The rapid atrial swirl sign for ultrasound-guided tip positioning of antegrade-tunneled hemodialysis catheters: A cross-sectional pilot study

BACKGROUND

We have previously reported that the rapid atrial swirl sign (RASS) is an accurate and safe procedure for ultrasound (US)-guided tip positioning of retrograde-tunneled hemodialysis catheters (HDCs). However, application of RASS for placement of antegrade HDCs has not been investigated yet. Therefore, we here report our first experience of applying RASS for US-guided tip positioning of antegrade-tunneled HDCs.

METHODS

We performed a cross-sectional study to assess the feasibility of applying the RASS for US-guided tip positioning of antegrade-tunneled HDCs. We included a total number of 15 antegrade-tunneled HDC insertions in 13 patients requiring placement of a HDC for the temporary or permanent treatment of ESKD in a single-center, cross-sectional pilot study.

RESULTS

The overall success rate of applying the RASS for US-guided tip positioning of antegrade-tunneled HDCs was 15/15 (100%) confirmed by portable anterior-posterior chest radiography, with no major adverse events after HDC insertions. In addition, this insertion technique demonstrated optimal HDC flow without any observed malfunction.

CONCLUSION

This study investigated the efficacy of the RASS for US-guided tip positioning of antegrade-tunneled HDCs in patients with ESKD. Application of the RASS for US-guided tip positioning is an accurate and safe procedure for proper placement of antegrade-tunneled HDCs.

Intrarenal Doppler ultrasonography in patients with HFrEF and acute decompensated heart failure undergoing recompensation

OBJECTIVES

Renal venous congestion due to backward heart failure leads to disturbance of renal function in acute decompensated heart failure (ADHF). Whether decongestion strategies have an impact on renal venous congestion is unknown. Objective was to evaluate changes in intrarenal hemodynamics using intrarenal Doppler ultrasonography (IRD) in patients with heart failure with reduced ejection fraction (HFrEF) and ADHF undergoing recompensation.

METHODS

Prospective observational study in patients with left ventricular ejection fraction (LV-EF) ≤ 35% hospitalized due to ADHF. IRD measurement was performed within the first 48 h of hospitalisation and before discharge. Decongestion strategies were based on clinical judgement according to heart failure guidelines. IRD was used to assess intrarenal venous flow (IRVF) pattern, venous impedance index (VII) and resistance index (RI). Laboratory analyses included plasma creatinine, eGFR and albuminuria.

RESULTS

A number of 35 patients with ADHF and LV-EF ≤ 35% were included into the study. IRD could be performed in 30 patients at inclusion and discharge. At discharge, there was a significant reduction of VII from a median of 1.0 (0.86-1.0) to 0.59 (0.26-1.0) (p < 0.01) as well as improvement of IRVF pattern categories (p < 0.05) compared to inclusion. Albuminuria was significantly reduced from a median of 78 mg/g creatinine (39-238) to 29 mg/g creatinine (16-127) (p = 0.02) and proportion of patients with normoalbuminuria increased (p = 0.01). Plasma creatinine and RI remained unchanged (p = 0.73; p = 0.43).

DISCUSSION

This is the first study showing an effect of standard ADHF therapy on parameters of renal venous congestion in patients with HFrEF and ADHF. Doppler sonographic evaluation of renal venous congestion might provide additional information to guide decongestion strategies in patients with ADHF.

Serum sodium levels associate with recovery of kidney function in immune checkpoint inhibitor nephrotoxicity

Background

Immune checkpoint inhibitors (ICIs) are novel drugs targeting programmed cell death protein 1-ligand 1 (PD-L1) or its receptor (PD-1). Enhancing the immune system has also been associated with a wide range of immune-related adverse events (irAE). Among them, acute interstitial nephritis (AIN) is a rare but deleterious irAE in the kidney. However, determinants of recovery and long-term kidney function after ICI withdrawal and steroid therapy thereafter remain elusive. Therefore, we here aimed to identify parameters associated with recovery of kidney function in this previous established cohort of AIN in the context of ICI therapy.

Methods

We here monitored kidney function over a mean follow-up time of 812 days in comparison with clinical, histopathological and laboratory parameters associated with recovery of kidney function after AIN related to ICI nephrotoxicity.

Results

Abundance of intrarenal PD-L1/PD-1 did not correlate with recovery of kidney function. Furthermore, cumulative steroid dose that was initiated for treatment of AIN related to ICI nephrotoxicity was also not associated with improvement of kidney function. Finally, chronic lesions in the kidney including glomerular sclerosis and interstitial fibrosis/tubular atrophy (IF/TA) did not correlate with eGFR change during the follow-up time. However, we here identified that lower levels of serum sodium at time of kidney biopsy were the strongest independent predictor of renal recovery in ICI-related nephrotoxicity.

Conclusion

Because low serum sodium levels associated with better improvement of kidney function, these observations might contribute to novel approaches to enhance recovery after AIN related to ICI nephrotoxicity.

Leukocyturia and hematuria enable non-invasive differentiation of Bowman's capsule rupture severity in PR3-ANCA glomerulonephritis

BACKGROUND

Renal involvement is a common and severe complication of anti-neutrophil cytoplasmic antibody-(ANCA)-associated vasculitis potentially resulting in pauci-immune necrotizing and crescentic ANCA glomerulonephritis (GN) with rapid deterioration of kidney function, progression to end stage kidney disease or, if left untreated, lethal exitus. Analysis of the urinary sediment routinely supports clinical management of ANCA GN, but histopathological implications of aberrancies in the urinary sediment mostly remain elusive. Therefore, we aimed to systematically assess the correlation of aberrancies in the urinary sediment and clinico-pathologic findings.

METHODS

A total of 42 kidney biopsies with ANCA GN were retrospectively analyzed in a single-center observational study. Laboratory and histopathological parameters were systematically analyzed and correlated with findings of the urinary sediment.

RESULTS

In the overall ANCA GN cohort, leukocyturia and hematuria were associated among each other, and with markers for non-selective glomerular damage, respectively. Non-invasive measurement of leukocyturia indicated focal (but not extensive) Bowman's capsule rupture (BCR) specifically in proteinase-3 (PR3)-ANCA GN, whereas hematuria correlated with extensive (but not focal) BCR. Concerning intrarenal immune cell infiltration, leukocyturia was associated with tubulointerstitial plasma cell infiltration in PR3-ANCA GN. Finally, none of these associations were detectable in myeloperoxidase-ANCA GN, implying different modes of kidney damage.

CONCLUSION

We herein expand our current knowledge by providing evidence that leukocyturia and hematuria enable non-invasive differentiation of BCR severity specifically in PR3-ANCA GN.

Comparative analysis of complement C3 and C4 serum levels for outcome prediction in ANCA-associated renal vasculitis

BACKGROUND

The activation of the complement system contributes essentially to the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis. We here aimed to directly compare levels of C3 and C4 for outcome prediction in ANCA-associated renal vasculitis.

METHODS

Serum levels of complement components C3 and C4 were directly compared in association with clinical and outcome data in a retrospective cohort of ANCA-associated renal vasculitis.

RESULTS

As compared to poor outcome prediction by low levels of complement C3 (p = 0.0093), low levels of complement C4 did not associate with early requirement of kidney replacement therapy (KRT) or death (p = 0.2396). In the subgroup that experienced KRT or death, low C3 levels identified 11/14 (78.6%, p = 0.0071) and C4 levels 9/14 (64.3%, p = 0.1786) cases. Interestingly, 2/14 (14.3%) patients that experienced KRT or death had isolated C4 lowering, and combining low C3 and/or C4 levels identified 13/14 (92.3%, p < 0.0001) cases in this subgroup. Non-superiority to predict poor outcome by low C3 and/or C4 as compared to C3 alone in the total cohort was attributed to 4/24 (16.7%) patients with isolated C4 lowering in the subgroup that did not experience KRT or death.

CONCLUSION

While low levels of complement C3 were superior in predicting poor outcome in ANCA-associated renal vasculitis, a minor fraction with poor outcome had isolated C4 lowering not captured by serum C3 measurements. Therefore, detailed knowledge of distinct complement components contributing to kidney injury could be of relevance to improve current strategies targeting the complement system in ANCA-associated renal vasculitis.

Molecular signatures of intrarenal complement receptors C3AR1 and C5AR1 correlate with renal outcome in human lupus nephritis

OBJECTIVE

Lupus nephritis is one of the most common and serious complications of systemic lupus erythematosus (SLE). Lupus nephritis is a major cause of kidney failure in patients with SLE, attributed to increased morbidity and mortality. The in situ deposition of intrarenal immune complexes promotes the accumulation of inflammatory cells and causes kidney injury.

METHODS

We here extracted transcriptome array datasets for expression of complement molecules in human lupus nephritis. Furthermore, we performed gene set enrichment analysis to identify molecular signatures associated with follow-up kidney function in lupus nephritis.

RESULTS

Within the glomerular compartment, intrarenal mRNA expression levels of C3AR1 (p=0.0333) and C5AR1 (p=0.0167) correlated with treatment success reflected by kidney function recovery specifically in class III lupus nephritis, while no such association was observed in class II or class IV lupus nephritis. Interestingly, mRNA expression levels of either glomerular C3AR1 or C5AR1 resulted in identical gene set and signalling pathways enrichments in human lupus nephritis, including interferon signalling and signalling by interleukins. Direct comparison of C3AR1 and C5AR1 confirmed a strong association between glomerular mRNA expression levels of both complement receptors (r=0.8955, p<0.0001).

CONCLUSIONS

This study provides additional insights into signalling pathways associated with intrarenal synthesis of complement components in lupus nephritis that might be also affected by targeted therapy of the complement system. These results require confirmation but may contribute to a personalised treatment approach in distinct classes of human lupus nephritis.

Intrarenal synthesis of complement C3 localized to distinct vascular compartments in ANCA-associated renal vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a small vessel vasculitis affecting multiple organ systems, including the kidney. The activation of the complement system contributes essentially to its pathogenesis by autoantibody-antigen recognition directed against host cells in ANCA-associated renal vasculitis. We herein provide evidence for intrarenal synthesis of complement C3 localized to distinct vascular compartments in ANCA-associated renal vasculitis that associated with distinct inflammatory signaling pathways. Therefore, a total number of 43 kidney biopsies with ANCA-associated renal vasculitis were retrospectively included and evaluated for presence/absence of C3 deposits localized to distinct vascular compartments in association with clinicopathological biopsy findings. In addition, intrarenal C3 mRNA expression levels specifically from microdissected tubulointerstitial and glomerular compartments were extracted from transcriptome datasets. C3 deposits were present in the glomerular tuft, interlobular arteries, peritubular capillaries, and venules in ANCA-associated renal vasculitis. Most C3 deposits are localized to the glomerular tuft overlapping with peritubular capillaries. The presence of C3 deposits in the glomerular tuft correlated with impaired kidney function and overall short-term survival. Intrarenal complement C3 deposits were not associated with consumption of respective serum levels, supporting the concept of intrarenal C3 synthesis. Finally, intrarenal synthesis of complement C3 was linked to distinct inflammatory signaling pathways in the kidney that is especially relevant in ANCA-associated renal vasculitis. Considering recent advances in AAV therapy with the emergence of new therapeutics that inhibit complement activation, we here provide novel insights into intrarenal complement synthesis and associated inflammatory signaling pathways in ANCA-associated renal vasculitis.

Implication of platelets and complement C3 as link between innate immunity and tubulointerstitial injury in renal vasculitis with MPO-ANCA seropositivity

Introduction

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a potentially life-threatening systemic small-vessel vasculitis that is characterized by pauci-immune glomerulonephritis, depicting in turn a major denominator of AAV mortality. It is well established that AAV patients feature an increased risk of developing thrombotic events, and platelets are activated in AAV patients being triggered by the alternative complement pathway. Platelets guard vessels integrity and initiate thrombus formation in response to endothelial damage, further constituting a triangular interconnection with the activation of neutrophils and the complement system. We here aimed to systematically assess the relevance of platelet counts and systemic complement system activation regarding distinct histopathological lesions in ANCA-associated renal vasculitis.

Methods

A cohort of 53 biopsy-proven cases of ANCA-associated renal vasculitis were retrospectively enrolled in a single-center observational study. Univariate and multivariate regression analysis was performed to identify parameters associated with platelet counts in ANCA-associated renal vasculitis compared to disease controls. Finally, the relevance of platelets for disease course and recovery was assessed by survival analysis.

Results

Lower platelet counts correlated with markers of kidney injury including eGFR loss (p=0.0004) and lower complement C3 levels (p=0.0037). Multivariate and subgroup analysis revealed that this association was only present in the subgroup with MPO-ANCA seropositivity (eGFR loss: p=0.0009, lower C3: p=0.0032). While lower platelet counts correlated with kidney injury in the PR3-ANCA subgroup (eGFR loss: p=0.0272), we did not observe an independent association with complement C3 levels (p=0.4497). Independent of any glomerular lesion, lower platelet counts correlated with interstitial fibrosis (p=0.0313), tubular atrophy (p=0.0073), and tubulitis in areas of interstitial fibrosis and tubular atrophy (p=0.0033). Finally, we observed significant differences with increased requirement of kidney replacement therapy (KRT) or death in the subgroup below median platelet counts (HR: 4.1, 95% CI: 1.6-10, p=0.0047), associated with a lower probability of discharge and prolonged hospitalization in this subgroup (HR: 0.5, 95% CI: 0.3-0.9, p=0.0113).

Conclusion

Based on our observation that an association between platelets and complement system activation is only observed in the MPO-ANCA subgroup, this could implicate that platelets and complement C3 link innate immunity to tubulointerstitial injury in the presence of MPO-ANCA autoantibodies.

Case report: Kinetics of human leukocyte antigen receptor HLA-DR during liver injury induced by potassium para-aminobenzoate as assessed for causality using the updated RUCAM

Potassium para-aminobenzoate (POTABA) is used to treat Peyronie’s disease by decreasing fibrosis and plaque size progression. Among potential side effects, drug-induced liver injury (DILI) attributed to POTABA administration has been reported in a few cases and inferred to immune hypersensitivity. In the present case, we investigated clinical, biochemical, and serological features as well as searched for non-drug-related causes, and applied the updated Roussel Uclaf Causality Assessment Method (RUCAM) confirming a highly probable causality of POTABA-induced liver injury. Moreover, we here observed specific activated CD3+ T lymphocytes during the acute phase of liver injury by monitoring of human leukocyte antigen receptor (HLA-DR) expression. Furthermore, improvement of biochemical markers of liver injury after POTABA withdrawal was associated with a rapid decline of CD3+ HLA-DR+ immune cells. In contrast, CD14+ monocytes expressing HLA-DR remained stable during recovery from liver injury. These observations implicate a specific involvement of activated T lymphocytes in liver injury mediated by POTABA. Clinicians should be aware of POTABA-induced liver injury, and measurement of activated immune cells by assessment of HLA-DR could provide pathomechanistic insights enabling biomonitoring of recovery from DILI.

Compartmentalization of Intrarenal Programmed Cell Death Protein 1-Ligand 1 and Its Receptor in Kidney Injury Related to Immune Checkpoint Inhibitor Nephrotoxicity

Background

Due to advances in cancer therapy, immune checkpoint inhibitors (ICIs) are new classes of drugs targeting programmed cell death protein 1-ligand 1 (PD-L1) or its receptor (PD-1) used in many cancer therapies. Acute interstitial nephritis (AIN) is a potential and deleterious immune-related adverse events (irAE) and the most common biopsy-proven diagnosis in ICI-related nephrotoxicity. AIN in patients receiving ICIs is was only seen in cases with tubular PD-L1 positivity, while PD-1 expression is limited to inflammatory cells and also observed in injured kidneys independent of ICI therapy. We have previously described that PD-L1 positivity can also be detected in glomerular and endothelial compartments. We here aimed to describe compartmentalization of renal PD-L1 expression specifically in injured kidneys with confirmed nephrotoxicity related to ICIs, its association with presence of PD-1, and clinical findings.

Methods

We included human kidney samples with AIN related to ICI therapy to describe PD-L1 and PD-1 expression localized to different renal compartments in association with clinical and laboratory parameters.

Results

We herein report compartmentalization of PD-L1 with tubular positivity in all cases, partially overlapping with glomerular and endothelial PD-L1 positivity. Furthermore, we provide evidence that tubular PD-L1 in ICI-related nephrotoxicity correlates with levels of C-reactive protein (CRP), while glomerular and endothelial PD-L1 positivity with lower serum levels of complement component C4. Interestingly, glomerular PD-L1 correlated with kidney function, while interstitial cell PD-1 positivity specifically with severity of kidney injury. Finally, we provide evidence for signaling pathways associated with intrarenal PD-L1/PD-1 expression.

Conclusion

Our findings implicate that that AIN related to ICI therapy requires presence of interstitial cells positive for PD-1, and that blocking PD-L1/PD-1 signaling may contribute to nephrotoxicity specifically related to these agents.

Determinants of Tunneled Hemodialysis Catheter Implantation Time by Ultrasound Guidance: A Single-Center Cross-Sectional Study

BACKGROUND

We have previously reported that the ultrasound (US)-guided tip positioning is an accurate and safe procedure for placement of retrograde- and antegrade-tunneled hemodialysis catheters (HDCs). However, determinants of tunneled hemodialysis catheter implantation time by using US guidance have not been described yet. Therefore, we here report a comparative analysis to identify determinants of implantation time for retrograde- and antegrade-tunneled HDCs placement by US guidance.

METHODS

We performed a cross-sectional study to compare implantation time for US-guided tip positioning of retrograde- and antegrade-tunneled HDCs. We included a total number of 47 tunneled HDC insertions, including 23 retrograde tunneled and 24 antegrade-tunneled HDCs in patients requiring placement of an HDC for the temporary or permanent treatment of end-stage kidney disease (ESKD) in a single-center, cross-sectional pilot study.

RESULTS

We show that clinical and laboratory parameters did not differ between retrograde- and antegrade-tunneled HDC implantations. There was a tendency for shorter implantation time in antegrade-tunneled HDCs, although not statistically significant. Finally, we identified an independent inverse association between body weight (BW) and platelet counts with HDC implantation time specifically in antegrade-tunneled HDCs.

CONCLUSION

In this study, we identified determinants for tunneled HDC implantation time that might be relevant for patients and interventionists.

Kinetics of human leukocyte antigen receptor HLA-DR+ monocytes and T lymphocytes during remission induction therapy in ANCA-associated vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is characterized by small vessel inflammation and the presence of autoantibodies against cytoplasmic proteases, most often proteinase-3 and myeloperoxidase. Peripheral blood monocytes are an important source of local macrophage accumulation within parenchymal organs, as evidenced by their presence in early lesions in ANCA-associated glomerulonephritis. Major histocompatibility complex (MHC) II cell surface receptor human leukocyte antigen receptor (HLA-DR) allows antigen presentation to T cells and is crucial for the initiation of an immune response. We herein report HLA-DR abundance in AAV and the kinetics of HLA-DR⁺ monocytes and T lymphocytes during remission induction therapy in AAV. Life-threatening AAV with pulmonary hemorrhage and renal involvement was associated with the presence of HLA-DR in a considerable population of peripheral blood monocytes and T lymphocytes, and relapsing disease manifested despite persistent B cell depletion after remission induction with rituximab. Moreover, remission induction in AAV with steroids, plasma exchange and intravenous cyclophosphamide, and improvement of clinical symptoms were associated with a decrease in HLA-DR⁺ differing between monocytes and T lymphocytes. Particularly, persistent suppression of HLA-DR⁺ monocytes was observed during remission induction, while an initial decrease in HLA-DR⁺ T lymphocytes was followed by recovery of this population during the further course. Detailed insights into HLA-DR kinetics could pave the way towards an increased understanding of immunopathology and identify patients that could mostly benefit from distinct remission induction regimens.

Case Report: Cytomegalovirus Reactivation and Pericarditis Following ChAdOx1 nCoV-19 Vaccination Against SARS-CoV-2

As the coronavirus disease 2019 (COVID-19) pandemic is ongoing and new variants of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) are emerging, there is an urgent need for vaccines to protect individuals at high risk for complications and to potentially control disease outbreaks by herd immunity. Surveillance of rare safety issues related to these vaccines is progressing, since more granular data emerge about adverse events of SARS-CoV-2 vaccines during post-marketing surveillance. Varicella zoster virus (VZV), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) reactivation has already been reported in COVID-19 patients. In addition, adverse events after SARS-CoV-2 mRNA vaccination have also been in the context of varicella zoster virus (VZV) reactivation and directly associated with the mRNA vaccine. We present the first case of CMV reactivation and pericarditis in temporal association with SARS-CoV-2 vaccination, particularly adenovirus-based DNA vector vaccine ChAdOx1 nCoV-19 against SARS-CoV-2. After initiation of antiviral therapy with oral valganciclovir, CMV viremia disappeared and clinical symptoms rapidly improved. Since huge vaccination programs are ongoing worldwide, post-marketing surveillance systems must be in place to assess vaccine safety that is important for the detection of any events. In the context of the hundreds of millions of individuals to be vaccinated against SARS-CoV-2, a potential causal association with CMV reactivation may result in a considerable number of cases with potentially severe complications.

Kinetics of Bilirubin and Ammonia Elimination during Hemadsorption Therapy in Secondary Sclerosing Cholangitis Following ECMO Therapy and Severe COVID-19

In critically ill patients, liver dysfunction often results in coagulopathy and encephalopathy and is associated with high mortality. Extracorporeal clearance of hepatotoxic metabolites, including bilirubin and ammonia, aims to attenuate further hepatocyte damage and liver injury, resulting in decreased mortality. The efficacy of hemadsorption combined with conventional hemodialysis to eliminate bilirubin and ammonia to support the liver's excretory function in acute liver injury has been described previously. However, the optimal use of liver support systems in chronic liver dysfunction due to secondary sclerosing cholangitis in critically ill patients (SSC-CIP) has not been defined yet. We herein describe the kinetics of successful bilirubin and ammonia elimination by hemadsorption in a patient with SSC-CIP after extracorporeal membrane oxygenation (ECMO) therapy for severe acute respiratory distress syndrome (ARDS) in a patient with coronavirus disease 2019 (COVID-19). During the course of the disease, the patient developed laboratory signs of liver injury during ECMO therapy before clinically detectable jaundice or elevated bilirubin levels. A diagnosis of SSC-CIP was confirmed by endoscopic retrograde cholangiopancreatography (ERCP) based on intraductal filling defects in the intrahepatic bile ducts due to biliary casts. The patient showed stable elevations of bilirubin and ammonia levels thereafter, but presented with progressive nausea, vomiting, weakness, and exhaustion. Based on these laboratory findings, hemadsorption was combined with hemodialysis treatment and successfully eliminated bilirubin and ammonia. Moreover, direct comparison revealed that ammonia is more efficiently eliminated by hemadsorption than bilirubin levels. Clinical symptoms of nausea, vomiting, weakness, and exhaustion improved. In summary, bilirubin and ammonia were successfully eliminated by hemadsorption combined with hemodialysis treatment in SSC-CIP following ECMO therapy and severe COVID-19. This observation is particularly relevant since it has been reported that a considerable subset of critically ill patients with COVID-19 suffer from liver dysfunction associated with high mortality.

Comparative Histological Subtyping of Immune Cell Infiltrates in MPO-ANCA and PR3-ANCA Glomerulonephritis

Background

Acute kidney injury (AKI) is a common and severe complication of anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV), potentially leading to chronic kidney disease (CKD), end-stage renal disease (ESRD), or death. Pathogenic ANCAs, in particular proteinase 3 (PR3) and myeloperoxidase (MPO), trigger a deleterious immune response with intrarenal immune cell infiltration resulting in a pauci-immune necrotizing and crescentic glomerulonephritis (GN). However, a systematic analysis of intrarenal immune cell subtypes concerning neutrophils, eosinophils, plasma cells, and mononuclear cell infiltrates (macrophages, lymphocytes) in ANCA GN remains elusive. Therefore, we aimed to compare distinct immune cell infiltrates in association with clinicopathological findings in ANCA GN.

Methods

A total of 53 kidney biopsies with ANCA GN at the University Medical Center Göttingen were retrospectively analyzed. Histological infiltrates of neutrophils, eosinophils, plasma cells, and mononucleated cells (macrophages, lymphocytes) were quantified as a fraction of the total area of inflammation.

Results

Neutrophilic infiltrates were associated with glomerular necrosis and severe kidney injury in ANCA GN. Among tubulointerstitial lesions, intrarenal neutrophils correlated with interstitial inflammation, tubulitis, and inflammation in areas of interstitial fibrosis/tubular atrophy (IFTA), representing active inflammatory lesions. Concerning eosinophils, infiltrates were associated with severe kidney injury, interstitial inflammation, and cellular casts independent of glomerular lesions, implicating a distinct role in inflammation and damage in ANCA GN. Plasma cell infiltrates correlated with tubulitis and interstitial fibrosis and were associated with renal replacement therapy during the short-term disease course. Finally, mononuclear cell infiltrates correlated with severe kidney injury and active histopathological lesions (glomerular crescents, interstitial inflammation, tubulitis, inflammation, and tubulitis in areas of IFTA) besides chronic lesions (interstitial fibrosis and tubular atrophy) in ANCA GN. Interestingly, intrarenal subtypes of immune cell infiltrates differed in MPO-ANCA versus PR3-ANCA GN and were associated with distinct glomerular and tubulointerstitial lesions, implicating different pathogenic mechanisms of kidney injury in ANCA subtypes.

Conclusion

Our observations imply distinct pathomechanisms contributing to inflammation and renal injury in MPO vs. PR3-associated ANCA GN and potentially contribute to new therapeutic targets in specific ANCA subtypes.

Comprehensive Analysis of Sex Differences at Disease Manifestation in ANCA-Associated Glomerulonephritis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a small vessel vasculitis affecting multiple organ systems, including the kidney. Besides investigations focusing on renal outcomes, sex differences associated with distinct clinical and histopathological findings in ANCA glomerulonephritis (GN) have not been systematically investigated. Therefore, we here aimed to systematically analyze sex differences in patients with AAV and biopsy-proven ANCA GN. We provide a comprehensive analysis of 53 kidney biopsies with ANCA GN retrospectively included between 2015 and 2020 and identified specific sex differences in ANCA GN concerning laboratory parameters and systematic scoring of renal histopathology glomerular and tubulointerstitial lesions, and extrarenal manifestations of AAV. We did not observe any correlation between sex and short-term clinical AAV course or disease severity by comparing general AAV parameters. AAV manifestations in females occurred at an older age with more joint involvement. Regarding histopathological findings, we, again, observed no sex difference among ANCA GN classification, but a significant correlation between females and distinct histopathological findings with less tubulointerstitial inflammation and vasculitis of peritubular capillaries. Finally, we here identified fewer associations between clusters of clinical, laboratory parameters, and histopathological findings in females as compared to males. These findings are of great relevance and further improve our understanding of sex differences in the pathogenesis of ANCA GN. While future studies about specific sex differences and conclusions in these clusters are crucial, our observations further support that sex differences are relevant, affect distinct parameters, and influence clinical, laboratory parameters, and histopathological findings in AAV, particularly ANCA GN.

Different Patterns of Kidney Fibrosis Are Indicative of Injury to Distinct Renal Compartments

Kidney fibrosis is a common manifestation and hallmark of a wide variety of chronic kidney disease (CKD) that appears in different morphological patterns, suggesting distinct pathogenic causes. Broad macroscopically visible scars are the sequelae of severe focal injury and complete parenchymal destruction, reflecting a wound healing response as a consequence of infarction. In the kidney, chronic glomerular injury leads to atrophy of the corresponding tubule, degeneration of this specific nephron, and finally interstitial fibrosis/tubular atrophy (IF/TA). Compared to this glomerulus-induced focal replacement scar, diffuse fibrosis independent of tubular atrophy appears to be a different pathogenic process. Kidney fibrosis appears to develop in a compartment-specific manner, but whether focal and diffuse fibrosis has distinct characteristics associated with other glomerular or tubulointerstitial lesions remains elusive. In the present study, we aimed to analyze renal fibrotic patterns related to renal lesions, which directly contribute to renal fibrogenesis, to unravel fibrotic patterns and manifestations upon damage to distinct renal compartments. Patterns of kidney fibrosis were analyzed in experimental models of CKD and various renal pathologies in correlation with histopathological and ultrastructural findings. After the induction of isolated crescentic glomerulonephritis (GN) in nephrotoxic serum-nephritis (NTN), chronic glomerular damage resulted in predominantly focal fibrosis adjacent to atrophic tubules. By contrast, using unilateral ureteral obstruction (UUO) as a model of primary injury to the tubulointerstitial compartment revealed diffuse fibrosis as the predominant pattern of chronic lesions. Finally, folic acid-induced nephropathy (FAN) as a model of primary tubular injury with consecutive tubular atrophy independent of chronic glomerular damage equally induced predominant focal IF/TA. By analyzing several renal pathologies, our data also suggest that focal and diffuse fibrosis appear to contribute as chronic lesions in the majority of human renal disease, mainly being present in antineutrophil cytoplasmic antibody (ANCA)-associated GN, lupus nephritis, and IgA nephropathy (IgAN). Focal IF/TA correlated with glomerular damage and irreversible injury to nephrons, whereas diffuse fibrosis in ANCA GN was associated explicitly with interstitial inflammation independent of glomerular damage and nephron loss. Ultrastructural analysis of focal IF/TA versus diffuse fibrosis revealed distinct matrix compositions, further supported by different collagen signatures in transcriptome datasets. With regard to long-term renal outcome, only the extent of focal IF/TA correlated with the development of end-stage kidney disease (ESKD) in ANCA GN. In contrast, diffuse kidney fibrosis did not associate with the long-term renal outcome. In conclusion, we here provide evidence that a focal pattern of kidney fibrosis seems to be associated with nephron loss and replacement scarring. In contrast, a diffuse pattern of kidney fibrosis appears to result from primary interstitial inflammation and injury.

Impact of the COVID-19 Pandemic on Kidney Diseases Requiring Renal Biopsy: A Single Center Observational Study

Background

The coronavirus disease-2019 (COVID-19) pandemic impacted healthcare services for kidney disease patients. Lockdown and social distancing were mandated worldwide, resulting in closure of medical services. The diagnosis of various kidney diseases may have been delayed during the COVID-19 pandemic because non-urgent tests and visits were postponed due to closure of medical services during the lockdown.

Methods

We here report the impact of the COVID-19 pandemic on a total number of 209 native kidney diseases requiring renal biopsy for diagnosis in a retrospective observational study from a tertiary hospital in Germany.

Results

The lockdown period in March and April 2020 primarily affected patients admitted to the normal medical ward with a compensatory increased rate of renal biopsies in the postlockdown phase. In addition, there was a shift toward more patients admitted with hemoglobinuria during the COVID-19 pandemic. This phenomenon of an increased number of patients with hemoglobinuria during the COVID-19 pandemic was specifically observed in a subgroup with hypertensive nephropathy requiring renal biopsy and associated with increased proteinuria, not attributed to the COVID-19 lockdown period itself.

Conclusion

To our knowledge, this is the first report of identifying a subpopulation susceptible to closure of medical services during the COVID-19 pandemic and diagnostic delay of specific kidney diseases. Therefore, the COVID-19 pandemic should be regarded as a risk factor especially in patients with diseases other than COVID-19 primarily admitted to the normal medical ward.

Consideration of Therapeutic Plasma Exchange in Association With Inflammatory Lesions in ANCA-Associated Glomerulonephritis: A Real-World Retrospective Study From a Single Center

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic vasculitis, most frequently presenting as microscopic polyangiitis (MPA) or granulomatosis with polyangiitis (GPA). Pathogenic ANCAs trigger a deleterious immune response resulting in pauci-immune necrotizing and crescentic glomerulonephritis (GN). Standard therapeutical regimens include aggressive immunosuppressive therapy. Since some patients require renal replacement therapy (RRT) despite intensive immunosuppressive therapy, additional therapeutic plasma exchange (PEX) to deplete pathogenic ANCAs has been recommended but its value has recently been questioned. Because therapeutic decision making is crucial in these critically ill patients, we here aimed to identify inflammatory lesions in association with PEX consideration in a retrospective study from a single center tertiary hospital in a real-world population of 46 patients with severe AAV requiring intensive care treatment. The decision to consider PEX was more likely in patients with need for intensive care treatment and severe renal dysfunction. In contrast, short-term outcomes did not depend on clinical, or laboratory characteristics assessed at admission. Histopathological analysis confirmed active disease reflected by increased glomerular necrosis and crescents, but these histopathological findings did not associate with short-term outcome either. Interestingly, only increased global glomerular sclerosis in renal biopsies associated with a detrimental short-term outcome. In conclusion, our study investigated determinants for the consideration of therapeutic PEX in patients with severe AAV requiring intensive care treatment. This aspect underscores the need for renal biopsy and requires further investigation in a prospective controlled setting for therapeutic decision making especially in patients with severe AAV requiring intensive care treatment, especially important for treating intensivists.

Urinary Levels of SARS-CoV-2 Nucleocapsid Protein Associate With Risk of AKI and COVID-19 Severity: A Single-Center Observational Study

Background: Acute kidney injury (AKI) is very common in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) disease 2019 (COVID-19) and considered as a risk factor for COVID-19 severity. SARS-CoV-2 renal tropism has been observed in COVID-19 patients, suggesting that direct viral injury of the kidneys may contribute to AKI. We examined 20 adult cases with confirmed SARS-CoV-2 infection requiring ICU supportive care in a single-center prospective observational study and investigated whether urinary markers for viral infection (SARS-CoV-2 N) and shedded cellular membrane proteins (ACE2, TMPRSS2) allow identification of patients at risk for AKI and outcome of COVID-19.

Objectives: The objective of the study was to evaluate whether urinary markers for viral infection (SARS-CoV-2 N) and shedded cellular membrane proteins (ACE2, TMPRSS2) allow identification of patients at risk for AKI and outcome of COVID-19.

Results: Urinary SARS-CoV-2 N measured at ICU admission identified patients at risk for AKI in COVID-19 (HR 5.9, 95% CI 1.4–26, p = 0.0095). In addition, the combination of urinary SARS-CoV-2 N and plasma albumin measurements further improved the association with AKI (HR 11.4, 95% CI 2.7–48, p = 0.0016). Finally, combining urinary SARS-CoV-2 N and plasma albumin measurements associated with the length of ICU supportive care (HR 3.3, 95% CI 1.1–9.9, p = 0.0273) and premature death (HR 7.6, 95% CI 1.3–44, p = 0.0240). In contrast, urinary ACE2 and TMPRSS2 did not correlate with AKI in COVID-19.

Conclusions: In conclusion, urinary SARS-CoV-2 N levels associate with risk for AKI and correlate with COVID-19 severity.

Proteinuria Indicates Decreased Normal Glomeruli in ANCA-Associated Glomerulonephritis Independent of Systemic Disease Activity

Background: Renal involvement is a common and severe complication of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), potentially resulting in a pauci-immune necrotizing and crescentic ANCA glomerulonephritis (GN) with acute kidney injury (AKI), end-stage renal disease (ESRD) or death. There is recent evidence that the degree of proteinuria at diagnosis is associated with long-term renal outcome in ANCA GN. Therefore, we here aimed to systematically describe the association between proteinuria and clinicopathological characteristics in 53 renal biopsies with ANCA GN and corresponding urinary samples at admission. Methods: A total number of 53 urinary samples at admission and corresponding renal biopsies with confirmed renal involvement of AAV were retrospectively included from 2015 to 2021 in a single-center study. Results: Proteinuria correlated with myeloperoxidase (MPO) subtype, diagnosis of microscopic polyangiitis (MPA) and severe deterioration of kidney function. Proteinuria was most prominent in sclerotic class ANCA GN and ANCA renal risk score (ARRS) high risk attributed to nonselective proteinuria, including both glomerular and tubular proteinuria. Finally, there was no association between proteinuria and systemic disease activity, suggesting that proteinuria reflected specific renal involvement in AAV rather that systemic disease activity. Conclusions: In conclusion, proteinuria correlated with distinct clinicopathological characteristics in ANCA GN, mostly attributed to a reduced fraction of normal glomeruli. Furthermore, proteinuria in ANCA GN reflected specific renal involvement in AAV rather than systemic disease activity. Therefore, urinary findings could further improve our understanding of mechanisms promoting kidney injury and progression of ANCA GN.

Bowman's capsule rupture links glomerular damage to tubulointerstitial inflammation in ANCA-associated glomerulonephritis

OBJECTIVES

We have recently described the frequency of Bowman's capsule (BC) rupture in a considerable subset of patients with antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (GN). Interestingly, recent reports established a better performance of glomerulocentric ANCA scoring systems after adding BC rupture to these classification systems, suggesting that characteristics of this lesion are independent from glomerular lesions. Since BC rupture may link glomerular damage to tubulointerstitial lesions via direct interaction with the surrounding interstitium, we here aimed to expand our current knowledge of this distinct lesion by a systematic description of tubulointerstitial lesions analogous to the Banff classification in association with the presence of BC rupture in ANCA GN.

METHODS

A total number of 44 kidney biopsies with confirmed renal involvement of ANCA GN were retrospectively included between 2015 till 2020 in a single-centre observational study.

RESULTS

We here show that presence of BC rupture was associated with severe deterioration of kidney function at disease onset, similar to previous findings regarding long-term renal survival. Furthermore, BC rupture in ANCA GN was associated with tubulointerstitial inflammation and ultrastructural analysis revealed direct cellular exchange between Bowman's space and the interstitium, potentially contributing to the observed deterioration of kidney function and worse renal outcome in ANCA GN.

CONCLUSIONS

BC rupture is associated with renal outcome in ANCA GN, therefore underscoring the need for further studies with regard to the glomerular-tubulointerstitial interaction in this disease.

Variable Expression of Programmed Cell Death Protein 1-Ligand 1 in Kidneys Independent of Immune Checkpoint Inhibition

Context

Due to recent advantages in cancer therapy, immune checkpoint inhibitors (ICIs) are new classes of drugs targeting programmed cell death protein 1 (PD-1) or its ligand programmed cell death protein 1-ligand 1 (PD-L1) used in many cancer therapies. Acute interstitial nephritis (AIN) is a potential and deleterious immune-related adverse events (irAE) in the kidney observed in patients receiving ICIs and the most common biopsy-proven diagnosis in patients who develop acute kidney injury (AKI). Based on previous reports, AIN in patients receiving ICIs is associated with tubular positivity for PD-L1, implicating that PD-L1 positivity reflects susceptibility to develop renal complications with these agents. It remains unclear if PD-L1 positivity is acquired specifically during ICI therapy or expressed independently in the kidney.

Methods

PD-L1 was analyzed in experimental mouse models of ischemia-reperfusion injury (IRI), folic acid-induced nephropathy (FAN), unilateral ureteral obstruction (UUO), and nephrotoxic serum nephritis (NTN) by immunostaining, SDS-PAGE, and subsequent immunoblotting. In addition, we included a total number of 87 human kidney samples (six renal biopsies with AIN related to ICI therapy, 13 nephrectomy control kidneys, and 68 ICI-naïve renal biopsies with various underlying kidney diseases to describe PD-L1 expression.

Results

We here report distinct PD-L1 expression in renal compartments in multiple murine models of kidney injury and human cases with various underlying kidney diseases, including ICI-related AIN and renal pathologies independent of ICI therapy. PD-L1 is frequently expressed in various renal pathologies independent of ICI therapy and could potentially be a pre-requisit for susceptibility to develop AKI and deleterious immune-related AIN. In addition, we provide evidence that tubular PD-L1 positivity in the kidney is associated with detection of urinary PD-L1⁺ tubular epithelial cells.

Conclusion

Our study implicates that PD-L1 is frequently expressed in various renal pathologies independent of ICI therapy and could potentially be a pre-requisit for susceptibility to develop AKI and deleterious immune-related AIN. Because non-invasive detection of PD-L1⁺ cells in corresponding urine samples correlates with intrarenal PD-L1 positivity, it is attractive to speculate that further non-invasive detection of PD-L1⁺ cells may identify patients at risk for ICI-related AIN.

Pharmacological induction of hypoxia-inducible transcription factor ARNT attenuates chronic kidney failure

Progression of chronic kidney disease associated with progressive fibrosis and impaired tubular epithelial regeneration is still an unmet biomedical challenge because, once chronic lesions have manifested, no effective therapies are available as of yet for clinical use. Prompted by various studies across multiple organs demonstrating that preconditioning regimens to induce endogenous regenerative mechanisms protect various organs from later incurring acute injuries, we here aimed to gain insights into the molecular mechanisms underlying successful protection and to explore whether such pathways could be utilized to inhibit progression of chronic organ injury. We identified a protective mechanism controlled by the transcription factor ARNT that effectively inhibits progression of chronic kidney injury by transcriptional induction of ALK3, the principal mediator of antifibrotic and proregenerative bone morphogenetic protein-signaling (BMP-signaling) responses. We further report that ARNT expression itself is controlled by the FKBP12/YY1 transcriptional repressor complex and that disruption of such FKBP12/YY1 complexes by picomolar FK506 at subimmunosuppressive doses increases ARNT expression, subsequently leading to homodimeric ARNT-induced ALK3 transcription. Direct targeting of FKBP12/YY1 with in vivo morpholino approaches or small molecule inhibitors, including GPI-1046, was equally effective for inducing ARNT expression, with subsequent activation of ALK3-dependent canonical BMP-signaling responses and attenuated chronic organ failure in models of chronic kidney disease, and also cardiac and liver injuries. In summary, we report an organ-protective mechanism that can be pharmacologically modulated by immunophilin ligands FK506 and GPI-1046 or therapeutically targeted by in vivo morpholino approaches.

Low-dose hydralazine prevents fibrosis in a murine model of acute kidney injury-to-chronic kidney disease progression

Acute kidney injury (AKI) and progressive chronic kidney disease (CKD) are intrinsically tied syndromes. In this regard, the acutely injured kidney often does not achieve its full regenerative capacity and AKI directly transitions into progressive CKD associated with tubulointerstitial fibrosis. Underlying mechanisms of such AKI-to-CKD progression are still incompletely understood and specific therapeutic interventions are still elusive. Because epigenetic modifications play a role in maintaining tissue fibrosis, we used a murine model of ischemia-reperfusion injury to determine whether aberrant promoter methylation of RASAL1 contributes causally to the switch between physiological regeneration and tubulointerstitial fibrogenesis, a hallmark of AKI-to-CKD progression. It is known that the antihypertensive drug hydralazine has demethylating activity, and that its optimum demethylating activity occurs at concentrations below blood pressure-lowering doses. Administration of low-dose hydralazine effectively induced expression of hydroxylase TET3, which catalyzed RASAL1 hydroxymethylation and subsequent RASAL1 promoter demethylation. Hydralazine-induced CpG promoter demethylation subsequently attenuated renal fibrosis and preserved excretory renal function independent of its blood pressure-lowering effects. In comparison, RASAL1 demethylation and inhibition of tubulointerstitial fibrosis was not detected upon administration of the angiotensin-converting enzyme inhibitor Ramipril in this model. Thus, RASAL1 promoter methylation and subsequent transcriptional RASAL1 suppression plays a causal role in AKI-to-CKD progression.

Early Endothelial Progenitor Cells (eEPCs) in systemic sclerosis (SSc) - dynamics of cellular regeneration and mesenchymal transdifferentiation

BACKGROUND

Patients with systemic sclerosis (SSc) are endagered by tissue fibrosis and by microvasculopathy, with the latter caused by endothelial cell expansion/proliferation. SSc-associated fibrosis potentially results from mesenchymal transdifferentiation of endothelial cells. Early Endothelial Progenitor Cells (eEPCs) act proangiogenic under diverse conditions. Aim of the study was to analyze eEPC regeneration and mesenchymal transdifferentiation in patients with limited and diffuse SSs (lSSc and dSSc).

METHODS

Patients with both, lSSc and dSSc were included into the study. The following parameters were evaluated: eEPC numbers and regeneration, concentrations of vasomodulatory mediators, mesenchymal properties of blood-derived eEPC. Serum samples of healthy subjects and SS patients were used for stimulation of cultured human eEPC, subsequently followed by analysis of mesenchymal cell characteristics and mobility.

RESULTS

Twenty-nine patients were included into the study. Regenerative activity of blood-derived eEPCs did not differ between Controls and patients. Circulating eEPC were significantly lower in all patients with SSc, and in limited and diffuse SSc (lSSc/dSSc). Serum concentrations of promesenchymal TGF-b was elevated in all patients with SSc. Cultured mononuclear cells from SS patients displayed higher abundances of CD31 and of CD31 and aSMA combined. Finally, serum from SSc patients inhibited migration of cultured eEPCs and the cells showed lower sensitivity towards the endothelin antagonist Bosentan.

CONCLUSIONS

The eEPC system, which represents an essential element of the endogenous vascular repair machinery is affected in SSc. The increased appearance of mesenchymal properties in eEPC may indicate that alterations of the cells potentially contribute to the accumulation of connective tissue and to vascular malfunction.

A primer on the epigenetics of kidney fibrosis

Despite extensive knowledge of the various molecular pathways that contribute to tubulointerstitial fibrosis, it remains an unsolved question why the progression rate of chronic kidney disease varies substantially from patient to patient, even among patients with common underlying nephropathies and comorbidities. Possible explanations for different susceptibilities of individual patients to develop end-stage renal failure include genetic or epigenetic variations, which modify how individual patients respond to kidney injury. Here we review principles of epigenetic mechanisms in context of chronic kidney disease and discuss how such insights may be utilized for future therapeutic strategies and may lead to novel diagnostic tools in the future.

Sinus venosus atrial septal defects: surgical follow-up

OBJECTIVE

To assess early and later results after surgery for sinus venous atrial septal defects (ASDs).

METHODS

Forty-four patients of sinus venosus ASDs with anomalous drainage of the right superior pulmonary vein into the superior vena cava, were operated upon between January 1985 and June 1995. Defects were approached by an incision starting from the tip of the right atrial appendage then extending upward along the atrial crest to the medial wall of the superior vena cava. Atrial defects were closed by an autologous pericardial patch. Another pericardial patch was used to enlarge the superior vena cava-right atrial junction to avoid the narrowing of the superior vena cava.

RESULTS

There was no operative mortality. The total duration of follow-up was 4 +/- 0.7 years. Follow-up of the echocardiographic study at 6 months and 2 years after surgery revealed a normal study. Two patients developed sinus node dysfunction of short duration in the immediate postoperative period. Follow-up of the electrocardiographic study at 6 months and 2 years revealed sinus node dysfunction in one and two patients, respectively.