Proximal tubular dysfunction in patients with COVID-19: what have we learnt so far?

A specific molecular signature in SARS-CoV-2-infected kidney biopsies

Acute kidney injury is one of the most important complications in patients with COVID-19 and is considered a negative prognostic factor with respect to patient survival. The occurrence of direct infection of the kidney by SARS-CoV-2, and its contribution to the renal deterioration process, remain controversial issues. By studying 32 renal biopsies from patients with COVID-19, we verified that the major pathological feature of COVID-19 is acute tubular injury (ATI). Using single-molecule fluorescence in situ hybridization, we showed that SARS-CoV-2 infected living renal cells and that infection, which paralleled renal angiotensin-converting enzyme 2 expression levels, was associated with increased death. Mechanistically, a transcriptomic analysis uncovered specific molecular signatures in SARS-CoV-2-infected kidneys as compared with healthy kidneys and non-COVID-19 ATI kidneys. On the other hand, we demonstrated that SARS-CoV-2 and hantavirus, 2 RNA viruses, activated different genetic networks despite triggering the same pathological lesions. Finally, we identified X-linked inhibitor of apoptosis-associated factor 1 as a critical target of SARS-CoV-2 infection. In conclusion, this study demonstrated that SARS-CoV-2 can directly infect living renal cells and identified specific druggable molecular targets that can potentially aid in the design of novel therapeutic strategies to preserve renal function in patients with COVID-19.

Kidney Biopsy Findings in Patients with SARS-CoV-2 Infection or After COVID-19 Vaccination

BACKGROUND

Emerging case series described a temporal association between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and de novo or relapsing kidney diseases. We aimed to further understand vaccination- and coronavirus disease 2019 (COVID-19)-associated kidney diseases.

METHODS

We present findings from native kidney biopsies of patients recently vaccinated against SARS-CoV-2 ( n =27) and those with COVID-19 ( n =15), reviewed at a single German center. Diagnoses were compared among all native kidney biopsies ( n =10,206) obtained between the prepandemic (2019), pandemic (2020), and vaccination periods (2021) to determine whether there was an increase in kidney diseases in the observed periods.

RESULTS

Biopsy indication was increased serum creatinine and/or new-onset proteinuria. Glomerulopathies (20/27, 74%) were more common than tubulointerstitial diseases in postvaccination patients, with necrotizing GN (8/27, 30%) and primary podocytopathies and other GN types (6/27, 22% each) the most common forms. Acute tubular injury was the most common kidney disease in patients with COVID-19, followed by thrombotic microangiopathy (TMA) and necrotizing GN. The postvaccination and COVID-19 infection groups had similar kidney function recovery rates (69% and 73%, respectively). Furthermore, the frequencies of necrotizing GN, pauci-immune GN, TMA, or primary podocytopathies at our center did not increase between 2019 and 2021.

CONCLUSIONS

We observed differences in entity frequencies between the SARS-CoV-2 vaccination or COVID-19 groups, with glomerulopathies being more common in patients after vaccination and tubulointerstitial diseases in patients with COVID-19. Cases of TMA were observed only in the COVID-19 group. We detected no increase in the frequency of necrotizing GN, TMA, or podocytopathies between 2019 and 2021.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Kidney Histopathology After COVID-19 and SARS-CoV-2 Vaccination, NCT05043168.

SARS-CoV-2 versus other minor viral infection on kidney injury in asymptomatic and mildly symptomatic patients

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has become a global pandemic since December 2019. Most of the patients are mild or asymptomatic and recovered well as those suffered from other respiratory viruses. SARS-CoV-2 infection is supposed to demonstrate more sequelae. Acute kidney injury (AKI) is common among COVID-19 patients and is associated with disease severity and outcomes. Only a few studies focused on a detailed analysis of kidney damage in asymptomatic or mildly symptomatic COVID-19 patients. Whether any minor viral infection is likely to exhibit similar minor effect on renal function as COVID-19 is still unclear, and the definite pathophysiology of viral invasion is not fully understood. Currently, the proposed mechanisms of AKI include direct effects of virus on kidney, dysregulated immune response, or as a result of multi-organs failure have been proposed. This study will discuss the difference between COVID-19 and other viruses, focusing on proposed mechanisms, biomarkers and whether it matters with clinical significance.

COVID-19 and Diabetic Nephropathy

Diabetic nephropathy is the most common condition that requires a chronic renal replacement therapy, such as hemodialysis, peritoneal dialysis, kidney transplantation, or simultaneous kidney-pancreas transplantation. Chronic kidney disease progression, that is the loss of nephrons, which causes the continuous decline of the eGFR, underlies the pathogenesis of diabetic nephropathy. During the COVID-19 pandemic, it became clear that diabetic nephropathy is amongst the independent risk factors that predicts unfavourable outcome upon SARS-CoV2 infection. While we still lack conclusive mechanistic insights into how nephrons are rapidly lost upon SARS-CoV2 infection and why patients with diabetic nephropathy are more susceptible to severe outcomes upon SARS-CoV2 infection, here, we discuss several aspects of the interface of COVID-19 with diabetic nephropathy. We identify the shortage of reliable rodent models of diabetic nephropathy, limited treatment options for human diabetic nephropathy and the lack of knowledge about virus-induced signalling pathways of regulated necrosis, such as necroptosis, as key factors that explain our failure to understand this system. Finally, we focus on immunosuppressed patients and discuss vaccination efficacy in these and diabetic patients. We conclude that more basic science and mechanistic understanding will be required both in diabetic nephropathy as well as in host immune responses to the SARS-CoV2 virus if novel therapeutic strategies are desired.

Dialysis During the COVID-19 Pandemic: Experiences from 4 Dialysis Centers in Iran

Background: Despite all of the research on the risk factors for severe COVID-19, there are still many unknowns about the course of COVID-19 in various populations. Inevitable exposure of dialysis patients, one of the more vulnerable groups for infectious diseases, to COVID-19 concerns many researchers. Furthermore, studies on the mortality rate and risk factors regarding dialysis patients are somewhat inconsistent. Also, it has been suggested that factors such as ethnicity can contribute to that matter. Objectives: We aimed to evaluate the mortality rate of dialysis patients who contracted COVID-19 in the Iranian population. Methods: In this cross-sectional study, we presented the experiences of 4 dialysis centers with a total of 309 dialysis patients (Tehran, Iran) during the COVID-19 pandemic to assess the mortality rate and associated risk factors. Results: Among 309 dialysis patients, 58 patients contracted the disease, and the total mortality rate in this study was 41%. It was observed that although the guidelines for screening patients were similar in these 4 centers, the centers with regular COVID-19 screening for staff members had much lower mortality and infection rate. The most common symptoms in patients were fever, dry cough, and chills. Furthermore, comorbidities such as diabetes can also increase the risk of mortality. Conclusions: This study, along with other studies, can be utilized in developing guidelines for dialysis centers in the COVID-19 pandemic and future pandemics.

Renal tubular dysfunction in COVID-19 patients

Introduction

SARS-CoV-2 infection can affect other organs aside from those of respiratory system, particularly the kidney, heart, blood, digestive tract, and nervous system. COVID-19 renal compromise consists of different syndromes since proteinuria, hematuria, and acute kidney injury (AKI), until chronic kidney disease. Since COVID-19-induced renal tubular damage has been described as a potential antecedent condition to AKI installation, it was decided to evaluate how COVID-19 affects tubular function.

Materials and method

Serum inflammatory parameters, urinalysis, and classical urinary indexes in COVID-19 admitted patients who had neither AKI nor chronic kidney disease (CKD) were evaluated. Statistical analysis was performed by applying Student t test.

Results

Renal tubular function was evaluated in 41 COVID-19 admitted patients who had neither AKI nor CKD. Patients’ mean age was 56 years, males (79%), and with normal creatininemia (0.8 ± 0.2 mg/dL) and eGFR (105.7 ± 6.5 mL/min) values. It was found mild hypocalcemia and a relative increased fractional excretion (FE) of sodium, FE of calcium, FE of phosphorus, calcium-creatinine index, urinary osmolarity, and relative alkaline urine pH values.

Conclusion

Tubular dysfunction was documented in COVID-19 patients.

Differences between COVID-19-induced acute kidney injury and chronic kidney disease patients

Introduction:

This article describes the main differences between COVID-19-induced acute kidney injury (AKI-COVID19) in patients with previous normal renal function (AKI-NRF) and those with chronic kidney disease (AKI-CKD) treated in a high complexity clinic in Barranquilla (Colombia).

Material and Methods:

The patients included in this study (n: 572) were those with a positive diagnosis of COVID-19 confirmed by detection of a positive PCR for SARS-CoV-2. Of these patients, 188 developed AKI during their hospital stay. Patients’ epidemiological data, serum parameters, and clinical frailty status were recorded. Statistical analysis and comparison among AKI-NRF, AKI-CKD, and non-AKI patients were performed.

Results:

The incidence of COVID-19-induced AKI was 33%, with the majority classified as AKIN 1, 16% requiring renal replacement therapy, and AKI-COVID19 mortality of 68%. A significantly higher prevalence of hypertension, cardiac disease, and serum reactive C-protein and lower albumin values in AKI-CKD patients was recorded. Mortality rate, invasive ventilation requirement, and D-dimer levels were significantly higher in AKI-NRF patients:

Conclusion:

Different clinical patterns between AKI-NRF and AKI-CKD were documented.

Kidneys in SARS-CoV-2 Era; a challenge of multiple faces

INTRODUCTION

With the evolution of SARS-CoV-2 pandemic, it was believed to be a direct respiratory virus. But, its deleterious effects were observed on different body systems, including kidneys.

AIM OF WORK

In this review, we tried as much as we can to summarize what has been discussed in the literature about the relation between SARS-CoV-2 infection and kidneys since December, 2019.

METHODS

Each part of the review was assigned to one or two authors to search for relevant articles in three databases (Pubmed, Scopus and Google scholar) and collected data were summarized and revised by two independent researchers.

CONCLUSION

The complexity of COVID-19 pandemic and kidney could be attributed to the direct effect of SARS-CoV-2 infection on the kidneys, different clinical presentation, difficulties confronting dialysis patients, restrictions of the organ transplant programs, poor outcomes and bad prognosis in patients with known history of kidney diseases who got infected with SARS-CoV-2. This article is protected by copyright. All rights reserved.

Evaluation of proximal tubule functions in children with COVID-19: a prospective analytical study

BACKGROUND

There are limited numbers of studies focusing on renal effects of coronavirus disease 2019 (COVID-19) infection and proximal tubular dysfunction in children with COVID-19 infections. The purpose of this study was to evaluate the functions of the proximal tubule in hospitalized children with confirmed acute COVID-19.

METHODS

The children who were hospitalized for confirmed COVID-19 were included in this prospective descriptive analysis. The presence of at least two of the following four abnormalities was used to diagnose proximal tubule injury: abnormal tubular reabsorption of phosphate, normoglycemic glycosuria, hyperuricosuria, and proteinuria.

RESULTS

A total of 115 patients were included in the study. About a third of the individuals had elevated blood creatinine levels or proteinuria. In addition, abnormal renal tubular phosphate loss measured by renal tubular phosphate loss was found in 10 (8.7%) patients, as was hyperuricosuria in 28.6%. As a result, total proximal tubular dysfunction was found in 24 (20.9%) patients.

CONCLUSIONS

One in every five children with acute COVID-19 infections had proximal tubular dysfunction, according to our data. Although, the rate of proximal tubular dysfunction was lower than in adults, it should be noted. The recovery of proximal tubular function in children with COVID-19 should be followed.

[Kidney damage in COVID-19]

COVID-19 is a disease caused by the RNA virus SARS-CoV-2. It is characterised by an attack mainly affecting the respiratory system. There is renal involvement which is characterised by three main types of damage, acute tubular necrosis occurring in the most severe cases, proximal tubulopathy which is a prognostic marker of the disease and segmental and focal hyalinosis occurring in a genetically predisposed terrain. The pathophysiology of SARS-CoV-2 renal involvement is not yet defined. The direct role of the virus is debated, whereas the cytokine storm and the hypoxic and thrombotic complications seem more important. The long-term outcome of the renal damage appears to be quite good. Long-term follow-up will allow us to say whether the renal damage is part of the long COVID.

[Coronavirus disease 2019 pandemic from a nephrological perspective]

Hintergrund

Die Coronavirus-disease-2019(COVID-19)-Pandemie hat auch die Nephrologie weltweit vor große Herausforderungen gestellt. Zum einen stellen Patienten mit Nierenerkrankungen in diesem Zusammenhang eine besonders vulnerable Patientengruppe dar, und zum anderen sind die Nieren bei schweren COVID-19-Verläufen nach den Lungen am häufigsten vom Organversagen betroffen.

Material und Methoden

Um zuverlässige Daten zu COVID-19-Prävalenz und -Mortalität bei Dialysepatienten in Deutschland zu erheben, hat die Deutsche Gesellschaft für Nephrologie bereits während der 1. Welle der Pandemie im Frühjahr 2020 ein Register aufgebaut. Wöchentlich wurden Angaben zu Anzahl und Verlauf der COVID-19-Dialysepatienten in Deutschland erhoben und ausgewertet.

Ergebnisse

Die Prävalenz von COVID-19 bei Dialysepatienten in Deutschland zeigte einen doppelgipfligen Verlauf ähnlich wie in der Allgemeinbevölkerung. Während diese im Frühjahr bei Dialysepatienten auf 1,4 % stieg, fiel sie im Sommer deutlich ab und erreichte im Dezember im Rahmen der 2. Pandemiewelle einen Wert von ca. 1,9 %, trotz mittlerweile flächendeckend eingeführter umfangreicher Hygienemaßnahmen in den Dialysezentren. Ähnlich wie in anderen Industriestaaten weisen auch Dialysepatienten in Deutschland eine sehr hohe COVID-19-Letalität von etwa 20 % auf.

Schlussfolgerung

Aus der ermittelten Letalität bei Dialysepatienten lassen sich unmittelbare Konsequenzen für Hygienemaßnahmen in den Dialyseeinrichtungen sowie zu Impfstrategie und -priorisierung dieser Patientengruppe und des sie behandelnden Personals ableiten. Eine Konsequenz des häufigen Befalls der Niere im Rahmen einer Infektion mit dem „severe acute respiratory syndrome coronavirus 2“ (SARS-CoV-2) bei zuvor noch nicht an einer fortgeschrittenen Nierenerkrankung leidenden Patienten sollte die konsequente nephrologische Nachsorge sein.

Pathology of COVID-19-associated acute kidney injury

Acute kidney injury (AKI) is common among hospitalized patients with coronavirus disease 2019 (COVID-19), with the occurrence of AKI ranging from 0.5% to 80%. An improved knowledge of the pathology of AKI in COVID-19 is crucial to mitigate and manage AKI and to improve the survival of patients who develop AKI during COVID-19. In this review, we summarize the published cases and case series of various kidney pathologies seen with COVID-19. Both live kidney biopsies and autopsy series suggest acute tubular injury as the most commonly encountered pathology. Collapsing glomerulopathy and thrombotic microangiopathy are other encountered pathologies noted in both live and autopsy tissues. Other rare findings such as anti-neutrophil cytoplasmic antibody vasculitis, anti-glomerular basement membrane disease and podocytopathies have been reported. Although direct viral infection of the kidney is possible, it is certainly not a common or even widespread finding reported at the time of this writing (November 2020).

[COVID-19 and kidney involvement]

Bei einer schweren COVID-19(„coronavirus disease 2019“)-Erkrankung ist neben der Lungenerkrankung das akute Nierenversagen eine der häufigsten und schwerwiegendsten Komplikationen. SARS-CoV‑2 („severe acute respiratory syndrome coronavirus 2“) konnte auch in der Niere nachgewiesen werden. Patienten mit chronischen Nierenerkrankungen und an der Dialyse wie auch nierentransplantierte Patienten scheinen eine besonders vulnerable Population darzustellen. Die zunehmende Anzahl SARS-CoV-2-infizierter Patienten hat das Interesse an der genauen Pathophysiologie und Morphologie der Nierenschädigung sowie am direkten Virusnachweis in der Niere geweckt, der im Gegensatz zur Lunge insgesamt schwieriger zu führen ist. Hierzu liegen mittlerweile Daten aus größeren Autopsie- und Nierenbiopsiestudien vor. Während der Nachweis von SARS-CoV-2-RNA im Gewebe zu gut reproduzierbaren Ergebnissen führt, wird insbesondere der Virusnachweis mittels Elektronenmikroskopie aufgrund zahlreicher Artefakte kritisch diskutiert. Die genauen und direkten Effekte von SARS-CoV‑2 auf die Niere sind noch nicht im Detail bekannt und derzeit im Fokus intensiver Forschung.