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

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.

Overexpression of Plasmalemmal Vesicle-Associated Protein-1 Reflects Glomerular Endothelial Injury in Cases of Proliferative Glomerulonephritis with Monoclonal IgG Deposits

Introduction

Proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) occasionally presents refractory nephrotic syndrome resulting in poor renal prognosis, but its etiology is not fully elucidated. Given that glomerular endothelial cell (GEC) stress or damage may lead to podocytopathy and subsequent proteinuria, as in thrombotic microangiopathy (TMA), diabetic kidney disease, and focal segmental glomerulosclerosis, we investigated the evidence of glomerular endothelial injury by evaluating the expression of plasmalemmal vesicle-associated protein-1 (PV-1), a component of caveolae in the cases of PGNMID.

Methods

We measured the immunofluorescent PV-1 intensities of 23 PGNMID cases and compared with those of primary membranoproliferative glomerulonephritis (MPGN) (n = 5) and IgA nephropathy (IgAN) (n = 54) cases. PV-1 localization was evaluated with Caveolin-1, and CD31 staining, and the ultrastructural analysis was performed using a low-vacuum scanning electron microscope (LVSEM). To check the association of podocyte injury, we also conducted 8-oxoguanine and Wilms tumor 1 (WT1) double stain. We then evaluated PV-1 expression in other glomerulitis and glomerulopathy such as lupus nephritis and minimal change disease.

Results

The intensity of glomerular PV-1 expression in PGNMID is significantly higher than that in the other glomerular diseases, although the intensity is not associated with clinical outcomes such as urinary protein levels or renal prognosis. Immunostaining and LVSEM analysis revealed that glomerular PV-1 expression is localized in GECs in PGNMID. 8-oxoguanine accumulation was detected in WT1-positive podocytes but not in PV-1-expressing GECs, suggesting GEC-derived podocyte injury in PGNMID.

Conclusion

PV-1 overexpression reflects glomerular endothelial injury, which could be associated with podocyte oxidative stress in PGNMID cases.

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.

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.

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.

Scanning ion conductance microscopy of live human glomerulus

Podocyte damage is a hallmark of glomerular diseases, such as focal segmental glomerulosclerosis, typically associated with marked albuminuria and progression of renal pathology. Podocyte structural abnormalities and loss are also linked to minimal change disease and more common diabetic kidney disease. Here we applied the first‐time scanning ion conductance microscopy (SICM) technique to assess the freshly isolated human glomerulus's topology. SICM provides a unique opportunity to evaluate glomerulus podocytes as well as other nephron structural segments with electron microscopy resolution but in live samples. Shown here is the application of the SICM method in the live human glomerulus, which provides proof of principle for future dynamic analysis of membrane morphology and various functional parameters in living cells.

Genetic Background and Clinicopathologic Features of Adult-onset Nephronophthisis

Introduction

Recently, nephronophthisis (NPH) has been considered a monogenic cause of end-stage renal disease (ESRD) in adults. However, adult-onset NPH is difficult to accurately diagnose and has not been reported in a cohort study. In this study, we assessed the genetic background and clinicopathologic features of adult NPH.

Methods

We investigated 18 sporadic adult patients who were suspected as having NPH by renal biopsy. We analyzed 69 genes that cause hereditary cystic kidney disease and compared clinicopathologic findings between patients with and without pathogenic mutations in NPH-causing genes.

Results

Seven of 18 patients had pathogenic NPH-causing mutations in NPHP1, NPHP3, NPHP4, or CEP164. Compared with patients without pathogenic mutations, those with pathogenic mutations were significantly younger but did not significantly differ in the classic NPH pathologic findings, such as tubular cysts. On the other hand, the number of tubules with thick tubular basement membrane (TBM) duplication, which was defined as >10-μm thickness, was significantly higher in patients with genetically proven adult NPH than in those without pathogenic mutations. α-Smooth muscle actin (α-SMA)-positive myofibroblasts were detected inside thick TBM duplication.

Conclusions

In adult patients with NPH, thick TBM duplication was the specific finding. Our analysis also suggested that older patients tended to have no pathogenic mutations, even when they were suspected to have NPH by renal biopsy. These findings could be the novel clinical clue for the diagnosis of NPH in adult patients.

Low-Vacuum Scanning Electron Microscopy to Assess Histopathological Resolution of Class V Lupus Nephritis: A Case Report

Lupus nephritis (LN) is most frequently associated with poor outcomes in patients with systemic lupus erythematosus (SLE). LN manifests as histopathological changes in the kidney caused by immune complex formation and deposition. In particular, immunoglobulin G (IgG) deposits are frequently observed by immunofluorescence staining, which helps to establish the diagnosis of LN. In this case report, we describe a 57-year-old woman with SLE who had been undergoing treatment on an outpatient basis for 11 years. Her first and second renal biopsies revealed class V LN with a coarsely granular pattern of IgG deposition in the peripheral capillary walls. However, her third renal biopsy showed no IgG deposition, which indicated histopathological resolution of her class V LN. We used low-vacuum scanning electron microscopy (LV-SEM) to examine the three-dimensional structural alterations in her glomerular basement membranes. In this report, we describe findings that indicated resorption of epithelial deposits, that is, resolution of LN. The results of repeated kidney biopsies confirmed by LV-SEM suggested the possibility of a state unrelated to LN.

Low-vacuum scanning electron microscopy may allow early diagnosis of human renal transplant antibody-mediated rejection

Antibody-mediated rejection (ABMR) is an important cause of both short- and long-term injury to renal allografts. Transplant glomerulopathy (TG) is strongly associated with ABMR and reduced graft survival. Ultrastructural changes in early-stage ABMR include TG as a duplication of the glomerular basement membrane (GBM), which can be observed only by transmission electron microscopy (TEM). Low-vacuum scanning electron microscopy (LVSEM) is a new technique that allows comparatively inexpensive, rapid, and convenient observations with high magnification. We analyzed human renal transplants using LVSEM and evaluated the ultrastructural changes representing TG in ABMR. GBM duplication was more clearly visible in the LVSEM images than in the light microscopy (LM) images. In the ABMR group, the cg score of the Banff classification was higher in 54% (7/13) of specimens for LVSEM images than for LM images. And 4 specimens exhibited duplication of the GBM analyzed by LVSEM, but not by LM. In addition, three-dimensional ultrastructural changes, such as coarse meshwork structures of GBM, were observed in ABMR specimens. The ABMR group also exhibited ultrastructural changes in the peritubular capillary basement membranes. In conclusion, analyses of renal transplant tissues using LVSEM allows the identification of GBM duplication and ultrastructural changes of basement membranes at the electron microscopic level, and is useful for early-stage diagnosis of ABMR.

Pathological Analysis of Early Transplant Glomerulopathy in Renal Allografts Using Low-Vacuum Scanning Electron Microscopy

AIM

Low-vacuum scanning electron microscopy (LVSEM) has been reported to aid in diagnosis of renal biopsy. This study evaluated early transplant glomerulopathy in kidney transplant recipients using LVSEM.

METHODS

We selected 4 biopsies of cg0, 5 biopsies of cg1a, 5 biopsies of cg1b, and 4 biopsies of cg2 lesions that had been evaluated by light microscopy (LM) and transmission electron microscopy from recipients with acute/active or chronic, active antibody-mediated rejection (AABMR or CAABMR). Renal allograft paraffin sections (1 µm thickness) were stained with periodic acid-methenamine silver and observed using LVSEM. The cg score was based on the Banff classification. The parameter "percentage of duplicated capillary number" was calculated as follows: in 1 glomerulus with glomerular basement membrane (GBM) duplication, the total duplicated capillary number/the total number of capillaries ×100.

RESULTS

In all 4 biopsy specimens with AABMR showing cg0, LVSEM revealed GBM duplication not identified by LM. The average percentage of duplicated capillary number per glomerulus with GBM duplication was higher when observed by LVSEM than when observed by LM in all cg1b and cg2 biopsy specimens.

CONCLUSION

LVSEM revealed early GBM duplication in AABMR. Early GBM duplication might progress in the very early phase of AABMR. GBM duplication was more frequently detected by LVSEM than by LM in biopsy specimens with early chronic, active antibody mediated rejection. Thus, LVSEM may be useful in diagnosis of early transplant glomerulopathy.

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.

Informative three-dimensional survey of cell/tissue architectures in thick paraffin sections by simple low-vacuum scanning electron microscopy

Recent advances in bio-medical research, such as the production of regenerative organs from stem cells, require three-dimensional analysis of cell/tissue architectures. High-resolution imaging by electron microscopy is the best way to elucidate complex cell/tissue architectures, but the conventional method requires a skillful and time-consuming preparation. The present study developed a three-dimensional survey method for assessing cell/tissue architectures in 30-µm-thick paraffin sections by taking advantage of backscattered electron imaging in a low-vacuum scanning electron microscope. As a result, in the kidney, the podocytes and their processes were clearly observed to cover the glomerulus. The 30 µm thickness facilitated an investigation on face-side (instead of sectioned) images of the epithelium and endothelium, which are rarely seen within conventional thin sections. In the testis, differentiated spermatozoa were three-dimensionally assembled in the middle of the seminiferous tubule. Further application to vascular-injury thrombus formation revealed the distinctive networks of fibrin fibres and platelets, capturing the erythrocytes into the thrombus. The four-segmented BSE detector provided topographic bird’s-eye images that allowed a three-dimensional understanding of the cell/tissue architectures at the electron-microscopic level. Here, we describe the precise procedures of this imaging method and provide representative electron micrographs of normal rat organs, experimental thrombus formation, and three-dimensionally cultured tumour cells.

In vitro and in vivo inhibition of mTOR by 1,25-dihydroxyvitamin D3 to improve early diabetic nephropathy via the DDIT4/TSC2/mTOR pathway

We investigated whether 1,25-dihydroxy-vitamin D₃ (1,25(OH)₂D₃) could improve early diabetic nephropathy through the DNA-damage-inducible transcript 4/tuberous sclerosis 2/mammalian target of rapamycin pathway. Rat mesangial cells were cultured in media containing normal glucose or high glucose and were treated with or without 1,25(OH)₂D₃. Mesangial cells proliferation was measured. Streptozotocin-induced diabetic rats were injected intravenously with a recombinant lentivirus against the rat vitamin D receptor gene. Urinary and serum albumin, fasting plasma glucose, serum triglyceride, total cholesterol, calcium, parathyroid hormone and serum 25-dihydroxy-vitamin D (25(OH)D) levels, mean glomerular volume, glomerular basement membrane thickness and total kidney volume were determined. The expressions of vitamin D receptor, DNA-damage-inducible transcript 4, and mammalian target of rapamycin were measured. 1,25(OH)₂D₃ inhibited the proliferation of mesangial cells induced by hyperglycemia. 1,25(OH)₂D₃ also significantly reduced albumin excretion, mean glomerular volume, glomerular basement membrane, and total kidney volume in rats with diabetic nephropathy. The expression of DNA-damage-inducible transcript 4 was elevated by 1,25(OH)₂D₃ treatment. The phosphorylation of mammalian target of rapamycin was reduced by 1,25(OH)₂D₃ treatment. Vitamin D receptor gene silencing blocked all of the above results. The current study demonstrates that 1,25(OH)₂D₃ can effectively inhibit mesangial cells proliferation induced by hyperglycemia, thus suppressing the development of diabetic nephropathy. This study also shows that the nephron-protective effect of 1,25(OH)₂D₃ occurs partly through the DDIT4/TSC2/mTOR pathway.

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.