Vascular Collagen Type-IV in Hypertension and Cerebral Small Vessel Disease

Figures

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  Figure 1.. Vascular collagen-IV in small arteries of human brain. A, C–F are from older people, whereas B is from a young adult (male, age 20). A, Small penetrating artery in subcortical white matter of aged human brain shows multilaminar collagen-IV (brown) in the subendothelial basement membrane (arrow) and an outer layer of adventitial collagen-IV (arrowhead). Hematoxylin chromatin counterstain (blue). B, A comparable artery in a young adult exhibits a qualitatively different collagen-IV pattern, with a thinner vessel wall spanned entirely by layers of collagen-IV positive matrix. C and D, Neighboring sections from an older person, treated with Masson trichrome stain (C) or collagen-IV immunolabeling (D). A small artery shows acellular, fibrotic thickening of the medial layer, stained green with the trichrome stain (C). Collagen-IV (brown) is clearly present in the subendothelial basement membrane (BM) and adventitial layers but not the fibrotic medial area. E and F, Example of automated measurement of the vascular collagen-IV labeled area fraction (AF). Pixels that are labeled within the vessel wall for collagen-IV (brown, E) are detected by an automated algorithm (red, F). Scale bars:…

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  Figure 2.. Vascular collagen-IV in older people. The extent of vascular collagen-IV within small penetrating arteries was quantified as the collagen-IV immunolabeled area fraction (AF) of the vessel wall. A, Average collagen-IV in relation to age at death. Straight line shows least-squares best fit. B, Collagen-IV in relation to the absence or presence of clinical history of hypertension. C, Radiological white matter lesion (WML) score in relation to the absence or presence of neuropathological diagnosis of small vessel disease (SVD). D, Collagen-IV in relation to absence or presence of neuropathological SVD diagnosis. E, Collagen-IV in relation to average sclerotic index for small arteries. Straight line shows least-squares best fit. F, Collagen-IV in relation to radiological WML score. In A, C, and E, each symbol represents a different person. Box-whisker plots show median, interquartile range (IQR), and full range, with outliers that depart more than 3×IQR. Data from 52 older people with minimal Alzheimer pathology.

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  Figure 3.. Immuno-electron microscopy of collagens I, III, and IV in small vessel disease (SVD). Transmission electron micrographs of small arteries in white matter from older persons with SVD. A–D, Semi-serial sections of a small arteriole, shown at low magnification in A and at higher magnification in B–D with immunogold labeling for collagen-IV (B), collagen-I (C), or collagen-III (D). The region shown at higher magnification in B–D is marked in A (box). Arrows show examples of immunogold particles. In B, collagen-IV labeling shows numerous gold particles over the homogenous basal laminae (BL), behind the endothelium. Mural collagen fibrils (Fib) and myocytes (My) are unlabeled. C, Collagen-I, in contrast to collagen-IV, is mainly localized to the collagen fibrils. D, Collagen-III also labels the banded collagen fibrils. A few gold particles are found over the basal laminae. E and F, Another small artery with severe fibrosis. Low magnification view (E) shows heavy deposits of fibrillar collagens in the vessel wall. In higher magnification, these are heavily labeled for collagen-I (F). Scale bars: 2 μm (A and E), 0.5 μm (B–D), and 0.2 μm (F).

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  Figure 4.. Collagen-IV in hypertensive primate brains. A, T2-weighted magnetic resonance imaging (MRI) scans of a normotensive (left) and chronically hypertensive primates (right) show no white matter lesion (WML), at 2 different horizontal planes. The normotensive animal was aged 7.5 y when scanned. The hypertensive animal was aged 16.9 y and had been hypertensive for 2.6 y when scanned. B, Collagen-IV immunolabeled (black) cerebral cortex of primate, with hematoxylin chromatin counterstain (blue). A low magnification view is shown, with examples of collagen-IV labeled vessels in gray matter (upper) and subcortical white matter (lower). Scale bars: 100 µm. C–E, Scatter plots showing age at death (C), systolic blood pressure (SBP; D), and extent of white matter collagen-IV labeling (E) in young normotensive and hypertensive (YN and YH) and aged normotensive and hypertensive primates (AN and AH). Open symbols represent individual animals, filled symbols show the group mean. Data from 17 animals.