Brain arterioles show more active vesicular transport of blood-borne tracer molecules than capillaries and venules after focused ultrasound-evoked opening of the blood-brain barrier.
Previously, activation of vesicular transport in the brain microvasculature was shown to be one of the mechanisms of focused ultrasound-induced blood-brain barrier (BBB) opening. In the present study, we aimed to estimate the rate of the transendothelial vesicular traffic after focused ultrasound sonication in the rabbit brain, using ultrastructural morphometry and horseradish peroxidase (HRP) as a tracer. In the capillaries, the mean endothelial pinocytotic densities (the number of HRP-containing vesicles per microm(2) of the cell cytoplasm) were 0.9 and 1.05 vesicles/microm(2) 1 h after sonication with ultrasound frequencies of 0.69 and 0.26 MHz, respectively. In the arterioles, these densities were 1.63 and 2.43 vesicles/microm(2), values 1.8 and 2.3 times higher. In control locations, the densities were 0.7 and 0.14 vesicles/microm(2) for capillaries and arterioles, respectively. A small number of HRP-positive vesicles were observed in the venules. Focal delivery of HRP tracer was also observed in light microscopy. The results indicate that the precapillary microvessels play an important role in macromolecular transcytoplasmic traffic through the ultrasound-induced BBB modulation, which should be considered in the future development of trans-BBB drug delivery strategies.
Sheikov
Nickolai
N
Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA. nsheikov@bwh.harvard.edu
McDannold
Nathan
N
Jolesz
Ferenc
F
Zhang
Yong-Zhi
YZ
Tam
Karen
K
Hynynen
Kullervo
K
D000818:Animals; D001160:Arterioles / Q000502:physiology* / Q000648:ultrastructure; D001692:Biological Transport / Q000502:physiology; D001812:Blood-Brain Barrier / Q000502:physiology*; D001921:Brain / Q000098:blood supply / Q000648:ultrastructure; D002196:Capillaries / Q000502:physiology / Q000648:ultrastructure; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006735:Horseradish Peroxidase / Q000493:pharmacokinetics; D008279:Magnetic Resonance Imaging; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008854:Microscopy, Electron; D011817:Rabbits; D013010:Sonication; D014699:Venules / Q000502:physiology / Q000648:ultrastructure
D006735:Horseradish Peroxidase