Synchrotron X-Ray Microdiffraction Reveals Intrinsic Structural Features of Amyloid Deposits In Situ

Abstract

Amyloidoses are increasingly recognized as a major public health concern in Western countries. All amyloidoses share common morphological, structural, and tinctorial properties. These consist of staining by specific dyes, a fibrillar aspect in electron microscopy and a typical cross-β folding in x-ray diffraction patterns. Most studies that aim at deciphering the amyloid structure rely on fibers generated in vitro or extracted from tissues using protocols that may modify their intrinsic structure. Therefore, the fine details of the in situ architecture of the deposits remain unknown. Here, we present to our knowledge the first data obtained on ex vivo human renal tissue sections using x-ray microdiffraction. The typical cross-β features from fixed paraffin-embedded samples are similar to those formed in vitro or extracted from tissues. Moreover, the fiber orientation maps obtained across glomerular sections reveal an intrinsic texture that is correlated with the glomerulus morphology. These results are of the highest importance to understanding the formation of amyloid deposits and are thus expected to trigger new incentives for tissue investigation. Moreover, the access to intrinsic structural parameters such as fiber size and orientation using synchrotron x-ray microdiffraction, could provide valuable information concerning in situ mechanisms and deposit formation with potential benefits for diagnostic and therapeutic purposes.

Amyloid structure exhibits polymorphism on multiple length scales in human brain tissue

“…The broad peak centered at roughly 4.7 Å appears typical of microdiffraction from a broad range of tissue devoid of amyloid and processed by standard histological methods. For instance, the diffuse scatter is remarkably similar to that reported for kidney tissue prepared by similar histological methods 42 and presumably reflects average properties of tissue that has undergone this treatment. The diffuse scatter does not exhibit orientation and does not vary markedly in shape from place to place in a single section.…”

Parkinson’s disease is a type of amyloidosis featuring accumulation of amyloid fibrils of α-synuclein

“…A cross-β diffraction pattern from amyloid fibrils consists primarily of a sharp reflection with a 0.47-nm spacing and a relatively broad reflection with an ∼1.0-nm spacing (25). However, there are very few XRD reports on in situ biological samples (26, 27).…”

Optimising complementary soft tissue synchrotron X-ray microtomography for reversibly-stained central nervous system samples

“…However, resins preclude the use of tissue for most subsequent histology techniques and if these were required, wax embedding would be the method of choice. Wax has some compromises, with small angle X-ray scattering by wax crystals 41 contributing to slight signal blurring during imaging. However, this did not undermine feature observation within our samples, or in earlier demonstrations successfully combining paraffin-based histology with SRμCT to image human cerebellar 3 , 4 and soft vascular tissue 1 .…”