Interstitial Fibrosis/tubular Atrophy Research Articles

#978 Interstitial fibrosis and tubular atrophy of immune checkpoint inhibitor-related interstitial nephritis associate mortality and kidney prognosis

Abstract Background and Aims Several studies have been conducted on immune checkpoint inhibitor (ICI)-associated nephrotoxicity. However, current clinical analyses for nephrotoxicity are inadequate owing to the diagnostic criteria, which are mostly based on an increase in serum Cre levels rather than on renal pathology. In addition, many studies have focused on the incidence of ICI-associated nephrotoxicity, and few have focused on its prognosis and effects on overall survival. One of the major pathological findings of ICI-associated nephrotoxicity is known to show tubulointerstitial nephritis (TIN). Therefore, this study aimed to clarify the clinical and pathological characteristics of biopsy-proven ICI-TIN and their effects on the clinical remission of kidney injury and renal or cancer prognosis using the nationwide database of the Japan Renal Biopsy Registry (J-RBR) of the Japanese Society of Nephrology. Method This is a multicenter study using J-RBR named “SUrvey of renal Biopsy database and Anti-cancer dRUg therapy in Japan (SUBARU-J)”. Fifty-four patients with renal biopsy-proven ICI-TIN, registered in the J-RBR between 2018 and 2021 was analyzed. We collected patient clinical characteristics, pathological scores of renal biopsy including glomerulosclerosis, interstitial fibrosis, tubular atrophy (IFTA), and cellular infiltration, as well as data on the clinical remission of kidney injury during the acute phase, defined as a recovery of serum Cre to <1.5 × above baseline within 90 days from renal biopsy, then performed a multivariable analysis to investigate factors associated with clinical remission of kidney, and finally calculated the adjusted hazard ratio of each factor for overall survival, progression-free survival (PFS) of cancer, and major kidney adverse events (MAKE), consisting of the composite endpoint of death, renal replacement therapy dependence, or a decrease in estimated glomerular filtration rate to <50% of baseline. Results The median (interquartile range) time from the initiation of immune checkpoint inhibitors to renal biopsy was 134 (IQR: 56.5–364) days. Extrarenal immune-related adverse events occurred in 10 (18.5%) patients and 44 (81.5%) patients were treated with steroids. Clinical remission of kidney injury was achieved in 28 (51.8%) patients. A shorter interval (within seven days) between renal biopsy and steroid treatment was independently associated with the clinical remission of kidney injury (OR 35.3, p = 0.0301). The observation period from renal biopsy was 415 (IQR 140-844) days, with one-year overall survival of 62.5% and two-year overall survival of 42.4%. Hypertension (aHR 0.37, 95% CI: 0.17-0.82, p = 0.0144), IFTA (aHR 2.50, 95% CI: 1.12-5.57, p = 0.0251), and clinical remission of kidney injury (aHR 0.43, 95% CI: 0.19-0.94, p = 0.0355) were independently associated with overall survival. Hypertension (aHR 0.31, 95% CI: 0.15-0.64, p = 0.0018) and clinical remission of kidney injury (aHR 0.47, 95% CI: 0.23-0.96, p = 0.0391) also had a significant association with PFS although IFTA did not (aHR 2.03, 95% CI: 0.98-4.21, p = 0.0560). Furthermore, Hypertension (aHR 0.37, 95% CI: 0.18-0.77, p = 0.0075), IFTA (aHR 2.40, 95% CI: 1.14-5.06, p = 0.0210), and clinical remission of kidney injury (aHR 0.39, 95% CI: 0.19-0.81, p = 0.0123) were independently associated with the incidence of MAKE. Conclusion These data suggested that the pathological IFTA score of ICI-TIN, along with hypertension and clinical remission of kidney injury during the acute phase, could be associated not only with kidney prognosis but also with overall survival.

#1253 Predicting renal outcomes in ANCA-associated vasculitis—validation of ANCA Renal Risk Score in a Portuguese cohort

Abstract Background and Aims Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare cause of glomerulonephritis and clinical presentation can be diverse. Despite recent developments in immunosuppressive treatments, AAV with renal involvement is still associated with poor renal prognosis and a high risk of end-stage renal disease (ESRD). Kidney biopsy confirms the diagnosis, details the degree of active inflammation and chronicity of disease, also informing of renal prognosis. Berden histological classification categorizes renal histological findings into four classes but the ability to accurately predict renal outcomes varies among studied cohorts. In 2018 Brix et al developed and validated a new risk score, ANCA Renal Risk Score (ARRS), to determine renal outcomes based on histopathological and clinical indicators, with accurate ESRD prediction at 36 months. This study aims to assess the predictive value of ARRS in renal survival on a Portuguese cohort with newly diagnosed AAV with kidney involvement. Method We designed a retrospective study examining ANCA vasculitis in native kidney biopsies evaluated in a Portuguese kidney histomorphology-dedicated center between 2004 and 2023. Data collected from biopsies included percentage of normal glomeruli (PNG) and interstitial fibrosis/tubular atrophy (IFTA). Clinical and demographical data was also collected, including age, sex, estimated glomerular filtration rate (eGFR) at presentation, date of diagnosis, ESRD and date of death. We calculated ARRS based on eGFR, PNG and IFTA, and patients were classified as being at low, intermediate and high risk of developing ESRD by 36 months. Primary endpoint was established as difference in kidney survival at 36 months. Secondary endpoint included difference in overall survival at 36 months and the contribution of each of the ARRS parameters in a Cox regression model. Results A total of 143 patients were obtained, 46.2% female, with a mean age at diagnosis of 67.1 years. There was a predominancy of MPO-related disease (77.2%) and 69% presented with rapidly progressive renal insufficiency. Median ARRS was 6.5, with 10.8%, 44.3% and 44.9% classified as low, intermediate, and high risk, respectively. Kaplan Meier estimates for renal survival computed at 36 months revealed an overall mean time to dialysis of 20 months, which decreased with an increase in risk category [33.4 (low risk), 24.7 (intermediate risk), 12.7 months (high risk), Log-R test: χ2(2) = 24.9, p < 0.001] with an ESRD survival of 92.9%, 63.6% and 29.7% at 36 months, respectively. Regarding secondary endpoints, overall survival at 36 months was not different between groups [33.7 (low risk) vs. 33.2 (intermediate risk) vs. 32.2 months (high risk), Log-R test: χ2(2) = 0.3, p = 0.9]. Cox regression, plotted for ESRD at 36 months using the three score variables, revealed eGFR at presentation as the strongest predictor of kidney survival (HR: 0.96, 95% CI: 0.93-0.99, p = 0.004) whereas PNG and IFTA did not achieve significance (p = 0.189 and p = 0.066, respectively). Conclusion Our results corroborate Brix et al ARRS, accurately predicting ESRD in a Portuguese cohort of patients with renal involvement by ANCA vasculitis. Patients assessed as high-risk of developing ESRD had a lower mean time to dialysis, although overall survival did not differ between groups. Contrary to Brix et al findings, which revealed PGN as the only independent predictor of ESRD, in our study lower eGFR at the time of diagnosis was an independent risk factor. Type of immunosuppression used in each patient was not considered in this study and could maybe alter results of renal and overall survival. Despite this, Brix et al reported that, in their population, validity of ARRS was not influenced by immunosuppressive treatment. This new scoring system still requires validation in a larger cohort, but results seem promising and, in the future, may aid clinicians with treatment decisions. This is relevant since full immunosuppression induction schemes may be halted in patients with high probability of ESRD, diminishing infectious complications and potentially decreasing morbidity and mortality associated with AAV.

#648 Relationship between renal tubular damage, interstitial fibrosis and semaphorin class 3C

Abstract Background and Aims The detailed mechanism of interstitial fibrosis in CKD has not been clarified. In this study, we focused on semaphorin class 3C (SEMA3C), a secreted protein expressed in the renal tubules, that is involved in embryonic kidney development [1], and investigated the relationship between SEMA3C and renal tubular damage and interstitial fibrosis. Methods < Clinical research> We investigated the correlation between serum SEMA3C concentration and the renal tubular damage marker urinary β2 microglobulin (β2MG) concentration in the 191 patients who underwent kidney biopsy from 2017 to 2021 at Yamagata University. < In vivo study> We generated proximal tubule-specific SEMA3C knockout mice (PT-SEMA3C KO) from male mice (C57BL/6) using the Cre/loxP system. The PT-SEMA3C KO group and control group were fed a 0.2% adenine diet for 5 weeks to induce CKD. The area of interstitial fibrosis/tubular atrophy (IFTA) region was assessed by Masson-Trichrome staining. Results < Clinical research> The median age of the patients was 54 (IQR 38-68) years, 94 men and 97 women. Median serum SEMA3C concentration was 0.14 (IQR 0.07-0.35) ng/ml. Median urinary β2MG levels was 0.22 (IQR 0-1.79) mg/gCr. Spearman's correlation analysis showed a significant negative correlation between serum SEMA3C and urinary β2MG levels (r=-0.208, P=0.005), but no correlation between eGFR and Urinary protein/ creatinine. < In vivo study> IFTA region was 5.6% in the control group, compared to 11.2% in the PT-SEMA3C KO group (p=0.031). Interstitial fibrosis was significantly suppressed in the PT-SEMA3C KO mice (Fig. 1). Conclusion Our clinical and in vivo results indicate that serum SEMA3C is associated with renal tubular damage and interstitial fibrosis.

#1505 Late-onset lupus nephritis: clinical-epidemiological, histological, prognostic and therapeutical implications: a single center experience

Abstract Background and Aims Systemic lupus erythematosus (SLE), a chronic autoimmune disease, and lupus nephritis (LN), are typically diagnosed in women in fertile age. Late-onset SLE is defined as a disease onset over 50 years. Our main objective was to analyze the clinical, histological, prognostic and therapeutical features related to LN in our late-onset SLE population. Method A single center and retrospective study was performed comparing clinical-demographic, histological, prognostic and therapeutical data of 45 LN biopsied patients from 1994 to 2023. We divided the study population according to the age of onset of LN into classic-onset (< 45 years) and late-onset (> 45 years). Results Late-onset LN patients showed a higher association with Sjögren's and antiphospholipid syndrome, more cardiovascular comorbidities at presentation, poorer renal function at diagnosis and higher SDI score. On histology they showed more non-proliferative LN classes (II followed by V). Late-onset LN responders needed more time to achieve response but had fewer relapses. Non responsive patients had more incidence of acute kidney injury (AKI) and more glomerulosclerosis and interstitial fibrosis-tubular atrophy (IFTA) at presentation, as well as more need for renal replacement therapy (RRT) at diagnosis and at follow-up. The principal independent variables associated with relapse were the younger age at SLE diagnosis and an initial partial renal response (PRR). Patients of both groups who experienced relapse received higher doses of intravenous cyclophosphamide and less mycophenolic acid (MFA) analogues. Patients who received induction with MFA analogues were more likely to achieve complete renal response (CRR) or non-renal response (NRR). Conclusion late-onset LN is often accompanied by poor renal function at presentation. It seems imperative to establish a tailored approach in this fragile population in order to avoid unnecessary immunosuppression.

The Influence of Tacrolimus Exposure and Metabolism on the Outcomes of Kidney Transplants.

Tacrolimus (TAC) has a narrow therapeutic window and patient-specific pharmacokinetic variability. In our study, we analyzed the association between TAC exposure, metabolism, and kidney graft outcomes (function, rejection, and histological lesions). TAC trough (C0), coefficient of variation (TAC CV), concentration/dose ratio (C/D), and biomarkers related to kidney injury molecule-1 (KIM-1) and neutrophil gelatinase lipocalin (NGAL) were analyzed. We examined 174 patients who were subjected to a triple immunosuppressive regimen and underwent kidney transplantation between 2017 and 2022. Surveillance biopsies were performed at the time of kidney implantation and at three and twelve months after transplantation. We classified patients based on their Tac C/D ratios, classifying them as fast (C/D ratio < 1.05 ng/mL × 1/mg) or slow (C/D ratio ≥ 1.05 ng/mL × 1/mg) metabolizers. TAC exposure/metabolism did not significantly correlate with interstitial fibrosis/tubular atrophy (IF/TA) progression during the first year after kidney transplantation. TAC CV third tertile was associated with a higher chronicity score at one-year biopsy. TAC C/D ratio at three months and Tac C0 at six months were associated with rejection during the first year after transplantation. A fast TAC metabolism at six months was associated with reduced kidney graft function one year (OR: 2.141, 95% CI: 1.044-4.389, p = 0.038) and two years after transplantation (OR: 4.654, 95% CI: 1.197-18.097, p = 0.026), and TAC CV was associated with reduced eGFR at three years. uNGAL correlated with IF/TA and chronicity scores at three months and negatively correlated with TAC C0 and C/D at three months and one year. Conclusion: Calculating the C/D ratio at three and six months after transplantation may help to identify patients at risk of suffering acute rejection and deterioration of graft function.

Rictor/mTORC2 signalling contributes to renal vascular endothelial-to-mesenchymal transition and renal allograft interstitial fibrosis by regulating BNIP3-mediated mitophagy.

Renal allograft interstitial fibrosis/tubular atrophy (IF/TA) constitutes the principal histopathological characteristic of chronic allograft dysfunction (CAD) in kidney-transplanted patients. While renal vascular endothelial-mesenchymal transition (EndMT) has been verified as an important contributing factor to IF/TA in CAD patients, its underlying mechanisms remain obscure. Through single-cell transcriptomic analysis, we identified Rictor as a potential pivotal mediator for EndMT. This investigation sought to elucidate the role of Rictor/mTORC2 signalling in the pathogenesis of renal allograft interstitial fibrosis and the associated mechanisms. The influence of the Rictor/mTOR2 pathway on renal vascular EndMT and renal allograft fibrosis was investigated by cell experiments and Rictor depletion in renal allogeneic transplantation mice models. Subsequently, a series of assays were conducted to explore the underlying mechanisms of the enhanced mitophagy and the ameliorated EndMT resulting from Rictor knockout. Our findings revealed a significant activation of the Rictor/mTORC2 signalling in CAD patients and allogeneic kidney transplanted mice. The suppression of Rictor/mTORC2 signalling alleviated TNFα-induced EndMT in HUVECs. Moreover, Rictor knockout in endothelial cells remarkably ameliorated renal vascular EndMT and allograft interstitial fibrosis in allogeneic kidney transplanted mice. Mechanistically, Rictor knockout resulted in an augmented BNIP3-mediated mitophagy in endothelial cells. Furthermore, Rictor/mTORC2 facilitated the MARCH5-mediated degradation of BNIP3 at the K130 site through K48-linked ubiquitination, thereby regulating mitophagy activity. Subsequent experiments also demonstrated that BNIP3 knockdown nearly reversed the enhanced mitophagy and mitigated EndMT and allograft interstitial fibrosis induced by Rictor knockout. Consequently, our study underscores Rictor/mTORC2 signalling as a critical mediator of renal vascular EndMT and allograft interstitial fibrosis progression, exerting its impact through regulating BNIP3-mediated mitophagy. This insight unveils a potential therapeutic target for mitigating renal allograft interstitial fibrosis.

Serum uric acid level is associated with glomerular ischemic lesions in patients with primary membranous nephropathy: an analytical, cross-sectional study

To investigate the relationship between serum uric acid level and glomerular ischemic lesions (GIL) in patients with primary membranous nephropathy (PMN) and identify relevant risk factors. A total of 201 patients with PMN but normal renal function confirmed by renal biopsy executed in the Liaocheng People’s Hospital, China, during January 2020-January 2023 were analyzed retrospectively. The enrolled patients were divided into a hyperuricemia group and a normal serum uric acid group (control group) according to their serum uric acid levels. Then, the participants were further divided into a non-GIL group or a GIL group based on the patient’s renal biopsy results. The two groups’ clinical and pathological data and meaningful indicators for differences were analyzed by binary logistic regression analysis. Additionally, the serum uric acid level prediction value on GIL was investigated using receiver operating characteristic (ROC) curves. Compared with the control group, the hyperuricemia group exhibited high serum uric acid, the prevalence of GIL, serum albumin, the prevalence of hypertension, and low-density lipoprotein cholesterol (LDL) levels (P < 0.05). Compared with the non-GIL group, the GIL group exhibited were older, had enhanced serum uric acid, serum albumin, and an increased prevalence of tubular atrophy/interstitial fibrosis (TA/IF), arteriolosclerosis, and low eGFR levels (P < 0.05). The binary logistic regression analysis revealed that the serum uric acid and the TA/IF are independent risk factors of GIL (P < 0.05). The AUC of ROC of GIL of PMN patients, predicted based on the serum uric acid concentration, was 0.736 (P < 0.05), wherein the threshold = 426.5 μmol/L and the Youden’s index = 0.41. Serum uric acid concentration and the TA/IF are independent risk factors of GIL in patients with PMN, and the former exhibits prediction value on GIL in patients with PMN.

Kidney Histopathology of Patients with Hepatitis C Infection and Diabetes Mellitus before and after Availability of Direct-Acting Antiviral Therapy.

Type 2 diabetes mellitus (DM) and diabetic kidney disease are increasing. Hepatitis C infection (HCV) occurs in 1% of the world population and can induce several kidney diseases. DM prevalence is increased in individuals with HCV; however, kidney diseases in those with both DM and HCV have not been assessed. Direct-acting antiviral agents (DAAs) became available for HCV treatment in 2014; it is unknown if DAAs altered the spectrum of kidney disease in patients with DM and HCV. Case review identifying patients with kidney biopsy and clinical history of DM and HCV between 2009-2013 (pre-DAA) and 2016-2020 (post-DAA), excluding kidney transplant, hepatitis B, HIV, and inadequate biopsy, identified 245 biopsies. Biopsies were evaluated for diabetic glomerulosclerosis (DGS) class, global and focal segmental glomerulosclerosis (FSGS), other glomerular diseases, interstitial fibrosis/tubular atrophy (IFTA), interstitial nephritis, acute tubular injury and degree of arterial and arteriolar sclerosis. Kidney disease differences in pre-DAA versus post-DAA eras and in mild versus severe DGS were assessed by χ2 and Fisher's exact tests. The most common non-DGS lesions were non-collapsing FSGS (41%), HCV-related IgM dominant immune complex glomerulonephritis (IgM-ICGN, 18%), IgA nephropathy (9%), and membranoproliferative glomerulonephritis (MPGN, 7%). Collapsing FSGS was more common pre-DAA versus post-DAA (8% vs. 1%, p = 0.03). Biopsies from patients with HCV and DM were reduced in post-DAA (0.7%) versus pre-DAA (1.3%) (p < 0.0001). Post-DAA there were less MPGN (2% vs. 10%, p = 0.02) and more advanced DGS (85% vs. 61%, p = 0.0002), non-collapsing FSGS (57% vs. 31%, p < 0.0001), IFTA (2.0 vs. 1.6, p = 0.0002), and vascular sclerosis (2.1 vs. 1.6, p < 0.0001). Post-DAA there were reduced biopsies and MPGN, with more severe DGS class, non-collapsing FSGS, IFTA, and chronic vascular changes. This suggests a modulating effect of DAAs on HCV-related kidney pathology with DM and chronic changes driving indications for kidney biopsy.

NSD2 modulates Drp1-mediated mitochondrial fission in chronic renal allograft interstitial fibrosis by methylating STAT1

Renal interstitial fibrosis/tubular atrophy (IF/TA) is a prominent pathological feature of chronic allograft dysfunction (CAD). Our previous study has demonstrated that epithelial-mesenchymal transition (EMT) plays a significant role in shaping the development of IF/TA. Nuclear SET domain (NSD2), a histone methyltransferase catalyzing methylation at lysine 36 of histone 3, is crucially involved in the development and progression of solid tumors. But its role in the development of renal allograft interstitial fibrosis has yet to be elucidated. Here, we characterize NSD2 as a crucial mediator in the mouse renal transplantation model in vivo and a model of tumor necrosis factor-α (TNF-α) stimulated-human renal tubular epithelial cells (HK-2) in vitro. Functionally, NSD2 knockdown inhibits EMT, dynamin-related protein 1 (Drp1)-mediated mitochondrial fission in mice. Conversely, NSD2 overexpression exacerbates fibrosis-associated phenotypes and mitochondrial fission in tubular cells. Mechanistically, tubular NSD2 aggravated the Drp-1 mediated mitochondrial fission via STAT1/ERK/PI3K/Akt signaling pathway in TNF-α-induced epithelial cell models. Momentously, mass spectrometry (MS) Analysis and site-directed mutagenesis assays revealed that NSD2 interacted with and induced Mono-methylation of STAT1 on K173, leading to its phosphorylation, IMB1-dependent nuclear translocation and subsequent influence on TNF-α-induced EMT and mitochondrial fission in NSD2-dependent manner. Collectively, these findings shed light on the mechanisms and suggest that targeting NSD2 could be a promising therapeutic approach to enhance tubular cell survival and alleviate interstitial fibrosis in renal allografts during CAD.

Multiomic profiling of transplant glomerulopathy reveals a novel T-cell dominant subclass

Kidney transplant (KTx) biopsies showing transplant glomerulopathy (TG) (glomerular basement membrane double contours (cg) > 0)) and microvascular inflammation (MVI) in the absence of C4d staining and donor-specific antibodies (DSA)s do not fulfill the criteria for chronic active antibody-mediated rejection (CA-AMR) diagnosis and do not fit into any other Banff category. To investigate this, we initiated a multicenter intercontinental study encompassing 36 cases, comparing the immunomic and transcriptomic profiles of 14 KTx biopsies classified as cg+MVI DSA-/C4d- with 22 classified as CA-AMR DSA+/C4d+ through novel transcriptomic analysis using the NanoString Banff-Human Organ Transplant (B-HOT) panel and subsequent orthogonal subset analysis using two innovative 5-marker multiplex immunofluorescent panels. Nineteen genes were differentially expressed between the two study groups. Samples diagnosed with CA-AMR DSA+/C4d+ showed a higher glomerular abundance of natural killer cells and higher transcriptomic cell type scores for macrophages in an environment characterized by increased expression of complement-related genes (i.e., C5AR1) and higher activity of angiogenesis, interstitial fibrosis tubular atrophy, CA-AMR, and DSA-related pathways when compared to samples diagnosed with cg+MVI DSA-/C4d-. Samples diagnosed with cg+MVI DSA-/C4d- displayed a higher glomerular abundance and activity of T-cells (CD3+, CD3+CD8+, and CD3+CD8-). Thus, we show that using novel multiomic techniques, KTx biopsies with cg+MVI DSA-/C4d- have a prominent T-cell presence and activity, putting forward the possibility that these represent a more T-cell-dominant phenotype.

Results of Temporary Drainage of Poorly Functioning Kidneys With Ureteropelvic Junction Obstruction: Does the Histology of Persistent Poor Functioning Kidneys Indicate an Increased Risk of Hypertension?

ObjectiveTo review our experience with managing poorly functioning kidneys with ureteropelvic junction obstruction (PFK-UPJO) with differential function (DRF) <10% by a trial of temporary drainage, as the management of such kidneys is controversial. We also studied the histopathologic changes in the nephrectomy specimens of persistent PFK-UPJO, as tubulointerstitial damage may predispose to hypertension. MethodsA retrospective review of cases undergoing treatment for unilateral UPJO over 5-year period in 2 centers was conducted. In PFK-UPJO, 4-6 weeks trial of drainage with double J stent or percutaneous nephrostomy was employed. Those kidneys that improved DRF to >10% underwent pyeloplasty, while persistent PFK underwent nephrectomy; the specimens were studied for interstitial fibrosis/tubular atrophy (IF/TA), arterial lesions and arteriole lesions. ResultsOf 402 patients with unilateral UPJO that underwent surgical management, 17 (4.1%) had PFK-UPJO. After 4-6 weeks trial of drainage, 6 kidneys (35.2%) with improved DRF underwent pyeloplasty, while 11 kidneys with persistent PFK underwent nephrectomy; significant IF/TA, arterial and arteriolar changes were noted in 9 (82%), 9 (82%) and 4 (36%) kidneys respectively, including 7 kidneys in normotensive children. Two (11.7%) children had hypertension at presentation; one child remains hypertensive even after nephrectomy. ConclusionsIn PFK-UPJO, trial of temporary drainage seems appropriate to decide plan of management; 35% of such kidneys improved function after drainage. Most persistent PFK demonstrated severe and irreversible histologic changes that may predispose to hypertension if they are preserved, and we suggest that such kidneys may be removed. Long-term follow-up of all preserved PFK-UPJO is strongly recommended.

Kidney Veno-Muscular Characteristics and Kidney Disease Progression: A Native Kidney-Biopsy Study

Assessment of kidney biopsies provides crucial information for diagnosis and disease activity, as well as prognostic value. Kidney-biopsy specimens occasionally contain veno-muscular complex (VMC), which consists of muscle tissues around the kidney venous system in the corticomedullary region. However, the role of VMC and the clinical significance of VMC variants are poorly understood. In the present study, we investigated kidney prognostic values of VMC variants. Retrospective cohort study. Among 808 patients who underwent a kidney biopsy from 2011 to 2019, 246 patients whose kidney biopsy specimens contained VMC were enrolled. VMC variants; inflammatory-VMC (an infiltration of≥80 inflammatory cells/mm2-VMC area) and VMC hypertrophy (hyper-VMC, a VMC average width≥850μm), and the interstitial fibrosis/tubular atrophy (IFTA) score. A decline in estimated glomerular filtration rate (eGFR)≥40% from the baseline or commencement of kidney replacement therapy. Cox proportional hazards model. Among 246 patients with data on VMC, mean baseline eGFR was 56.0±25.6ml/min per 1.73m2; 80 had high inflammatory-VMC, and 62 had VMC hypertrophy. There were 51 kidney events over median follow-up of 2.5 years. We analyzed 2 VMC variants. Multivariable logistic regression analysis revealed that eGFR negatively correlated with the presence of both inflammatory-VMC and hyper-VMC. A Cox proportional hazards analysis revealed that inflammatory-VMC (but not hyper-VMC) was independently associated with the primary outcome after adjustments for known risk factors of progression, including proteinuria, eGFR, and the interstitial fibrosis/tubular atrophy (IFTA) score (hazard ratio, 1.97; 95% confidence interval, 1.00-3.91). Single-center study and small sample size. Assessment of inflammatory-VMC provides additional kidney prognostic information to known indicators of kidney disease progression in patients who undergo kidney biopsy. Assessment of kidney biopsies provides crucial information for diagnosis, disease activity, and prognostic value. Kidney-biopsy specimens occasionally contain veno-muscular complex (VMC), which consists of muscle tissues around the kidney venous system. Currently, the role of VMC in kidney health and diseases and the clinical significance of VMC variants are poorly understood. In the present study, we have shown that an infiltration of≥80 inflammatory cells/mm2-VMC area (inflammatory-VMC) is independently associated with kidney disease progression after adjustments for known risk factors of progression. Therefore, assessment of inflammatory-VMC provides additional kidney prognostic information to known indicators of kidney disease progression in patients who undergo kidney biopsy.

Clinical significance of kidney immune complex deposition in children with acute interstitial nephritis disease

Background Acute interstitial nephritis (AIN) is a relatively rare cause of acute kidney injury (AKI) in children. Immune complex (IC) deposition was rare in renal pathology of AIN. Methods Based on the status and position of IC deposition, a total of 78 children with AIN were divided into two groups: the non-IC group and IC group. IC group was further divided into two subgroups: intraglomerular (IG)-IC group and extraglomerular (EG)-IC group. To compare the clinical and histological features, renal outcomes between groups. Results The IC deposition, IG-IC and EG-IC deposition were observed in 22 (28.21%), 12 (15.38%) and 10 (12.82%) children, respectively. The IC group demonstrated a higher frequency of AKI, higher level of Scr, urine N-acetyl-β-D-glucosidase (NAG) enzyme, retinol-binding protein (RBP), neutrophil gelatinase-associated lipocalin (NGAL), higher frequency of neutrophils, plasma cells and eosinophils infiltrate, higher scores of interstitial inflammation (i), total inflammation (ti) and interstitial edema, lower level of estimated glomerular filtration rate (eGFR) as compared to non-IC group (p < 0.05, p < 0.01). EG-IC deposition positively moderate correlated with levels of RBP, IG-IC deposition positively moderate correlated with plasma cell infiltrate, interstitial inflammation (i), total inflammation (ti) and interstitial edema. Interstitial inflammation, EG-IC deposition and interstitial edema were risk factors for AKD in AIN, and interstitial fibrosis/tubular atrophy (IF/TA) was a risk factor for CKD in children with AIN. Conclusion IG-IC and EG-IC deposition positively correlated with severe clinical manifestations, glomerular and tubular injuries, and EG-IC deposition was risk factor for the progression of AIN in children.

The correlation of interstitial change with renal prognosis in patients with myeloperoxidase-ANCA-associated glomerulonephritis: a single-center retrospective analysis.

We aim to explore the correlation between active/chronic tubulointerstitial injury and renal survival, and to compare their predictive value in patients with myeloperoxidase (MPO)-anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN). A total of 225 patients with MPO-AAGN diagnosed between February 2004 and December 2020 were included. Survival and univariate/multivariate Cox regression analyses were used to analyze the prognostic value of interstitial inflammation and interstitial fibrosis/tubular atrophy (IF/TA). Of the 225 patients, 73 (32.4%) patients developed end-stage renal disease (ESRD) requiring maintenance dialysis. Interstitial inflammation>50% and IF/TA>50% were important predictors for ESRD in MPO-AAGN in multivariate Cox regression analysis adjusted by age, gender, estimated glomerular filtration rate (eGFR)≤15 ml/min/1.73m2, and normal glomeruli% (classified by <25%, 25-50%, >50%). Furthermore, we conducted stratified Cox regression analysis and found different results in the subgroups of eGFR>15 ml/min/1.73m2 and eGFR≤15 ml/min/1.73m2. Interstitial inflammation>50% and IF/TA>50% were significant risk factors for ESRD in the subgroup of eGFR>15 ml/min/1.73m2, but not or less significant in the subgroup of eGFR≤15 ml/min/1.73m2. Similarly, the survival analysis according to interstitial inflammation>50%/≤50% and IF/TA>50%/≤50% showed significant differences in the subgroup of eGFR>15 ml/min/1.73m2, but not or less significant in the subgroup of eGFR≤15 ml/min/1.73m2. Interstitial inflammation>50% and IF/TA>50% were prognostic factors for renal survival in MPO-AAGN. In particular, interstitial inflammation and IF/TA had a better predictive ability in the subgroup of eGFR>15 ml/min/1.73m2. Key Points • Interstitial inflammation>50% and IF/TA>50% can help to predict renal survival in MPO-AAGN. • Both interstitial inflammation and IF/TA had a better predictive ability in the subgroup of eGFR>15 ml/min/1.73m2 than those in the subgroup of eGFR≤15 ml/min/1.73m2.

Crescentic glomerulonephritis in children: short-term follow-up predicts long-term outcome.

Crescentic glomerulonephritis (CrGN) is a relatively rare but severe condition in childhood with the clinical feature of rapidly progressive glomerulonephritis (RPGN). The aim of this study is to investigate the clinicopathological features and prognosis of CrGN in children. We retrospectively analyzed the clinical and laboratory data, renal pathological results, treatment, and outcome of 147 CrGN in two Chinese pediatric nephrology centers. Among the 147 children, there were 22 cases of type I (15.0%), 69 cases of type II (46.9%), and 56 cases of type III (38.1%). The mean percentages of crescents in CrGN I, II, and III were 85.3%, 68.7%, and 73.6%, respectively. The children with type I CrGN presented with more severe clinical manifestations and pathological lesions. The 3-month cumulative renal survival rates of types I, II, and III CrGN were 66.3%, 93.6%, and 75.6%, respectively. The 1-year cumulative renal survival rates of types I, II, and III CrGN were 56.9%, 85.3%, and 73.1%, respectively, and the 5-year cumulative renal survival rates of types I, II, and III CrGN were 33.8%, 73.5%, and 47.1%, respectively. The Kappa Consistency Test between the 3-month and 1-year total renal survival (82.1% vs. 74.7%) of the children was 0.683 (P < 0.001), and between the 1-year and 5-year total renal-free survival (78.3% vs. 69.1%) of the children was 0.476 (P < 0.001). The Bowman's Capsule Rupture (BCR), crescent, interstitial inflammation, and interstitial fibrosis/tubular atrophy (IF/TA) score were predictors of end-stage kidney disease (ESKD) risk but BCR showed better predictive value for ESKD than interstitial inflammation score (P = 0.027) and IF/TA score (P = 0.047). Patients with type I tended to have the worst renal survival rates. The three-month renal prognosis could partially reflect the 1-year renal prognosis, and the 1-year mortality rate could partially reflect the 5-year mortality rate of children with CrGN.

Disruption of RCAN1.4 expression mediated by YY1/HDAC2 modulates chronic renal allograft interstitial fibrosis

Chronic allograft dysfunction (CAD) is a major factor that hinders kidney transplant survival in the long run. Epithelial–mesenchymal transition (EMT) has been confirmed to significantly contribute to interstitial fibrosis/tubular atrophy (IF/TA), which is the main histopathological feature of CAD. Aberrant expression of the regulator of calcineurin 1 (RCAN1), recognized as an endogenous inhibitor of the calcineurin phosphatase, has been shown to be extensively involved in various kidney diseases. However, it remains unclear how RCAN1.4 regulates IF/TA formation in CAD patients. Herein, an in vivo mouse renal transplantation model and an in vitro model of human renal tubular epithelial cells (HK-2) treated with tumor necrosis factor-α (TNF-α) were employed. Our results proved that RCAN1.4 expression was decreased in vivo and in vitro, in addition to the up-regulation of Yin Yang 1 (YY1), a transcription factor that has been reported to convey multiple functions in chronic kidney disease (CKD). Knocking in of RCAN1.4 efficiently attenuated chronic renal allograft interstitial fibrosis in vivo and inhibited TNF-α-induced EMT in vitro through regulating anti-oxidative stress and the calcineurin/nuclear factor of activated T cells cytoplasmic 1 (NFATc1) signaling pathway. In addition, suppression of YY1 mediated by shRNA or siRNA alleviated TNF-α-induced EMT through abolishing reactive species partly in an RCAN1.4-dependent manner. Notably, we confirmed that YY1 negatively regulated RCAN1.4 transcription by directly interacting with the RCAN1.4 promoter. In addition, histone deacetylase 2 (HDAC2) interacted with YY1 to form a multi-molecular complex, which was involved in TNF-α-induced RCAN1.4 transcriptional repression. Therefore, RCAN1.4 is suggested to be modulated by the YY1/HDAC2 transcription repressor complex in an epigenetic manner, which is a mediated nephroprotective effect partly through modulating O2⋅− generation and the calcineurin/NFATc1 signaling pathway. Thus, the YY1–RCAN1.4 axis constitutes an innovative target for IF/TA treatment in CAD patients.

#6073 MAGNETIC RESONANCE RADIOMIC ANALYSIS FOR THE PREDICTION OF GRAFT FAILURE IN PATIENTS WITH KIDNEY TRANSPLANTATION

Abstract Background and Aims Prediction of future graft failure with non-invasive investigations is a relevant objective for transplant clinicians. We previously demonstrated a promising discrimination capacity for interstitial fibrosis / tubular atrophy (IFTA) &amp;gt;50% in kidney biopsy of a machine learning (ML) based magnetic resonance imaging (MRI) radiomic algorithm. Aim of the present study is to evaluate accuracy of MRI radiomic-based ML algorithms in predicting future graft failure. Method Single-center retrospective observational cohort study on a previously characterized cohort of kidney transplant recipients who underwent graft biopsy and graft MRI imaging within 6 months from biopsy, both on clinical indication, at the “Azienda Ospedaliero-Universitaria di Modena”, Italy, from 1/1/2012 to 1/3/2021. The primary outcome was to identify the best combination of MRI radiomic features for the prediction of graft failure during follow-up. Segmentation of renal parenchyma, cortex and medulla on MRI sequences was performed using the 3DSlicer software. Radiomic features were then extracted using an in-house software based on pyradiomics applying Wavelet and Gaussian filters. LASSO algorithm was employed to select correlated features with outcome and summarize them in a radiomic signature. Using radiomic signature alone and then merged with meaningful clinical data we trained ML-algorithms using 70% of cases for training/validation, with a 10-fold internal cross-validation, and 30% for model testing. Model performance was assessed using AUC with a 95% confidence interval (CI). Results Seventy coupled tests (63 patients) were included and randomly subdivided into a training/validation cohort (n = 50) and a test cohort (n = 20). Median follow-up was 24.73 months (interquartile range 13.64-46.57). Radiomic model had an AUC of 0.88 (95%_CI 0.70-0.97) in training and 0.57 (95%_CI 0.23-0.86) in test cohort. Radiomic-clinical mixed model had an AUC of 0.90 (95%_CI 0.73-0.98) in training and 0.66 (95%_CI 0.33-0.88) in test cohort. Conclusion We produced an MRI radiomic-based ML algorithm with good prediction ability for future graft failure in patients with kidney transplant. Given the limited number of enrolled patients, validation in larger (and ideally prospective) cohorts is required to confirm our findings. Comparison of radiomic-based ML with histological parameters (i.e., IFTA) for the prediction of graft failure in our cohort is currently under assessment.

Evolution of kidney allograft loss causes over 40 years (1979–2019)

IntroductionThe improvement of kidney allograft recipient and graft survival showed a decrease over the last 40 years. Long-term graft loss rate remained stable during a 25-year time span. Knowing the changing causes and the risk factors associated with graft loss requires special attention.The present study aimed to assess the causes of graft loss and kidney allograft recipient death. Also, we aimed to compare two different periods (1979−1999 and 2000−2019) to identify changes in the characteristics of the failed allografts and recipient and donors profile. Methods and patientsWe performed a single-center cohort study. We included all the kidney transplant recipients at the Hospital del Mar (Barcelona) between May 1979 and December 2019. Graft loss was defined as recipient death with functioning graft and as loss of graft function (return to dialysis or retransplantation). We assessed the causes of graft loss using clinical and histological information. We also analyzed the results of the two different transplant periods (1979−1999 and 2000−2019). ResultsBetween 1979 and 2019, 1522 transplants were performed. The median follow-up time was 56 (IQR 8–123) months. During follow-up, 722 (47.5%) grafts were lost: 483 (66.9%) due to graft failure and 239 (33.1%) due to death with functioning graft. The main causes of death were cardiovascular (25.1%), neoplasms (25.1%), and infectious diseases (21.8%). These causes were stable between the two periods of time. Only the unknown cause of death has decreased in the last period.The main cause of graft failure (loss of graft function) was the allograft chronic dysfunction (75%). When histologic information was available, antibody-mediated rejection (ABMR) and interstitial fibrosis/tubular atrophy (IF/TA) were the most frequent specific causes (15.9% and 12.6%). Of the graft failures, 213 (29.5%) were early (<1 year of transplantation). Vascular thrombosis was the main cause of early graft failure in the second period (2000−2019) (46.7%) and T-cell-mediated rejection (TCMR) was the main cause (31.3%) in the first period (1979−1999). The causes of late graft loss were similar between the two periods. ConclusionsThe causes of kidney allograft recipient death are still due to cardiovascular and malignant diseases. Vascular thrombosis has emerged as a frequent cause of early graft loss in the most recent years. The evaluation of the causes of graft loss is necessary to improve kidney transplantation outcomes.

Kidney injury molecule 1 (KIM-1): a potential biomarker of acute kidney injury and tubulointerstitial injury in patients with ANCA-glomerulonephritis.

Kidney injury molecule 1 (KIM-1) is a transmembrane glycoprotein expressed by proximal tubular cells, recognized as an early, sensitive and specific urinary biomarker for kidney injury. Blood KIM-1 was recently associated with the severity of acute and chronic kidney damage but its value in antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis with glomerulonephritis (ANCA-GN) has not been studied. Thus, we analyzed its expression at ANCA-GN diagnosis and its relationship with clinical presentation, kidney histopathology and early outcomes. We assessed KIM-1 levels and other pro-inflammatory molecules (C-reactive protein, interleukin-6, tumor necrosis factor α, monocyte chemoattractant protein-1 and pentraxin 3) at ANCA-GN diagnosis and after 6 months in patients included in the Maine-Anjou registry, which gathers data patients from four French Nephrology Centers diagnosed since January 2000. Blood KIM-1 levels were assessed in 54 patients. Levels were elevated at diagnosis and decreased after induction remission therapy. KIM-1 was associated with the severity of renal injury at diagnosis and the need for kidney replacement therapy. In opposition to other pro-inflammatory molecules, KIM-1 correlated with the amount of acute tubular necrosis and interstitial fibrosis/tubular atrophy (IF/TA) on kidney biopsy, but not with interstitial infiltrate or with glomerular involvement. In multivariable analysis, elevated KIM-1 predicted initial estimated glomerular filtration rate (β = -19, 95% CI -31, -7.6, P=.002). KIM-1 appears as a potential biomarker for acute kidney injury and for tubulointerstitial injury in ANCA-GN. Whether KIM-1 is only a surrogate marker or is a key immune player in ANCA-GN pathogenesis remain to be determined.

The association of plasma NT-proBNP level and progression of diabetic kidney disease

Aims Diabetic kidney disease (DKD) is the most common cause of end-stage kidney disease (ESKD). The identification of risk factors involved in the progression of DKD to ESKD is expected to result in early detection and appropriate intervention and improve prognosis. This study aimed to explore whether plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) was associated with kidney outcomes in patients with type 2 diabetes mellitus (T2DM) and biopsy-proven DKD. Methods Patients with biopsy-proven DKD who were followed up at West China Hospital over 12 months were enrolled. The kidney outcome was defined as progression to ESKD. The cutoff value of plasma NT-proBNP concentration was calculated by using receiver operating characteristic (ROC) curve analysis. The influence of NT-proBNP levels on kidney outcome in patients with DKD was assessed using Cox regression analysis. Results A total of 30 (24.5%) patients reached ESKD during a median follow-up of 24.1 months. The baseline serum NT-proBNP level had a significant correlation with baseline proteinuria, kidney function, glomerular lesions, interstitial fibrosis tubular atrophy (IFTA), and arteriolar hyalinosis. Multivariate Cox regression analysis indicated that increased NT-proBNP level was significantly associated with a higher risk of progression to ESKD (HR 6.43; 95% CI (1.65–25.10, p = 0.007), and each 1 SD increase in LG (NT-proBNP) was also associated with a higher risk (HR 2.43; 95% CI 1.94–5.29, p = 0.047) of an adverse kidney outcome after adjusting for confounding factors. Conclusions A higher level of plasma NT-proBNP predicts kidney prognosis in patients with biopsy-proven DKD. This warrants further investigation into the potential mechanisms.