COVID-19-Associated Glomerular Disease

Pathophysiology and Clinical Manifestations of COVID-19-Related Acute Kidney Injury-The Current State of Knowledge and Future Perspectives

The continually evolving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has resulted in a vast number of either acute or chronic medical impairments of a pathophysiology that is not yet fully understood. SARS-CoV-2 tropism for the organs is associated with bilateral organ cross-talks as well as targeted dysfunctions, among which acute kidney injury (AKI) seems to be highly prevalent in infected patients. The need for efficient management of COVID-related AKI patients is an aspect that is still being investigated by nephrologists; however, another reason for concern is a disturbingly high proportion of various types of kidney dysfunctions in patients who have recovered from COVID-19. Even though the clinical picture of AKI and COVID-related AKI seems to be quite similar, it must be considered that regarding the latter, little is known about both the optimal management and long-term consequences. These discrepancies raise an urgent need for further research aimed at evaluating the molecular mechanisms associated with SARS-CoV-2-induced kidney damage as well as standardized management of COVID-related AKI patients. The following review presents a comprehensive and most-recent insight into the pathophysiology, clinical manifestations, recommended patient management, treatment strategies, and post-mortem findings in patients with COVID-related AKI.

Renal allograft function in kidney transplant recipients infected with SARS-CoV 2: An academic single center experience

BACKGROUND

Kidney transplant recipients are a unique cohort in regard to SARS-CoV 2 susceptibility and clinical course, owing to their immunosuppressed state and propensity for kidney injury. The primary purpose of this study is to ascertain if, in kidney transplant recipients, SARS-CoV 2 infection impacts long term renal allograft function.

METHODS

This retrospective, single-center study reviewed 53 kidney transplant recipients with a positive SARS-CoV-2 PCR at NMH from January 1, 2020 to June 30, 2020.

RESULTS

Change in eGFR from baseline kidney function prior to infection to 90 days after the first positive SARS-CoV 2 test was +1.76%, -17.5% and -23.16% the mild, moderate and severe disease groups respectively. There was a significant decline in kidney function in the moderate and severe disease cohorts as compared to the mild disease cohort, with respective p values of p = 0.0002 and p = 0.021. Relative to the mild disease cohort, the moderate and severe disease cohorts also demonstrated significantly increased risk of developing AKI (66%, 85%), both with p values of P = 0.0001.

CONCLUSIONS

Clinically severe SARS-CoV 2 infection is associated with greater risk of acute kidney injury and greater decline in renal allograft function at 90 days post infection, compared to mild disease.

Coronavirus disease 2019 and kidney injury

PURPOSE OF REVIEW

In this paper, we seek to review coronavirus disease 2019 (COVID-19) associated kidney injury with a focus on what is known about pathophysiology.

RECENT FINDINGS

Kidney injury is a common complication of SARS-CoV-2 infection and is associated with increased morbidity and mortality. Acute tubular necrosis and glomerular injury are two common findings. Direct viral effect, endothelial dysfunction, and podocyte and tubular epithelial injury have been described. COVID-19-related glomerular injury may also be associated with high-risk APOL1 genotype.

SUMMARY

Data on COVID-19 renal involvement have suggested novel mechanisms of kidney injury that need to be further elucidated. More data are needed on renal involvement in milder disease, renal-specific therapeutic interventions, and long-term sequelae.

Initial experience of bamlanivimab monotherapy use in solid organ transplant recipients

The widespread transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to propagate the coronavirus disease 2019 (COVID-19) pandemic with solid organ transplant (SOT) recipients being an exceptionally vulnerable population for poor outcomes. Treatments for COVID-19 are limited; however, monoclonal antibodies are emerging as a potential therapeutic option to change the trajectory of high-risk patients. This retrospective single center cohort study evaluated the outcomes of SOT recipients with mild to moderate COVID-19 who received bamlanivimab monotherapy. Eighteen SOT recipients (15 kidney, 2 liver, and 1 heart) received the medication between November 9, 2020 and February 10, 2021 with no reported infusion reactions. One patient experienced headache and fatigue following the infusion that resolved within 3 days. Fourteen patients continued their recovery as an outpatient with no further escalation in care. Three patients required hospitalization: two for suspected bacterial pneumonia 9 and 32 days postinfusion, respectively, and one for acute kidney injury 7 days postinfusion. One patient had an emergency room visit for gastrointestinal symptoms 24 days postinfusion. In this small cohort of SOT recipients, bamlanivimab monotherapy appeared to be a well-tolerated option for treatment of mild to moderate COVID-19, but it was not completely effective in preventing hospitalization. One month following the end of this cohort, COVID-19 treatment guidance changed due to the rising prevalence of resistant variants. For this reason, bamlanivimab is now recommended to be used only in combination with etesevimab. Further studies are needed to fully elucidate the role of this therapy in SOT recipients.

De novo collapsing glomerulopathy in a pediatric kidney transplant recipient with COVID-19 infection

The negative impact of COVID-19 on adults with underlying chronic kidney disease, including kidney transplant recipients, has been well documented. Children have a less severe presentation and better prognosis compared to adults. However, little is known regarding the spectrum of COVID-19 infection in children and adolescents with underlying autoimmune disorders necessitating solid organ transplant and long-term immunosuppressive therapy. Case Report. An adolescent male developed end-stage kidney disease secondary to microscopic polyangiitis requiring a living-donor kidney transplant. Six years later, he developed antibody-mediated rejection of his kidney transplant. During his rejection treatment course, he contracted SARS-CoV-2 and developed new-onset nephrotic syndrome with severe acute kidney injury. Kidney transplant biopsy revealed de novo collapsing focal segmental glomerulosclerosis on a background of chronic active antibody mediated rejection. Immunostaining for SARS-CoV-2 on the biopsy specimen demonstrated positive staining of the proximal tubular epithelium consistent with intra-renal viral infection. Pulse corticosteroids, intravenous immunoglobulin, and temporary reduction of anti-metabolite therapy resulted in successful recovery with return of graft function back to pre-infection baseline. This case highlights the clinical conundrum of treating kidney transplant recipients with active rejection in the midst of the COVID-19 pandemic. Pediatric kidney transplant recipients can develop severe COVID-19-related kidney complications. Judicious immunosuppression modulation is necessary to balance infection and rejection risk.

Organoids: A New Model for SARS-CoV-2 Translational Research

The 2019-novel coronavirus (SARS-CoV-2) pneumonia epidemic is a thorny public health problem faced by health officials and a major cause of concern for health professionals. However, the currently used immortalized cell lines and animal models, though easy to manipulate, can not thoroughly simulate real viral activity due to a lack of target cells, species isolation, and insufficient adequate tissues and organs for clinical research. Organoid that emerges as an effective model and time-saving approach can simulate the viral life cycle in vitro and explore a therapeutic target for antiviral drug development. The 3D tissue cultures contain patient-specific stem cells in vitro to mimic the complexity of real tissue within the 3D microstructure that has the same functionality as the tissue of interest. It avoids the problems such as the distortion of genetic markers and animal ethics of using 2D cultures for animal testing and can be employed in studies of specific-organ viral infections to fully understand the physiopathological mechanism of SARS-CoV-2 infection for vaccine research and development.

Pathophysiology of infection with SARS-CoV-2-What is known and what remains a mystery

Coronavirus disease 2019 (COVID‐19), caused by coronavirus severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has caused extensive disruption and mortality since its recent emergence. Concomitantly, there has been a race to understand the virus and its pathophysiology. The clinical manifestations of COVID‐19 are manifold and not restricted to the respiratory tract. Extrapulmonary manifestations involving the gastrointestinal tract, hepatobiliary system, cardiovascular and renal systems have been widely reported. However, the pathophysiology of many of these manifestations is controversial with questionable support for direct viral invasion and an abundance of alternative explanations such as pre‐existing medical conditions and critical illness. Prior research on SARS‐Co‐V and NL63 was rapidly leveraged to identify angiotensin‐converting enzyme 2 (ACE2) receptor as the key cell surface receptor for SARS‐CoV‐2. The distribution of ACE2 has been used as a starting point for estimating vulnerability of various tissue types to SARS‐CoV‐2 infection. Sophisticated organoid and animal models have been used to demonstrate such infectivity of extrapulmonary tissues in vitro, but the clinical relevance of these findings remains uncertain. Clinical autopsy studies are typically small and inevitably biased towards patients with severe COVID‐19 and prolonged hospitalization. Technical issues such as delay between time of death and autopsy, use of inappropriate antibodies for paraffin‐embedded tissue sections and misinterpretation of cellular structures as virus particles on electron micrograph images are additional problems encountered in the extant literature. Given that SARS‐CoV‐2 is likely to circulate permanently in human populations, there is no doubt that further work is required to clarify the pathobiology of COVID‐19.

Acute Kidney Injury in Hospitalized Children with COVID19

BACKGROUND

Acute kidney injury (AKI) has been recognized as a significant risk factor for mortality among adults with severe acute respiratory syndrome coronavirus infection.

AIM

The aim of this study is to assess the prevalence and risk factors for AKI and mortality in children with coronavirus disease 2019 (COVID19) from a resource-limited setting.

METHODS

Cross-sectional analysis of laboratory confirmed COVID19 children admitted from 1 March to 30 November 2020 in a tertiary care hospital in New Delhi, India was done. Clinical features and associated comorbidities of COVID19 were noted. Baseline serum creatinine (height-independent Hoste's equation) and peak serum creatinine were used for staging of AKI by the 2012 Kidney Disease Improving Global Outcomes serum creatinine criteria. Univariate analysis and Kaplan-Meier survival analysis were used to compare the overall outcome in the AKI vs. the non-AKI group.

RESULTS

A total of 64 810 children between 1 month and 18 years visited the hospital; 3412 were tested for suspected COVID19, 295 tested positive and 105 (54% boys) were hospitalized. Twenty-four hospitalized children (22.8%) developed AKI; 8 in Stage 1 (33.3%), 7 in Stage 2 (29.2%) and 9 in Stage 3 (37.5%) respectively. Overall, three patients received KRT. Highest reported mortality was (66.6%) in AKI Stage 3. Risk factors for AKI included associated sepsis (OR 95% CI, 1.22-9.43, p < 0.01), nephrotic syndrome (OR 95% CI, 1.13-115.5, p < 0.01), vasopressor support (OR 3.59, 95% CI, 1.37-9.40, p value< 0.007), shock at presentation (OR 2.98, 95% CI, 1.16-7.60, p value 0.01) and mechanical ventilation (OR 2.64, 95% CI, 1.04-6.71, p value< 0.03). Mortality (25.71%) was higher in the AKI group (OR 95% CI, 1.14-8.35, p < 0.023) with shock (OR 45.92; 95% CI, 3.44-612.0, p value <0.004) and ventilation (OR 46.24; 95% CI, 1.6-1333.0 p value< 0.02) as significant risk factors for mortality.

CONCLUSION

AKI is an important modifiable risk factor for mortality in children with COVID19 in a resource-limited setting. Our study supports the strengthening of kidney replacement therapy and its timely initiation to reduce the progression of AKI and thus mortality in children.

Apolipoprotein L1 and mechanisms of kidney disease susceptibility

PURPOSE OF REVIEW

Allelic variants in the gene for apolipoprotein L1 (APOL1), found only in individuals of African ancestry, explain a majority of the excess risk of kidney disease in African Americans. However, a clear understanding how the disease-associated APOL1 variants cause kidney injury and the identity of environmental stressors that trigger the injury process have not been determined.

RECENT FINDINGS

Basic mechanistic studies of APOL1 biochemistry and cell biology, bolstered by new antibody reagents and inducible pluripotent stem cell-derived cell systems, have focused on the cytotoxic effect of the risk variants when APOL1 gene expression is induced. Since the APOL1 variants evolved to alter a key protein-protein interaction with the trypanosome serum resistance-associated protein, additional studies have begun to address differences in APOL1 interactions with other proteins expressed in podocytes, including new observations that APOL1 variants may alter podocyte cytoskeleton dynamics.

SUMMARY

A unified mechanism of pathogenesis for the various APOL1 nephropathies still remains unclear and controversial. As ongoing studies have consistently implicated the pathogenic gain-of-function effects of the variant proteins, novel therapeutic development inhibiting the synthesis or function of APOL1 proteins is moving toward clinical trials.

Pathogenesis of coronavirus disease 2019-associated kidney injury

PURPOSE OF REVIEW

The current review summarizes the pathologic findings in kidneys from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected patients who have had autopsies or undergone biopsy, and the pathogenic mechanisms implicated in coronavirus disease 2019 (COVID-19)-associated kidney diseases.

RECENT FINDINGS

Direct infection of the kidney by SARS-CoV-2 is not common, and convincing morphologic evidence of substantive kidney infection by SARS-CoV-2 is lacking. Severe COVID-19-associated acute kidney injury is likely multifactorial and results from the physiologic disturbances and therapies used to treat this illness. COVID-19-associated collapsing glomerulopathy (COVAN) is seen almost exclusively in patients with apolipoprotein L1 high-risk genotypes with no evidence of direct infection of the kidney by SARS-CoV-2.

SUMMARY

The prevailing evidence does not support substantive or persistent infection of kidneys in COVID-19 and indirect means of tissue injury are favored, although a 'hit and run' model cannot be excluded. COVAN frequently occurs in patients with mild respiratory systems, suggesting that innate and adaptive immune responses to SARS-CoV-2 infection may provide the second hit needed for the development of collapsing glomerulopathy in susceptible individuals.

Is it Safe to Be Transplanted From Living Donors Who Recovered From COVID-19? Experience of 31 Kidney Transplants in a Multicenter Cohort Study From India

BACKGROUND

There is lack of data on feasibility and safety of kidney transplants from living donors who recovered from COVID-19.

METHODS

Here, we present a retrospective cohort study of 31 kidney transplant recipients (KTR) from living donors who recovered from polymerase chain reaction confirmed COVID-19 across 19 transplant centers in India from July 3, 2020, to December 5, 2020. We detailed demographics, clinical manifestations, immunosuppression regimen, treatment, and outcomes. Donors with a previous diagnosis of COVID-19 were accepted after documenting 2 negative polymerase chain reaction tests with complete symptom resolution for at least 28 days and significant social distancing for 14 days before surgery.

RESULTS

COVID-19 clinical severity in donors ranged from completely asymptomatic (71%, n = 22) to mild infection (29%, n = 9). None progressed to moderate or severe stages of the disease in the entire clinical course of home treatment. Patient and graft survival was 100%, respectively, with acute cellular rejection being reported in 6.4% (n = 2) recipient. All recipients and donors were asymptomatic with normal creatinine at median follow-up of 44 days after surgery without any complications relating to surgery and COVID-19.

CONCLUSIONS

Our data support safety of proceeding with living donation for asymptomatic individuals with comprehensive donor, recipients screening before surgery, using a combination of clinical, radiologic, and laboratory criteria. It could provide new insights into the management of KTR from living donors who have recovered from COVID-19 in India. To the best of our knowledge, this remains the largest cohort of KTR from living donors who recovered from COVID-19.

Continuous renal replacement therapy and the COVID pandemic

Severe COVID‐19 illness and the consequent cytokine storm and vasodilatory shock commonly lead to ischemic acute kidney injury (AKI). The need for renal replacement therapies (RRTs) in those with the most severe forms of AKI is considerable and risks overwhelming health‐care systems at the peak of a surge. We detail the challenges and considerations involved in the preparation of a disaster response plan in situations such as the COVID‐19 pandemic, which dramatically increase demand for nephrology services. Taking careful inventory of all aspects of an RRT program (personnel, consumables, and machines) before a surge in RRT arises and developing disaster contingency protocol anticoagulation and for shared RRT models when absolutely necessary are paramount to a successful response to such a disaster.

COVID-19 effects on the kidney

Apart from pulmonary disease, acute kidney injury (AKI) is one of the most frequent and most severe organ complications in severe coronavirus disease 2019 (COVID-19). The SARS-CoV‑2 virus has been detected in renal tissue. Patients with chronic kidney disease (CKD) before and on dialysis and specifically renal transplant patients represent a particularly vulnerable population. The increasing number of COVID-19 infected patients with renal involvement led to an evolving interest in the analysis of its pathophysiology, morphology and modes of virus detection in the kidney. Meanwhile, there are ample data from several autopsy and kidney biopsy studies that differ in the quantity of cases as well as in their quality. While the detection of SARS-CoV‑2 RNA in the kidney leads to reproducible results, the use of electron microscopy for visualisation of the virus is difficult and currently critically discussed due to various artefacts. The exact contribution of indirect or direct effects on the kidney in COVID-19 are not yet known and are currently the focus of intensive research.

Pathogenesis of Acute Kidney Injury in Coronavirus Disease 2019

Since the outbreak of Coronavirus Disease 2019 (COVID-19) in Wuhan, China, in December of 2019, it has rapidly become a global pandemic. Although acute respiratory disorder is the main manifestation of COVID-19, acute kidney injury (AKI) is another important extrapulmonary complication, which has a critical impact on the prognosis and mortality of patients. Current understanding about the exact pathogenesis of AKI in COVID-19 is unclear. Several studies have suggested that intrarenal, pre-renal and post-renal factors mediated collaboratively by direct virus attack, overloaded immune responses, drugs, sepsis, coagulation dysfunction, and underlying diseases may all be involved in the pathogenesis of AKI. This article reviews the current understanding of the pathogenesis of AKI in COVID-19.

COVID-19-associated Nephropathy Includes Tubular Necrosis and Capillary Congestion, with Evidence of SARS-CoV-2 in the Nephron

Background

Kidney damage has been reported in patients with COVID-19. Despite numerous reports about COVID-19-associated nephropathy, the factual presence of the SARS-CoV-2 in the renal parenchyma remains controversial.

Methods

We consecutively performed 16 immediate (≤3 hours) postmortem renal biopsies in patients diagnosed with COVID-19. Kidney samples from five patients who died from sepsis not related to COVID-19 were used as controls. Samples were methodically evaluated by three pathologists. Virus detection in the renal parenchyma was performed in all samples by bulk RNA RT-PCR (E and N1/N2 genes), immunostaining (2019-nCOV N-Protein), fluorescence in situ hybridization (nCoV2019-S), and electron microscopy.

Results

The mean age of our COVID-19 cohort was 68.2±12.8 years, most of whom were male (69%). Proteinuria was observed in 53% of patients, whereas AKI occurred in 60% of patients. Acute tubular necrosis of variable severity was found in all patients, with no tubular or interstitial inflammation. There was no difference in acute tubular necrosis severity between the patients with COVID-19 versus controls. Congestion in glomerular and peritubular capillaries was respectively observed in 56% and 88% of patients with COVID-19, compared with 20% of controls, with no evidence of thrombi. The 2019-nCOV N-Protein was detected in proximal tubules and at the basolateral pole of scattered cells of the distal tubules in nine out of 16 patients. In situ hybridization confirmed these findings in six out of 16 patients. RT-PCR of kidney total RNA detected SARS-CoV-2 E and N1/N2 genes in one patient. Electron microscopy did not show typical viral inclusions.

Conclusions

Our immediate postmortem kidney samples from patients with COVID-19 highlight a congestive pattern of AKI, with no significant glomerular or interstitial inflammation. Immunostaining and in situ hybridization suggest SARS-CoV-2 is present in various segments of the nephron.

[COVID-19 effects on the kidney]

Bei einer schweren Coronavirus-Erkrankung-2019 (COVID-19) ist neben der Lungenerkrankung selbst das akute Nierenversagen (ANV) eine der häufigsten und schwerwiegendsten Komplikationen. Das SARS-CoV-2-Virus konnte hierbei auch in der Niere nachgewiesen werden. Patienten mit chronischen Nierenerkrankungen (CKD), dialysepflichtige sowie v. a. 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 Autopsie- und Nierenbiopsiestudien mit unterschiedlichen Patientenzahlen und von sehr unterschiedlicher Qualität vor. Während der Nachweis von SARS-CoV-2-RNA im Nierengewebe mit gut reproduzierbaren Ergebnissen erfolgt, ist insbesondere der Virusnachweis mittels Elektronenmikroskopie schwierig und wird aufgrund zahlreicher Artefakte derzeit kritisch diskutiert. Die genauen direkten oder indirekten Effekte von SARS-CoV‑2 auf die Niere sind noch nicht im Detail bekannt und derzeit der Fokus intensiver Forschung.

Molecular Mechanisms of Renal Progenitor Regulation: How Many Pieces in the Puzzle?

Kidneys of mice, rats and humans possess progenitors that maintain daily homeostasis and take part in endogenous regenerative processes following injury, owing to their capacity to proliferate and differentiate. In the glomerular and tubular compartments of the nephron, consistent studies demonstrated that well-characterized, distinct populations of progenitor cells, localized in the parietal epithelium of Bowman capsule and scattered in the proximal and distal tubules, could generate segment-specific cells in physiological conditions and following tissue injury. However, defective or abnormal regenerative responses of these progenitors can contribute to pathologic conditions. The molecular characteristics of renal progenitors have been extensively studied, revealing that numerous classical and evolutionarily conserved pathways, such as Notch or Wnt/β-catenin, play a major role in cell regulation. Others, such as retinoic acid, renin-angiotensin-aldosterone system, TLR2 (Toll-like receptor 2) and leptin, are also important in this process. In this review, we summarize the plethora of molecular mechanisms directing renal progenitor responses during homeostasis and following kidney injury. Finally, we will explore how single-cell RNA sequencing could bring the characterization of renal progenitors to the next level, while knowing their molecular signature is gaining relevance in the clinic.