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Calprotectin is produced by neutrophils and macrophages, and released during the acute phase of the ANCA vasculitis. The aim of our study was to determine if serum and urine calprotectin are disease activity and prognosis biomarkers in ANCA vasculitis patients during remission. Forty-two ANCA vasculitis patients were included. Twenty-seven patients were in remission phase under immunosuppressive therapy, and 15 patients were in the acute phase. Four healthy controls were included. We determined calprotectin in serum and urine samples at the time of the inclusion. We recorded the incidence of relapse and the evolution of GFR, proteinuria, hematuria, and C reactive protein and ANCA titer during 24 months of follow-up. In remission phase, serum calprotectin was higher than in healthy controls but lower compared to acute patients (p = 0.05). Serum calprotectin at inclusion was higher in patients who increased proteinuria during follow-up (p = 0.04), with hematuria (p = 0.08), and with non-decreasing ANCA titer (p = 0.0019). Serum calprotectin at inclusion in stable patients who subsequently decreased GFR during follow-up was higher compared with those with a stable or improving GFR (p = 0.03). Urine calprotectin was lower in patients with sclerotic histology in remission (p = 0.03) and acute phase (p = 0.12) compared to the rest of histologies. Worsening of renal function, hematuria, rising proteinuria and non-decreasing ANCA correlated with higher levels of serum calprotectin at recruitment. Low urine calprotectin was found in patients with sclerotic histology. Calprotectin during remission in ANCA vasculitis may be useful to identify subclinical inflammation and worse renal prognosis patients.

Background Prognostication in glomerulonephritis with severe kidney function impairment is critical for evaluating the benefit-to-risk ratio of immunosuppression. We hypothesized that the urine biomarker epidermal growth factor (EGF) could have good discrimination power to identify subjects who might ultimately recover kidney function. Methods We included 82 subjects with glomerulonephritis and severe kidney function impairment at admission (estimated glomerular filtration rate [eGFR] ≤ 30 mL/min/1.73m 2 ): 58 with lupus nephritis (LN) and 24 with ANCA-associated vasculitis (AAV). Thirty-five subjects required kidney replacement therapy (KRT) at presentation. Urine epidermal growth factor was measured and corrected by urine creatinine (uEGF/Cr) and the population was analyzed by uEGF/Cr tertiles. The primary outcome was time to recovery of eGFR ≥ 30 mL/min/1.73m 2 and time to recovery of kidney function with dialysis independence in those with initial KRT. Results Forty-four (54%) participants met the primary outcome of recovery of eGFR ≥ 30 mL/min/1.73m 2 . The 6-month recovery rates were 93%, 57%, and 0% for participants in the highest, middle, and lowest uEGF/Cr tertile, respectively. Recovery of the kidney function was faster and led to a higher post-therapy eGFR in the highest uEGF/Cr tertile. In the ROC analysis, uEGF/Cr was a predictor of recovery with an area under the curve (AUC) of 0.92 (95% CI 0.87–0.98), and a cutoff of 2.60 ng/mg had 100% sensitivity to detect patients who recovered kidney function. In the subgroup of participants with initial KRT, the cut-off of uEGF/Cr of 2.0 ng/mg had 100% sensitivity to detect participants who recovered kidney function with dialysis independence by 6 months. Conclusions Urine EGF/Cr is a promising biomarker to aid in the prediction of recovery of kidney function in glomerulonephritis with severe kidney function impairment. Graphical abstract

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is an autoimmune disease characterized by systemic small-vessel inflammation. Complement activation, particularly through the alternative pathway, has been implicated in AAV pathogenesis. However, the role and clinical significance of urinary complement C3 fragments as non-invasive biomarkers for disease activity remain unclear. This cross-sectional study enrolled 22 AAV patients and 20 healthy controls. Urinary levels of C3a, C3b, iC3b, C3c, and C3d were measured using enzyme-linked immunosorbent assay (ELISA) and normalized to urinary creatinine. Between-group comparisons were performed using independent t-tests or Mann–Whitney U tests. Correlations and independent predictors of urinary complement fragments were evaluated using Spearman correlation and multivariate linear regression, respectively. All urinary complement C3 fragment levels were significantly elevated in AAV patients compared to healthy controls (all p  < 0.01). Among AAV patients, urinary C3 fragments correlated strongly with Birmingham Vasculitis Activity Score (BVAS, r  = 0.793–0.900), proteinuria ( r  = 0.551–0.735), and hematuria ( r  = 0.643–0.752) (all p  < 0.01), but not with serum creatinine ( p  > 0.05). BVAS was an independent predictor of all C3 fragments (β = 0.458–0.760, all p  < 0.05), while proteinuria independently predicted all except iC3b (β = 0.302–0.455, all p  < 0.05). Urinary complement C3 fragments are elevated in AAV patients and closely associated with disease activity, independent of renal function. These findings support their potential utility as non-invasive biomarkers for monitoring AAV disease activity.

Activin A, a member of the transforming growth factor-beta superfamily, is a critical modulator of inflammation and plays a key role in controlling the cytokine cascade that drives the inflammatory response. However, the role of activin A in inflammatory kidney diseases remains unknown. To address this issue, we examined here whether activin A can be detected in the kidney and/or urine from patients with antineutrophil cytoplasmic antibody (ANCA) -associated vasculitis (AAV). Fifty-one patients who had been diagnosed with AAV and were treated in our department between November 2011 to March 2018 were included in this study. Forty-one patients had renal complications (renal AAV). Serum and urinary activin A levels were measured by enzyme-linked immunosorbent assay. Correlation of urinary activin A concentration with clinical parameters was analyzed. Urinary activin A was undetectable in healthy volunteers. In contrast, urinary activin A concentration was significantly increased in patients with renal AAV but not in those with non-renal AAV. Urinary activin A concentration decreased rapidly after immunosuppressive treatment. There was a significant correlation of urinary activin A level with urinary protein, L-FABP, and NAG. Histologic evaluation revealed that urinary activin A levels were significantly higher in patients with cellular crescentic glomeruli than in those lacking this damage. In situ hybridization demonstrated that the mRNA encoding the activin A βA subunit was undetectable in normal kidneys but accumulated in the proximal tubules and crescentic glomeruli of the kidneys of patients with renal AAV. Immunostaining showed that activin A protein also was present in the proximal tubules, crescentic glomeruli, and macrophages infiltrating into the interstitium in the kidneys of patients with renal AAV. These data suggested that urinary activin A concentration reflects renal inflammation and tubular damage in AAV and may be a useful biomarker for monitoring renal AAV.

Accurate prediction of renal outcomes in ANCA-associated vasculitis (AAV) is critical. This study evaluated the predictive value of urinary biomarkers for end-stage kidney disease (ESKD) progression. A prospective cohort of 88 AAV patients with renal involvement was followed for a median of 27 months. Urinary β-catenin, IL-18, trehalase, and NGAL were measured. Cox regression and ROC analyses assessed associations and predictive performance. 65 patients (73.9%) progressed to ESKD. Urinary trehalase and NGAL were significantly elevated in the ESKD group and were independent predictors of ESKD in multivariable analysis (both  < 0.05), with AUCs of 0.857 and 0.852, respectively. Their combination improved predictive accuracy (AUC = 0.869). β-catenin showed moderate predictive value (AUC = 0.705). Although urinary IL-18 showed statistical significance when analyzed as a continuous variable in an initial model, this association was not consistent across alternative modeling strategies and therefore was not considered a stable independent predictor. Stratified and landmark analyses confirmed the robustness of trehalase and NGAL's prognostic value. Urinary trehalase and NGAL are strong, noninvasive predictors of ESKD in AAV, and their combination enhances risk stratification, supporting potential clinical utility for personalized treatment decisions.

IntroductionThe current study aimed to investigate the association between urinary epidermal growth factor (uEGF) and renal disease severity and outcomes in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV).MethodsIntrarenal EGFmRNA expression was extracted from transcriptomic data of microdissected tubulointerstitial compartments of kidney biopsies of patients with AAV. uEGF was measured in 173 patients with AAV in active stage and 143 in remission, and normalised to urine creatinine excretion (uEGF/Cr). The association between uEGF/Cr (or EGFmRNA) and clinical–pathological parameters was tested using linear regression analysis. The ability of uEGF/Cr to predict renal outcomes was analysed using Cox’s regression analysis.ResultsIn patients with AAV, intrarenal EGFmRNA expression was significantly associated with estimated glomerular filtration rate (eGFR)(log2) at time of biopsy (β=0.63, p<0.001). The level of uEGF/Cr was significantly higher in patients in remission than in patients with active disease, both when looking at patients with sequential measurements (2.75±1.03vs 2.08±0.98, p<0.001) and in cross-sectional comparison. uEGF/Cr level was positively associated with eGFR(log2) at time of sampling in both active and remission stage (β=0.60, p<0.001; β=0.74, p<0.001, respectively). Patients with resistant renal disease had significantly lower uEGF/Cr levels than responders (1.65±1.22vs 2.16±1.26, p=0.04). Moreover, after adjusting for other potential predictors, uEGF/Cr was independently associated with composite endpoint of end-stage renal disease or 30% reduction of eGFR (HR 0.61, 95% CI 0.45 to 0.83, p=0.001).ConclusionLower uEGF/Cr levels are associated with more severe renal disease, renal resistance to treatment and higher risk of progression to composite outcome in patients with AAV.

ObjectiveThe PD-1 axis promotes protection against autoimmunity. Immune checkpoint (IC) molecules performance in anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) remains unknown. This study aims to assess the IC pathway’s role in the AAV’s pathophysiology.MethodsWe recruited 88 AAV from our centre as a discovery cohort (acute=42, remission=46) and 30 patients from another institution for external validation (acute=16, remission=14).Serum, urine and peripheral blood mononuclear cells (PBMCs) were collected. In vitro IC molecules production by lymphocytes was studied with and without MPO/PR3 antigen stimulus. Cell culture supernatant (SN) was obtained by centrifugation. PD-1, PD-L1 and PD-L2 concentrations were assessed in serum (s), urine (u) and SN of AAV and healthy controls (HC) using a multiplex assay. PD-1 and PD-L1’s expression was analysed in six diagnostic kidney biopsies.ResultsuPD-1 and uPD-L2’s concentration was lower in AAV than HC (p<0.0001, p=0.0075). Acute patients exhibited lower uPD-L2 levels compared with those in remission (p=0.036). Similarly, PBMCs showed reduced PD-1 production than HC (stimulated group p=0.04, unstimulated p=0.0074). Furthermore, patients with inflammatory renal lesions had fewer PD-1-positive interstitial cells/staining intensity compared with those with sclerotic lesions. Contradictorily, sPD-1 and sPD-L1’s concentration was higher in AAV than HC (p=0.007, p<0.0001) with acute patients exhibiting elevated sPD-1 levels compared with those in remission (p=0.0051). Serum and urine findings were confirmed in the validation cohort.ConclusionsResults in urine, SN and histology suggest IC pathway abolition during acute disease restored in remission and contribute to understand PD-1 axis’s role in AAV proposing it as a new biomarker of disease activity.

BackgroundWhen we encounter glomerulonephritis of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides demonstrating many plasma cell infiltrations, histological overlapping of immunoglobulin G4-related disease (IgG4-RD) often comes into the differential diagnosis. No previous study has focused on the degree of plasma cells in the kidney infiltrate in ANCA-associated glomerulonephritis (ANCA-GN), and the significance of massive plasma cell infiltrate has not been investigated.MethodsTo clarify the plasma cell ratio in renal biopsy specimens of ANCA-GN and the histological characteristic of “plasma cell-rich” ANCA-GN, 20 cases of ANCA-GN were reviewed and clinicopathologically analyzed.ResultsPlasma cell ratio was widely distributed between 1.4 and 81%, and the median ratio was 10%. Three patients were categorized in “plasma cell-rich” ANCA-GN, defined as over 45% plasma cell ratio. They tended to include many active glomerular lesions compared to chronic lesions and to display severe tubulointerstitial inflammation. It is suggested that plasma cell-rich ANCA-GN may be acute onset of the disease, and the target of early inflammation may also be in the tubulointerstitial region. Two of the three plasma cell-rich ANCA-GN cases demonstrated numerous IgG4+ cells, but no bird’s-eye pattern fibrosis or obliterative phlebitis.ConclusionsPlasma cell-rich ANCA-GN is not rare and demonstrates distinct clinicopathological characteristics. This study also reminds us that the presence of the significant number of plasma cells in ANCA-GN, as such, is not a histological diagnostic basis for overlap ANCA-GN and IgG4-related disease.

Biospectroscopy offers the ability to simultaneously identify key biochemical changes in tissue associated with a given pathological state to facilitate biomarker extraction and automated detection of key lesions. Herein, we evaluated the application of machine learning in conjunction with Raman spectroscopy as an innovative low-cost technique for the automated computational detection of disease activity in anti-neutrophil cytoplasmic autoantibody (ANCA)-associated glomerulonephritis (AAGN). Consecutive patients with active AAGN and those in disease remission were recruited from a single UK centre. In those with active disease, renal biopsy samples were collected together with a paired urine sample. Urine samples were collected immediately prior to biopsy. Amongst those in remission at the time of recruitment, archived renal tissue samples representative of biopsies taken during an active disease period were obtained. In total, twenty-eight tissue samples were included in the analysis. Following supervised classification according to recorded histological data, spectral data from unstained tissue samples were able to discriminate disease activity with a high degree of accuracy on blind predictive modelling: F-score 95% for >25% interstitial fibrosis and tubular atrophy (sensitivity 100%, specificity 90%, area under ROC 0.98), 100% for necrotising glomerular lesions (sensitivity 100%, specificity 100%, area under ROC 1) and 100% for interstitial infiltrate (sensitivity 100%, specificity 100%, area under ROC 0.97). Corresponding spectrochemical changes in paired urine samples were limited. Future larger study is required, inclusive of assigned variables according to novel non-invasive biomarkers as well as the application of forward feature extraction algorithms to predict clinical outcomes based on spectral features.

Recognizing patients at early phases of chronic kidney disease (CKD) is difficult, and it is even more challenging to predict acute kidney injury (AKI) and its transition to CKD. The gold standard to timely identify renal fibrosis is the kidney biopsy, an invasive procedure not usually performed for this purpose in clinical practice. SerpinA3 was identified by high-resolution-mass-spectrometry in urines from animals with CKD. An early and progressive elevation of urinary SerpinA3 (uSerpinA3) was observed during the AKI to CKD transition together with SerpinA3 relocation from the cytoplasm to the apical tubular membrane in the rat kidney. uSerpinA3/alpha-1-antichymotrypsin was significantly increased in patients with CKD secondary to focal and segmental glomerulosclerosis (FSGS), ANCA associated vasculitis (AAV) and proliferative class III and IV lupus nephritis (LN). uSerpinA3 levels were independently and positively associated with renal fibrosis. In patients with class V LN, uSerpinA3 levels were not different from healthy volunteers. uSerpinA3 was not found in patients with systemic inflammatory diseases without renal dysfunction. Our observations suggest that uSerpinA3 can detect renal fibrosis and inflammation, with a particular potential for the early detection of AKI to CKD transition and for the differentiation among lupus nephritis classes III/IV and V.