Super-resolution STED microscopy for investigating the brain extracellular space in live tissue
The brain extracellular space (ECS) is a reticular continuum of interconnected channels and reservoirs. The ranges of ECS channel widths, lengths, and shapes easily exceed the morphological complexity of individual neural cells, so that on one hand the ECS is comparatively vast in extent, while at the same time its even more geometrically complex. The combination of spatial continuity and a fine mesh-like structure makes the ECS geometry extremely difficult to visualize in live tissue, because conventional light- microscopy simply blurs out structural details beyond cell somata and large dendrites. Current data on ECS structure are therefore based largely on volume-averaging imaging techniques or on electron microscopy in fixed tissue. Accordingly, our knowledge about ECS structure and putative dynamics, not to mention functional roles, is rudimentary.
In a step forward, we recently introduced super-resolution shadow imaging (SUSHI) as a new way to image the extracellular space in live brain slices by combining fluorescent perfusion-labeling of the interstitial fluid with STED microscopy. This approach reveals the complex geometry and dynamics of the ECS, while simultaneously outlining all cellular structures in the field of view at around 50 nm resolution.
In this talk I will introduce STED microscopy for imaging in live organotypic mouse brain slices, and how we went from imaging individual synapses on neurons to also imaging the extracellular space. I will show preliminary results from a computational diffusion model we are establishing based on SUSHI images of the ECS, which may help us understand functional aspects of extrasynaptic signaling, and metabolite clearance from dense parenchyma.
Host: Aitzol Garcia-Etxarri
Hybrid Seminar: Donostia International Physics Center
Jan Tonnesen, University of the Basque Country and Achucarro Basque Center for Neuroscience