrastructure, however the grayscale images make quantitative analysis challenging. 8,11 By using IAT, we have addressed many of these limitations. The z-axis resolution depends only on the section thickness (70-200 nm thick).…”

“…2,3,6,8,11,16 Although vast amounts of information have been garnered from these techniques, each method has its own unique limitations. Weaknesses associated with these microscopy techniques include limitations in resolution, quantitative analysis capabilities, and multiplexing capabilities, as well as difficulty in applying the technique to gather three-dimensional (3D) volumetric information.…”