FIGURE 2.

Ageing associates with increased blood‐brain barrier permeability through decreased tight junction protein levels. A, Representative images showing endogenous IgG extravasation (red) into the brain parenchyma 48 h after tMCAO in the two study groups. BBB permeability of old mice was increased as compared to that observed in young animals. B, Immunostaining for claudin‐5 (light yellow) and the endothelial marker CD31 (red) in ipsilateral hemispheres 48 h after tMCAO showed significantly reduced endothelial expression of this molecule in old animals as compared to young ones. C, The expression of occludin (blue) showed a similar (although not significant) trends in endothelial cells (CD31, red) of the penumbra area of the two study groups. D, The endothelial expression (CD31, red) of another protein involved in regulation of BBB function VE‐cadherin (dark yellow) did not show any difference between young and old mice. n = 6‐8 different mice per group. A‐D: unpaired two‐tailed Student's t test. *P <.05, **P < .01, (white bar = 50μm for all). IgG, immunoglobulin G; tMCAO, transient middle cerebral artery occlusion; TNF, tumour necrosis factor; VE‐cadherin, vascular endothelium cadherin