Renal Biopsy In Patients Research Articles

Glomerulonephritis during Mycobacterium tuberculosis infection: scoping review

IntroductionPeople with Tuberculosis (TB) infection may present with glomerulonephritis (GN). The range of presentations, renal pathologies, and clinical outcomes are uncertain. Whether clinical features that establish if GN etiology is medication or TB related, and possible benefits of immunosuppression remain uncertain.MethodsA scoping review was completed, searching MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Web of Science and Conference s from Inception to December, 2023. The study population included patients with TB infection who developed GN and underwent renal biopsy. All data regarding presentation, patient characteristics, renal pathology, management of TB and GN, and outcomes were summarized.ResultsThere were 62 studies identified, with 130 patients. These cases included a spectrum of presentations including acute kidney injury, nephrotic syndrome and hypertension, and a range of 10 different renal pathology diagnoses. Cases that included immunosuppression and outcomes ranged from complete remission to long-term dialysis dependence. The presence of granulomas (4/4, 100%), anti-glomerular basement membrane disease (3/3, 100%), amyloidosis (75/76, 98.7%), and focal segmental glomerulosclerosis (2/2, 100%) were specific for GN being TB-infection related. On the other hand, minimal change disease was specific for anti-TB therapy related (7/7, 100%). While patients with more aggressive forms of GN commonly were prescribed immunosuppression, this study was unable to confirm efficacy. Only rifampin or isoniazid were implicated in drug-associated GN.DiscussionThis study provides a clear rationale for renal biopsy in patients with TB and GN, and outlines predictors for the GN etiology. Thus, this study establishes key criteria to optimize diagnosis and management of patients with TB and GN.

Tonabersat suppresses priming/activation of the NOD-like receptor protein-3 (NLRP3) inflammasome and decreases renal tubular epithelial-to-macrophage crosstalk in a model of diabetic kidney disease

BackgroundAccompanied by activation of the NOD-like receptor protein 3 (NLRP3) inflammasome, aberrant connexin 43 (Cx43) hemichannel-mediated ATP release is situated upstream of inflammasome assembly and inflammation and contributes to multiple secondary complications of diabetes and associated cardiometabolic comorbidities. Evidence suggests there may be a link between Cx43 hemichannel activity and inflammation in the diabetic kidney. The consequences of blocking tubular Cx43 hemichannel-mediated ATP release in priming/activation of the NLRP3 inflammasome in a model of diabetic kidney disease (DKD) was investigated. We examined downstream markers of inflammation and the proinflammatory and chemoattractant role of the tubular secretome on macrophage recruitment and activation.MethodsAnalysis of human transcriptomic data from the Nephroseq repository correlated gene expression to renal function in DKD. Primary human renal proximal tubule epithelial cells (RPTECs) and monocyte-derived macrophages (MDMs) were cultured in high glucose and inflammatory cytokines as a model of DKD to assess Cx43 hemichannel activity, NLRP3 inflammasome activation and epithelial-to-macrophage paracrine-mediated crosstalk. Tonabersat assessed a role for Cx43 hemichannels.ResultsTranscriptomic analysis from renal biopsies of patients with DKD showed that increased Cx43 and NLRP3 expression correlated with declining glomerular filtration rate (GFR) and increased proteinuria. In vitro, Tonabersat blocked glucose/cytokine-dependant increases in Cx43 hemichannel-mediated ATP release and reduced expression of inflammatory markers and NLRP3 inflammasome activation in RPTECs. We observed a reciprocal relationship in which NLRP3 activity exacerbated increased Cx43 expression and hemichannel-mediated ATP release, events driven by nuclear factor kappa-B (NFκB)-mediated priming and Cx43 hemichannel opening, changes blocked by Tonabersat. Conditioned media (CM) from RPTECs treated with high glucose/cytokines increased expression of inflammatory markers in MDMs, an effect reduced when macrophages were pre-treated with Tonabersat. Co-culture using conditioned media from Tonabersat-treated RPTECs dampened macrophage inflammatory marker expression and reduced macrophage migration.ConclusionUsing a model of DKD, we report for the first time that high glucose and inflammatory cytokines trigger aberrant Cx43 hemichannel activity, events that instigate NLRP3-induced inflammation in RPTECs and epithelial-to-macrophage crosstalk. Recapitulating observations previously reported in diabetic retinopathy, these data suggest that Cx43 hemichannel blockers (i.e., Tonabersat) may dampen multi-system damage observed in secondary complications of diabetes.

#1076 DNA hypomethylation of Syk induces oxidative stress and apoptosis via the PKCβ/ P66shc signaling pathway in diabetic kidney disease

Abstract Background and Aims Epigenetic alterations, especially DNA methylation, have been shown to play a role in the pathogenesis of diabetes mellitus (DM) and its complications, including diabetic kidney disease (DKD). Spleen tyrosine kinase (Syk) is known to be involved in immune and inflammatory disorders. We, therefore, investigated the possible involvement of Syk promoter methylation in DKD, and the mechanisms underlying this process. Method Kidney tissues were obtained from renal biopsies of patients with early and advanced DKD. A diabetic mouse model (ApoE−/−DM) was generated from ApoE knockout (ApoE−/−) mice using a high fat and high glucose diet combined with low-dose streptozocin (STZ) intraperitoneal injection. We also established an in vitro model using HK2 cells. Results A marked elevation in the expression levels of Syk, PKCβ, and P66shc in renal tubules was observed in patients with DKD. In ApoE−/− DM mice, Syk expression and the binding of Sp1 to the Syk gene promoter were both increased in the kidney. In addition, the promoter region of the Syk gene exhibited hypomethylation. Syk inhibitor (R788) intervention improved renal function and alleviated pathologic changes in ApoE−/− DM mice. Moreover, R788 intervention alleviated oxidative stress and apoptosis and down-regulated the expression of PKCβ/ P66shc signaling pathway proteins. In HK2 cells, oxLDL combined with high glucose stimulation upregulated Sp1 expression in the nucleus (compared with control and oxLDL groups), and this was accompanied by an increase in the binding of Sp1 to the Syk gene promoter. SP1 silencing down-regulated the expression of Syk and inhibited the production of reactive oxygen species and cell apoptosis. Finally, PKC agonist intervention reversed the oxidative stress and apoptosis induced by Syk inhibitor (R406). Conclusion In DKD, hypomethylation at the Syk gene promoter was accompanied by an increase in Sp1 binding at the promoter. As a consequence of this enhanced Sp1 binding, Syk gene expression was upregulated. Syk inhibitors could attenuate DKD-associated oxidative stress and apoptosis via down-regulation of PKCβ/ P66shc signaling pathway proteins. Together, our results identify Syk as a promising target for intervention in DKD.

#1071 The effect and mechanism of SGLT2 inhibitor on improving inflammatory injury of glomerular endothelial cells in diabetes

Abstract Background and Aims ATP-binding cassette transporter A1 (ABCA1), which reduces intracellular cholesterol accumulation, is highly expressed in the kidney. Studies have shown that sodium-glucose co-transporter 2 inhibitors (SGLT2) inhibitors promote ABCA1 expression in multiple tissues and organs. However, the effect of SGLT2 inhibitors on ABCA1 expression in diabetic kidney disease (DKD) is unclear. In this study, the effect of empagliflozin, an SGLT2 inhibitor, on ABCA1 in glomerular endothelial cells(GECs) of DKD and the possible mechanisms linking ABCA1 to GECs inflammatory injury were investigated. Method Kidney tissues were obtained from renal biopsies of patients with early and advanced DKD. db/db mice were used as animal models of type 2 diabetes and the effects of SGLT2 inhibitors on ABCA1 were analyzed by treatment with empagliflozin. The effects of ABCA1 overexpression on glomerular lipid deposition and kidney injury were examined in a type 2 diabetic mouse model with ABCA1 overexpression (db/db + ABCA1 mice), and human renal glomerular endothelial cells (HRGECs) cultured in high glucose and high cholesterol conditions, which simulated type 2 diabetes in vitro. Results The expression of ABCA1 in the glomeruli of DKD patients and db/db mice was significantly decreased. Enhancing ABCA1 expression in the kidney tissue of diabetic mice by adenovirus transduction improved renal cholesterol deposition, inhibited the overactivation of C3a/C5a, and improved renal inflammatory injury. In addition, in cultured HRGECs under high glucose and high cholesterol conditions, ABCA1 deficiency increased the deposit of cellular cholesterol, contributed to overactivation of C3a/C5a, and induced inflammatory injury. Overexpression of ABCA1 enhancing cholesterol efflux or inhibition of C3a/C5a activation in vitro significantly protected against glomerular endothelial injury stimulated by high glucose and high cholesterol. Moreover, SGLT2 inhibitor empagliflozin up-regulated the expression of ABCA1 and down-regulated the levels of cholesterol, C3a/C5a and inflammatory cytokines in diabetic mice and HRGECs. Conclusion SGLT2 inhibitor (empagliflozin) might play a renal protective role by up-regulating ABCA1-mediated cholesterol outflow, inhibiting the activation of C3a/C5a, and then ameliorating the inflammatory injury of GECs.

DNA hypomethylation of Syk induces oxidative stress and apoptosis via the PKCβ/P66shc signaling pathway in diabetic kidney disease.

Epigenetic alterations, especially DNA methylation, have been shown to play a role in the pathogenesis of diabetes mellitus (DM) and its complications, including diabetic kidney disease (DKD). Spleen tyrosine kinase (Syk) is known to be involved in immune and inflammatory disorders. We, therefore, investigated the possible involvement of Syk promoter methylation in DKD, and the mechanisms underlying this process. Kidney tissues were obtained from renal biopsies of patients with early and advanced DKD. A diabetic mouse model (ApoE-/- DM) was generated from ApoE knockout (ApoE-/-) mice using a high-fat and high-glucose diet combined with low-dose streptozocin intraperitoneal injection. We also established an invitro model using HK2 cells. A marked elevation in the expression levels of Syk, PKCβ, and P66shc in renal tubules was observed in patients with DKD. In ApoE-/- DM mice, Syk expression and the binding of Sp1 to the Syk gene promoter were both increased in the kidney. In addition, the promoter region of the Syk gene exhibited hypomethylation. Syk inhibitor (R788) intervention improved renal function and alleviated pathologic changes in ApoE-/- DM mice. Moreover, R788 intervention alleviated oxidative stress and apoptosis and downregulated the expression of PKCβ/P66shc signaling pathway proteins. In HK2 cells, oxLDL combined with high-glucose stimulation upregulated Sp1 expression in the nucleus (compared with control and oxLDL groups), and this was accompanied by an increase in the binding of Sp1 to the Syk gene promoter. SP1 silencing downregulated the expression of Syk and inhibited the production of reactive oxygen species and cell apoptosis. Finally, PKC agonist intervention reversed the oxidative stress and apoptosis induced by Syk inhibitor (R406). In DKD, hypomethylation at the Syk gene promoter was accompanied by an increase in Sp1 binding at the promoter. As a consequence of this enhanced Sp1 binding, Syk gene expression was upregulated. Syk inhibitors could attenuate DKD-associated oxidative stress and apoptosis via downregulation of PKCβ/P66shc signaling pathway proteins. Together, our results identify Syk as a promising target for intervention in DKD.

Analysis of glomerular deposition of IgM and C3 in patients with podocytopathies

Minimal Change Disease (MCD) and Focal Segmental Glomerulosclerosis (FSGS) are the main causes of nephrotic syndrome in the world. The complement system appears to play an important role in the pathogenesis of these diseases. To evaluate the deposition of immunoglobulins and particles of the complement system in renal biopsies of patients with FSGS and MCD and relate to laboratory data, we selected 59 renal biopsies from patients with podocytopathies, 31 from patients with FSGS and 28 with MCD. Epidemiological, clinical, laboratory information and the prognosis of these patients were evaluated. Analysis of the deposition of IgM, IgG, C3, C1q and C4d in renal biopsies was performed. We related IgM and C3 deposition with laboratory parameters. Statistical analysis was performed using GraphPad Prism version 7.0. Glomerular deposition of IgM was significantly higher in the FSGS group, as was codeposition of IgM and C3. The clinical course of patients and laboratory data were also worse in cases of FSGS, with a higher percentage progressing to chronic kidney disease and death. Patients with C3 deposition had significantly higher mean serum creatinine and significantly lower eGFR, regardless of disease. Patients with FSGS had more IgM and C3 deposition in renal biopsies, worse laboratory data and prognosis than patients with MCD. C3 deposition, both in FSGS and MCD, appears to be related to worsening renal function.

Evaluation of C4d expression and staining patterns by immunohistochemistry in renal biopsy samples with focal segmental glomerulosclerosis and minimal change disease

IntroductionC4d is an activation product of lectin pathway of complement. Glomerular deposition of C4d is associated with poor prognosis in different types of immune-related glomerulonephritis. The present study was conducted to investigate expression level of C4d and its staining pattern in renal biopsy of patients with focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) by immunohistochemistry method. Materials and methodsIn this retrospective cross-sectional study, renal biopsy specimens from 46 samples of MCD, 47 samples of FSGS, and 15 samples without glomerular disease as the controls, were subjected to immunohistochemistry staining with C4d. Demographic characteristics and information obtained from light and electron microscopy (EM) of patients were also extracted from their files. ResultsC4d positive staining was observed in 97.9 % of FSGS and 43.5 % of MCD samples, which showed a statistically significant difference (P < 0.001). The sensitivity and specificity of C4d expression for diagnosing FSGS were 97.9 % and 56.5 %, respectively. There was no significant correlation between C4d expression and any of the light and electron microscopy findings, including presence of foam cells, mesangial matrix expansion, interstitial fibrosis and tubular atrophy, and basement membrane changes in MCD patients. Also, no significant correlation was observed between C4d expression and clinical symptoms of proteinuria or prolonged high level of creatinine in patients with MCD. Discussion and conclusionThe expression of C4d marker had a good sensitivity and negative predictive value in the diagnosis of FSGS.

Ultrastructural Examination of Glomerular Fibrillary Deposits in Diabetic Nephropathy

Glomerular fibrillary deposits have occasionally been reported in diabetic nephropathy, but no large-scale, ultrastructural evaluation of these deposits has been reported so far. Here, we report our study of glomerular non-Congophilic, DnaJ homolog subfamily B member 9 negative fibrillary deposits in diabetic nephropathy as characterized by transmission electron microscopy. Clinical data from 55 patients with biopsy-confirmed diabetic nephropathy and 18 healthy living donors were reviewed, and their biopsies were evaluated by light microscopy, immunofluorescence, and electron microscopy. Small fibrillary structures with a diameter of 10 ± 1 nm were present in all cases with diabetic nephropathy, regardless of the histologic class. In addition, glomerular fibrillary structures with a diameter of 23 ± 5 nm or 30 ± 7 nm were present in 35 cases. Interestingly, especially the small- and medium-sized fibrils, usually without apparent organization, were comparable with fibrils in fibrillary glomerulopathy. We conclude that glomerular fibrillary deposits occur far more commonly in renal biopsies of patients with diabetic nephropathy than generally considered. This is an important finding because their similarity to fibrils in fibrillary glomerulonephritis may complicate the histologic diagnostic process, especially in cases of overlapping clinical manifestations. Therefore, when encountering fibrillary deposits on electron microscopy, it is important to consider diabetic nephropathy as an alternative diagnosis.

Clinical and pathological characteristics of diquat poisoning-related acute kidney injury

Objectives Diquat has replaced paraquat in agricultural areas as a herbicide but has led to extensive poisoning. Unlike paraquat, which targets the lungs, diquat primarily targets the kidneys. Autopsies and animal experiments suggest that interstitial kidney damage is the most critical renal lesion. Diquat is a nonselective chemical widely used for terrestrial and aquatic plants after the ban on paraquat. Although diquat is known to affect the kidneys mainly, no study has reported renal biopsy in patients with diquat poisoning. Methods We investigated the histopathologic feature in a young man with diquat poisoning who developed acute kidney injury by renal biopsy. Results Autopsy and animal experiments suggest that interstitial kidney inflammation is the most critical renal lesion. Surprisingly, our results showed that lipid degeneration and acute tubular injury with limited interstitial inflammation were the dominant histologic findings in this patient. Conclusions Based on a renal biopsy, this was the first study describing the characteristics of the kidney affected by diquat poisoning. Our findings might provide information for managing patients who develop AKI due to diquat poisoning.

Chapter 3: Management of kidney injury caused by cancer drug therapy, from clinical practice guidelines for the management of kidney injury during anticancer drug therapy 2022.

Cisplatin should be administered with diuretics and Magnesium supplementation under adequate hydration to avoid renal impairment. Patients should be evaluated for eGFR (estimated glomerular filtration rate) during the treatment with pemetrexed, as kidney injury has been reported. Pemetrexed should be administered with caution in patients with a CCr (creatinine clearance) < 45mL/min. Mesna is used to prevent hemorrhagic cystitis in patients receiving ifosfamide. Febuxostat is effective in avoiding hyperuricemia induced by TLS (tumor lysis syndrome). Preventative rasburicase is recommended in high-risk cases of TLS. Thrombotic microangiopathy could be triggered by anticancer drugs and there is no evidence of efficacy of plasma exchange therapy. When proteinuria occurs during treatment with anti-angiogenic agents or multi-kinase inhibitors, dose reductions or interruptions based on grading should be considered. Grade 3 proteinuria and renal dysfunction require urgent intervention, including drug interruption or withdrawal, and referral to a nephrologist should be considered. The first-line drugs used for blood pressure elevation due to anti-angiogenic agents are ACE (angiotensin-converting enzyme) inhibitors and ARBs (angiotensin receptor blockers). The protein binding of drugs and their pharmacokinetics are considerably altered in patients with hypoalbuminemia. The clearance of rituximab is increased in patients with proteinuria, and the correlation with urinary IgG suggests similar pharmacokinetic changes when using other antibody drugs. AIN (acute interstitial nephritis) is the most common cause of ICI (immune checkpoint inhibitor)-related kidney injury that is often treated with steroids. The need for renal biopsy in patients with kidney injury that occurs during treatment with ICI remains controversial.

#6323 RENAL CONTRAST-ENHANCED ULTRASOUND AND GLOMERULONEPHRITIS: A GOOD MARKER OF DISEASE ACTIVITY

Abstract Background Contrast-enhanced ultrasound (CEUS) could provide a lot of information of renal blood flow. Renal blood flow is an excellent marker of inflammatory and fibrotic processes in the kidney such as glomerulonephritis. Therefore, in patients with these diseases, renal CEUS can be both a prognostic marker and an index of response to therapy. Currently in the literature there are preliminary studies showing the role of CEUS in terms of histology and outcome in the evaluation of patients with glomerulonephritis. In this pilot study we used perfusion CEUS parameters (WiR and WoR; WiAUC and WoAUC) as possible markers of renal microvascular damage. We compared the perfusion parameters with the clinical and histological findings of our patients. Method Eighteen patients with clinical and laboratory signs of glomerulonephritis were enrolled. All patients underwent ultrasound-assisted renal biopsy and B-mode ultrasound examination, color Doppler ultrasound and contrast-enhanced ultrasound. Time Intensity (TI) curves were obtained from renal CEUS. TI curves and several quantitative perfusion parameters were defined using VueBox® Quantitation Software. Results From April to October 2022, 18 patients (12 men and 6 women) with clinical and laboratory suspicion of glomerular disease were enrolled. Median age was 48.05 years, all patients underwent renal biopsy and contrast-enhanced ultrasound at basal condition. Table 1 shows patients characteristics. CKD patients were stratified into two groups according to their eGFR: group I (eGFR &amp;lt; 60 ml/min/1.73 m2, n. = 4) and group II (eGFR ≥ 60 ml/min/1.73 m2, n. = 3). Moreover, we divided patients into two groups based on the presence of nephrotic-range proteinuria (≥ 3.5 g/24h). At this time, seven patient data are suitable for analysis. The small sample size at present does not allow for statistical significance. However, in our study, the persistence of contrast agent signal during the wash-out phase was differed markedly in correlation with the degree of CKD. In particular, we observed a slower wash-in phase in the presence of vascular hyalinosis (Fig. 1). Conclusion Our experience seems to confirm that CEUS parameters can be excellent indicators both in terms of patient disease outcomes and histological data. CEUS can effectively and quantitatively demonstrate renal microvascular perfusion in patients with glomerulonephritis. Future goal is that CEUS could also be a prognostic and follow-up marker after renal biopsy in patients with glomerulonephritis.

#4466 EXPLAINABILITY OF A DEEP LEARNING BASED CLASSIFICATION MODEL FOR ANCA-ASSOCIATED GLOMERULONEPHRITIS

Abstract Background and Aims The histopathological classification for ANCA-associated glomerulonephritis (ANCA-GN) is a well-established tool to reflect the variety of patterns and severity of lesions that can occur in renal biopsies of patients with ANCA-associated vasculitis. As with many fields, medicine saw a rapid emergence of Artificial Intelligence (AI) and Deep learning (DL) approaches. In the field of digital pathology AI can now serve as decision-support for pathologists, with the potential for gains in productivity and time-saving. It was demonstrated previously that AI can aid in identifying histopathological classes of renal diseases, e.g. of diabetic nephropathy. Although these models reach high prediction accuracies, their black box structure makes them very non-transparent. The disadvantage is that the networks’ decisions are not easily interpretable by humans and it is not clear what information in the input data underlies their decisions. This necessitates the use of Explainable AI (XAI), so that decisions made by AI models become accessible for validation by a human expert. Method Renal biopsy slides of 80 patients with ANCA-GN from 3 European centers, who underwent a diagnostic renal biopsy between 1991 and 2011, were included. On the scanned slides glomeruli were labelled as ‘normal’, ‘sclerotic’, ‘crescentic’ or ‘abnormal - other’. We developed a DL-based computational pipeline, which detects and classifies the glomeruli. We investigated the explainability of our model, using XAI techniques to shed light on the decision-making criteria of our trained DL classifier using saliency maps. These maps were analyzed by pathologists to compare the decision-making criteria of humans and the DL model. Results Our DL model shows a prediction accuracy of 93% for classifying glomeruli. The saliency maps from our trained DL models help us to better understand the decision-making criteria of the DL black box. Conclusion AI and DL play an increasingly important role in (nephro)pathology. To ultimately enable safe implementation of these models in clinical practice, validation of their decisions is needed. To achieve this, we used XAI techniques, which showed great potential for illuminating the decision-making criteria of the DL black box.

#5924 LATE DIAGNOSIS OF IGA NEPHROPATHY IN LOWER SAXONY (GERMANY) – CLINICAL AND HISTOPATHOLOGICAL DATA FROM 246 PATIENTS AT TIME OF INITIAL RENAL BIOPSY

Abstract Background and Aims IgA Nephropathy (IgAN) is the most frequent glomerulonephritis and contributes significantly to the burden of dialysis dependence. If not detected in the context of screening health examinations e.g. for the military service, decline in renal function is usually unnoticed due to the lack of specific symptoms. After decades of limited pharmacological options, the advent of new therapies provides opportunities for early intervention. Age and renal function as well as proteinuria at the time of renal biopsy varies depending on healthcare systems but might influence the use of novel interventions. Publications from outside Germany report that eGFR at the time of first renal biopsy in IgAN varies between 73.8 and 94.9ml/min/1,73 m2. The age at the time of diagnosis is between 27 and 40 years. The aim of our study was to investigate renal function, degree of proteinuria as well as histological parameters at the time of first renal biopsy in patients with IgA nephropathy. Method This retrospective study evaluated data from two different tertiary care hospitals in Germany that that sent their renal biopsies to the Nephropathology Department at the Hannover Medical School from January 2012 – October 2022. Only initial biopsies from native kidneys were included. Histopathological parameters and clinical as well as laboratory parameters at the month of biopsy were obtained. eGFR was calculated according to the CKD-EPI formula. Results First time diagnosis of IgA nephropathy was made in 246 patients at a median age at of 45 (range 4–79) years, 76.8% were male. The median serum creatinine level was 1.44mg/dl, corresponding to a median eGFR of 43.0 (3.8–132) ml/min/1.73 m2. Surprisingly 49.5% of all patients were at CKD KDIGO GFR stage 3B or higher at the time of first biopsy (Figure 1). Median proteinuria was 1.84 (0.08 – 16.5) g/d in those patients where 24h urine collection was performed. 156 of 246 patients had microhematuria at the time of biopsy. Based on the Oxford classification &amp;gt;50% had hypercellularity. Endocapillary hypercellularity was present in 24%. Segmental glomerulosclerosis was almost evenly distributed (S0:116 | S1:112). Tubular atrophy and interstitial fibrosis were visible in most biopsies in 0-25% of cortical area (T0:153 | T1:59 | T2:16). In 27.2% the C-score was analyzed, showing cellular and/or fibrocellular crescent in 26.8% of those patients. Thrombosis and necrosis were rather uncommon in initial biopsies of IgA Nephropathy. Conclusion The study shows that an IgA Nephropathy shows severe renal impairment at the time of diagnosis i.e. first renal biopsy, suggesting that patients are referred rather late for this diagnostic procedure. These regional data have to be validated in larger cohorts. If confirmed, measures for earlier screening and referral should be implemented to allow timely intervention thus lowering need for renal replacement therapy.

#4041 THE INTERSTITIAL TUBULAR INJURY IN THE COURSE OF LUPUS NEPHRITIS

Abstract Background and Aims Tubulo-interstitial involvement in lupus nephritis (LN) refers to the presence of interstitial fibrosis and tubular atrophy (IFTA) in the renal biopsies of patients with lupus. The impact of these features on patient outcomes has not been fully established. The aim of this study was to determine the correlation between IFTA and patient outcomes in LN. Method A retrospective descriptive study was conducted on 160 patients with systemic lupus erythematosus who underwent renal biopsy between 2020 and 2022. Clinical and biological data, as well as histologic findings, were analyzed to determine the outcomes associated with IFTA in LN. Other causes of tubulointerstitial nephritis like drugs and toxins were excluded. Results The study population consisted of 148 females and 12 males, with a mean age of 37.2 years (ranging from 18 to 62 years) at the time of renal biopsy. Hematuria was observed in 62.5% of patients, nephrotic syndrome in 28.1%, hypertension in 24.3%, and renal failure in 17.5% with a mean proteinuria of 2.4±0.6 g/24 h. ANA was positive in a diffuse pattern in all cases, positive anti-ds-DNA,mean C3 was 29 (84-122 mg/dL), and mean C4 was 16.2 (20-40 mg/dl). Other serology C-ANCA and P-ANCA were all negative as well as negative HBV and HCV serology. However serology for Sjogren's syndrome was positive in 61 cases (41%). The histopathological study showed mild mononuclear and plasma cell infiltration of the interstitium, and tubular hyaline casts in 87% of cases. Examination of renal vessels was unremarkable in 94.5% of cases. IFTA was present in 72 patients (45%), with the most frequent glomerular involvement being LN class IV (55.5%) followed by LN class III (32.4%) with respectively (P = .09, P = .2)and was associated significantly with the anti-DNA antibody titer (P = .003). The severity of these lesions was found to be independently correlated with worsening of renal failure at 6 months follow-up (P = .02). Conclusion The findings of this study suggest that IFTA is a significant prognostic factor for the progression of renal failure in lupus nephritis, regardless of the class of the disease. The pathogenesis of tubulointerstitial lesions seems to be the result of circulating immune complexes specifically interacting with tubulointerstitial autoantigens.

Inhibition of Fatty Acid β-Oxidation by Fatty Acid Binding Protein 4 Induces Ferroptosis in HK2 Cells Under High Glucose Conditions.

Ferroptosis, which is caused by an iron-dependent accumulation of lipid hydroperoxides, is a type of cell death linked to diabetic kidney disease (DKD). Previous research has shown that fatty acid binding protein 4 (FABP4) is involved in the regulation of ferroptosis in diabetic retinopathy. The present study was constructed to explore the role of FABP4 in the regulation of ferroptosis in DKD. We first detected the expression of FABP4 and proteins related to ferroptosis in renal biopsies of patients with DKD. Then, we used a FABP4 inhibitor and small interfering RNA to investigate the role of FABP4 in ferroptosis induced by high glucose in human renal proximal tubular epithelial (HG-HK2) cells. In kidney biopsies of DKD patients, the expression of FABP4 was elevated, whereas carnitine palmitoyltransferase-1A (CP-T1A), glutathione peroxidase 4, ferritin heavy chain, and ferritin light chain showed reduced expression. In HG-HK2 cells, the induction of ferroptosis was accompanied by an increase in FABP4. Inhibition of FABP4 in HG-HK2 cells changed the redox state, sup-pressing the production of reactive oxygen species, ferrous iron (Fe2+), and malondialdehyde, increasing superoxide dismutase, and reversing ferroptosis-associated mitochondrial damage. The inhibition of FABP4 also increased the expression of CPT1A, reversed lipid deposition, and restored impaired fatty acid β-oxidation. In addition, the inhibition of CPT1A could induce ferroptosis in HK2 cells. Our results suggest that FABP4 mediates ferroptosis in HG-HK2 cells by inhibiting fatty acid β-oxidation.

Blind Spot in the Radar of MEST-C Score: Type and Severity of Tubulointerstitial Nephritis in IgA Nephropathy.

The updated version of predictive classification for immunoglobulin A nephropathy (IgAN) prognosis "The Oxford Classification" identifies five histopathological features including mesangial hypercellularity (M), endocapillary proliferation (E), segmental glomerulosclerosis (S), tubular atrophy/interstitial fibrosis (T) and crescents (C), the MEST-C. However, few studies suggest that tubulointerstitial inflammation, which is not included in the MEST-C, is also linked to disease progression and is, consequently, a neglected determinant of prognosis among others. Therefore, there is a need to evaluate this histopathological parameter in patients with IgA nephropathy. This cross-sectional descriptive study was conducted at Shaukat Khanum Memorial Cancer Hospital and Research Center, Lahore, Pakistan. Data of histopathological and immunofluorescence proven renal biopsies (300) of IgA nephropathy patients from January 2016 through May 2022 were extracted using a convenient sampling technique. Biopsies were histologically reviewed for type and severity of tubulointerstitial inflammation, in addition to the MEST-C score. Renal biopsies of patients who had a history of transplant, autolyzed tissue, no glomeruli on histological examination, and/or a tubular atrophy/interstitial fibrosis score of 2 (T2) in MEST-C scoring were excluded. Data were analyzed using SPSS 20. An association between the variables was analyzed using the chi-square and Fischer exact tests. A p value less than 0.05 was considered statistically significant. A total of 247/300 biopsies were eligible for inclusion. The mean age at the time of biopsy was 31.90 ± 12.48 with 63.6% in the age group between 21 and 40 years, and 69.6% were male. Tubulointerstitial inflammation was observed in 90.2% cases with 49.4% showing moderate while 4.5% showing severe degree of inflammation. A strong association of both the type and severity of tubulointerstitial inflammation was found with M, E, T, and C scores (p value < 0.05). The high-frequency and strong statistical association of tubulointerstitial inflammation with the M, E, T, and C scores in our study elucidate its prognostic role in the progression and management of IgA nephropathy.

Simulation for ultrasound-guided renal biopsy using boiled egg.

Real-time ultrasound-guided renal biopsy is generally applied to diagnose multiple kidney diseases. A practical simulation model is desired since it is an invasive technique with higher risks of complications such as bleeding. We developed a simple simulation tool for ultrasound-guided renal biopsy using boiled eggs. Boiled chicken eggs were embedded in the agar, and a biopsy simulation was performed using a real-time ultrasound-guided technique as the renal biopsy simulator by trainees and biopsy-proficient nephrologists, and the feedback from the participants was obtained. The ultrasonographic evaluation revealed a clear contrast between egg yolk and white, which clearly mimicked the kidney cortex and medulla region. In addition, we observed the needle entering the egg white under needle penetration, and we obtained the biopsy core consisting of egg white. As for the simulations, all the participants succeeded in obtaining the appropriate samples. A total of 92% of the trainees agreed that the simulation could reduce their fears of performing renal biopsies in patients. In addition, all the trainees and biopsy-proficient nephrologists recommend using the simulator for trainees before conducting renal biopsies on patients. The total cost of the simulator was low (<USD 1/simulator). Collectively, our simulation tool using boiled eggs may be a good candidate for practical simulation models of renal biopsy.

POS-038 ALTERNATIVE COMPLEMENT PATHWAY INHIBITION WITH IPTACOPAN TO ARREST DISEASE PROGRESSION IN C3 GLOMERULOPATHY (APPEAR-C3G): A PHASE 3 STUDY

IntroductionComplement 3 glomerulopathy (C3G) is a rare kidney disease characterized by dysregulation of the alternative pathway (AP) of the complement system. Around 50% of patients progress to kidney failure within 10 years of diagnosis. Currently, there are no approved therapies for C3G. Iptacopan (LNP023) is an oral, first-in-class, potent and selective inhibitor of factor B, a key regulator of the AP. In a previously reported phase 2 study, 12 weeks treatment with iptacopan was associated with 45% reduction in proteinuria (p=0.0003), stabilization of eGFR in native kidneys of C3G patients and reduction in C3 deposit scores on renal biopsy in patients with recurrent C3G after transplantation (p=0.03). Iptacopan showed a favorable safety and tolerability profile in both cohorts.MethodsResultsRecruitment ongoing.ConclusionsThis Phase 3 study will provide valuable evidence towards the efficacy and safety of iptacopan in C3G patients with native kidney disease.Conflict of interest Corporate sponsored research or other substantive relationships:Richard JH Smith: research funding from NIH, consultant for Novartis. David G Kavanagh: grant support from Medical Research Council Wellcome Trust Kidney Research UK Complement UK Fight For Sight, Macular Society, consultant for Silence Therapeutics, Alexion Pharmaceuticals, Novartis, Apellis and Sarepta, Founder and Scientific Advisor, Gyroscope Therapeutics, Advisory board involvement includes Novartis, Sarepta Gyroscope Therapeutics, Silence Therapeutics. Ronda Tawfik, Angelo J Trapani, Yaqin Wang, Nicholas Webb and Matthias Meier are employees and stockholders of Novartis. Marina Vivarelli: honoraria for advisory boards and consulting fees, participation in clinical studies sponsored by the following pharmaceutical companies: Achillion Alexion Apellis Bayer Catalyst Novartis Roche Retrophin/Travere. Andrew S Bomback: consulting honoraria from Achillion, Alexion, Chemocentryx, Novartis, Silence, Catalyst, and Principio. IntroductionComplement 3 glomerulopathy (C3G) is a rare kidney disease characterized by dysregulation of the alternative pathway (AP) of the complement system. Around 50% of patients progress to kidney failure within 10 years of diagnosis. Currently, there are no approved therapies for C3G. Iptacopan (LNP023) is an oral, first-in-class, potent and selective inhibitor of factor B, a key regulator of the AP. In a previously reported phase 2 study, 12 weeks treatment with iptacopan was associated with 45% reduction in proteinuria (p=0.0003), stabilization of eGFR in native kidneys of C3G patients and reduction in C3 deposit scores on renal biopsy in patients with recurrent C3G after transplantation (p=0.03). Iptacopan showed a favorable safety and tolerability profile in both cohorts. Complement 3 glomerulopathy (C3G) is a rare kidney disease characterized by dysregulation of the alternative pathway (AP) of the complement system. Around 50% of patients progress to kidney failure within 10 years of diagnosis. Currently, there are no approved therapies for C3G. Iptacopan (LNP023) is an oral, first-in-class, potent and selective inhibitor of factor B, a key regulator of the AP. In a previously reported phase 2 study, 12 weeks treatment with iptacopan was associated with 45% reduction in proteinuria (p=0.0003), stabilization of eGFR in native kidneys of C3G patients and reduction in C3 deposit scores on renal biopsy in patients with recurrent C3G after transplantation (p=0.03). Iptacopan showed a favorable safety and tolerability profile in both cohorts. Methods ResultsRecruitment ongoing. Recruitment ongoing. ConclusionsThis Phase 3 study will provide valuable evidence towards the efficacy and safety of iptacopan in C3G patients with native kidney disease.Conflict of interest Corporate sponsored research or other substantive relationships:Richard JH Smith: research funding from NIH, consultant for Novartis. David G Kavanagh: grant support from Medical Research Council Wellcome Trust Kidney Research UK Complement UK Fight For Sight, Macular Society, consultant for Silence Therapeutics, Alexion Pharmaceuticals, Novartis, Apellis and Sarepta, Founder and Scientific Advisor, Gyroscope Therapeutics, Advisory board involvement includes Novartis, Sarepta Gyroscope Therapeutics, Silence Therapeutics. Ronda Tawfik, Angelo J Trapani, Yaqin Wang, Nicholas Webb and Matthias Meier are employees and stockholders of Novartis. Marina Vivarelli: honoraria for advisory boards and consulting fees, participation in clinical studies sponsored by the following pharmaceutical companies: Achillion Alexion Apellis Bayer Catalyst Novartis Roche Retrophin/Travere. Andrew S Bomback: consulting honoraria from Achillion, Alexion, Chemocentryx, Novartis, Silence, Catalyst, and Principio. This Phase 3 study will provide valuable evidence towards the efficacy and safety of iptacopan in C3G patients with native kidney disease.

Discussion on Current Consensus and Ambiguity of Renal Biopsy Based on the Case of a Male Patient with Type 1 Diabetic Nephropathy

本個案為37歲男性，患第一型糖尿病及糖尿病腎病變，一年內腎功能逐漸下降、並出現噁心及食慾減退等尿毒症狀，經家庭醫學科醫師轉介腎臟科門診，進行腎臟切片之適應症評估與透析準備。本個案報告從第一型糖尿病腎病變之自然史進而探討現今腎臟切片適應症及禁忌症的共識，以期第一線醫師對有需要經腎臟切片診斷、且能受益於此的族群有所覺察並適時轉介。A 37-year-old man with type 1 diabetes and diabetic nephropathy was followed at a family medicine clinic. His renal function had declined in the past year while uremic symptoms of nausea and anorexia also developed. As causes other than diabetes leading to deterioration of his renal function were suspected, he was referred to a renal specialist for discussion on receiving renal biopsy. After initial assessment with serology tests, sonography, as well as follow-up serum creatinine and blood urea nitrogen, renal biopsy was deferred given the chronicity of his condition and the inevitability of dialysis at the point. Current consensus and ambiguity concerning indications and contraindications of renal biopsy were examined via the case. Family medicine doctors are front-line physicians who should be able to detect the slightest change in manifestation of patients’ renal function. The importance of timely referral in yielding greatest possible benefits from renal biopsy for patients in need should be emphasized.

The Amphiregulin/EGFR axis protects from lupus nephritis via downregulation of pathogenic CD4+ T helper cell responses

Systemic lupus erythematosus (SLE) is a common autoimmune disorder with a complex and poorly understood immuno-pathogenesis. Lupus nephritis (LN) is a frequent and difficult to treat complication, which causes high morbidity and mortality. The multifunctional cytokine amphiregulin (AREG) has been implicated in SLE pathogenesis, but its function in LN currently remains unknown. We thus studied the model of pristane-induced LN and found increasing renal and systemic AREG expression during the course of disease. Importantly, renal injury was significantly aggravated in the absence of AREG, revealing a net anti-inflammatory role. Analyses of immune responses showed dual effects. On the one hand, AREG enhanced activation of pro-inflammatory myeloid cells, which however did not play a major role for the course of LN. More importantly, on the other hand, AREG strongly suppressed pathogenic cytokine production by T helper effector cells. This effect was more general in nature and could be reproduced in response to antigen immunization. Since AREG has been postulated to downregulate T cell responses via enhancing Treg suppressive capacity, we followed up on this aspect. Interestingly, however, in vitro studies revealed potential direct and Treg independent effects of AREG on T helper effector cells. In favor of this notion, we found significantly enhanced T cell responses and consecutive aggravation of LN, only if epidermal growth factor receptor (EGFR) signaling was abrogated in total T cells, but not if the EGFR was absent on Tregs alone. Finally, we also found enhanced AREG expression in plasma and renal biopsies of patients with LN, supporting the relevance of our findings for human disease. In summary, our data identify AREG as an anti-inflammatory mediator of LN via broad downregulation of pathogenic T cell immunity. These findings further highlight the AREG/EGFR axis as a potential therapeutic target.