Fig. 1

Variable degree of permeability to different tracers across the CNS arteriole-wall uncovers atypical cellular barrier properties. Confocal-microscopy of arteriole-wall permeability, with immunostaining for NVU components: endothelium (anti-CD31), smooth-muscle (anti-SMA), astrocyte end-feet (anti-AQP4), and basement membranes (anti-pan Laminin) of wild-type adult mouse cortical sections. a Schematic illustration of the experimental design: tracers of different size and molecular compositions are introduced into the blood stream and circulated for 10 min. Arteriole cross sections are used to locate fluorescent tracer signals (green circles) in the vessel wall from luminal side (blood) towards the tissue (arrow showing the path crossing the endothelial cell layer-purple, smooth-muscle layer-red each surrounded by basement membranes and all surrounded by the astrocyte end-feet) Created with BioRender.com. b Tracer challenges with Alexa-647 conjugated albumin for 10 min (70 kDa) demonstrating that albumin is mostly co-localized with the endothelium (arrow). c Challenges with Alexa-647 conjugated dextran for 10 min (10 kDa) demonstrates tracer signals co-localized with the endothelium and reaching the smooth-muscle layer (upper panel, arrow), and beyond reaching the astrocyte end-feet (lower panel, arrow). d Challenges with perfused sulfo-biotin (443 Da), stained with Alexa-647 conjugated streptavidin demonstrates tracer signals passed the smooth-muscle layer (upper panel, arrow), but confined by the basement membranes (lower panel, arrow). Images are representative of n = 27 arterioles profiles of n = 9 mice (3 for each tracer), Scale Bars 10 µm