Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of an ongoing pandemic, with increasing deaths worldwide. To date, documentation of the histopathological features in fatal ...cases of the disease caused by SARS-CoV-2 (COVID-19) has been scarce due to sparse autopsy performance and incomplete organ sampling. We aimed to provide a clinicopathological report of severe COVID-19 cases by documenting histopathological changes and evidence of SARS-CoV-2 tissue tropism.
In this case series, patients with a positive antemortem or post-mortem SARS-CoV-2 result were considered eligible for enrolment. Post-mortem examinations were done on 14 people who died with COVID-19 at the King County Medical Examiner's Office (Seattle, WA, USA) and Snohomish County Medical Examiner's Office (Everett, WA, USA) in negative-pressure isolation suites during February and March, 2020. Clinical and laboratory data were reviewed. Tissue examination was done by light microscopy, immunohistochemistry, electron microscopy, and quantitative RT-PCR.
The median age of our cohort was 73·5 years (range 42–84; IQR 67·5–77·25). All patients had clinically significant comorbidities, the most common being hypertension, chronic kidney disease, obstructive sleep apnoea, and metabolic disease including diabetes and obesity. The major pulmonary finding was diffuse alveolar damage in the acute or organising phases, with five patients showing focal pulmonary microthrombi. Coronavirus-like particles were detected in the respiratory system, kidney, and gastrointestinal tract. Lymphocytic myocarditis was observed in one patient with viral RNA detected in the tissue.
The primary pathology observed in our cohort was diffuse alveolar damage, with virus located in the pneumocytes and tracheal epithelium. Microthrombi, where observed, were scarce and endotheliitis was not identified. Although other non-pulmonary organs showed susceptibility to infection, their contribution to the pathogenesis of SARS-CoV-2 infection requires further examination.
None.
Podocyte Detachment and Reduced Glomerular Capillary Endothelial Fenestration in Human Type 1 Diabetic Nephropathy
Masao Toyoda 1 ,
Behzad Najafian 2 3 ,
Youngki Kim 2 ,
M. Luiza Caramori 4 and
...Michael Mauer 2 4
1 Division of Nephrology and Metabolism, Department of Internal Medicine; Tokai University School of Medicine, Kanagawa, Japan
2 Division of Pediatric Nephrology, Department of Pediatrics; University of Minnesota, Minneapolis, Minnesota
3 Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota
4 Department of Medicine, University of Minnesota, Minneapolis, Minnesota
Address correspondence and reprint requests to Michael Mauer, MD, Professor of Pediatrics and Medicine, University of Minnesota,
420 Delaware St. SE, MMC 491, Minneapolis, MN 55455. E-mail: mauer002{at}umn.edu
Abstract
The aim of this study was to investigate the structural characteristics of podocytes and endothelial cells in diabetic nephropathy.
We studied 18 patients with type 1 diabetes (seven normoalbuminuric, six microalbuminuric, and five proteinuric), and six
normal control subjects. Groups were not different for age. Type 1 diabetic groups were not different for diabetes duration
or age at diabetes onset. Podocyte foot process width (FPW), fraction of glomerular basement membrane (GBM) surface with intact
nondetached foot processes (IFP), fraction of glomerular capillary luminal surface covered by fenestrated endothelium S S (Fenestrated/cap) and classic diabetic glomerulopathy lesions were morphometrically measured. Albumin excretion (AER) and
glomerular filtration (GFR) rates were also measured. GFR correlated inversely and AER directly with GBM and mesangial measurements
in diabetic patients. FPW correlated inversely with GFR ( r = −0.71, P = 0.001) and directly with AER ( r = 0.66, P = 0.003), GBM, and mesangial parameters. The GBM fraction covered by IFP was decreased in proteinuric versus control subjects
( P = 0.001), normoalbuminuric patients ( P = 0.0002) and microalbuminuric patients ( P = 0.04) and correlated with renal structural and functional parameters, including AER ( r = −0.52, P = 0.03). Only 78% of GBM was covered by IFP in proteinuric patients. S S (Fenestrated/cap) was reduced in normoalbuminuric ( P = 0.03), microalbuminuric ( P = 0.03), and proteinuric ( P = 0.002) patients versus control subjects. S S (Fenestrated/cap) correlated with mesangial fractional volume per glomerulus ( r = −0.57, P = 0.01), IFP ( r = 0.61, P = 0.007), and FPW ( r = −0.58, P = 0.01). These novel studies document that podocyte detachment and diminished endothelial cell fenestration are related to
classical diabetic nephropathy lesions and renal function in type 1 diabetic patients and support a need for further studies
of podocyte/GBM adherence and podocyte/endothelial cell functional interactions in diabetic nephropathy.
AER, albumin excretion rate
FPW, foot process width
FSGS, focal and segmental glomerulosclerosis
GBM, glomerular basement membrane
GFR, glomerular filtration rate
LS(Slit/PGBM), slit diaphragm length density per PGBM
LS(Slit/MGBM), slit diaphragm length density per MGBM
MGBM mesangial GBM
PGBM, peripheral GBM
SS(IFP/PGBM), fraction of PGBM covered by intact foot processes
SS(IFP/MGBM), fraction of MGBM covered by intact foot processes
SS(Fenestrated/cap), surface density of fenestrated endothelium per glomerular capillary lumen
SV(PGBM/glom), surface density of PGBM per glomerulus
TBCA, tuft to Bowman's capsule adhesions
VV(MC/glom), mesangial cell fractional volume per glomerulus
VV(Mes/glom), mesangial fractional volume per glomerulus
VV(MM/glom), mesangial matrix fractional volume per glomerulus
Footnotes
Published ahead of print at http://diabetes.diabetesjournals.org on 29 May 2007. DOI: 10.2337/db07-0019.
This manuscript and its contents are solely the responsibility of the authors and do not necessarily represent the official
views of NCRR or NIH.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore
be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Accepted May 12, 2007.
Received January 8, 2007.
DIABETES
Fabry nephropathy is associated with progressive accumulation of globotriaosylceramide (GL3) in podocytes. Reducing this GL3 burden may reduce podocyte injury. Sensitive methods to quantify podocyte ...GL3 content may determine whether a given strategy can benefit podocytes in Fabry disease. We developed an unbiased electron microscopic stereological method to estimate the average volume of podocytes and their GL3 inclusions in 6 paired pre- and post-enzyme replacement therapy (ERT) biopsies from 5 men with Fabry disease. Podocyte GL3 content was regularly reduced (average 73%) after 11-12 months of ERT. This was not detectable using a semi-quantitative approach. Parallel to GL3 reduction, podocytes became remarkably smaller (average 63%). These reductions in podocyte GL3 content or size were not significantly correlated with changes in foot process width (FPW). However, FPW after ERT was significantly correlated with the magnitude of the decrease in podocyte GL3 content from baseline to 11-12 months of ERT. Also podocytes exocytosed GL3 inclusions, a phenomenon correlated with their reduction in their GL3 content. Demonstrable after11-12 months, reduction in podocyte GL3 content allows for early assessment of treatment efficacy and shorter clinical trials in Fabry disease.
Chronic kidney disease is a major complication of Fabry disease. Podocytes accumulate globotriaosylceramide inclusions more than other kidney cell types in Fabry patients. Podocyte injury occurs ...early in age, and is progressive. Since injured podocytes detach into the urine (podocyturia), we hypothesized that podocyturia would increase in Fabry patients and correlate with clinical severity of Fabry nephropathy. Urine specimens from 39 Fabry patients and 24 healthy subjects were evaluated for podocyturia. Most of the Fabry patients and many healthy subjects had podocyturia. The number of podocytes per gram of urine creatinine (UPodo/g Cr) was 3.6 fold greater in Fabry patients (3,741 ± 2796; p = 0.001) than healthy subjects (1,040 ± 972). Fabry patients with normoalbuminuria and normoproteinuria had over 2-fold greater UPodo/g Cr than healthy subjects (p = 0.048). UPodo/gCr was inversely related to eGFR in male patients (r = -0.69, p = 0.003). UPodo/gCr was directly related to urine protein creatinine ratio (r = 0.33; p = 0.04) in all Fabry patients. These studies confirm increased podocyturia in Fabry disease, even when proteinuria and albuminuria are absent. Podocyturia correlates with clinical severity of Fabry nephropathy, and potentially may be of prognostic value.
Reversal of diabetic nephropathy (DN) has been achieved in humans and mice, but only rarely and under special circumstances. As progression of DN is related to podocyte loss, reversal of DN requires ...restoration of podocytes. Here, we identified and quantified potential glomerular progenitor cells that could be a source for restored podocytes. DN was identified in 31 human renal biopsy cases and separated into morphologically early or advanced lesions. Markers of podocytes (WT-1, p57), parietal epithelial cells (PECs) (claudin-1), and cell proliferation (Ki-67) were identified by immunohistochemistry. Podocyte density was progressively reduced with DN. Cells marking as podocytes (p57) were present infrequently on Bowman’s capsule in controls, but significantly increased in histologically early DN. Ki-67-expressing cells were identified on the glomerular tuft and Bowman’s capsule in DN, but rarely in controls. Cells marking as PECs were present on the glomerular tuft, particularly in morphologically advanced DN. These findings show evidence of phenotypic plasticity in podocyte and PEC populations and are consistent with studies in the BTBR ob/ob murine model in which reversibility of DN occurs with podocytes potentially regenerating from PEC precursors. Thus, our findings support, but do not prove, that podocytes may regenerate from PEC progenitors in human DN. If so, progression of DN may represent a modifiable net balance between podocyte loss and regeneration.
Current therapies for Fabry disease are based on reversing intracellular accumulation of globotriaosylceramide (Gb3) by enzyme replacement therapy (ERT) or chaperone-mediated stabilization of the ...defective enzyme, thereby alleviating lysosomal dysfunction. However, their effect in the reversal of end-organ damage, like kidney injury and chronic kidney disease, remains unclear. In this study, ultrastructural analysis of serial human kidney biopsies showed that long-term use of ERT reduced Gb3 accumulation in podocytes but did not reverse podocyte injury. Then, a CRISPR/Cas9-mediated α-galactosidase knockout podocyte cell line confirmed ERT-mediated reversal of Gb3 accumulation without resolution of lysosomal dysfunction. Transcriptome-based connectivity mapping and SILAC-based quantitative proteomics identified α-synuclein (SNCA) accumulation as a key event mediating podocyte injury. Genetic and pharmacological inhibition of SNCA improved lysosomal structure and function in Fabry podocytes, exceeding the benefits of ERT. Together, this work reconceptualizes Fabry-associated cell injury beyond Gb3 accumulation, and introduces SNCA modulation as a potential intervention, especially for patients with Fabry nephropathy.
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