Excretion Patterns of Urinary Sediment and Supernatant Podocyte Biomarkers in Patients with Chronic Kidney Disease

Background: Podocyte depletion causes glomerulosclerosis, and persistent podocyte loss drives progression to end-stage kidney disease. Urinary sediment podocyte (u-sed Pod) mRNA excretion and urinary supernatant podocyte (u-sup PCX) protein have been used to monitor disease activity in glomerular diseases. However, the differences in these markers among pathologies have not been investigated. We examined the roles of these markers in kidney diseases. Methods: From January 2013 to March 2016, early morning urine samples were collected from 12 healthy controls and 172 patients with kidney disease (minor glomerular abnormality with mild proteinuria and/or microscopic hematuria, n = 15; minimal change nephrotic syndrome [MCNS], n = 15; membranous nephropathy [MN], n = 15; IgA nephropathy [IgAN], n = 60; crescentic glomerulonephritis [Cres GN], n = 19; lupus nephritis [LN], n = 10; others, n = 38). We examined u-sed Pod mRNA excretion, u-sup PCX protein and the urinary protein:creatinine ratio (u-PCR). Results: U-sed Pod mRNA excretion was significantly correlated with u-sup PCX protein (r = 0.37, p < 0.001). Both u-sed Pod mRNA excretion and u-sup PCX protein were significantly correlated with u-PCR (r = 0.53, p < 0.001 and r = 0.35, p < 0.001, respectively). Interestingly, u-sed Pod mRNA excretion was significantly increased in proliferative-type glomerulonephritis-including IgAN with extracapillary proliferative lesions, Cres GN and LN class IV-and significantly correlated with the rate of crescent formation, whereas u-sup PCX protein was significantly increased only in MN and subepithelial dense deposit-type LN compared with controls. Conclusions: Higher u-sed Pod mRNA excretion and u-sup PCX protein were associated with proliferative-type glomerulonephritis indicating podocyte detachment and subepithelial dense deposit-type glomerulonephritis, respectively. The results suggest that u-sed Pod mRNA excretion and u-sup PCX protein have usefulness for the diagnosis and measurement of disease activity with regard to glomerular diseases.

Single-cell RNA sequencing of urinary cells reveals distinct cellular diversity in COVID-19-associated AKI

Background: Acute kidney injury (AKI) is a common sequela of infection with SARS-CoV-2 and contributes to the severity and mortality from COVID-19. Here, we tested the hypothesis that kidney alterations induced by COVID-19-associated AKI could be detected in cells collected from urine. Methods: We performed single-cell RNA sequencing (scRNAseq) on cells recovered from the urine of eight hospitalized COVID-19 patients with (n=5) or without AKI (n=3) as well as four non-COVID-19 AKI patients (n=4) to assess differences in cellular composition and gene expression during AKI. Results: Analysis of 30,076 cells revealed a diverse array of cell types, most of which were kidney, urothelial, and immune cells. Pathway analysis of tubular cells from patients with AKI showed enrichment of transcripts associated with damage-related pathways compared to those without AKI. ACE2 and TMPRSS2 expression were highest in urothelial cells amongst cell types recovered. Notably, in one patient we detected SARS-CoV-2 viral RNA in urothelial cells. These same cells were enriched for transcripts associated with anti-viral and anti-inflammatory pathways. Conclusions: We successfully performed scRNAseq on urinary sediment from hospitalized patients with COVID-19 to noninvasively study cellular alterations associated with AKI and established a dataset that includes both injured and uninjured kidney cells. Additionally, we provide preliminary evidence of direct infection of urinary bladder cells by SARS-CoV-2. The urinary sediment contains a wealth of information and is a useful resource for studying the pathophysiology and cellular alterations that occur in kidney diseases.

Changes in the urinary system in children with enterovirus infection

A significant increase in the incidence of enterovirus infections (EVI) with the development of multiple organ damage does not exclude the involvement of the urinary system organs in the pathological process. Materials and methods. 151 EVI children (103 cases with enterovirus meningitis (EVM), 48 children with other forms of EVI without damage of central nervous system) aged from 1 to 18 years. The frequency and nature of changes in urinary sediment and kidney function in patients with various EVI forms were studied. A highly sensitive marker of acute kidney injury - KIM-1 was used as a marker along with standard methods (determination of blood creatinine level with calculation of glomerular filtration rate) in 25 EVM patients. Results. Pathological changes in urinary sediment in EVI are registered in 37.75% of cases (27.1-42.72%, depending on the clinical form), more often in preschool children, are represented by unexpressed proteinuria and abacterial leukocyturia, and are of a short-term transient nature. 40% of EVM children patients showed an increase in the KIM-1 level above the standard values. Conclusion. The detection of KIM-1 in the urine of EVM children patients indicates the possible development of acute transient tubulointerstitial renal damage. At risk there are children with cerebrospinal fluid pleocytosis greater than 200×106/L, abacterial leukocyturia, and decreased glomerular filtration rate.

A morphological classification of the fat particles found in the urinary sediment of patients with Fabry disease

Objectives The search in the urinary sediment (U-sed) of fat particles with peculiar morphology is a simple and inexpensive tool for the diagnosis of Fabry disease (FD) nephropathy. In this study we investigated the morphology of a high number of such fat particles with the aim to obtain a morphological classification to be used for their identification. Methods Study of the morphology of fat particles in the U-sed of a cohort of FD patients using: bright field plus phase contrast microscopy (BF + PC), polarized light microscopy (POL), and transmission electron microscopy (TEM). Comparison of these results with those obtained for the fat particles seen in the U-sed of a control group (CG) of patients with non-FD glomerulopathies. Results FD: 18 U-sed from six patients (three samples/patient) were prospectively investigated and 506 fat particles identified. With BF + PC, these were classified in eight morphological categories (seven of which were confirmed by TEM), and with POL in 10 others. CG: eight U-sed from eight patients were investigated and 281 fat particles identified. These fell into four BF + PC morphological categories and into eight POL categories. While some categories were significantly more frequent in FD others were more frequent in the CG. Conclusions Our study demonstrates that 1. The morphology of fat particles found in the U-sed of FD patients is much wider and complex than that described so far 2. Several significant differences exist in the morphology of such fat particles between FD and CG patients.

Atypical presentation of allergic interstitial nephritis likely induced by ciprofloxacin

Though the prevalence of drug induced allergic interstitial nephritis (AIN) appears to be increasing, the diagnostic and treatment strategies still remain vague. We present a 56-year-old man with a history of hypertension, chronic kidney disease stage IIIa, recent exposure to ciprofloxacin who presented with acute kidney injury. Though the suspicion of AIN was high, his urinary sediment was bland, that is, no leucocytes or leucocyte casts. A renal biopsy subsequently showed features of AIN correlating with a resolving phase of inflammation. Given the resolving nature of the pathology, we chose not to complete a course of corticosteroids despite his need for temporary haemodialysis. He was able to fully recover his renal function. In this report, we emphasise the unreliable nature of the urinary sediment in the diagnosis of AIN, the utility of a renal biopsy in helping to guide treatment, and the controversial data in corticosteroid treatment.

Cytomegalovirus in urinary sediment in patients with acute kidney injury

Background Immunosuppression in solid organ transplantation is associated with frequent infections. Renal allograft recipients are susceptible to opportunistic infections and can acquire human cytomegalovirus (HCMV) infections even within the allograft. There, HCMV can be found in both the glomerulus and tubular cells, but is mostly restricted to specific and circumscribed sites. Therefore, not all organ infections are identifiable by immunohistology for HCMV proteins in fine needle core biopsies. Thus, we performed a urinalysis study to search for HCMV-specific RNA transcripts in the urine sediment of patients with acute kidney injury. Methods Urinary sediment of 90 patients with acute kidney injury (AKI), including 48 renal transplant recipients (RTX) and 42 non-transplant recipients (nRTX), was collected from morning urine for RNA extraction and reverse transcription. The copy number of HCMV transcripts was evaluated using a UL132 HCMV-specific probe set and by real-time quantitative polymerase chain reaction (RT-qPCR). Results Of the 48 RTX patients, ten showed HCMV copies in their urine sediment cells. Within this group, three recipients had negative HCMV serology and received an allograft from an HCMV-seropositive donor. In addition, all three RTX patients on a belatacept-based immunosuppressive regimen had HCMV transcripts in their urine. Of the 42 nRTX patients, only two had detectable HCMV transcripts in urine sediment cells and both were under immunosuppression. Conclusions Ten immunosuppressed renal allograft recipients and two immunosuppressed non-transplant patients with AKI showed HCMV copies in urine sediment. Thus, HCMV positivity in urinary sediment appears to be associated with immunosuppression. This study describes a novel noninvasive method for detection of HCMV in urinary sediment. Whether all HCMV infections can be detected or only those with viral replication warrants further investigation.