Fig. 3

Caveolae vesicles in arteriole endothelial and smooth muscle cells are functional transcytosis machinery components. HRP and sulfo-biotin tracers, imaged by TEM, demonstrate cargo trafficking in CNS arteriole cells. a Representative TEM image of a cortical arteriole (wild-type adult mice) following 30 min HRP tracer challenge. HRP signal is found in vessel lumen (L) as well as in basement membranes; in between the endothelial layer and smooth muscle layer (arrows), and between the smooth-muscle layer and astrocyte end-feet (arrows). Scale bar 5 µm. Inset (a’) ample caveolae vesicles, some of which showing HRP signals at luminal and abluminal membranes of a smooth muscle cell (arrowheads). Scale bar 500 nm. b Representative TEM image of perfused sulfo-biotin tracer challenge following staining with HRP conjugated streptavidin. Scale bar 5 µm. Inset (b’) high magnification image showing abundant tracer-field vesicles, adjacent to the abluminal membrane of a smooth-muscle cell (arrowheads). Tracer signal is found also in basement membranes (arrows). SMC Smooth-muscle cell, EC Endothelial cell, AC Astrocyte, L lumen. Scale bar 500 nm (n = 6 mice, 12 arterioles). c Vesicular density in mouse arterial endothelial cells compared to capillary endothelial cells. Mean vesicular density in cECs and aECs. Data are mean ± s.e.m. **p < 0.05 (Two tailed Mann–Whitney U- test)