Application of low-vacuum scanning electron microscopy for renal biopsy specimens

Direct observation of epoxy resin blocks for renal biopsy by low-vacuum scanning electron microscopy

To improve the resolution of low-vacuum scanning electron microscopy (LVSEM), the epoxy resin block for the transmission electron microscopy (TEM) was observed directly with LVSEM. After observing ultrathin sections from renal biopsies of IgA nephropathy, membranous nephropathy, lupus nephritis, diabetic nephropathy (DM), thin basement membrane disease (TBMD), Alport's syndrome, Fabry's disease, and renal amyloidosis, the epoxy resin blocks of the same sites were observed by LVSEM and compared. The LVSEM image of the epoxy resin block corresponds to the negative of the TEM image, and when the gradation is reversed, the LVSEM image was comparable to the TEM image. At a low magnification of 100 ×, the entire specimen, including the glomerulus, was obtained. LVSEM at 5000 × magnification was sufficient to identify paramesangial deposits in IgA nephropathy and subepithelial electron-dense deposits (EDD) and spikes in membranous nephropathy. Glomerular basement membrane thickening in DM and thinning in TBMD could be sufficiently diagnosed with LVSEM at 6000 ×. Accumulation of ceramide in Fabry's disease was easily identified, but amyloid fibril could not be identified by LVSEM. LVSEM of renal biopsy epoxy resin blocks can replace TEM up to moderate magnification.

A Novel Multi-Observation System to Study the Effects of Anterior Ocular Inflammation in Zinn’s Zonule Using One Specimen

Zinn’s zonule is a fragile and thin tissue, and little is known about its pathogenesis. The aim of this study was to develop an experimental setup for a comprehensive analysis of Zinn’s zonule. Rats were divided into two groups: a control group (n = 4) and an alkali injury group (n = 4). Seven days after injury, the eyes were enucleated, the anterior eye was dissected and embedded in gelatin, and macroscopic observations were made. The gelatin specimens were then embedded in paraffin and observed in detail by low-vacuum scanning electron microscopy, immunofluorescence, and quantitative reverse transcription polymerase chain reaction (RT-qPCR). The results show qualitative changes in Zinn’s zonules in both macroscopic and microscopic observations. In addition, macrophage infiltration and increased matrix metalloproteinase 2 (MMP2) expression were observed in the injured group, consistent with the RT-qPCR results. The experimental system in this study allowed us to capture the morphological and molecular biological changes of Zinn’s zonule and to gain insight into its pathogenesis. In conclusion, this study presents a new experimental setup for the comprehensive analysis of the rat Zinn’s zonule. The results suggest that this system can be used in the future to study and analyze a variety of paraffin-embedded tissues and specimens.

A novel technique of STEM observation of TEM section using LVSEM and application of pathological diagnosis of renal biopsy

The usefulness of the transmission electron microscope (TEM) for pathological diagnosis is apparent. However, high operating costs and other disadvantages have limited the ability to maintain and operate a TEM. In recent years, a general-purpose benchtop low-vacuum scanning electron microscope (LVSEM), which is inexpensive and easy to operate, has been developed and is expected to be applied in electron microscopic pathological diagnosis. To date, we have previously observed TEM ultrathin sections of Immunoglobulin A (IgA) nephropathy with a benchtop LVSEM using an ultra variable-pressure detector (UVD) and a newly developed holder for observing scanning transmission electron microscope (STEM) images (UVD-STEM holder) and compared the images with those obtained with typical TEM observations. We reported the results in the 53rd Annual Meeting of the Japanese Society for Clinical Molecular Morphology and the 64th Symposium of The Japanese Society of Microscopy and discussed the validity of the methods in the pathological diagnosis of IgA nephropathy and other renal diseases. As a result, we demonstrated the potential for pathological diagnosis using benchtop LVSEM. In this study, we similarly examined typical kidney diseases such as membranous nephropathy, lupus nephritis and amyloidosis. We could obtain sufficient data for the pathological diagnosis of IgA nephropathy, membranous nephropathy and lupus nephritis. However, it is difficult to detect amyloid fibres that are characteristic of amyloidosis. The development of this method is expected to expand the possibilities for pathological diagnosis using electron microscopy, including its application to other diseases.

Imaging of Liver Tissues Using a Combination of Silver Impregnation and Low-Vacuum Scanning Electron Microscopy; A Simple Method for the High-Resolution Visualization of Reticulin Structures with Applicability to a Quantitative Analysis

Background

Low-vacuum scanning electron microscopy (LVSEM) enables the detailed three-dimensional imaging of archival tissues without special pretreatments. The clinical utility of LVSEM in the assessment of liver diseases has not yet been defined. So, we investigated the utility of LVSEM imaging in morphological assessments of normal and diseased liver tissues, with a focus on reticulin structures.

Methods

Formalin-fixed tissue samples of two normal livers and two hepatocellular carcinomas with background regenerative nodules/areas were stained with platinum blue stain or silver-impregnated using Watanabe's method and then comparatively observed under LVSEM. We also evaluated the applicability of LVSEM imaging of liver tissues to a quantitative analysis using a digital image analysis technique.

Results

Optimal high-resolution images of reticulin structures were obtained using 10-μm-thick silver-impregnated sections. Reticulin fibers were clearly observed to run dendritically around sinusoids in normal livers, and markedly increased in regenerative nodules/areas. Normal reticulin frameworks were lost in hepatocellular carcinoma, leaving a few fragments of reticulin fibers within tumors. Moreover, when a quantitative analysis was applied to these images, we successfully demonstrated a significantly higher reticulin fiber density in regenerative nodules/areas than in the normal liver (P < 0.05).

Conclusion

We not only obtained detailed three-dimensional images of reticulin structures in various liver tissues by LVSEM combined with silver impregnation but also showed their applicability to a quantitative analysis. The method presented herein may be applied to future studies for the more accurate diagnosis and better classification/risk stratification of various liver diseases.

Heavy Metal Enhancement Technique for Diaminobenzidine in Immunohistochemistry Enables Ultrastructural Observation by Low-vacuum Scanning Electron Microscopy

Low-vacuum scanning electron microscopy (LV-SEM) is a powerful tool that allows to observe light microscopic specimens with periodic acid-silver methenamine (PAM) staining at a higher magnification, simply by removing the coverslip. However, it is not suitable for observation of immunohistochemistry (IHC) using 3,3'-diaminobenzidine (DAB) due to insufficient backscattered electron image. Traditional heavy metal enhancement techniques for DAB in IHC, (1) osmium tetroxide and iron, (2) cobalt, (3) methenamine silver (Ag), (4) gold chloride (Gold), and (5) both Ag and Gold (Ag + Gold), were examined by LV-SEM. Tissue specimens from Thy1.1 glomerulonephritis rat kidney stained with α-smooth muscle actin and visualized with DAB were enhanced by each of these enhancement methods. We found, in light microscopic and LV-SEM, that the enhancement with Ag, Gold, or Ag + Gold had better intensity and contrast than others. At a higher magnification, Ag + Gold enhancement showed high intensity and low background, although only Ag or Gold enhancement had nonspecific background. Even after observation by LV-SEM, the quality of specimens was maintained after remounting the coverslip. It was also confirmed that Ag + Gold enhancement could be useful for IHC using clinical human renal biopsy. These findings indicate that Ag + Gold provided an adequate enhancement in IHC for both LM and LV SEM observation.

3D imaging for driving cancer discovery

Our understanding of the cellular composition and architecture of cancer has primarily advanced using 2D models and thin slice samples. This has granted spatial information on fundamental cancer biology and treatment response. However, tissues contain a variety of interconnected cells with different functional states and shapes, and this complex organization is impossible to capture in a single plane. Furthermore, tumours have been shown to be highly heterogenous, requiring large-scale spatial analysis to reliably profile their cellular and structural composition. Volumetric imaging permits the visualization of intact biological samples, thereby revealing the spatio-phenotypic and dynamic traits of cancer. This review focuses on new insights into cancer biology uniquely brought to light by 3D imaging and concomitant progress in cancer modelling and quantitative analysis. 3D imaging has the potential to generate broad knowledge advance from major mechanisms of tumour progression to new strategies for cancer treatment and patient diagnosis. We discuss the expected future contributions of the newest imaging trends towards these goals and the challenges faced for reaching their full application in cancer research.

Analysis of purple urine bag syndrome by low vacuum scanning electron microscopy

Purple urine bag syndrome (PUBS) is seen in the prolonged indwelling bladder catheters, and the mechanism of its onset was investigated using low vacuum scanning electron microscopy (LVSEM), which enables us to study the 3D structure of urinary sediments and urine bag walls. The urinary sediment and urine bags of 2 cases of PUBS were observed by LVSEM. The urine was brown turbid urine with a pH of 8.5, and magnesium phosphate stones and granules were observed in the urinary sediment together with Gram-positive and Gram-negative bacilli. Bacteria that moved by Brownian motion were observed with a dark-field microscope. LVSEM showed granular crystals around the bacilli, cocci, or mycelium that adhered to the walls of the bag. Granular crystals were dissolved in chloroform and presumed to be a mixture of the bacterial metabolites indigo blue and indirubin red. LVSEM also detected unusual tubular and honeycomb-like graphene in the urinary sediments, which were derived from the inner layer of the silicon elastomer-coated rubber catheter. LVSEM revealed purple crystals produced by bacteria or fungi attached to the urine bag that caused PUBS.

Tutorial: methods for three-dimensional visualization of archival tissue material

Analysis of three-dimensional patient specimens is gaining increasing relevance for understanding the principles of tissue structure as well as the biology and mechanisms underlying disease. New technologies are improving our ability to visualize large volume of tissues with subcellular resolution. One resource often overlooked is archival tissue maintained for decades in hospitals and research archives around the world. Accessing the wealth of information stored within these samples requires the use of appropriate methods. This tutorial introduces the range of sample preparation and microscopy approaches available for three-dimensional visualization of archival tissue. We summarize key aspects of the relevant techniques and common issues encountered when using archival tissue, including registration and antibody penetration. We also discuss analysis pipelines required to process, visualize and analyze the data and criteria to guide decision-making. The methods outlined in this tutorial provide an important and sustainable avenue for validating three-dimensional tissue organization and mechanisms of disease.

Evaluation of ultrastructural alterations of glomerular basement membrane and podocytes in glomeruli by low-vacuum scanning electron microscopy

Background

Low-vacuum scanning electron microscopy (LV-SEM) is applied to diagnostic renal pathology.

Methods

To demonstrate the usefulness of LV-SEM and to clarify the optimal conditions of pathology samples, we investigated the alterations of glomerular basement membrane (GBM) and podocytes in control and experimental active Heymann nephritis (AHN) rats by LV-SEM.

Results

On week 15 following induction of AHN, spike formation on GBM with diffuse deposition of IgG and C3 developed. Using LV-SEM, diffuse crater-like protrusions were clearly noted three-dimensionally (3D) on surface of GBM in the same specimens of light microscopy (LM) and immunofluorescence (IF) studies only after removal coverslips or further adding periodic acid-silver methenamine (PAM) staining. These 3D ultrastructural findings of GBM surface could be detected in PAM-stained specimens by LV-SEM, although true GBM surface findings could not be obtained in acellular glomeruli, because some subepithelial deposits remained on surface of GBM. Adequate thickness was 1.5–5 μm for 10% formalin-fixed paraffin-embedded (FFPE) and 5–10 μm for the unfixed frozen sections. The foot processes and their effacement of podocytes could be observed by LV-SEM using 10%FFPE specimens with platinum blue (Pt-blue) staining or double staining of PAM and Pt-blue. These findings were obtained more large areas in 2.5% glutaraldehyde-fixed paraffin-embedded (2.5%GFPE) specimens.

Conclusion

Our findings suggest that LV-SEM is a useful assessment tool for evaluating the alterations of GBM and podocytes in renal pathology using routine LM and IF specimens, as well as 2.5%GFPE specimens.

Complexities of the glomerular basement membrane

The glomerular basement membrane (GBM) is a key component of the glomerular capillary wall and is essential for kidney filtration. The major components of the GBM include laminins, type IV collagen, nidogens and heparan sulfate proteoglycans. In addition, the GBM harbours a number of other structural and regulatory components and provides a reservoir for growth factors. New technologies have improved our ability to study the composition and assembly of basement membranes. We now know that the GBM is a complex macromolecular structure that undergoes key transitions during glomerular development. Defects in GBM components are associated with a range of hereditary human diseases such as Alport syndrome, which is caused by defects in the genes COL4A3, COL4A4 and COL4A5, and Pierson syndrome, which is caused by variants in LAMB2. In addition, the GBM is affected by acquired autoimmune disorders and metabolic diseases such as diabetes mellitus. Current treatments for diseases associated with GBM involvement aim to reduce intraglomerular pressure and to treat the underlying cause where possible. As our understanding about the maintenance and turnover of the GBM improves, therapies to replace GBM components or to stimulate GBM repair could translate into new therapies for patients with GBM-associated disease.

Hydrogen promotes the activation of Cu, Zn superoxide dismutase in a rat corneal alkali-burn model

AIM

To investigate the effects of hydrogen (H₂) on Cu, Zn superoxide dismutase (SOD1) activation in a rat model of corneal alkali burn.

METHODS

In each rat, one cornea was subjected to alkali exposure. Physiological saline (saline group) or H₂-dissolved saline (H₂ group) was instilled continuously on the cornea for 5min before and after alkali exposure. Inflammatory cells, neovascularization, and cytoplasmic SOD1 levels were evaluated immunohistochemically in enucleated eyes from both groups. Three-dimensional ultrastructural tissue changes in the eyes were analyzed using low-vacuum scanning electron microscopy.

RESULTS

The numbers of both inflammatory and vascular endothelial cells were significantly reduced in the corneas of the H₂ group (P<0.01). Furthermore, H₂ treatment increased both cytoplasmic SOD1 levels (P<0.01) and activity in corneal epithelial cells (P<0.01). Notably, the SOD1 activity level in the H₂ group was approximately 2.5-fold greater than that in the saline group.

CONCLUSION

H₂ treatment suppresses inflammation and neovascularization in the injured cornea and indirectly suppresses oxidative insult to the cornea by upregulating the SOD1 enzyme protein level and activity.

Observation of Corneal Wound Healing and Angiogenesis Using Low-Vacuum Scanning Electron Microscopy

Purpose

Wound healing processes in a rat corneal alkali burn model were observed using low-vacuum scanning electron microscopy (LV-SEM), a new observation method that can use paraffin sections for light microscopic immunostaining.

Methods

Injured cornea was observed under immunohistochemistry, LV-SEM, and transmission electron microscopy. In LV-SEM, periodic acid-methenamine silver staining was used to observe collagen and platinum blue staining was used to observe vascular endothelial cells. Analyses of the messenger RNA expression involved in neovascularization processes after wound creation were also performed.

Results

LV-SEM depicted progression of corneal wound healing in a stereoscopic fashion. In neovascularization processes after wound creation, LV-SEM with osmification clearly demonstrated detachment of pericytes from the vascular endothelial cells, in association with up-regulation of angiopoietin-2 messenger RNA expression.

Conclusions

LV-SEM enables high magnification observation of paraffin sections used for immunohistochemistry. LV-SEM provides easy, detailed observations and offers a promising new observational modality in the field of ophthalmology.

Translational Relevance

High magnification analysis was easily available using LV-SEM with conventional paraffin sections for light microscopy.

Morphological characteristics of preparator air-scribe marks: Implications for taphonomic research

Taphonomic analyses of bone-surface modifications can provide key insights into past biotic involvement with animal remains, as well as elucidate the context(s) of other biostratinomic (pre-burial) processes, diagenesis, excavation, preparation and storage. Such analyses, however, first require researchers to rigorously disambiguate between continuums of damage morphologies prior to attributing individual marks to specific actors and effectors (e.g., carnivore tooth, stone tool cutting edge, etc.). To date, a number of bone-modifying agents have been identified, and criteria for identifying their traces have been published. Relatively little research, however, has focused on bone-surface modifications imparted during specimen preparation. Herein we report that air scribes, small pneumatic tools commonly used for preparation in museum contexts, can generate unintentional marks that may mimic surficial modification caused by carnivores. To aid investigators in assessing the hypothesis that a mark in question is derived from air-scribe preparation activities, we provide high-resolution, detailed morphological information imaged with scanning electron microscopy (SEM). The main diagnostic characteristic of air-scribe damage is the occurrence of sequential, variously spaced, sub-millimeter scallop-like stepped bone removals. This morphology can resemble damage imparted by carnivore teeth. In contrast to marks produced by trampling, stone tools and carnivores, however, no continuous internal features, such as linear microstriations, were observed within grooves produced by the air scribe. Thus, the presence of such features can be used to disprove an air-scribe origin. A culmination of the morphological criteria presented herein, cross-cutting relationships with other surficial features (e.g., diagenetic discoloration, weathering textures), the position of occurrence, and an overall contextual framework for the assemblage is suggested for accurate identification of such traces. The ability to recognize or disprove air-scribe damage will allow researchers to confidently proceed with interpreting past biological and sedimentological interactions with animal remains.

Application of low vacuum scanning electron microscopy for Papanicolaou-stained slides for cytopathology examinations

Papanicolaou (Pap)-stained slides are usually observed using a transmitted light microscope for cytopathology. However, progress in pathological examinations has created a need for new diagnostic tools, because cytopathological preparations do not allow additional examinations without a loss of specimen, unlike histopathology. Low-vacuum scanning electron microscopy (LVSEM) can reveal the surface topography at an ultrastructual resolution without metal coating. The aim of this study was to determine the conditions required for observing Pap-stained slides of oral smears using LVSEM without any loss of specimen and to reexamine the same slides again using light microscopy, while preserving the cytopathological information.

Morphological diagnosis of Alport syndrome and thin basement membrane nephropathy by low vacuum scanning electron microscopy

Alport syndrome (AS) and thin basement membrane nephropathy (TBMN) are genetic disorders caused by mutations of the type IV collagen genes COL4A3, COL4A4, and/or COL4A5. We here aimed to investigate the three-dimensional ultrastructure of the glomerular basement membrane (GBM) in order to introduce a novel method of diagnosing AS and TBMN. The subjects were 4 patients with AS and 6 patients with TBMN. Conventional renal biopsy paraffin sections from AS and TBMN patients were stained with periodic acid methenamine silver (PAM) and observed directly under low vacuum scanning electron microscopy (LVSEM). The PAM-positive GBMs were clearly visible under LVSEM through the overlying cellular components. The GBMs showed characteristic coarse meshwork appearances in AS, and thin and sheet-like appearances in TBMN. At the cut side view of the capillary wall, the GBMs in AS appeared as fibrous inclusions between a podocyte and an endothelial cell, while the GBMs in TBMN showed thin linear appearances. These different findings of GBMs between AS and TBMN were easily observed under LVSEM. Thus, we conclude that three-dimensional morphological evaluation by LVSEM using conventional renal biopsy paraffin sections will likely be useful for the diagnosis of AS and TBMN, including for retrospective investigations.

A novel approach to the histological diagnosis of pediatric nephrotic syndrome by low vacuum scanning electron microscopy

Despite intensive treatment, steroid-resistant nephrotic syndrome (NS) often progresses to endstage renal disease. Therefore, a more accurate and quick histological diagnosis is required to properly treat such patients. The aim of this study was to introduce a novel approach to the histological diagnosis of pediatric NS by low vacuum scanning electron microscopy (LVSEM) and to describe the morphological differences in glomeruli between steroid-sensitive and steroid-resistant NS specimens. The subjects were three patients with steroid-sensitive NS and four patients with steroid-resistant NS. Conventional renal biopsy paraffin sections were stained with platinum-blue (Pt-blue) or periodic acid methenamine silver (PAM) and directly observed under LVSEM at magnifications between ×50 and ×10,000. The Pt-blue-stained sections showed three-dimensional structural alterations in glomerular podocytes and foot processes. PAM-stained sections showed changes in the structure and thickness of the glomerular basement membrane (GBM). Consequently, many round-shaped podocytes and elongated primary foot processes were exclusively recognized in steroid-resistant NS, although irregularities in foot process interdigitation, fusions, effacements, and microvillus transformations were observed in both steroid-sensitive and steroidresistant NS. Irregularities in thickness and the wrinkling of GBMs were clearly detected in steroid-resistant NS. The evaluation by LVSEM is probably useful for the renal histological diagnosis of pediatric NS.

Glomerular basement membrane injuries in IgA nephropathy evaluated by double immunostaining for α5(IV) and α2(IV) chains of type IV collagen and low-vacuum scanning electron microscopy

BACKGROUND

The glomerulus contains well-developed capillaries, which are at risk of injury due to high hydrostatic pressure, hyperfiltration, hypertension and inflammation. However, the pathological alterations of the injured glomerular basement membrane (GBM), the main component of the glomerular filtration barrier, are still uncertain in cases of glomerulonephritis.

METHODS

We examined the alterations of the GBM in 50 renal biopsy cases with IgA nephropathy (31.8 ± 17.6 years old) using double immunostaining for the α2(IV) and α5(IV) chains of type IV collagen, and examining the ultrastructural alterations by transmission electron microscopy (TEM) and low-vacuum scanning electron microscopy (LV-SEM).

RESULTS

The GBM of IgA nephropathy cases showed various morphological and qualitative alterations. In the TEM findings, thinning, gaps, rupture, thickening with a lamellar and reticular structure and double contours were detected in the GBM. Double immunostaining for α5(IV) and α2(IV) showed thickening of the GBM with reduced α5(IV) and increased α2(IV), or mosaic images of α5(IV) and α2(IV), and holes, fractures, spiny projections and rupture of α5(IV) in the GBM. In addition, LV-SEM showed an etched image and multiple holes in a widening and wavy GBM. These findings might be associated with the development of a brittle GBM in IgA nephropathy.

CONCLUSION

Glomerular basement membrane alterations were frequently noted in IgA nephropathy, and were easily evaluated by double immunostaining for α2(IV) and α5(IV) of type IV collagen and LV-SEM. The application of these analyses to human renal biopsy specimens may enhance our understanding of the alterations of the GBM that occur in human glomerular diseases.