IgA Nephropathy Patients Research Articles

A preliminary probabilistic nomogram model for predicting renal arteriolar damage in IgA nephropathy from clinical parameters.

IgA nephropathy (IgAN) is a significant contributor to chronic kidney disease (CKD). Renal arteriolar damage is associated with IgAN prognosis. However, simple tools for predicting arteriolar damage of IgAN remain limited. We aim to develop and validate a nomogram model for predicting renal arteriolar damage in IgAN patients. We retrospectively analyzed 547 cases of biopsy-proven IgAN patients. Least absolute shrinkage and selection operator (LASSO) regression and logistic regression were applied to screen for factors associated with renal arteriolar damage in patients with IgAN. A nomogram was developed to evaluate the renal arteriolar damage in patients with IgAN. The performance of the proposed nomogram was evaluated based on a calibration plot, ROC curve (AUC) and Harrell's concordance index (C-index). In this study, patients in the arteriolar damage group had higher levels of age, mean arterial pressure (MAP), serum creatinine, serum urea nitrogen, serum uric acid, triglycerides, proteinuria, tubular atrophy/interstitial fibrosis (T1-2) and decreased eGFR than those without arteriolar damage. Predictors contained in the prediction nomogram included age, MAP, eGFR and serum uric acid. Then, a nomogram model for predicting renal arteriolar damage was established combining the above indicators. Our model achieved well-fitted calibration curves and the C-indices of this model were 0.722 (95%CI 0.670-0.774) and 0.784 (95%CI 0.716-0.852) in the development and validation groups, respectively. With excellent predictive abilities, the nomogram may be a simple and reliable tool to predict the risk of renal arteriolar damage in patients with IgAN.

Predictors of glomerular IgA immunostaining patterns and disease progression in IgA nephropathy patients; a 13-year study of clinical and morphological features of renal biopsies

Introduction: IgA nephropathy (IgAN) is a common primary glomerulonephritis with highly heterogeneous clinical and histopathological features. The MEST-C scoring system has been developed to improve prognostic assessment but lacks elements related to immunostaining study. Objectives: This study aimed to investigate the association between the immunofluorescence (IF) deposits’ patterns of IgA (mesangiocapillary versus pure mesangial) with demographic, clinical, biochemical, and morphological parameters of MEST-C classification in IgAN patients. Patients and Methods: This retrospective, cross-sectional study was conducted on 268 biopsy-proven cases of IgAN from July 2009 to July 2022 at a single laboratory in Isfahan in Iran. The demographic, clinical, and laboratory data including age, gender, serum creatinine, and proteinuria were collected from the biopsy request forms. The morphological parameters of MEST-C classification and IF study patterns were collected from the biopsy reports. Results: The average age of all patients was 37.7 ± 13.47 years, with 67% being males. The mean serum creatinine and proteinuria levels were 1.43 mg/dL and 1730.94 mg/day, respectively. MEST-C score analysis revealed that 171 patients (63.8%) had mesangial expansion (M1), while 105 patients (39.2%) exhibited endocapillary hypercellularity (E1). Additionally, segmental glomerulosclerosis (S1) and tubular atrophy/interstitial fibrosis (T1 and T2) was observed in 160 biopsy samples (59.7%). Moreover, crescent (C) formation was noted in 76 (28.4%) of biopsies. Data analysis using univariate logistic regression demonstrated that E, T, and C on morphology, complement C3, IgG, IgM deposits on IF, and the total MEST score were all associated with an increased risk for mesangiocapillary deposits of IgA. However, using the multivariate method, the results indicated that only the total MEST score (OR: 2.4), presence of crescent (OR: 3.22), presence of endocapillary hypercellularity (OR: 4.86), tubular atrophy/interstitial fibrosis grade II (OR: 34.4), and IgG deposition (OR: 3.37) were independent risk factors for mesangiocapillary deposits of IgA. Conclusion: The total MEST score is significantly higher in mesangiocapillary patterns. Furthermore, the presence of E1, T2, and C1-2 morphological parameters of the updated Oxford classification in renal biopsies are independent risk factors for IgA mesangiocapillary deposits. Hyperactivation of immunoglobulins and the complement system appears to contribute to mesangial-capillary proliferation.

Complement C3a/C3aR and C5a/C5aR deposits accelerate the progression of advanced IgA nephropathy to end-stage renal disease

IgA nephropathy (IgAN) is still one of the leading causes of end-stage kidney disease (ESRD), and complement system activation is a key to the pathogenesis of IgAN. The role of complement C3a/C3aR and C5a/C5aR in late stage of IgAN remains unknown. Renal specimens of 75 IgAN patients at the stage 4 CKD were stained using immunofluorescence and immunohistochemistry. The primary outcome was a composite of end-stage renal disease (ESRD) and death. Associations of complement components with baseline clinicopathological characteristics and outcomes were assessed using multivariable Cox regression and Spearman analyses. During a median follow-up of 15.0 months, 27 patients progressed to ESRD and none died. Lower eGFR [hazards ratio (HR), 0.827, 95% confidence interval (CI), 0.732–0.935; P = 0.002] and glomerular C3 deposition (HR, 3.179, 95% CI, 1.079–9.363; P = 0.036) were predictive of time to ESRD in stage 4 CKD IgAN. Higher expression of C3a (P = 0.010), C3aR (P = 0.005), C5a (P = 0.015), and C5aR (P < 0.001) was identified in ESRD group than in non-ESRD group. Glomerular C3a/C3aR and C5a/C5aR deposits were both correlated with a lower baseline eGFR, higher baseline 24 h-urinary protein (24 h-UP) and faster decline of eGFR. Besides, C3a and C5a deposits were found in patients with high S (S1) and T (T1/2) scores, respectively. Complement C3a/C3aR and C5a/C5aR in IgAN patients with stage 4 CKD may portend a faster deterioration of kidney function.

The successful use of rituximab in IgA nephropathy patients with podocytopathy: a case series.

Immunoglobulin A nephropathy (IgAN) with podocytopathy is a rare pathological type of glomerular disease. The use of rituximab (RTX) in the treatment of glomerular diseases has increased in recent decades, but the efficacy of RTX in the treatment of patients with IgAN and podocytopathy has rarely been reported. This was a single-centre retrospective study of IgAN patients with podocytopathy who were treated with RTX as second-line therapy was conducted at our centre from 2019 to 2022. The aim of this study was to investigate the efficacy and safety of RTX in IgAN patients with podocytopathy. Seven out of eight patients met the criteria for complete remission following RTX therapy. Only one patient experienced adverse events (infectious diarrhoea and pulmonary infection) and experienced relapse 6 months after RTX therapy. The maximum relapse-free time after RTX therapy was 20 months, while the maximum relapse-free time before RTX therapy was only 6 months. The number of relapses before RTX therapy (per year) was one to four; moreover, seven patients did not relapse and maintained remission at the last follow-up despite steroid withdrawal after RTX therapy. Overall, RTX effectively reduced proteinuria, increased the maximum relapse-free time, reduced the number of relapses per year and helped patients stop steroid use as soon as possible. RTX also helped most patients achieve clinical remission. RTX appears to be an effective and safe alternative for treating IgAN patients with podocytopathy with steroid dependence or frequent relapse.

Cathepsin S (CTSS) in IgA nephropathy: an exploratory study on its role as a potential diagnostic biomarker and therapeutic target.

IgA nephropathy (IgAN), a prevalent form of glomerulonephritis globally, exhibits complex pathogenesis. Cathepsins, cysteine proteases within lysosomes, are implicated in various physiological and pathological processes, including renal conditions. Prior observational studies have suggested a potential link between cathepsins and IgAN, yet the precise causal relationship remains unclear. We conducted a comprehensive bidirectional and multivariable Mendelian randomization (MR) study using publicly available genetic data to explore the causal association between cathepsins and IgAN systematically. Additionally, immunohistochemical (IHC) staining and enzyme-linked immunosorbent assay (ELISA) were employed to evaluate cathepsin expression levels in renal tissues and serum of IgAN patients. We investigated the underlying mechanisms via gene set variation analysis (GSVA), gene set enrichment analysis (GSEA), and immune cell infiltration analysis. Molecular docking and virtual screening were also performed to identify potential drug candidates through drug repositioning. Univariate MR analyses demonstrated a significant link between increased cathepsin S (CTSS) levels and a heightened risk of IgAN. This was evidenced by an odds ratio (OR) of 1.041 (95% CI=1.009-1.073, P=0.012) as estimated using the inverse variance weighting (IVW) method. In multivariable MR analysis, even after adjusting for other cathepsins, elevated CTSS levels continued to show a strong correlation with an increased risk of IgAN (IVW P=0.020, OR=1.037, 95% CI=1.006-1.069). However, reverse MR analyses did not establish a causal relationship between IgAN and various cathepsins. IHC and ELISA findings revealed significant overexpression of CTSS in both renal tissues and serum of IgAN patients compared to controls, and this high expression was unique to IgAN compared with several other primary kidney diseases such as membranous nephropathy, minimal change disease and focal segmental glomerulosclerosis. Investigations into immune cell infiltration, GSEA, and GSVA highlighted the role of CTSS expression in the immune dysregulation observed in IgAN. Molecular docking and virtual screening pinpointed Camostat mesylate, c-Kit-IN-1, and Mocetinostat as the top drug candidates for targeting CTSS. Elevated CTSS levels are associated with an increased risk of IgAN, and this enzyme is notably overexpressed in IgAN patients' serum and renal tissues. CTSS could potentially act as a diagnostic biomarker, providing new avenues for diagnosing and treating IgAN.

Mendelian Randomization Analysis of Systemic Iron Status and Risk of Different Types of Kidney Disease.

With rapid increases in incidence, diverse subtypes, and complicated etiologies, kidney disease remains a global public health problem. Iron, as an essential trace element, has pleiotropic effects on renal function and the progression of kidney diseases. A two-sample Mendelian randomization (MR) analysis was implemented to determine the potential causal effects between systemic iron status on different kidney diseases. Systemic iron status was represented by four iron-related biomarkers: serum iron, ferritin, transferrin saturation (TfSat), and total iron binding capacity (TIBC). For systemic iron status, 163,511, 246,139, 131,471, and 135,430 individuals were included in the genome-wide association study (GWAS) of serum iron, ferritin, TfSat, and TIBC, respectively. For kidney diseases, 653,143 individuals (15,658 cases and 637,485 controls), 657,076 individuals (8160 cases and 648,916 controls), and 659,320 individuals (10,404 cases and 648,916 controls) were included for immunoglobulin A nephropathy (IgAN), acute kidney disease (AKD), and chronic kidney disease (CKD), respectively. Our MR results showed that increased serum iron [odds ratio (OR): 1.10; 95% confidence interval (95% CI): 1.04, 1.16; p < 0.0042], ferritin (OR: 1.30; 95% CI: 1.14, 1.48; p < 0.0042), and TfSat (OR: 1.07; 95% CI: 1.04, 1.11; p < 0.0042)] and decreased TIBC (OR: 0.92; 95% CI: 0.88, 0.97; p < 0.0042) were associated with elevated IgAN risk. However, no significant associations were found between systemic iron status and AKD or CKD. In our MR study, the genetic evidence supports elevated systemic iron status as a causal effect on IgAN, which suggests a potential protective effect of iron chelation on IgAN patients.

Urinary exosomal mRNAs as biomarkers for predicting the therapeutic effect of renin-angiotensin system inhibitors in IgA nephropathy patients

BackgroundRenin-angiotensin system inhibitors (RASi) treatment is the basic therapy for IgA nephropathy (IgAN) patients. However, there is few of biomarker that can predict the efficacy of RASi. This study aimed to find urinary exosomal mRNAs related to the therapeutic effect of RASi in the treatment of proteinuria in IgAN patients. Methods: We divided IgAN patients in screening cohort into A1 (proteinuria increase at 3 months), B1 (proteinuria decrease less than 50 % at 3 months), C1 (proteinuria decrease more than 50 % at 3 months) groups according to changes of proteinuria after treatment. The urinary exosomes were collected before biopsy, RNAs were extracted and analyzed with the microarray assay. The candidate genes were screened by differentially expressed genes (DEGs) analysis and then validated by quantitative real-time polymerase chain reaction (qPCR) in a validation cohort. A receiver operating characteristic (ROC) curve was used to evaluate gene performance in predicting therapeutic effect on RASi reducing proteinuria in IgAN patients. Results: ECE1 and PDE1A mRNAs were significantly different among the three groups, and were gradually decreased among A1, B1 and C1 groups. In the validation cohort, the level of urinary exosomal ECE1 and PDE1A mRNAs were also significantly lower in A2 group compared with C2 group(ECE1, P < 0.001;PDE1A, P < 0.01). Besides, the level of ECE1 mRNA was also lower in B2 group compared with C2 group (P < 0.01). The ROC curve verified that urinary exosomal ECE1 and PDE1A gene level predicted RASi efficacy in IgAN patients with area under curve (AUC) 0.68 and 0.63 respectively. Conclusion: Urinary exosomal ECE1 and PDE1A mRNAs expression can serve as potential biomarkers for predicting the RASi efficacy to reduce proteinuria in IgAN patients.

The impact of mild and moderate COVID-19 infection on the progression of kidney dysfunction in patients with IgA nephropathy.

Previous research indicates that coronavirus disease 2019 (COVID-19) infection may have a role in triggering immunoglobulin A (IgA) nephropathy. However, limited research has explored the clinical implications of COVID-19 infection in individuals already diagnosed with IgA nephropathy. This study aimed to determine whether COVID-19 infection independently affects the subsequent trajectory of kidney function in IgA nephropathy patients. This was a single-center cohort study. The study included 199 patients diagnosed with IgA nephropathy. The COVID-19 infection status was determined using a combined method: a questionnaire and the Health Code application, both administered at the end of 2022 in northern China. Kidney function trajectory was assessed by the estimated glomerular filtration rate (eGFR), calculated based on serum creatinine levels measured during follow-up outpatient visits. The primary endpoint of interest was the eGFR trajectory. Out of the 199 participants, 75% (n=181) reported a confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, determined through antigen or polymerase chain reaction tests, accounting for 79% (n=143) of the infected patients. A significant majority (98%) experienced mild to moderate symptoms. Over a median follow-up period of 10.7months post-COVID-19 infection, notable clinical events included gross hematuria in 30 patients (16.6%), which normalized within an average of 3days. Additionally, a 2-fold increase in proteinuria or progression to the nephrotic range was observed in 10 individuals (5.5%). No cases of acute kidney injury were noted. COVID-19 exposure was associated with an absolute change in eGFR of 2.98mL/min/1.73m2 per month (95% confidence interval 0.46 to 5.50). However, in a fully adjusted model, the estimated changes in eGFR slope post-COVID-19 were -0.39mL/min/1.73m2 per month (95% confidence interval -0.83 to 0.06, P=.088) which included the possibility of no significant effect. Notably, a higher rate of kidney function decline was primarily observed in patients with a baseline eGFR <45mL/min/1.73m2 [-0.56mL/min/1.73m2 (-1.11 to -0.01), P=.048]. In the cohort, there were few instances of severe COVID-19 cases. The absence of long-term follow-up outcomes was observed. Overall, mild to moderate COVID-19 infection does not appear to significantly exacerbate the subsequent decline in kidney function among IgA nephropathy patients, particularly in those with preserved baseline kidney function.

#366 Humanistic burden of immunoglobulin A nephropathy and focal segmental glomerulosclerosis on patients and care-partners (HONUS): results for Europe

Abstract Background and Aims Rare proteinuric kidney diseases are associated with clinical and economic burden, however, the humanistic burden associated with these conditions has not been directly evaluated. HONUS is a multi-national, cross-sectional survey study designed to evaluate the humanistic burden associated with two rare kidney diseases, immunoglobulin A nephropathy (IgAN) and focal segmental glomerulosclerosis (FSGS), from the patient and caregiver perspectives in the United States and Europe. The current analysis presents preliminary results from adults with IgAN or FSGS and their care-partners in Spain, Germany, France, or the United Kingdom. Method The study recruited adult patients (≥ 18 years old) with IgAN or FSGS and their adult care-partners. Participants completed an online survey including demographic and clinical characteristics, health-related quality of life (HRQoL) (i.e., Kidney Disease Quality of Life Instrument [KDQoL] including 12-Item Short Form Survey [SF-12]), anxiety and depression (i.e., Generalized Anxiety Disorder Assessment [GAD-7], Patient Health Questionnaire [PHQ-9]), and disease impact on work productivity (i.e., Work Productivity and Activity Impairment [WPAI]). Descriptive analyses were conducted. Results From Europe, 26 IgAN patients, 9 FSGS patients, and their care-partners (4 IgAN and 2 FSGS patients did not report having a care-partner) participated in the survey before November 2023. Mean age for IgAN and FSGS patients was 42.2 years and 51.4 years, with 61.5% and 44.4% being female, respectively. Over two-fifths of both IgAN (42.3%) and FSGS patients (44.4%) were in chronic kidney disease (CKD) stage 3, 4 or 5 (on dialysis), while over one-quarter had received a kidney transplant (IgAN: 26.9%; FSGS: 44.4%). Most patients had worse CKD status since diagnosis (IgAN: 61.5%; FSGS: 77.8%). Hypertension and anemia were the most common comorbidities in both groups. In terms of HRQoL, mean (SD) SF-12 physical and mental component scores (PCS, MCS) indicated IgAN patients were more impacted on the mental component (PCS: 47.3 [11.6], MCS: 43.2 [10.9]), with FSGS patients more impacted on the physical component (PCS: 40.6 [6.0], MCS: 43.8 [9.1]), reflecting generally worse HRQoL (lower scores) than previously published European general population scores (50.0 for PCS and MCS). Moderate to severe anxiety was reported by 30.8% of IgAN and 33.3% of FSGS patients, and moderate to severe depression by 30.8% of IgAN and 44.4% of FSGS patients. Among employed IgAN patients (69.2%), mean percent absenteeism (work time missed) was reported at 13.3%, presenteeism (impairment while working) at 17.7%, and overall work productivity loss at 17.7% due to IgAN-related reasons (only 3 FSGS patients [33.3%] were employed; outcomes not shown). Mean percent activity impairment was reported at 27.3% in IgAN and 43.3% in FSGS patients. Most paired care-partners were partners of patients (IgAN: 81.8%, FSGS: 71.4%), with a mean age of 46.6 years (IgAN) and 50.1 years (FSGS). Mean (SD) SF-12 PCS and MCS of IgAN care-partners were 53.3 (8.8) and 47.9 (10.8), respectively (FSGS: 47.0 [10.6], 49.4 [9.5]). Mild to moderate anxiety was reported in 31.8% (IgAN) and 42.9% (FSGS) of care-partners, with one IgAN care-partner (4.6%) reporting severe anxiety. Mild to moderate depression was reported in 27.3% (IgAN) and 71.4% (FSGS) of care-partners, with two IgAN care-partners (9.1%) reporting moderately severe or severe depression. Among employed IgAN care-partners (86.4%), mean percent absenteeism was reported at 14.2%, presenteeism at 9.3%, and overall work productivity loss at 9.9% due to IgAN-related reasons. Mean percent activity impairment was reported at 18.6% in IgAN and 17.1% in FSGS care-partners. Conclusion Patients with IgAN and FSGS in Europe experience impaired HRQoL compared to previously published European population estimates, as well as anxiety, depression, and impaired productivity. Care-partners of these patients also experience impaired HRQoL, in terms of mental components, and reduced overall productivity.

#2615 Altered peroxidasin expression pattern in IgA nephropathy

Abstract Background and Aims PXDN is a multifunctional heme peroxidase responsible for the crosslinking of type IV collagen protomers at basement membranes, playing a crucial role in the extracellular matrix dynamics. In renal pathophysiology, increased PXDN expression has been associated with pro-fibrotic and pro-carcinogenic mechanisms and we have shown that PXDN is expressed throughout all kidney compartments since the early stages of nephrogenesis. However, the role of PXDN in kidney health and disease remains largely unknown. In this work we performed a comparative analysis of PXDN expression between renal biopsy samples from IgA nephropathy (IgAN) patients and healthy kidney biopsy samples. IgAN was the selected CKD model due to its straightforward diagnosis by standard protocols for histopathological evaluation of kidney biopsies, and to the fact that the renal outcomes are consistently associated with several key pathologic features, including tubular atrophy and interstitial fibrosis. Correlations between PXDN expression and IgAN disease and kidney function parameters as well as with ECM proteins were also explored. Method Fluorescence immunohistochemistry for PXDN was performed in biopsy samples from IgAN patients (n = 20) and in biopsies from healthy kidney donors (n = 7). Proximal tubules were assessed by anti-CD15 fluorescent staining. Collagen III (COLIII) deposition was investigated in IgAN samples (n = 7) by immunofluorescence. Brightfield images were manually segmented into glomeruli, proximal and distal tubules, and interstitium, using QuPath software, and the fluorescence intensity measurements were obtained with ImageJ/Fiji. Results Results showed that, in comparison with healthy kidney samples, PXDN is significantly decreased in proximal and distal tubules of IgAN patients (P &amp;lt; 0.001 and P &amp;lt; 0.05, respectively) whereas it is increased in IgAN interstitium (P &amp;lt; 0.001). When IgAN samples were stratified by the presence or absence of chronic lesions (glomerular sclerosis and interstitial fibrosis) we observed that in the proximal tubules, PXDN is decreased even in areas without lesions while in the distal tubules the expression is compromised only in the lesioned areas. In the interstitium, PXDN shows a tendency of increase from healthy tissue to IgAN in areas without and with tubulointerstitial fibrosis, presenting a significant increase in the lesioned areas (P &amp;lt; 0.001). Concerning ECM deposition, results showed a significant correlation between the expression of PXDN and COLIII in sclerotic glomeruli (R = 0.8214; P = 0.0341) and in the tubulointerstitial fibrotic areas (R = 0.93; P = 0.0067). Moreover, although no differences were observed in the glomerular expression of PXDN between healthy and IgAN samples, when considering eGFR, a significant increase of PXDN was observed in both non-lesioned and sclerotic glomeruli from IgAN patients with eGFR bellow 60 ml/min/1,73 m2. In the interstitium, the expression of PXDN was also increased in tubulointerstitial fibrotic areas of IgAN patients with eGFR bellow 60 ml/min/1,73 m2, in comparison with the same areas in patients with higher eGFR values. Conclusions Overall, our study shows a differential expression of PXDN in IgAN, with loss in the tubular region that relates with the state of interstitial fibrosis, and gain in the glomerular and interstitial region where it correlates with COLIII compartment-specific deposition and with kidney function as assessed by eGFR. These data support, for the first time, the enrollment of PXDN in the topographic mechanism of IgA-mediated kidney lesion that deserves further investigations. Given that sclerosis and fibrosis are a common pathogenic mechanism of CKD, irrespective of the underlying etiology, we postulate that PXDN may serve as a novel therapeutic target for this disease.

#1089 Urinary Protein Biomarkers for Assessing Disease Activity and Chronicity in IgA Nephropathy

Abstract Background and Objectives IgA nephropathy (IgAN) is a progressive kidney disease characterized by the mesangial deposition of galactose-deficient IgA1, leading to kidney damage and may eventually lead to end-stage kidney disease. Current treatment decisions for IgAN patients rely on the degree of proteinuria. However, this is a non-specific parameter that can be the result of inflammatory disease activity and/or chronic glomerular damage. In this study, we employed the Olink proximity extension assay to comprehensively analyze the urinary proteome of IgAN patients. Our goal was to identify biomarkers capable of distinguishing between IgAN disease activity and disease chronicity. Method Urine samples were collected from 41 IgAN patients and 41 age- and eGFR-matched controls. Patient characteristics are shown in Table 1. Using Olink Proteomics, we measured 276 proteins in urine, from the inflammation, organ damage, and cardiometabolic panels. Comparisons were made between IgAN patients and controls, as well as between those with mild (eGFR ≥ 60 ml/min/1.73 m2 and uPCR &amp;lt; 100 mg/mmol) and active IgAN (eGFR ≥ 60 ml/min/1.73 m2 and uPCR ≥ 100 mg/mmol) to identify biomarkers for disease activity. Additionally, we compared IgAN patients with eGFR ≥ 60 ml/min/1.73 m2 to those with eGFR ≤ 30 ml/min/1.73 m2 to identify biomarkers associated with disease chronicity. Mann-Whitney U tests were used for group comparisons. Correction for multiple testing was performed using the Benjamini-Hochberg procedure. Disease activity and chronicity scores were calculated by averaging the z-scores of the identified biomarkers. Results L-Selectin (SELL), leukocyte inhibitory factor (LIF), interleukin-6 (IL-6), and carbonic anhydrase 1 (CA1) were most prominently elevated in IgAN patients compared to controls (Fig. 1A). SELL and CA1 were also markedly elevated in the active versus mild IgAN patients, and were therefore selected as biomarkers of disease activity (Fig. 1B). Contactin 2 (CNTN2) and chemokine (C-C motif) ligand 25 (CCL25) were most prominently elevated in IgAN patients with eGFR ≤ 30 ml/min/1.73 m2, and were selected as biomarkers of disease chronicity (Fig. 1C). We plotted the disease activity and chronicity scores calculated from the identified biomarkers to distinguish the different IgAN disease stages (Fig. 1D). Conclusion This study identified urine biomarkers indicative of IgAN disease activity and chronicity. Calculating an activity and chronicity score using these biomarkers offers a new approach to distinguish between inflammatory disease activity and chronicity, providing an alternative to proteinuria for guiding treatment decisions in IgAN patients. Validation of these biomarkers, and the scores calculated from them, in a larger cohort of IgAN patients is currently underway.

#2954 A comparative view of IgA nephropathy care across four global regions

Abstract Background and Aims IgA nephropathy (IgAN) is a chronic, rare, and slow progressing glomerular disease. IgAN treatment currently consists of angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARB), sodium-glucose co-transporter 2 (SGLT2) inhibitors, corticosteroids, and recently approved Nefecon and sparsentan in select markets. This research compares approaches to IgAN treatment in four regions of the world. Method Data was collected in partnership with 730 nephrologists submitting chart data from 1,570 of their most recently seen IgAN patients to create a representative sample across the US, EU5 (UK, Germany, Italy, France, and Spain), Japan, and China via parallel online surveys in 2023. Results Regardless of their geographic location, audited patient charts revealed that hypertension, hyperlipidemia, obesity, and diabetes were the leading comorbid conditions among IgAN patients. Across the four regions evaluated, Japanese patients were the healthiest (44% have no comorbid conditions vs. 28% EU5, 25% China, 18% US) and Japanese nephrologists perceived 79% of their IgAN patients to be in “excellent” overall health. Comparatively, patients in the US had the highest calculated body mass index (28.2) and the most comorbid conditions reported. Audited records also revealed that patients in Japan and China were referred to nephrology care earlier in their CKD progression as measured by eGFR levels, with over 50% of patients referred to their current nephrologist in CKD Stages 1 or 2, compared to approximately 35% of patients in the US and EU5. Chinese nephrologists (59%) and those in the US (53%) were most likely to agree that it is easy to identify IgAN patients who are likely to have rapid progression (vs. 43% EU5 and 40% Japan). When treating their IgAN patients, Japanese nephrologists ordered labs on a more frequent basis compared to those in the US, EU5, and China and on average, Japanese patients had blood work and urinalysis labs conducted six times within the past twelve months (versus four in the other countries.) Most audited patients had a calculated annual eGFR decline of 1 ml/year or more. Chinese patients (77%) were most notable for their IgAN progression, while those in Japan were least likely to be progressing in their disease (41%). Due to its chronic nature, most IgAN patients will eventually need dialysis, and while still representative of the majority of their audited patients, US nephrologists projected the lowest percentage of IgAN patients to eventually progress to end stage renal disease (66% vs. 73% Japan, 75% EU5, and 85% China). Most participating nephrologists reported that they closely adhere to the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines when treating their IgAN patients. Nearly all audited IgAN patients were on baseline therapy of ACE inhibitors or ARBs, while the uptake of SGLT2 inhibitors has been notable in China (44%), the US (43%), and EU5 (43%), with Japan (33%) trailing in current treatment rates. Meanwhile, the use of corticosteroid was also higher in patients in Japan (65%) and China (59%) compared to those in the EU5 (51%) and US (43%). Of note, tonsillectomies are frequently used as a treatment approach for IgAN patients in Japan, with 45% of patients having received the procedure, whereas this approach is used much less often in the other regions. Following a tonsillectomy, nearly all Japanese patients received a pulse of steroids, leading to higher overall corticosteroid use compared to other regions. At the time of fielding, Nefecon was available to prescribe in the US and Germany with 9% and 7% of patients currently on treatment, respectfully; however, sparsentan had not been approved in any regions. Conclusion The comparison of patient chart data across various regions reveals differences in perspectives and IgAN treatment approaches among nephrologists. Prognostic and predictive tools are available and utilized globally, but the reliability and correlation between results, lab values, and disease progression calls for better education and alignment of global treatment guidelines.

#1805 Renal progenitor cells isolated from urine of IgA nephropathy patients formed renal spheroids that can recapitulate the typical IgA1 deposition

Abstract Background and Aims Recent developments in stem cell biology have made it possible to create spheroids and kidney organoids from human and mouse pluripotent stem cells and renal stem cells. Spheroids are a suitable in vitro model for studies of drug studies and can transform into organoids whose rapidly developing field has proven useful in simulating nephrotoxicity, kidney disorders, and kidney development. However, to date in all studies the generation of organoids and tubuloids required the use of sophisticated and complex differentiation protocols involving external administration of several growth factors and needs compliance with a precise and specific timescale. Here we showed for the first time that human adult renal progenitor cells (ARPCs) can be isolated from urines of healthy subjects (HS) or IgA Nephropathy (IgAN) patients and can form spheroids generating very long tubule-like structures naturally, without the external use of chemokines or growth factors to artificially induce the process and recapitulating the IgA1 deposition that is the typical characteristic of the disease. Method Spheroids and tubule-like structures were characterized by whole-mounting and frozen section immunofluorescence (IF) assays and by Flow Cytometry Analysis using CD133, NanoG, Oct3/4, GATA-3, SSEA4, CD249, Aminopepidase N, ZO-1, Uromodulin, and Lotus Tetragonolobus Lectin (LTL) antibodies. ELISA was used to determine the renin secretion and CAM assays to determine ARPCs and ARPC-derived Spheroids angiogenic properties. PKH-26 labeling was used for their in vitro and in vivo tracking. Serum of HS and IgAN patients in culture with spheroids was used to recapitulate the disease and IgA1 deposits were measured by IF. Results ARPC-derived spheroids reflected the renal progenitor properties and recapitulated organoids generating very long tubule-like structures that expressed structural and functional renal tubule markers such as CD249, Aminopepidase N, ZO-1, Uromodulin, and LTL and in some cases shared many structural similarities with some regions of nephrons, such as the distal convoluted tubule, the loop of Henle and proximal convoluted tubules. Moreover, ARPC-derived spheroids secreted elevated levels of renin and, as the cellular counterpart, showed angiogenic properties. To study the proof of concept that ARPC-derived spheroids can be used to establish in vitro models recapitulating renal diseases, we generated IgAN patient-specific renal spheroids using the ARPC mixed cell population method. ARPC-derived spheroids of IgAN patients showed deposits of IgA1 already after four days of culture with patient serum (p = 0.004) and, with a different pattern, after 8 and 15 days (p = 0.0029 and p = 0.0012, respectively). The IgA1 deposition resembled that in the glomeruli of patients diagnosticated with IgAN. In contrast, no positive signal was detected in either IgAN spheroids in culture with FBS, or with inactivated IgAN serum, as well as in spheroids derived from urine of HS in culture with IgAN serum. Conclusion The ability of ARPCs to form spheroids and differentiate into tubular-like structures without the need for external chemokines or growth factors is a significant advancement in the field, even more considering that these cells can be isolated from the urine of patients. These findings open up new possibilities for the regenerative medicine in studying kidney development, disease mechanisms, and regenerative therapy development for renal disorders.

#1261 A small-molecule inhibitor of Bruton's tyrosine kinase reduces production of galactose-deficient IgA1 in IgA nephropathy

Abstract Background and Aims IgA nephropathy (IgAN) is a chronic kidney disease characterized by glomerular immunodeposits that contain aberrantly glycosylated IgA1, i.e., IgA1 with some hinge-region O-glycans deficient in galactose (galactose-deficient IgA1; Gd-IgA1). These immunodeposits originate from circulating immune complexes that contain Gd-IgA1 bound by IgG autoantibodies. Consistent with this hypothesis, serum levels of Gd-IgA1 and IgG autoantibodies independently predict disease progression in IgAN patients. Biochemical studies using IgA1-secreting cell lines derived from peripheral blood of IgAN patients and healthy controls have revealed that Gd-IgA1 production is driven by altered biosynthetic pathways of IgA1 O-glycans. Specifically, cell lines from IgAN patients have altered expression and activity of several glycosyltransferases, C1GalT1 and ST6GalNAc2, and a C1GalT1-specific chaperone, C1GalT1C1. Genetic studies have shown that serum levels of Gd-IgA1 are genetically co-determined and genome-wide association studies (GWAS) identified genetic variations that impact the expression C1GALT1 and C1GALT1C1 genes. Moreover, macroscopic hematuria during an upper-respiratory-tract infection is common at the clinical onset of IgAN and during episodes of accentuated disease activity, indicating a connection between IgAN and mucosal inflammation. Notably, a pro-inflammatory cytokine interleukin-6 (IL-6), enhances production of Gd-IgA1 exclusively in the cell lines derived from IgAN patients. Leukemia inhibitory factor (LIF) has similar effects. LIF-induced effects are mediated by abnormal STAT1 signaling and pathways that include Lyn, a Src-family kinase. The corresponding gene, LYN, was recently identified in one of the 16 new IgAN-associated GWAS loci. Lyn, together with spleen tyrosine kinase (Syk) and Bruton's tyrosine kinase (Btk), is involved in B-cell-receptor (BCR)-signaling pathways that include activation and inhibitory signals. The aim of this study was to assess if Btk may be involved in Gd-IgA1 production in IgAN. Method IgA1-producing cell lines were cloned by limiting dilution of Epstein-Barr-virus-immortalized peripheral-blood B cells from patients with IgAN (n = 5) and healthy controls (n = 5). Cell signaling, induced by LIF or by BCR crosslinking with anti-IgA antibody, was assessed by flow cytometry or SDS-PAGE/immunoblotting using antibodies for specific phosphorylated sites of selected proteins. Data were normalized using antibodies for specific proteins. Total IgA and Gd-IgA1 were quantified in cell-culture medium using standard ELISA and lectin-ELISA, respectively. Gd-IgA1, normalized to IgA, was expressed in Units (U) of standard Gd-IgA1 protein. Results IgA1-producing cell lines from patients with IgAN and healthy controls secreted similar amounts of total IgA (17.2 ± 9.3 ug/ml vs. 14.6 ± 9.5 ug/ml), but the cells from IgAN patients secreted more Gd-IgA1 (24.2 ± 7.5 U vs. 15.5 ± 2.7 U; p &amp;lt; 0.05). Baseline phosphorylation of Btk (Y223), but not Syk (Y551), was higher in the cells from patients with IgAN than in those from healthy controls. We used an IgA1-secreting cell line from an IgAN patient to confirm that BCR crosslinking with F(ab’)2 anti-IgA antibody in IgA + CD19+ cells lines induced phosphorylation of Btk (Y223). Conversely, anti-IgM antibody, used as a negative control, did not activate Btk. LIF stimulation did not affect phosphorylation of Btk or Syk. A Btk inhibitor, PCI-32765 (ibrutinib), reduced Gd-IgA1 production in a dose-dependent fashion exclusively in the IgAN-derived cells. Notably, 1 uM PCI-32765 reduced Gd-IgA1 production to that for healthy controls (25.7 ± 1.2 U to 17.3 ± 1.8 U; p &amp;lt; 0.01). Conclusion Inhibition of Btk with a small-molecule inhibitor normalized Gd-IgA1 production in IgA1-secreting cells from patients with IgAN, revealing a previously unknown role of Btk in aberrant O-glycosylation of IgA1. Btk may thus represent a potential new target for disease-specific therapy of IgAN.

#2389 Enhancing immunoglobulin A nephropathy management: insights from the IGAN-MIC project

Abstract Background and Aims Immunoglobulin A nephropathy (IgAN) comprises a substantial proportion of primary glomerulonephritis cases in China, yet comprehensive nationwide data regarding its diagnosis and treatment are lacking. The Immunoglobulin A Nephropathy Management Quality Improvement Initiative Project in China (IGAN-MIC) seeks to establish an IgAN cohort collaboration network to comprehend real-world IgAN management practices in China. Method The IGAN-MIC project convened 15 Chinese experts from 14 regions to form an expert committee to develop a registry of IgAN patients to evaluate regional differences in IgAN management from 2015 to 2024. The registry will involve comprehensive data collection from electronic medical records, encompassing key aspects including demographic and clinical characteristics, renal biopsies, diagnoses, comorbidities, laboratory findings, and treatment modalities, facilitating a detailed analysis of disease progression and changes in treatment strategies from initial diagnosis through subsequent follow-up periods. Results The IGAN-MIC project has garnered applications from 78 healthcare institutions, with 7 of them already incorporated into the initiative and initiated data collection. As of January 1, 2024, the project has enrolled 543 pathologically confirmed IgAN patients diagnosed between 2015 and 2023 from these 7 centers. At the time of diagnosis, the median (IQR) of age was 38.00 (30.00, 48.00) years; 54.51% were females; the median (IQR) of eGFR was 75.41 (51.93, 104.09) mL/min/1.73 m2 and the median (IQR) 24-hour urinary protein was 1263.50 (645.30, 2362.64) mg/day. For these patients, the utilization rates of RAS inhibitors (RASi), SGLT2 inhibitors (SGLT2i) and glucocorticoids at initial treatment were 53.41%, 3.51%, and 42.73% respectively. The utilization rate of SGLT2i from 2022 to 2023 was 9.90%, as the first indication for SGLT2i in CKD was approved in China in September 2022. A detailed outline of patient baseline characteristics is presented in Table 1 below. Conclusion These initial findings in the registry showed that the Chinese IgAN patients were young, had mildly reduced renal function, and with massive proteinuria at the time of initial diagnosis. For initial treatment, only half of the patients received RASi, and only one tenth received SGLT2i. More education needs to be focused on promoting guideline-directed medical therapies in the future. Given that nationwide data on Chinese IgAN patients are limited, the IGAN-MIC project is anticipated to broaden its registry to include more healthcare institutions and Chinese IgAN patients in the future, with the aim of providing a more in-depth understanding of the changing clinical presentations and ongoing follow-up scenarios among IgAN patients, contributing crucial insights to the clinical management of IgAN.

#260 Epidemiology of immunoglobulin A nephropathy (IgAN) in Germany

Abstract Background and Aims Immunoglobulin A nephropathy (IgAN) is a rare kidney disease characterized by proteinuria, persistent micro- or macrohematuria, and arterial hypertension. It can take a variety of courses from long-term minor symptoms to rapid progressive loss of kidney function with terminal renal failure. Epidemiological measures often refer to the proportion of IgAN among patients with glomerulonephritis instead of the entire population. Therefore, we estimated the prevalence and incidence of IgAN in Germany. Method Statutory health insurance (SHI) claims data from a large German database (InGef research database) with approximately four million insurees was retrospectively analyzed. The database represents about 5% of the German population and is representative of the German demographic and clinical structure in terms of age, gender, region, morbidity, mortality, and medication usage. As there is no specific IgAN code in ICD-10-GM and coding practices vary between physicians, two algorithms with different sets of codes were developed to estimate a lower and upper bound of the 1-year prevalence and incidence from 2017-2022. The lower bound considered specific diagnosis codes which usually rely on biopsies (N00.3, N02.3, N06.3). The upper bound included a broader field of specific and unspecific codes (N00.3, N02.3, N02.5, N02.7, N02.8, N02.9, N06.3, N06.8) that are potentially used by physicians to diagnose IgAN. Identified patients were described in terms of age and gender. Results were extrapolated to the German overall population, and a trend for the upcoming five years was estimated by applying the mean prevalence and incidence from the years 2017 to 2022 to the forecasted German population for the years 2023 to 2027. Results In 2022, the 1-year prevalence of IgAN ranged from 5 (lower bound) to 38 (upper bound) per 100 000 individuals in Germany. This corresponds to approximately 4 000 and 32 200 affected patients in Germany, respectively. There was no significant change from 2017 to 2022 with mean rates ranging from 4 (lower bound) to 38 (upper bound) per 100 000 individuals in Germany. The number of prevalent patients in Germany is expected to slowly increase in the coming years due to a forecasted increasing German overall population. About 57% of the prevalent IgAN patients in 2022 were male and the mean age was 59 years for the upper bound. For the lower bound about 73% of the prevalent IgAN patients in 2022 were male and the mean age was 53. The 1-year incidence of IgAN in 2022 ranged from 0.2 (lower bound) to 0.6 (upper bound) per 100 000 individuals in Germany. Extrapolation to the German population resulted in 164 to 538 newly diagnosed IgAN patients, respectively. Both the lower and the upper bound remained stable from 2017 to 2022 with slight fluctuations and a mean incidence rate of 0.2 (lower bound) and 0.6 (upper bound) per 100 000. The trend estimation showed steady numbers of incident patients in Germany until 2027 with a minor tendency towards an increase. About 86% (lower bound) and 83% (upper bound) of the incident IgAN patients in 2022 were male and the mean age was 36 years (lower bound) and 44 years (upper bound). Conclusion Estimating the epidemiology of IgAN is challenging as physicians use different ICD codes for diagnosis. To capture the uncertainty, an upper and lower bound of the prevalence and incidence were assessed as a minimum and maximum of patient numbers. Overall, IgAN was shown to be a rare disease with a prevalence of less than 50 per 100 000 in Germany. The upper bound of the incidence rate dropped in 2020 which may be associated with the onset of the global COVID-19 pandemic in March 2020, but the rate picked up in 2021 and the lower bound did not indicate an effect caused by the pandemic. Due to the forecasted rising population in Germany until 2027, the total number of prevalent and incident IgAN patient is expected to increase slowly.

#1258 Moderate-severe intrarenal arteriosclerosis and circulating GDF-15 levels may influence the cardiac-renal prognosis of IgAN patients

Abstract Background and Aims The cardiovascular risk among patients with IgA nephropathy (IgAN) is gradually garnering increased attention. The KDIGO guidelines explicitly emphasize the importance of evaluating cardiovascular risk in the management of IgAN patients and implementing appropriate interventions when necessary. The aim of this study was to investigate the risk factors affecting cardiac-renal prognosis in patients with IgAN. Method This is a retrospective study. A total of 353 IgAN patients with regular follow-up for at least 1 year at Beijing Anzhen Hospital were recruited. Patients were divided into group A (n = 85, yes) and group B (n = 268, no) according to the occurrence of cardio-renal composite endpoint events. Clinical and pathological characteristics of the two groups were compared and analyzed. The risk factors affecting the cardiac and renal prognosis in IgAN patients were analyzed by univariate and multivariate Cox models. In addition, serum GDF-15 of IgAN patients were detected. Results Approximately 14.7% (52/353) of IgAN patients presented with cardiovascular diseases at the time of renal biopsy. 55.8% (197/353) patients presented with hypertension. Prognostic analysis showed that hypertension (HR, 1.810; 95% confidence interval, 1.073 to 3.053; P = 0.026), 24-hour urinary protein (24 hUTP) (HR, 1.081; 95% confidence interval, 1.006 to 1.162; P = 0.033), eGFR (HR, 0.980; 95% confidence interval, 0.973 to 0.987; P&amp;lt;0.001), the presence of endocapillary proliferation (E1) (HR, 1.697; 95% confidence interval, 1.079 to 2.669; P = 0.022), tubular atrophy/interstitial fibrosis (T2) (HR, 3.757; 95% confidence interval, 1.959 to 7.203; P &amp;lt; 0.001), and moderate-severe intrarenal arteriosclerosis (HR, 3.320; 95% confidence interval, 1.289 to 8.548; P = 0.013) are independent risk factors affecting the cardiac-renal prognosis of IgAN. In IgAN patients with moderate-severe intrarenal arteriosclerosis, 24-hour urinary protein (24 hUTP) (HR, 1.131; 95% confidence interval, 1.014 to 1.261; P = 0.028), eGFR (HR, 0.982; 95% confidence interval, 0.971 to 0.993; P = 0.001) and E1 (HR, 2.583; 95% confidence interval, 1.379 to 4.841; P = 0.003) are independent risk factors affecting the cardiac-renal prognosis of IgAN patients. The serum GDF-15 level is positively correlated with 24 hUTP (r = 0.405, P &amp;lt; 0.001) and negatively correlated with eGFR (r = −0.606, P &amp;lt; 0.001). Compared with those with benign cardio-renal composite outcome, the serum level of GDF-15 in IgAN with poor cardio-renal composite outcome were significantly higher (1591.69 (1001.65, 2546.36) pg/ml vs 775.85 (546.82, 1310.29) pg/ml, P &amp;lt; 0.001). Conclusion The occurrence of cardiovascular diseases in patients with IgAN is frequently observed. In addition to the conventional risk factors associated with IgAN, including hypertension, initial proteinuria, eGFR, E1 and T2 lesion, moderate-severe intrarenal arteriosclerosis also contributes to the cardiac-renal prognosis of individuals with IgAN. In IgAN patients with moderate-severe intrarenal arteriosclerosis, Oxford-E lesion is an independent risk factor affecting the cardiac-renal prognosis of IgAN patients. This study suggested that the impairment of endothelial cells could potentially serve as a link between heart and kidney disease. The circulating levels of GDF-15 might contribute to the cardiac-renal prognosis of IgAN.

#2644 Clinical impact of proteinuria and hematuria remission criteria in IgA nephropathy patients defined by the Japanese Society of Nephrology

Abstract Background and Aims IgA nephropathy (IgAN) is one of the most common glomerulonephritis worldwide, especially in the Pacific Rim and Mediterranean countries. Hematuria is almost inevitable clinical findings and massive proteinuria is well established risk factor in IgAN. However, a few studies reported hematuria and proteinuria remission in IgAN, and their definition varies in clinical studies. The Japanese Society of Nephrology (JSN) defined new criteria for hematuria and proteinuria remission and relapse for IgAN patients. The objective of the present study was to analyze the utility of JSN criteria to predict renal prognosis among IgAN patients after immunosuppressive treatment. Method One hundred IgAN patients were recruited between 2003 and 2014 at Nagoya University Hospital and followed up until December 2017. According to JSN criteria, hematuria remission (HR) and proteinuria remission (PR) are defined as &amp;lt; 5 RBC/HPF, and &amp;lt; 0.3 g/g Cr, in three consecutive urine exams over six months of observation, respectively. Clinical remission (CR) is defined as both HR and PR in 3 consecutive urinalysis over six months. HR, PR and CR were analysed with 30% eGFR decline as a renal outcome. Results Baseline proteinuria, serum creatinine, and eGFR were 1.3g/day, 0.8 mg/dL, and 80 mL/min/1.73 m2. The mean age was 34.7 ± 12.5 years old, and 61% of the study population was female. Seventy-two percent of patients received intensive methylprednisolone pulse therapy (mPSL), and the incidence of HR, PR and CR were 76, 50 and 46%, 50%, respectively. Kaplan-Meier curves analyses showed a significant difference between HR and non-HR, PR and non-PR, and CR and non-CR groups (Fig.). In univariate analyses, hypertension, eGFR, HR, PR, CR, and T-score in the Oxford classification of IgAN were significantly associated with renal outcome. In multivariate Model-A, HR, and PR were significant factors for renal outcome after adjusting with sex, hypertension, eGFR and T-score. While in multivariate model-B, CR was also significantly associated with renal outcome after adjustment (Table). However, 36% and 46% of patients demonstrated hematuria and proteinuria relapses after remission. Conclusion JSN novel criteria for HR and PR predict renal outcomes in IgAN patients. Further studies are required to verify their clinical utility of JSN criteria in a larger sample size with different ethnicities.

#1422 Exploring BAFF, APRIL, and clinical characteristics in IgA nephropathy: a decade-long study in the Bulgarian population

Abstract Background and Aims IgA nephropathy (IgAN) represents a significant global health concern, contributing substantially to chronic kidney disease and renal failure. Despite its widespread impact, the Bulgarian population lacks comprehensive epidemiological data and specific biomarkers for IgAN. This decade-long retrospective study, conducted at a tertiary Nephrology Clinic in Bulgaria, aims to explore the clinical characteristics and serum levels of BAFF and APRIL in biopsy-confirmed IgAN patients and healthy controls. Method The study includes 125 biopsy-confirmed IgAN patients and 30 healthy controls. Notably, 70.4% of IgAN patients were male, with an average age of 35.94 ± 11.91 years. Baseline characteristics reveal advanced disease stages at diagnosis, possibly linked to delayed biopsy (24.22 ± 32.9 months from initial symptoms) and the absence of a screening program. Analyses of serum biomarkers (C3, BAFF, and APRIL) are conducted to identify any significant variations between IgAN patients and healthy volunteers. Results The average baseline estimated glomerular filtration rate (eGFR) was 61.78 ± 27.72 ml/min/1.73 m², with a mean serum creatinine of 126 ± 67.83 μmol/l at the time of kidney biopsy. Among the patients, 51.2% had an eGFR below 60 ml/min, indicating CKD stage 3 or worse according to the KDIGO classification Binary logistic regression analysis identifies anemia as a significant contributor to disease progression, with a risk influence approximately 3.3 times higher for GFR decline over time. Anemia emerges as a crucial predictor for serum creatinine doubling, carrying a higher risk than hyperuricemia. Analyses of C3 (p = 0.658), BAFF (p = 0.432), and APRIL (p = 0.227), demonstrated no significant differences in their serum levels between IgAN patients and healthy volunteers. Conclusion This study provides comprehensive insights into IgAN in the Bulgarian population, addressing the dearth of epidemiological data and biomarkers. Anemia emerges as a significant predictor for disease progression, emphasizing its potential clinical relevance. However, C3, BAFF, and APRIL exhibit no notable variations, underscoring the need for additional biomarker exploration to enhance understanding of IgAN dynamics in this population.

#1940 Plasma complement activation profile in kidney transplant recipients with IgAN supports the importance of the complement alternative pathway in IgAN

Abstract Background and Aims The alternative complement and lectin pathways are key players in IgA nephropathy (IgAN). However, the precise dynamics of complement activation in IgAN remain poorly understood. Non-invasive complement biomarkers are urgently needed in view of the evolving landscape of complement-targeting therapies under evaluation in IgAN. Method We analyzed plasma complement activation biomarkers in a cohort of 87 kidney transplant recipients (KTR) with IgAN and 30 controls consisting of autosomal dominant polycystic kidney disease (ADPKD) KTR (NCT05234463, DC-2013-1990). Patients were excluded if 1) they had a biological inflammatory syndrome at the time of sampling or 2) they had experienced a cellular/humoral rejection in the year prior to or after sampling. We simultaneously measured a large panel of complement activation and regulation fragments (C3a, C5a, C4a, sC5b-9, Ba, Bb) and intact proteins (C3, C4, FI, FH, properdin) in plasma using multiplex ELISA (Quidel Ortho®, A900), nephelometry and in-house ELISA. Results There was no consumption of C3 and C4 proteins in IgAN patients. However, C3a and Bb concentrations were elevated in IgAN patients compared to ADPKD patients (161 [98-227] vs. 102 [66-172] ng/mL, p = 0.007; 3.0 [2.6-4.0] vs. 2.5 [2.0-2.8] µg/mL, p &amp;lt; 0.0001). Overall, 70/87 IgAN patients (80.5%) had elevated Bb levels. The plasma concentration of C5a was elevated in IgAN patients compared to ADPKD patients (6.3 [3.8-9.2] vs. 4.9 [2.8-6.3] ng/mL, p = 0.0274), with values within the reference range in 92.0% of IgAN patients. There was no difference in plasma levels of sC5b-9 between the two groups (p = 0.186). The combined analysis of C3a, C5a and sC5b-9 allowed us to distinguish 4 clusters of patients (Fig. 1). A total of 48 patients (55.2%) show evidence of C3 convertase activity in plasma (clusters 3 and 4), including 16 patients (18.4%) with the highest plasma concentrations of sC5b-9, C3a and Bb. In contrast, 15 patients (17.2%, cluster 1) have no (or very low) complement activation. The last group (n = 32, 36.8%, cluster 2) shows an isolated increase in sC5b-9 without evidence of plasma C3 convertase activity. Proteinuria was significantly increased in groups 3 and 4, which had the highest C3a concentrations, compared to groups 1 and 2 (p = 0.0051). Conclusion This study provides insights into the mechanisms of complement activation in IgAN, with a pivotal role for the activity and regulation of the alternative C3 pathway convertase. In addition, the combined analysis of complement biomarkers identified, for the first time, clusters of patients who may benefit from complement targeting therapies.