Aging is associated with increased collagen type IV accumulation in the basal lamina of human cerebral microvessels

Background: Microvascular alterations contribute to the development
of stroke and vascular dementia. The goal of this study was to
evaluate age and hypertension related changes of the basal lamina
in cerebral microvessels of individuals, who died from non-cerebral
causes. Results: We examined 27 human brains: 11 young and 16 old
patients. Old patients were divided into two subgroups, those with
hypertension (n = 8) and those without hypertension (n = 8). Basal
lamina changes of the cerebral microvessels were determined in the
putamen using antibodies against collagen type IV and by
quantitative analysis of vessel number, total stained area of
collagen, thickness of the vessel wall and lumen, and relative
staining intensity using immunofluorescence. The total number of
collagen positive vessels per microscopic field was reduced in old
compared to young subjects (12.0+/-0.6 vs. 15.1+/-1.2, p = 0.02).
The relative collagen content per vessel (1.01+/-0.06 vs.
0.76+/-0.05, p = 0.01) and the relative collagen intensity
(233.1+/-4.5 vs. 167.8+/- 10.6, p < 0.0001) shown by
immunofluorescence were higher in the older compared to the younger
patients with a consecutive reduction of the lumen / wall ratio
(1.29+/-0.05 vs. 3.29+/-0.15, p < 0.0001). No differences were
observed for these parameters between old hypertensive and
nonhypertensive patients. Conclusions: The present data show
age-related changes of the cerebral microvessels in sections of
human putamen for the first time. Due to the accumulation of
collagen, microvessels thicken and show a reduction in their lumen.
Besides this, the number of vessels decreases. These findings might
represent a precondition for the development of vascular cognitive
impairment. However, hypertension was not proven to modulate these
changes.