Correlated disorder in myelinated axons orientational geometry and structure

TL;DR

This study investigates the orientational fluctuations of myelinated axons in nerves, revealing a transition from correlated Levy flight disorder in fresh nerves to random disorder in aged nerves, using non-invasive X-ray diffraction techniques.

Contribution

It introduces the application of Scanning micro X-ray Diffraction to analyze axonal disorder and tracks its evolution during nerve degeneration.

Findings

Fresh axons exhibit Levy flight correlated disorder.

Aged nerves show a transition to random disorder.

Technique can detect nanoscale structural changes in nerves.

Abstract

While the ultrastructure of the myelin has been considered to be a quasi-crystalline stable system, nowadays its multiscale complex dynamics appears to play a key role for its functionality, degeneration and repair processes following neurological diseases and trauma. In this work, we have investigated the axons interactions associated to the nerve functionality, measuring the spatial distribution of the orientational fluctuations of axons in a Xenopus Laevis sciatic nerve. At this aim, we have used Scanning micro X-ray Diffraction (SmXRD), a non-invasive already applied to other heterogeneous systems presenting complex geometries from microscale to nanoscale. We have found that the orientational spatial fluctuations of fresh axons show a correlated disorder described by Levy flight distribution. Thus, we have studied how this correlated disorder evolves during the degeneration of the nerve. Our results show that the spatial distribution of axons orientational fluctuations in unfresh, aged nerve loose the correlated disorder assuming a randomly disordered behaviour. This work allows a deeper understanding of nerve states and paves the way to study other materials and biomaterials with the same technique to detect and to characterize their states and supramolecular structure, associated with dynamic structural changes at the nanoscale and mesoscale.