Nanostructure-specific X-ray tomography reveals myelin levels, integrity and axon orientations in mouse and human nervous tissue

Marios Georgiadis,M Augath ,Dmitry S Novikov,Thomas Weiß ,Jennifer A Mcnab,Oliver Bunk,Valerio Zerbi,Phillip Digiacomo,Jiangyang Zhang,Aleezah Balolia,Zirui Gao,Sung-Lyoung Kim ,Timothy M Shepherd ,Michael Zeineh,Stefan Sommer,Marianne Liebi,Aileen Schroeter,Piotr Walczak,Benjamin Ades‐Aron ,Lin Yang,Ivan Rajković ,Manuel Guizar‐Sicairos ,Christoph Leuze,Gergely Dávid ,Jelle Veraart,Shirish Chodankar,Els Fieremans,Choong Heon Lee ,Markus Rudin

doi:10.1038/s41467-021-22719-7

Abstract

Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease. Yet, myelin-specific imaging of macroscopic samples remains a challenge. Here, we exploit myelin’s nanostructural periodicity, and use small-angle X-ray scattering tensor tomography (SAXS-TT) to simultaneously quantify myelin levels, nanostructural integrity and axon orientations in nervous tissue. Proof-of-principle is demonstrated in whole mouse brain, mouse spinal cord and human white and gray matter samples. Outcomes are validated by 2D/3D histology and compared to MRI measurements sensitive to myelin and axon orientations. Specificity to nanostructure is exemplified by concomitantly imaging different myelin types with distinct periodicities. Finally, we illustrate the method’s sensitivity towards myelin-related diseases by quantifying myelin alterations in dysmyelinated mouse brain. This non-destructive, stain-free molecular imaging approach enables quantitative studies of myelination within and across samples during development, aging, disease and treatment, and is applicable to other ordered biomolecules or nanostructures.

Highlights

Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease
We demonstrate the nanostructural specificity of SAXSTT by separately reconstructing central and peripheral nervous system (CNS/PNS) myelin signals based on their distinct nanostructure periodicities, and quantify alterations in CNS myelin levels and nanostructural integrity in a murine model of dysmyelination, the shiverer mouse
We have presented a non-destructive framework for nanostructurespecific imaging of myelin, myelin-sheath integrity, and axon orientations in macroscopic samples, demonstrated for mouse and human tissue samples

Summary

Introduction

Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease. We exploit myelin’s nanostructural periodicity, and use small-angle X-ray scattering tensor tomography (SAXS-TT) to simultaneously quantify myelin levels, nanostructural integrity and axon orientations in nervous tissue. We illustrate the method’s sensitivity towards myelin-related diseases by quantifying myelin alterations in dysmyelinated mouse brain This non-destructive, stain-free molecular imaging approach enables quantitative studies of myelination within and across samples during development, aging, disease and treatment, and is applicable to other ordered biomolecules or nanostructures. We perform SAXS-TT experiments on intact macroscopic nervous tissue specimens such as mouse brain, mouse spinal cord, human white matter, and cortex, and use tensor reconstruction on the myelin-specific signal to quantify myelin levels and determine myelinated axon orientation and fiber tracts non-destructively. We propose a method for nanostructurespecific imaging of macroscopic samples, which can serve as a reference method for quantifying myelin levels, nanostructure integrity, and axon orientations within and across samples

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Conclusion