IgAN Patients Research Articles

IgA nephropathy recurrence after living donor kidney transplantation: a retrospective analysis of postoperative outcomes at a single high-volume transplant center

BackgroundIgA nephropathy (IgAN) is a common primary glomerulonephritis leading to end-stage renal disease. Living donor kidney transplantation (LDKT) is considered a favorable treatment option, but IgAN recurrence rates and the impact on outcome is unclear. In the present study, we retrospectively analyzed the rate of IgAN recurrence, risk factors and clinical outcomes in LDKT recipients.MethodsWe analyzed 193 adult patients who received a LDKT between 2011 and 2017 of which 32 (16.7%) had IgAN as underlying disease. Demographic data and clinical outcomes, especially regarding IgAN recurrence, were evaluated. Mean follow-up period was 102.13 months in the IgAN group vs. 97.27 months in the control group.ResultsAmong the IgAN cohort, five (15.63%) experienced IgAN recurrence. Patients with IgAN underwent LDKT at a significantly younger age (p < 0.001). No significant differences were observed in demographic factors, HLA-mismatches, or AB0-compatibility. Patients receiving an immunosuppressive regimen including Cyclosporine A (60% vs. 7.4%) instead of Tacrolimus (40% vs. 92.6%) were significantly more likely to develop IgAN recurrences (p < 0.001). Moreover, early post-surgery serum creatinine levels were higher in the recurrence group at one week (4.25 vs. 1.65 mg/dl; p < 0.001), one month (2.13 vs. 1.53 mg/dl; p = 0.027) and two years (2.65 vs. 1.34 mg/dl; p = 0.008). Although graft survival displayed a tendency towards inferior outcomes after recurrence, significance was not reached (p = 0.14, log-rank test).ConclusionLiving donor kidney transplantation continues to be recommended as the preferred treatment option for IgAN patients, despite the potential risk of recurrence and graft loss.

#2837 Novel therapeutic for crescentic glomerulonephritis through targeting CLDN1 in parietal epithelial cells

Abstract Background and Aims Crescentic glomerulonephritis (CrGN) is the final mode of kidney injury common to several immune-mediated kidney diseases. CrGN is characterized by extensive glomerular parietal epithelial cells (PECs) proliferation forming crescents. The destructive crescent is then progressively replaced by fibrosis. Currents therapies for CrGN do not directly target the deleterious response of resident kidney cells. In a pathological context, claudin-1 (CLDN1), a transmembrane protein involved in epithelial tight junctions, can be exposed outside the tight junctions and mediate pro-fibrotic pathways and extracellular matrix (ECM) remodelling. Lixudebart (formerly ALE.F02) is a first-in-class monoclonal antibody that specifically targets and blocks exposed CLDN1 in injured epithelial cells. A phase II clinical trial is under way for patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV) with rapidly progressive glomerulonephritis which induces kidney fibrosis (RENAL-F02, NCT06047171). CLDN1 is highly expressed by glomerular PECs. This study investigated the functional role of CLDN1 in CrGN and the potential benefit to target CLDN1 in CrGN. Method CLDN1 expression in renal tissues of CrGN patients was analyzed using kidney multicolor immunofluorescence staining and spatial transcriptomics. Correlation between CLDN1 expression and clinical endpoints (eGFR, proteinuria), disease biomarkers and crescent evolution were studied. A spatially resolved molecular roadmap from CLDN1+ crescentic glomeruli was conducted. Proof-of-concept studies using anti-CLDN1 mAb were performed in preclinical models of CrGN. Results In tissues (n = 150) of patients with AAV and IgAN, multicolor immunofluorescence revealed up-regulated CLDN1 expression by cellular and fibrocellular crescents. At the time of diagnostic kidney biopsy, glomerular CLDN-1 expression was correlated with podocyte loss (as measured with P57 staining) and fibronectin area. The extent of dual expression of CLDN1 and CD44 at the surface of active PECs was associated with poor renal outcome (eGFR &amp;lt; 30 ml/min) in AAV and IgAN patients with a median follow-up of 2.5 and 3.7 years respectively. Spatial transcriptomics analysis highlighted the association between CLDN1+ crescentic glomeruli and ECM genes. Treatment with anti-CLDN1 mAb reduced albuminuria, improved kidney function and decreased fibrosis biomarkers in nephrotoxic serum-induced CrGN in mice. Conclusion Our results suggest a functional role of CLDN1 in the pathogenesis of CrGN, providing preclinical proof-of-concept for anti-CLDN1 antibodies as a novel therapeutic approach in patients with CrGN.

#1464 Alterations of podocytes in focal segmental glomerulosclerosis: a pilot study

Abstract Background and Aims The molecular features of idiopathic podocytopathies remain unexplored, preventing the development of effective therapies to control the mechanisms of disease initiation and progression. This includes idiopathic focal segmental glomerulosclerosis (FSGS), one of the most common forms of immune glomerulopathies (IG) and the cause of renal failure and replacement therapy. In FSGS, podocytes undergo pronounced cytoskeletal alterations. Along with a decrease in Wilms tumor protein (WT1) and α-SMA expression, there is evidence for increased expression of intermediate filament proteins (vimentin, desmin, nestin) and Wnt/β-catenin signaling upregulation in IG. Decrease in WT1 is associated with upregulation in Wnt/β-catenin and p53 to promote podocyte dysfunction and albuminuria. Upregulation desmin increases the mechanical stability of cells, allowing podocytes to undergo morphological changes on the tensile glomerular capillary wall. This pilot study was aimed to evaluate the significance of WT1, β-catenin, and desmin glomerular expression in early primary FSGS. Method We reviewed the histopathological and clinical data of patients with biopsy proven FSGS (N = 14, experimental group), IgA nephropathy (N = 12, positive control), without AKI, infectious diseases, heart failure, respiratory insufficiency and cancer pathology. Renal surgery specimens from patients without IG (N = 12) were studied as negative control. Glomerulosclerosis was assessed as percentage of all glomeruli. Mesangial lesions were measured semi-quantitatively in scores (0-3). Glomerular WT1, β-catenin, and desmin expression was assessed by IHC-P with quantitative morphometry of IHC-staining area (open software QuPath, Orbit Image Analysis). Molecule's co-expression was analyzed by IF-p and confocal microscopy (Zeiss LSM 710; study conducted in the Center for Collective Use “Confocal microscopy” by Pavlov Institute of Physiology Russian Academy of Sciences). Results We examined young and middle-aged patients with CKD stages 1-3 and moderate morphological changes in the glomeruli. Gender, age, eGFR and the percentage of glomeruli with segmental sclerosis were not significantly different between IG groups (all p for interaction &amp;gt;0.05). Patients with FSGS have lower levels of serum albumin (p &amp;lt; 0.001) and higher levels of proteinuria (p &amp;lt; 0.001) as compared to IgAN. Glomeruli from IgAN patients showed more mesangial cell proliferation (p = 0.001), expansion of the mesangial matrix (p = 0.05) and global glomerular sclerosis (p = 0.003) as compared to FSGS. An immunomorphological study showed lower WT1 expression in both IG groups compared to the negative control. In the IgAN, lower WT1 expression was associated with higher BC area (Fig. 1A, D). BC expression did not differ between FSGS and negative control (Fig. 1B,D). In the combined IG group, BC directly correlated with global (r = 0.63, p = 0.001) and segmental (r = 0.63, p = 0.001) glomerular sclerosis. In FSGS, a trend towards to increase in the area of desmin IHC-staining was detected, however, no significant differences between groups were found (Fig. 1C,D). BC and desmin were co-localized with the podocyte marker WT1 (Fig. 2). BC and desmin were also expressed in WT1-negative glomerular cells (Fig. 2). Differential molecular expression patterns in glomeruli have been identified. In IgAN, co-expressing WT1 and BC (orange) was dominate in glomerular cells (Fig. 2A); the proportion of IHC expression of WT1 and BC in glomerular cells was directly correlated (r = 0.63, p = 0.031). In FSGS, WT1+ cells predominantly co-expressed desmin (magenta) but not BC; some glomerular cells were only desmin-positive (Fig. 2B). BC was expressed to a lesser extent compared to IgAN, and in some cells it was co-expressed with desmin (Fig. 2B). Conclusion In FSGS, an increase in desmin expression could be an early feature of pathogenesis before significant decrease in the number of WT1+ podocytes and changes in β-catenin expression. Activation of desmin likely characterizes damage and decrease in the number of functioning podocytes.

External Validation of the International IgA Nephropathy Prediction Tool in Older Adult Patients.

The International IgA Nephropathy Prediction Tool (IIgAN-PT) can predict the risk of End-stage renal disease (ESRD) or estimated glomerular filtration rate (eGFR) decline ≥ 50% for adult IgAN patients. Considering the differential progression between older adult and adult patients, this study aims to externally validate its performance in the older adult cohort. We analyzed 165 IgAN patients aged 60 and above from six medical centers, categorizing them by their predicted risk. The primary outcome was a ≥50% reduction in estimated glomerular filtration rate (eGFR) or kidney failure. Evaluation of both models involved concordance statistics (C-statistics), time-dependent receiver operating characteristic (ROC) curves, Kaplan-Meier survival curves, and calibration plots. Comparative reclassification was conducted using net reclassification improvement (NRI) and integrated discrimination improvement (IDI). The study included 165 Chinese patients (median age 64, 60% male), with a median follow-up of 5.1 years. Of these, 21% reached the primary outcome. Both models with or without race demonstrated good discrimination (C-statistics 0.788 and 0.790, respectively). Survival curves for risk groups were well-separated. The full model without race more accurately predicted 5-year risks, whereas the full model with race tended to overestimate risks after 3 years. No significant reclassification improvement was noted in the full model without race (NRI 0.09, 95% CI: -0.27 to 0.34; IDI 0.003, 95% CI: -0.009 to 0.019). : Both models exhibited excellent discrimination among older adult IgAN patients. The full model without race demonstrated superior calibration in predicting the 5-year risk.

Identifying functional subtypes of IgA nephropathy based on three machine learning algorithms and WGCNA

BackgroundIgA nephropathy (IgAN) is one of the most common primary glomerulonephritis, which is a significant cause of renal failure. At present, the classification of IgAN is often limited to pathology, and its molecular mechanism has not been established. Therefore we aim to identify subtypes of IgAN at the molecular level and explore the heterogeneity of subtypes in terms of immune cell infiltration, functional level.MethodsTwo microarray datasets (GSE116626 and GSE115857) were downloaded from GEO. Differential expression genes (DEGs) for IgAN were screened with limma. Three unsupervised clustering algorithms (hclust, PAM, and ConsensusClusterPlus) were combined to develop a single-sample subtype random forest classifier (SSRC). Functional subtypes of IgAN were defined based on functional analysis and current IgAN findings. Then the correlation between IgAN subtypes and clinical features such as eGFR and proteinuria was evaluated by using Pearson method. Subsequently, subtype heterogeneity was verified by subtype-specific modules identification based on weighted gene co-expression network analysis(WGCNA) and immune cell infiltration analysis based on CIBERSORT algorithm.ResultsWe identified 102 DEGs as marker genes for IgAN and three functional subtypes namely: viral-hormonal, bacterial-immune and mixed type. We screened seventeen genes specific to viral hormonal type (ATF3, JUN and FOS etc.), and seven genes specific to bacterial immune type (LIF, C19orf51 and SLPI etc.). The subtype-specific genes showed significantly high correlation with proteinuria and eGFR. The WGCNA modules were in keeping with functions of the IgAN subtypes where the MEcyan module was specific to the viral-hormonal type and the MElightgreen module was specific to the bacterial-immune type. The results of immune cell infiltration revealed subtype-specific cell heterogeneity which included significant differences in T follicular helper cells, resting NK cells between viral-hormone type and control group; significant differences in eosinophils, monocytes, macrophages, mast cells and other cells between bacterial-immune type and control.ConclusionIn this study, we identified three functional subtypes of IgAN for the first time and specific expressed genes for each subtype. Then we constructed a subtype classifier and classify IgAN patients into specific subtypes, which may be benefit for the precise treatment of IgAN patients in future.

Combined Effects of the Serum IgA/C3 Ratio and Glomerular C3 Staining on the Renal Outcome in Adult Immunoglobulin A Nephropathy

Introduction: The aim of this study was to evaluate the predictive value of the serum IgA/C3 ratio and glomerular C3 deposits in kidney biopsy in adult IgA nephropathy. Methods: The study included 718 adult IgAN patients diagnosed based on kidney biopsy. Patients without corticosteroids or immunosuppressive drugs >1 month were regularly followed up for at least 1 year or until the study endpoint. The optimum serum IgA/C3 ratio was calculated by the AUROC-based cutoff ratio. Proteinuria, creatinine, eGFR, serum IgA, and serum C3 were evaluated at baseline. Kidney biopsy was categorized using the Oxford classification, with a calculation of the MEST-C score. The degree of glomerular C3 staining was semiquantitatively determined (grade 0, no or trace; grade 1, mild; grade 2, moderate; grade 3, marked) by immunofluorescence microscopy. The patients were divided into four groups by the serum IgA/C3 ratio and glomerular C3 staining. Results: The baseline data suggested that when the serum IgA/C3 ratio was at the same level, patients with a high glomerular C3 staining score (≥2) always had mesangial proliferation, segmental glomerulosclerosis, and tubular atrophy/interstitial fibrosis (group 1 vs. group 2; group 3 vs. group 4). When glomerular C3 staining was at the same level, proteinuria was significantly higher in patients with serum IgA/C3<2.806 (group 1 vs. group 3; group 2 vs. group 4), which was contrary to previous studies that have suggested that the serum level of IgA/C3 was associated with disease severity. Hence, this study set out to investigate the combined effects of the serum IgA/C3 ratio and glomerular C3 staining on the renal outcome in adult IgA nephropathy. Renal survival analysis indicated that serum IgA/C3 ≥2.806 and glomerular C3 staining ≥2 (group 1) may be correlated with a poorer prognosis, especially in different clinicopathological characteristics of IgAN patients based on the subgroup analysis. Multivariate Cox analysis demonstrated that hypertension, serum creatinine, CKD stage, T1/2 and C3 staining were independent predictive factors of renal survival. Conclusions: The combination of serum IgA/C3 and C3 staining may contribute to improved optimization of the prognostic model in IgAN patients, especially patients with different sexes and degrees of disease. However, further study is required for validation in the future.

Corticosteroid in IgA nephropathy with moderate proteinuria: A retrospective cohort study.

Corticosteroids remain contentious as a therapeutic option for IgA nephropathy. We conducted a retrospective cohort study to explore whether corticosteroid therapy is efficient and safe for IgAN patients with moderate proteinuria. A total of 336 patients with renal biopsy-confirmed IgAN, estimated glomerular filtration (eGFR) over 15 mL/min/1.73 m2 and urine protein levels of 0.75-3.5 g/d were enrolled. According to the treatment protocol, we classified the enrolled patients into two groups: one receiving corticosteroids and the other receiving supportive care. Complete remission, partial remission, and no remission were applied to describe the efficacy assessments. The endpoint was defined as a 40% reduction in eGFR, the onset of ESRD, or renal disease-related death. Clinical and pathological progression risk factors were higher in corticosteroid-treated individuals. Logistic regression analysis revealed that the corticosteroid group was considerably related to a higher remission rate after adjustment for confounding factors. The occurrence of serious adverse events between the two groups was not found to be statistically significantly different. Then, we matched 95 couples of patients with similar baseline levels in both groups by propensity score matching. The results showed that corticosteroid-treated patients showed higher overall and complete remission rates than untreated patients. However, due to the relatively short follow-up period, no significant differences in the incidence of endpoint and survival analyses have been observed thus far. Corticosteroid therapy may benefit IgAN patients with moderate proteinuria via proteinuria reduction and renal function preservation.

Effectiveness and Safety of Spironolactone in the Treatment of IgA Nephropathy: A Retrospective Self-Controlled Study.

It is crucial to utilize combination therapy for immunoglobulin A nephropathy (IgAN) patients to reduce proteinuria and maintain stable kidney function. We demonstrate the safety and efficacy of low-dose spironolactone in the management of IgAN patients. Adult IgAN patients treated with spironolactone were evaluated. Patients were separated into two categories according to whether 24-h proteinuria was reduced by more than 20% after 2 months of spironolactone treatment compared to baseline levels. Eighty-eight patients were analyzed and 24-h proteinuria decreased from 0.93 g to 0.70 g (p &lt; 0.001) after 2 months of treatment with spironolactone, accompanied by a slight decrease in eGFR from 75.7 to 73.9 mL/min/1.73 m2 (p = 0.033). Intriguingly, 47 patients in the effective mineralocorticoid receptor antagonist (MRA) group showed less endocapillary hypercellularity (p = 0.040). In the ineffective group, 18 patients discontinued MRA treatment because 24-h proteinuria increased from 0.83 g to 1.04 g, while the other 23 patients continued with spironolactone and proteinuria decreased to 0.57 g in the sixth month (p = 0.001). Furthermore, 12 patients with persistent high proteinuria during prednisone therapy were added with spironolactone. 24-proteinuria was dropped from 0.95 g to 0.73 g at the second month and to 0.50 g at the sixth month. In our study, we confirmed spironolactone's efficacy in reducing urine protein excretion in IgA nephropathy patients within 2 months of treatment. However, response varied among patients, with those showing endocapillary proliferation (E1) in renal biopsies having poor spironolactone responsiveness. Administering MRAs to patients with eGFR over 30 mL/min did not result in hyperkalemia, indicating the treatment's safety.

The effect of fibrinoid necrosis on the clinical features and outcomes of primary IgA nephropathy

BackgroundTo explore the clinicopathologic features and outcomes of IgAN patients who presented with fibrinoid necrosis (FN) lesions or not and the effect of immunosuppressive (IS) treatment in IgAN patients with FN lesions as well.MethodsThis was a retrospective cohort study with 665 patients diagnosed with primary IgAN from January 2010 to December 2020 in Tianjin Medical University General Hospital and having detailed baseline and follow-up characteristics. Patients were divided into two groups depending on the appearance of FN lesions. Patients with FN lesions were recruited into Group FN1, while patients who were not found FN lesions in their renal biopsy specimens were recruited into Group FN0. Compare the differences between Group FN0 and Group FN1 in baseline clinicopathologic features, treatment solutions and follow-up data as well. To evaluate the impact of different fractions of FN lesions on baseline characteristics and prognosis of IgAN, we subdivided patients in Group FN1 into 3 groups depending on the FN lesions distribution, Mild Group: 0 < FN% < 1/16; Moderate Group: 1/16 < FN% < 1/10; Severe Group: FN% > 1/10. Furthermore, we compared the differences in baseline clinicopathologic features, treatment solutions and follow-up data among these three groups. Kidney endpoint event was defined as patients went into end-stage kidney disease (ESKD), which estimated glomerular filtration rate (eGFR) < 15 ml/min/1.73 m^2, regularly chronic dialysis over 6 months or received renal transplantation surgery. The kidney composite endpoint was defined by a ≥ 30% reduction in eGFR, double Scr increase than on-set, ESKD, chronic dialysis over 6 months or renal transplantation. Compare the survival from a composite endpoint rate in different groups by Kaplan-Meier survival curve. The univariate and multivariate Cox models were used to establish the basic model for renal outcomes in patients with FN lesions.Results(1) A total of 230 patients (34.59%) were found FN lesions in all participants. Patients with FN lesions suffered more severe hematuria than those without. On the hand of pathological characteristic, patients with FN lesions showed higher proportions of M1, E1, C1/C2 and T1/T2 lesions compared with those without FN lesions. (2) The 1-year, 3-year, and 5-year survival of the composite endpoint were lower in the FN1 group than FN0 group. (3) After adjusting for clinicopathological variables, the presence of FN lesions was a significantly independent risk factor for composite endpoint. By using multivariate Cox regression analyses, we also found when the fraction of FN lesions exceeded 10%, the risk of progression into composite endpoint increased 3.927 times.ConclusionFibrinoid necrosis of capillary loops is an independent risk factor of poor renal outcomes. More effective treatment should be considered for those who had FN lesions.

Prognostic factors affecting long-term outcomes in patients with concurrent IgA nephropathy and membranous nephropathy

BackgroundThe incidence of concurrent immunoglobulin A nephropathy and membranous nephropathy (cIgAN/MN) is low and rarely reported, and the prognosis of patients with cIgAN/MN remains unclear. This study was designed to compare the clinical and prognostic characteristics of cIgAN/MN with IgAN and MN and to identify crucial factors influencing the outcomes of patients with cIgAN/MN. MethodsWe included biopsy-proven cIgAN/MN patients between December 2012 and December 2020 at Xijing Hospital. In the same period, propensity score matching was employed to select an equal number of IgAN and MN patients according to the following criteria: age, sex, and follow-up time. The primary endpoint was defined as a composite of eGFR decline ≥30 %, end-stage renal disease, or death. The patient survival rate was examined using Kaplan–Meier survival curves. Univariate and multivariate Cox regression analysis models were utilized to identify the risk factors affecting renal prognosis. ResultsA total of 135 patients were finally included in this study and 35 (25.9 %) reached the primary endpoint. The median follow-up time of cIgAN/MN was 45.9 (24.0, 72.0) months. Compared to the IgAN group, the cIgAN/MN group exhibited a lower cumulative incidence rate of composite renal endpoints (P = 0.044), while no significant difference was found between MN and cIgAN/MN patients (P = 0.211). Univariate Cox analysis revealed that mean arterial pressure, serum potassium, blood urea nitrogen, serum IgA, segmental glomerulosclerosis (S1), and MN staging were associated with an increased risk of renal composite endpoints. The multivariate Cox regression analysis of clinical variables plus histological lesion scoring demonstrated that potassium (HR = 14.350, 95 % CI 2.637–78.090, P = 0.002), serum IgA (HR = 1.870, 95 % CI 1.109–3.153, P = 0.019), and S1 (HR = 11.965, 95 % CI 2.166–66.105, P = 0.004) were independent risk factors influencing renal outcomes in cIgAN/MN patients. ConclusionThe prognosis of cIgAN/MN patients may exhibit an intermediate pattern between IgAN and MN, leaning towards being more similar to MN in certain aspects. Within the cIgAN/MN cohort, potassium, and serum IgA may be more predictive of rapid progression of renal endpoints, and S1 may indicate a more aggressive disease course.

Relationship between arterial stiffness, left ventricular diastolic function, and renal function in chronic kidney disease

AimIn chronic kidney disease, IgA nephropathy, and left ventricular diastolic dysfunction have prognostic significance as well. However, the relationship between diastolic dysfunction, arterial stiffness, and renal function has not been fully elucidated.Methods79 IgA nephropathy patients (aged 46 ± 11 years) and 50 controls were investigated. Tissue Doppler imaging was used to measure early (Ea) and late (Aa) diastolic velocities. Arterial stiffness was measured by a photoplethysmographic (stiffness index (SI)) and an oscillometric method (aortic pulse wave velocity (PWVao)).ResultsWe compared the IgAN patients to a similar cardiovascular risk group with a preserved eGFR. A strong correlation was found between Ea/Aa and SI (p < 0.001), also with PWVao (p < 0.001), just in IgAN, and with eGFR (p < 0.001) in both groups. IgAN patients were divided into groups CKD1-2 vs. CKD3-5. In the CKD 3–5 group, the incidence of diastolic dysfunction increased significantly: 39% vs. 72% (p = 0.003). Left ventricle rigidity (LVR) was calculated, which showed a close correlation with SI (p = 0.009) and eGFR (p = 0.038). By linear regression analysis, the independent predictors of SI were age, E/A, and E/Ea; SI was the predictor of LVR; and E/A and hypertension were the predictors of eGFR.ConclusionIn chronic kidney disease, increased cardiac rigidity and vascular stiffness coexist with decreased renal function, which is directly connected to diastolic dysfunction and vascular stiffness. On the basis of comparing the CKD group to the control group, vascular alterations in very early CKD can be identified.

Clinical and pathological characteristics in elderly patients with IgA nephropathy.

Immunoglobulin A nephropathy (IgAN) is the most common cause of primary glomerulonephritis, with highly variable manifestations. Although the peak incidence of IgAN is in young adults, the diagnosis among elderly people is increasing. Here we explored the effect of aging on IgAN features, as well as cellular senescence in the kidney of IgAN. A total of 910 patients with IgAN were enrolled, which contained 182 individuals in each age stage (aged ≥60, 50-59, 40-49, 30-39 and 20-29 years). Clinical and pathological manifestations at the time of renal biopsy were compared. Additionally, 38 patients with IgAN (19 aged over or equal to 60 years and 19 aged below 60 years) were randomly selected for p16INK4a staining by immunohistochemistry. The percentage of p16INK4a-positive cells in glomeruli, renal tubule and interstitium were separately quantified. Compared with young IgAN patients, elderly patients presented with higher levels of circulating IgA, uric acid and proteinuria, but lower estimated glomerular filtration rates (eGFR), as well as lower red blood cell counts, platelet counts and lymphocyte counts. Moreover, elderly IgAN patients showed higher incidence of hypertension, and lower incidence of prodromic infection. Regarding histological lesions in the kidney, young IgAN patients had higher degree of IgA and C3 deposits, while elderly IgAN patients had more severe Oxford-E lesions, but less severe Oxford-S lesions. The percentage of glomerular and tubular p16INK4a-positive cells in elderly patients showed an increasing trend, but statistical significance was not reached. The percentage of p16INK4a-positive nuclei in renal interstitium was positively associated with T score, while increased percentage of p16INK4a-positive nuclei in renal tubule was associated with eGFR and 24-h urinary protein level. In our IgAN cohort, elderly IgAN patients presented with some aging-related features, and both aging- and IgAN-induced pathological injury contributed to the kidney lesions in patients with IgAN.

T Follicular Helper Cells in Tertiary Lymphoid Structure Contribute to Renal Fibrosis by IL-21.

Tertiary lymphoid structure (TLS) represents lymphocyte clusters in non-lymphoid organs. The formation and maintenance of TLS are dependent on follicular helper T (TFH) cells. However, the role of TFH cells during renal TLS formation and the renal fibrotic process has not been comprehensively elucidated in chronic kidney disease. Here, we detected the circulating TFH cells from 57 IgAN patients and found that the frequency of TFH cells was increased in IgA nephropathy patients with renal TLS and also increased in renal tissues from the ischemic-reperfusion-injury (IRI)-induced TLS model. The inducible T-cell co-stimulator (ICOS) is one of the surface marker molecules of TFH. Remarkably, the application of an ICOS-neutralizing antibody effectively prevented the upregulation of TFH cells and expression of its canonical functional mediator IL-21, and also reduced renal TLS formation and renal fibrosis in IRI mice in vivo. In the study of this mechanism, we found that recombinant IL-21 could directly promote renal fibrosis and the expression of p65. Furthermore, BAY 11-7085, a p65 selective inhibitor, could effectively alleviate the profibrotic effect induced by IL-21 stimulation. Our results together suggested that TFH cells contribute to TLS formation and renal fibrosis by IL-21. Targeting the ICOS-signaling pathway network could reduce TFH cell infiltration and alleviate renal fibrosis.

Elevated levels of IL-6 in IgA nephropathy patients are induced by an epigenetically driven mechanism modulated by viral and bacterial RNA

BackgroundImmunoglobulin A nephropathy (IgAN) is the most frequent primary glomerulonephritis and the role of IL-6 in pathogenesis is becoming increasingly important. A recent whole genome DNA methylation screening in IgAN patients identified a hypermethylated region comprising the non-coding RNA Vault RNA 2–1 (VTRNA2–1) that could explain the high IL-6 levels. MethodsThe pathway leading to IL-6 secretion controlled by VTRNA2–1, PKR, and CREB was analyzed in peripheral blood mononuclear cells (PBMCs) isolated from healthy subjects (HS), IgAN patients, transplanted patients with or without IgAN. The role of double and single-strand RNA in controlling the pathway was investigated. ResultsVTRNA2–1 was downregulated in IgAN compared to HS and in transplanted IgAN patients (TP-IgAN) compared to non-IgAN transplanted (TP). The loss of the VTRNA2–1 natural restrain in IgAN patients caused PKR hyperphosphorylation, and consequently the activation of CREB by PKR, which, in turn, led to high IL-6 production, both in IgAN and in TP-IgAN patients. IL-6 levels could be decreased by the PKR inhibitor imoxin. In addition, PKR is normally activated by bacterial and viral RNA, and we found that both the RNA poly(I:C), and the COVID-19 RNA-vaccine stimulation significantly increased the IL-6 levels in PBMCs from HS but had an opposite effect in those from IgAN patients. ConclusionThe discovery of the upregulated VTRNA2–1/PKR/CREB/IL-6 pathway in IgAN patients may provide a novel approach to treating the disease and may be useful for the development of precision nephrology and personalized therapy by checking the VTRNA2–1 methylation level in IgAN patients.

#3764 SINGLE-CELL RNA-SEQ REVEALS IMMUNE AND KIDNEY CELL TYPE–SPECIFIC MOLECULAR ASSOCIATIONS TO IGA NEPHROPATHY

Abstract Background and Aims IgA nephropathy is the most common primary glomerulonephritis worldwide. There is growing evidence of host immunity is closely related to the pathogenesis of IgAN, but the detailed mechanism in the early stages of IgAN remain largely unknown. In this study, we applied single-cell RNA-seq technology to investigate the transcriptomic changes in PBMCs and kidney tissues of early stage IgAN patients at the single-cell resolution. This study aims to establish a immune and kidney cell landscape of IgAN, and offers new insights for the diagnosis and treatment of IgAN. Method In strict accordance to the admission criteria, collect peripheral venous blood and kidney samples of healthy donors and newly diagnosed IgAN patients, prepare single cell solution, verify cell viability by flow cytometry, and perform single-cell RNA-seq using a BD Rhapsody platform. Meanwhile, the clinical data of healthy donors and IgAN patients were collected and analysed. Finally, the correlation and association of differential expressed genes (DEGs) and cell clusters-identified by single-cell RNA-seq with the clinical data of IgAN were investigated. Results First, we established immune cells and kidney cells landscape of IgAN. The differentially expressed genes (DEGs) between the control group and IgAN were mainly concentrated in the NK cell-mediated cytotoxicity and cell killing pathways. Interestingly, we found significant decreases in NK cell numbers and cytotoxicity, and NK cell numbers and marker genes were negatively correlated with clinical parameters, including urinary protein creatinine ratio (UPCR) and serum galactose-deficient IgA1 and IgA. In contrast, B cell DEGs were enriched in different viral infection pathways, and one specific B cell subgroup showed inhibition of NFκB signaling, which was positively correlated with clinical parameters. In addition, a subpopulation of monocytes expressing interferon-inducing genes was positively associated with clinical severity of IgAN. In case of the kidney tissue, compared with the control group, mesangial cells of IgAN patients up-regulated extracellular matrix, transcription factors, kidney development and genes related to the regulation of Wnt signaling pathway. The expression of structural protein ITGA8 on mesangial cells was significantly decreased, indicating the mesangial cells were damaged in early IgAN. Pseudo-time analysis indicated that extracellular matrix-related genes were involved in mesangial cell lesion. We also found that the patie'ts' glomerular endothelial cells expressed high level of angiogenesis and VEGF- related genes. Moreover, podocytes of IgAN patients expressed genes of cytoskeletal recombination and FGFR activation. Conclusion We successfully established the single-cell landscapes of peripheral blood immune cells and kidney cells in early IgAN patients, which revealed changes in the number and status of immune cells and kidney cells closely related to clinical manifestations and phenotypic transformation. Our study offers new insights for the diagnosis and treatment of IgAN.

#5419 INVESTIGATING THE ROLE OF CFH VARIANTS AND HAPLOTYPES AS A RISK FACTOR OF IGA NEPHROPATHY IN A FRENCH COHORT

Abstract Background and Aims Excessive complement activation is particularly important in the pathogenesis of IgAN nephropathy (IgAN). The relationship of complement CFH gene genetics and IgAN phenotype has not been clearly established in IgAN. Method We performed a genetic analysis of 234 French IgAN patients by next generation sequencing and Sanger. CFH polymorphisms were combined into haplotypes using the Michigan imputation Server1. CFH rare variants (MAF&amp;lt;0.1%) and haplotypes frequencies were compared to the 1k genome population of European ancestry. Recombinant full-length FH rare variants were produced and studied functionally in vitro. Results Genetic analysis revealed an enrichment in CFH non synonymous rare variants in IgAN patients (n = 234) compared to the reference population (n = 503) (5.1 versus 1.8%, p = 0.010). Interestingly, the identified variants preferentially located in FH functional domains. In vitro functional studies based on new functional Luminex® assays showed a decrease in C3b-binding, C3bBb decay-accelerating activity and/or FI-cofactor activity for 4 variants, classifying a newly identified variant as a pathogenic variant. CFH haplotypes distribution differed between the IgAN patients and controls (p&amp;lt;0.001), with a higher prevalence of the H3 haplotype (rs80029 c.184G&amp;gt;A, rs1061170 c.1204T&amp;gt;C, rs7542235 chr1:196854483 A&amp;gt;G, GTA) in IgAN patients (28.2 versus 21.1%, p = 0.0029), but this haplotype was not associated with renal survival. Conclusion In our series of French IgAN patients, CFH rare variants and haplotypes are associated with disease's susceptibility. Our results support the hypothesis of a complement dysregulation underlying the IgAN pathogenesis.

#4458 SINGLE CELL RNA SEQUENCING OF CIRCULATING LEUKOCYTES FROM IGA NEPHROPATHY PATIENTS IDENTIFIES AN IMPORTANT ROLE FOR INNATE IMMUNE CELLS

Abstract Background and Aims IgA-nephropathy (IgAN) is a slowly progressive disease characterized by mesangial deposition of IgA1 that causes kidney injury and can eventually lead to end stage renal disease. A key factor underlying the development of IgAN is the presence of galactose-deficient IgA1 (Gd-IgA1) in the circulation. The formation of IgA and IgG antibodies against Gd-IgA1 results in the formation of immune complexes which deposit in the kidney mesangium. Production of Gd-IgA1 hints to defects in B cell regulation. However, the exact immunological dysregulation leading to the formation of Gd-IgA1, and the subsequent antibody formation against it, remains elusive. Here we use single cell RNA sequencing (scRNA-seq) of circulating leukocytes for in depth analysis of immune cell populations in patients with active IgAN to gain a better understanding of the pathogenesis of this disease. Method Peripheral blood mononuclear cells were isolated for scRNA-seq from the blood of four patients with active IgAN, and four controls, matched for age and estimated glomerular filtration rate (eGFR). Cell hashing (Biolegend) of individual samples was performed before pooling samples for scRNA-seq. scRNA expression libraries were performed using the chromium X machine (10xgenomics) according to 10XGenomics single cell 5’ V2 user guide. Libraries were sequenced on an Illumina Nextseq500 and reads were mapped to GrCh38 using CellRanger. Differential gene expression analysis was performed for each immune cell type (FDR &amp;lt; 0.05). Reactome pathway enrichment analysis was performed on the differentially expressed genes. Results Identification of immune cell subtypes in IgAN patients and matched controls did not show a significant difference in cell numbers or ratios. B cells showed only minor changes in gene expression between IgAN patients and controls, and T cell populations showed changes in a limited set of genes, whereas interestingly, most differentially expressed genes were found in monocytes and NK cells (Figure 1A). Analysis of the differentially expressed genes showed enrichment for genes in interferon signaling pathways, mostly in monocytes and NK cells (Figure 1B). Gene enrichment analysis showed differential expression of type I IFN genes and antigen presentation genes, also mainly in monocytes and NK cells. Conclusion Our data shows the specific endotype of circulating immune cells from patients with active IgAN. While gene expression changes in T and B cells are discrete, changes in monocytes and NK cells appear especially prominent. In these cell types, we observed an important role for interferon signaling. Further analysis of scRNA-seq data in a larger patient cohort will follow, as well as analysis of T and B cell receptor clones in IgAN patients, with which we aim to gain new insights into immune dysregulation in IgAN.

#4052 IMMUNOSUPPRESSIVE TREATMENT RESULTS IN PATIENTS WITH PRIMARY IGA NEPHROPATHY IN TURKIYE: A NATIONWIDE STUDY

Abstract Background and Aims IgA nephropathy (IgAN) is the most common cause of primary glomerulonephritis in Turkey, as well as all over the world. Along with the frequent occurrence, deleterious renal outcome odds make treatment approaches important. Additionally, for high-risk individuals immunosuppressive treatment (IST) is recommended. However, studies to date revealed conflicting results regarding IST. Therefore, we aimed to investigate IST results among IgAN patients which is the leading primary glomerulonephritis in Turkiye. Method The data of 1656 IgAN patients in the Primary Glomerular Diseases Study of the Turkish Society of Nephrology Glomerular Diseases Study Group (TSN-GOLD) were analyzed. A total of 506 primary IgAN patients (63.4% male, mean age 38.9±12.5 years) were included and divided into two groups according to treatment protocols as isolated corticosteroid (69.6%) and combined IST (30.4%) groups. The median follow-up duration was 24 (3-218) months. Results Remission (66.6% partial remission, 33.4% complete remission) was achieved in 70.6% of patients. Systolic and diastolic blood pressures, urea, creatinine, and proteinuria levels were lower, and eGFR levels were higher in responsive patients (Table 1). There was no difference between the treatment groups in terms of remission rates (p = 0.147) and remission types’ rates (p = 0.279). Remission rates were different between treatment subgroups. However, there was no difference between the treatment subgroups according to the remission types (p = 0.132) (Table 2). Complete remission was lower in the S1 and T1 categories (p = 0.003 and 0.039, respectively). The serious infection was higher in the combined IST group (17.1% vs 2.9%). The outcome data of 229 individuals was evaluated, 40 of 229 (17.5%) developed ESRD and 8 were dead. In the multivariate analysis, eGFR (OR 1.007, 95%CI 1.001-1.013, p = 0.020), proteinuria (OR 1.000, p = 0.009), MEST-C S1 (OR 1.912, 95%CI 1.216-3.005, p = 0.005), MEST-C T2 (OR 0.226, 95%CI 0.102-0.501, p = &amp;lt; 0.001) were found to be significant regarding remission. Conclusion IST provides remission in high-risk IgAN patients but was associated with serious adverse events. The fact that the remission rates were similar between the treatment groups and that the complete remission rate was low in chronic changes supports the necessity of determining the treatment choice according to patient characteristics.

#5514 IGA NEPHROPATHY: A REAL-WORLD COMPARISON BETWEEN DISEASE SEVERITY, SYMPTOM BURDEN, AND TREATMENT SATISFACTION REPORTED BY PATIENTS AND NEPHROLOGISTS

Abstract Background and Aims Immunoglobulin A nephropathy (IgAN) is the most common form of primary glomerulonephritis worldwide, with an estimated annual incidence of ∼25/1000000. IgAN presents with many clinical manifestations, including hematuria, proteinuria, and hypertension (high blood pressure). This analysis aims to compare perceptions of symptom burden, disease severity and treatment satisfaction between patients living with IgAN and their treating nephrologists in Europe, the United States (US) and Asia. Method Data were drawn from the Adelphi IgAN Disease Specific Programme, a point-in-time survey of IgAN-treating nephrologists and their consulting IgAN patients, conducted in the US, Europe (EU5; France, Germany, Italy, Spain, United Kingdom [UK]), Japan, and China, June-October 2021. Nephrologists completed structured online patient record forms for successive patients presenting with IgAN. Patients voluntarily completed questionnaires that corresponded with the nephrologist records. Both the nephrologist and patient-reported data included demographics, IgAN signs and symptoms, disease severity and treatment satisfaction. Results Data was collected for 991 patients with IgAN, where matched nephrologist and patient- reported forms were completed. Mean (standard deviation [SD]) patient age was 42.1 (13.8) years, and 57% were male. Nephrologists and patients reported their perceived severity of the patient's IgAN, on a scale of mild, moderate, and severe (n = 981). Nephrologists and patients agreed on severity for 77% of patients (US 82%, EU5 77%, Japan 70%, China 78%). The level of nephrologist awareness of patient-reported symptoms was analysed. Where patients reported nausea/vomiting, it was not recognised by nephrologists in 85% of cases. This was similarly seen for appetite loss (80%), headaches/migraines (69%), and aching joints (67%). Patients and nephrologists were asked to score the patient's fatigue and pain on a scale from 0 (none) to 10 (worst possible). Overall, nephrologists and patients agreed on the patient's fatigue score in 33% of cases (n = 991). Fatigue was under-reported by nephrologists in comparison to what patients reported in 46% of cases with a mean (SD) difference in score of 2.47 (1.46), and over-reported in 21% of cases with a mean (SD) score difference of 1.95 (1.27). Patients and nephrologists agreed on the patient's self-reported pain score in 53% of cases (n = 988). Pain was under-reported by nephrologists in 26% of cases with a mean (SD) score difference of 2.24 (1.44) and over-reported in 21% of cases with a mean (SD) 2.06 (1.48) score difference. Nephrologists and patients reported their satisfaction with the patients’ current IgAN treatment as satisfied, neither satisfied or dissatisfied, or dissatisfied (n = 982). There was a 65% agreement between the nephrologists and patients’ treatment satisfaction. Percentage agreement varied across countries: EU5 76%, US 77%, China 61%, Japan 58%. Conclusion Although there seemed to be a good level of agreement between nephrologists and patients on their overall IgAN severity, nephrologists under-reported patient symptoms, notably nausea/vomiting and appetite loss, and fatigue. Although not IgAN specific, these symptoms can decrease a patient's quality of life. Satisfaction with current treatment also differed in around a third of cases. This highlights that communication between nephrologists and their patients can be improved, especially when it comes to appreciating IgAN symptom burden. This could be combated through more investment in a holistic patient evaluation. Cultural differences may impact symptom perception and reporting, as evidenced by differences between nephrologists and patients in different countries/regions. An improvement in communication may lead to a better management of IgAN patients, including treatment, and subsequently a better quality of life for patients with IgAN.

#4337 UPDATED INTERIM RESULTS OF A PHASE 1/2 STUDY OF BION-1301 IN PATIENTS WITH IGA NEPHROPATHY

Abstract Background and Aims Immunoglobulin A nephropathy (IgAN) is the leading cause of primary glomerulonephritis worldwide with limited treatment options, especially for high-risk patients. Approximately 30-45% of IgAN patients progress to end-stage kidney disease over a period of 20-25 years and proteinuria is the strongest predictor of disease progression [1]. BION-1301 is a novel humanized monoclonal antibody that blocks a proliferation-inducing ligand (APRIL), a cytokine that is elevated in patients with IgAN. APRIL promotes the production of pathogenic galactose-deficient IgA1 (Gd-IgA1), leading to immune complex deposition and subsequent kidney injury. Blocking APRIL with BION-1301 is a potential disease-modifying approach to directly target the pathogenesis of IgAN. In a Phase 1/2 study (NCT 03945318) in healthy volunteers and patients with IgAN, BION-1301 was well-tolerated with no serious adverse events (SAEs) and durably reduced free APRIL, IgA, Gd-IgA1, IgM and to a lesser extent, IgG [2]. Method For the ongoing phase 1/2 open-label, multicohort trial, eligibility criteria include adults with biopsy-proven IgAN, eGFR ≥30 mL/min per 1.73 m2, baseline urine protein excretion ≥0.5 g/24 hrs or UPCR ≥0.5 g/g, and on stable/optimized RASi (or intolerant). Cohort 1 received 450 mg of BION-1301 administered IV every 2 weeks, transitioning to SC at 600 mg every 2 weeks after at least 24 weeks. Cohort 2 receives 600 mg of BION-1301 SC every 2 weeks. Results In both Cohorts 1 and 2, BION-1301 was generally well-tolerated, with no SAEs or terminations due to AEs as of the last reported interim analysis (November 2022) [2]. Durable reductions in serum levels of free APRIL and immunoglobulins were observed in both cohorts. No anti-drug antibodies have been observed in patients with IgAN to date. In Cohort 1, clinically meaningful reductions in proteinuria were seen as early as 12 weeks (30.4% geometric mean UPCR reduction, n = 7), and were sustained through 24 weeks (48.8% geometric mean UPCR reduction, n = 8) and 52 weeks (66.9% geometric mean UPCR reduction, n = 8). Reductions in proteinuria were consistent in Cohort 2 (53.8% geometric mean UPCR reduction, n = 9) at 24 weeks. Significant and durable reductions in serum Gd-IgA1 concentrations were observed and were consistent across both cohorts. Updated data will be reported at the time of presentation. Conclusion BION-1301 offers disease-modifying potential by directly targeting the initiating pathogenesis of IgAN. Interim biomarker and clinical activity responses support advancement of BION-1301 into later-stage development for patients with IgAN.