Visualization and molecular characterization of whole-brain vascular networks with capillary resolution

Takeyuki Miyawaki,Haruki Takeuchi,Yuji Ikegaya,Shun Yamaguchi,Shota Morikawa,Hiroki R Ueda,Etsuo A Susaki,Ai Nakashima

doi:10.1038/s41467-020-14786-z

Abstract

Structural elucidation and molecular scrutiny of cerebral vasculature is crucial for understanding the functions and diseases of the brain. Here, we introduce SeeNet, a method for near-complete three-dimensional visualization of cerebral vascular networks with high signal-to-noise ratios compatible with molecular phenotyping. SeeNet employs perfusion of a multifunctional crosslinker, vascular casting by temperature-controlled polymerization of hybrid hydrogels, and a bile salt-based tissue-clearing technique optimized for observation of vascular connectivity. SeeNet is capable of whole-brain visualization of molecularly characterized cerebral vasculatures at the single-microvessel level. Moreover, SeeNet reveals a hitherto unidentified vascular pathway bridging cerebral and hippocampal vessels, thus serving as a potential tool to evaluate the connectivity of cerebral vasculature.

Highlights

Structural elucidation and molecular scrutiny of cerebral vasculature is crucial for understanding the functions and diseases of the brain
We designed a fluorescent compound termed RITC–Dex–GMA consisting of rhodamine isothiocyanate (RITC), a fluorescent group; glycidyl methacrylate (GMA), a crosslinkable group; and dextran (Dex), a macromolecule that makes the compound have a molecular weight large enough to prevent it from crossing the blood–brain barrier (BBB) and small enough to not clog microvessels (Fig. 1a)
RITC–Dex–GMA can be synthetized through a few simple chemical reactions and can be purified with ethanol precipitation (Supplementary Fig. 1a, b)[22,23]

Summary

Introduction

Structural elucidation and molecular scrutiny of cerebral vasculature is crucial for understanding the functions and diseases of the brain. We introduce SeeNet, a method for near-complete three-dimensional visualization of cerebral vascular networks with high signalto-noise ratios compatible with molecular phenotyping. SeeNet employs perfusion of a multifunctional crosslinker, vascular casting by temperature-controlled polymerization of hybrid hydrogels, and a bile salt-based tissue-clearing technique optimized for observation of vascular connectivity. SeeNet is capable of whole-brain visualization of molecularly characterized cerebral vasculatures at the single-microvessel level. We introduce SeeNet, a method for 3D visualization and molecular characterization of the entire vascular network, including virtually all microvessels, in the whole brain. SeeNet includes (i) intravascular perfusion of a blood–brain barrier (BBB)-impermeable fluorescent crosslinker, (ii) thermally controlled polymerization of a hybrid hydrogel, and (iii) bile saltbased tissue clearing

Methods

Results

Conclusion