CD163 and CD206 expression define distinct macrophage subsets involved in active ANCA-associated glomerulonephritis

Innate immune cells in acute and chronic kidney disease

Acute kidney injury (AKI) and chronic kidney disease (CKD) are inter-related clinical and pathophysiological disorders. Cells of the innate immune system, such as granulocytes and macrophages, can induce AKI through the secretion of pro-inflammatory mediators such as cytokines, chemokines and enzymes, and the release of extracellular traps. In addition, macrophages and dendritic cells can drive the progression of CKD through a wide range of pro-inflammatory and pro-fibrotic mechanisms, and by regulation of the adaptive immune response. However, innate immune cells can also promote kidney repair after acute injury. These actions highlight the multifaceted nature of the way by which innate immune cells respond to signals within the kidney microenvironment, including interaction with the complement and coagulation cascades, cells of the adaptive immune system, intrinsic renal cells and infiltrating mesenchymal cells. The factors and mechanisms that underpin the ability of innate immune cells to contribute to renal injury or repair and to drive the progression of CKD are of great interest for understanding disease processes and for developing new therapeutic approaches to limit AKI and the AKI-to-CKD transition.

The CD163 + tissue-infiltrating macrophages regulate ferroptosis in thyroid-associated ophthalmopathy orbital fibroblasts via the TGF-β/Smad2/3 signaling pathway

BACKGROUND

Thyroid-associated ophthalmopathy (TAO) is a thyroid function-related, organ-specific autoimmune disease that primarily leads to specific reactive changes and tissue remodeling in the periocular region. The exact pathogenesis of TAO remains unclear.

METHODS

High-throughput gene expression datasets related to TAO were comprehensively retrieved from the Gene Expression Omnibus (GEO) database, selecting GSE174139 and GSE158464 for analysis. Differentially expressed genes (DEGs) between TAO patients and healthy controls were identified, and ferroptosis-related genes (FRGs) were obtained from the FerrDb database. The intersection of DEGs and FRGs yielded ferroptosis-related genes associated with TAO.The transcriptional expression of FRGs was validated using real-time quantitative polymerase chain reaction (RT-qPCR) on orbital adipose tissue samples from TAO patients and healthy controls. Single-cell sequencing of six human tissue samples further analyzed changes in cellular subpopulations within the TAO microenvironment.Additionally, a co-culture model of CD163 + macrophages and TAO orbital fibroblasts, along with an in vitro TGF-β1-induced orbital fibroblast (OF) model, was constructed to validate the role of the TGF-β1/SMAD2/3 axis in ferroptosis regulation. Finally, potential clinical drugs targeting CD163 + macrophages with high ferroptosis activity in TAO were predicted using the Random Walk with Restart (RWR) algorithm combined with the DGIdb database.

RESULTS

We first utilized TAO-related datasets from the GEO database, combined with the FerrDb ferroptosis database, to identify changes in iron metabolism genes during TAO progression through differential expression analysis, screening 7 key ferroptosis-related proteins. In vitro validation revealed that all but AOPQ and LGMN, which were upregulated, exhibited downregulated expression.Single-cell sequencing of orbital connective tissue from 4 TAO patients and 2 healthy controls identified 16,364 cells spanning 18 cell types. Analysis of the 7 key ferroptosis-related proteins revealed that fibroblasts and macrophages displayed elevated ferroptosis signaling during TAO progression. Subcluster analysis of macrophages identified 4 distinct subpopulations, with the C2 subpopulation-characterized by high expression of CD163 and CCL18-exhibiting prominent ferroptosis activation signals.Further validation using clinical tissue samples, a co-culture model of CD163 + macrophages and TAO orbital fibroblasts, and an in vitro TGF-β1-induced orbital fibroblast (OF) model confirmed aberrant activation of the TGF-β1/SMAD2/3 pathway as a key regulator of ferroptosis. Hub gene analysis of C2 subpopulation marker genes, combined with the DGIdb database, predicted potential clinical drugs targeting the C2 macrophages.

CONCLUSION

This study, integrating single-cell RNA-Seq and bulk transcriptome analysis, revealed the involvement of CD163 + tissue-infiltrating macrophages in regulating ferroptosis of orbital fibroblasts during TAO progression and identified therapeutic candidates targeting macrophage ferroptosis signaling in TAO. Furthermore, in vitro experiments demonstrated that activation of the TGF-β1/SMAD2/3 axis promotes ferroptosis in TAO orbital fibroblasts, highlighting a novel pathway for potential therapeutic intervention.

Haptoglobin as a novel predictor of visceral involvement and relapse in adult IgAV patients

INTRODUCTION

IgA vasculitis (IgAV) can present as skin-limited or systemic disease, which can be severe in adults. Predictive markers for visceral involvement are suboptimal. Considering haptoglobin's role as an acute phase reactant, we evaluated whether its differential expression in IgAV patients' skin and leukocytes is also reflected systemically in a larger cohort of adult IgAV patients. Additionally, soluble form of haptoglobin scavenger receptor CD163 was measured in IgAV patient serum.

METHODS

We re-analyzed RNA sequencing data from leukocytes and skin biopsies of treatment-naïve adult IgAV patients: (1) IgAV nephritis (n = 3), (2) skin-limited IgAV (n = 3), and healthy controls (n = 3). Haptoglobin serum level was measured in 178, and haptoglobin genotyping was performed in 91 treatment-naïve adult IgAV patients. Serum sCD163 was measured in 60 IgAV patients and 22 HC.

RESULTS

Transcriptomic data of leukocytes and skin of IgAV nephritis patients identified haptoglobin as a hub gene, based on protein-protein interaction network. Haptoglobin serum level was elevated in IgAV patients with nephritis or gastrointestinal involvement compared to other IgAV patients. Patients who relapsed during follow-up had decreased haptoglobin serum level at disease presentation compared to non-relapsing patients. Haptoglobin genotyping did not show differences between genotype groups regarding clinical presentation and laboratory parameters. Serum sCD163 was significantly higher in IgAV nephritis patients compared to HC.

CONCLUSION

We identified haptoglobin as a novel marker of visceral involvement and relapse in adult IgAV, while sCD163 is linked to renal involvement. Further studies will confirm the clinical utility of haptoglobin as biomarker in IgAV. Key Points • Haptoglobin expression is upregulated in leukocytes and skin of adult IgAV with renal involvement. • Haptoglobin serum level is elevated in IgAV patients with visceral involvement. • Patients with IgAV relapse have lower haptoglobin at disease presentation.

CD163 detection in immune check-point inhibitors-related acute interstitial nephritis

Background

Acute interstitial nephritis (AIN) is the most common renal immune-related adverse event after immune check-point inhibitors (ICI). We hypothesized that alternatively activated macrophages (CD163-M) could be involved in ICI-AIN and wished to evaluate the use of their soluble urinary form (us)CD163 as a non-invasive diagnostic marker.

Methods

CD163-M infiltrates were evaluated by both immune-histochemistry and multiplex immunofluorescence and imaging. usCD163 was detected with ELLA technology and evaluated together with urinary creatinine to be expressed as a ratio to creatinuria in ng/mmol. Clinical data were collected to perform correlations with renal function assessed by estimated glomerular filtration rate (eGFR).

Results

A retrospective cohort of 63 ICI-exposed patients with tubular acute kidney injury profile requiring a biopsy were selected. AIN patients (n = 44) were compared to acute tubular necrosis (ATN) patients (n = 19). CD163-M staining was detectable in all ICI-AIN patients, which was significantly higher than in ATN patients (18.4% vs 3.6% of area, P  = .005). CD163-M staining was restricted to the interstitial compartment. CD163-M infiltrate inversely correlated with initial eGFR (r = -0.6, P  = .003), and was positively correlated with delta eGFR, reflecting a renal improvement outcome (r = 0.48; P  = .02). usCD163 was well detected in urines of patients, but did not allow us to distinguish ATN from AIN patients at diagnosis. No correlation was observed, neither between usCD163 and CD163-M staining nor with renal response after 3 months of glucocorticoid tapering.

Conclusion

CD163-M are detected in ICI-AIN and correlate both with severity at diagnosis and better prognosis at 3 months. CD163-M may help us to distinguish AIN from ATN but, it does not allow us to assess ICI imputability. Although detected in urine, usCD163 is clearly not a surrogate biomarker for AIN diagnosis.

Immune landscape in the glomerular transcriptome of nephrotic syndrome and anca-associated vasculitis

BACKGROUND

ANCA-associated vasculitis (AAV), and nephrotic syndrome encompassing diseases including minimal change disease (MCD), focal and segmental glomerulosclerosis (FSG), membranous nephropathy (MN), remain a challenge due to their varied immunological characteristics. Recent therapeutic advancements have highlighted the importance of understanding these diseases' immunological landscapes.

METHODS

This study analyzed transcriptomics data from renal glomerular tissues of patients with AAV, FSG, MCD, MN, and normal controls. Utilizing an immune-related gene set of 883 genes, methods including Gene Set Variation Analysis (GSVA), LASSO regression, and Weighted Correlation Network Analysis (WGCNA) were used. Predictions of immune cell compositions were made through CIBERSORT, TIMER, MCPcounter, and quanTIseq algorithms.

RESULTS

The study revealed distinct immunogenetic pathways enriched in each disease: hematopoietic cell lineage in ANCA, linoleic acid metabolism in FSG, PPAR signaling in MCD, and drug metabolism in MN. Classifiers based on immune gene expression showed high accuracy (AUC: ANCA 0.812, FSG 0.99, MCD 1, MN 0.888). Co-expression modules and PPI networks highlighted unique pathways for each disease. Predictions of immune cell composition showed elevated macrophages in FSG and MN, with Treg levels elevated across all four diseases compared to normal controls and highest in FSG. Correlation analyses demonstrated significant associations between classifier scores and immune cell types.

CONCLUSION

This study offers accurate classifiers for AAV, FSG, MCD, and MN, and reveals distinct immunological pathways. These findings advance personalized treatments and highlight potential therapeutic targets in AAV and nephrotic syndrome. Further research should validate these results for clinical applications.

Risk factors for renal outcomes in children with antineutrophil cytoplasmic antibody-associated vasculitis: a nationwide retrospective study in China

BACKGROUND

Pediatric antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is a life-threatening systemic vasculitis featured by liability to renal involvement. However, there are few studies on the risk factors and predictive models for renal outcomes of AAV in children.

METHODS

Data from 179 AAV children in multiple centers between January 2012 and March 2020 were collected retrospectively. The risk factors and predictive model of end-stage renal disease (ESRD) in AAV were explored.

RESULTS

Renal involvement was the most typical manifestation (95.5%), and the crescent was the predominant pathological lesion (84.9%). The estimated glomerular filtration rate (eGFR) was evaluated in 114 patients, of whom 59.6% developed ESRD, and the median time to ESRD was 3.20 months. The eGFR [P = 0.006, odds ratio (OR) = 0.955, 95% confidence interval (CI) = 0.924-0.987] and the percentages of global glomerulosclerosis (pGGS; P = 0.018, OR = 1.060, 95% CI = 1.010-1.112) were independent risk factors for ESRD of renal biopsy. Based on the pGGS and eGFR at renal biopsy, we developed three risk grades of ESRD and one predictive model. The Kaplan‒Meier curve indicated that renal outcomes were significantly different in different risk grades (P < 0.001). Compared with serum creatinine at baseline, the predictive model had higher accuracy (0.86 versus 0.58, P < 0.001) and a lower coefficient of variation (0.07 versus 0.92) in external validation.

CONCLUSIONS

Renal involvement is the most common manifestation of pediatric AAV in China, of which more than half deteriorates into ESRD. The predictive model based on eGFR at renal biopsy and the pGGS may be stable and accurate in speculating the risk of ESRD in AAV children. Supplementary file 2 (MP4 18937 KB).

CD109 identified in circulating proteomics mitigates postoperative recurrence in chronic rhinosinusitis with nasal polyps by suppressing TGF-β1-induced epithelial-mesenchymal transition

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a common inflammatory disorder with a high rate of recurrence. This study aimed to explore biomarkers for identifying patients with recurrent CRSwNP (rCRSwNP).

METHODS

We recruited two independent cohorts. In the discovery cohort, rCRSwNP patients and non-recurrent CRSwNP (non-rCRSwNP) patients were recruited, and the serum proteomic profile was characterized. The top 5 upregulated and downregulated proteins were confirmed in the validation cohort by ELISA, WB, and qRT-PCR, and their predictive values for postoperative recurrence were assessed. In vitro, human nasal epithelial cells (HNEpCs) were employed to assess the ability of candidate proteins to induce epithelial-mesenchymal transition (EMT).

RESULTS

Serum proteomics identified 53 different proteins, including 30 increased and 23 decreased, between the rCRSwNP and non-rCRSwNP groups. ELISA results revealed that serum levels of CD163 and TGF-β1 were elevated, CD109 and PRDX2 were decreased in the rCRSwNP group compared to the non-rCRSwNP group, and serum CD163, TGF-β1, and CD109 levels were proved to be associated with the risk of postoperative recurrence. In addition, qRT-PCR and WB revealed that tissue CD163, TGF-β1, and CD109 expressions in rCRSwNP patients were enhanced compared to those non-rCRSwNP patients. Kaplan-Meier analysis showed that increased CD163 and TGF-β1 expression and decreased CD109 expression are associated with the risk of recurrence in CRSwNP patients. Receiver operating characteristic curves showed that TGF-β1 and CD109 had superior diagnostic performances for rCRSwNP. In vitro experiments showed that TGF-β1 promoted EMT in HNEpCs, and overexpression of CD109 reversed this effect. Functional recovery experiments confirmed that CD109 could attenuate EMT in HNEpCs by inhibiting the TGF-β1/Smad signaling pathway, attenuating EMT in epithelial cells.

CONCLUSION

Our data suggested that TGF-β1 and CD109 might serve as promising predictors of rCRSwNP. The TGF-β1/Smad pathway was implicated in fostering EMT in epithelial cells, particularly those exhibiting low expression of CD109. Consequently, the absence of CD109 expression in epithelial cells could be a potential mechanism underlying rCRSwNP.

Urinary isomorphic red blood cells for the prediction of disease severity and renal outcomes in MPO-ANCA-associated vasculitis: a retrospective cohort study

BACKGROUND

Hematuria is common in myeloperoxidase anti-neutrophil cytoplasmic antibody associated vasculitis (ANCA-MPO). Previous studies have mainly focused on urinary dysmorphic red blood cells and few have reported the clinical significance of isomorphic urinary red blood cells. Therefore, the main aim of this study was to assess the predictive yield  of urinary isomorphic red blood cells for disease severity and renal outcomes in patients with ANCA-MPO associated vasculitis.

METHODS

A total of 191 patients with ANCA-MPO associated vasculitis with hematuria were retrospectively selected and were divided into two groups (with isomorphic red blood cells versus dysmorphic red blood cells) according to the percentage of isomorphic red blood cells on urinary sediment analysis. Clinical, biological and pathological data at diagnosis were compared. Patients were followed up for a median of 25 months and progression to end-stage kidney disease and death were regarded as main outcome events. Additionally, univariate and multivariate Cox regression models were used to estimate the risk factors for end-stage kidney disease.

RESULTS

Out of 191 patients, 115 (60%) had ≥ 70% and 76 (40%) had < 30% urine isomorphic red blood cells. Compared with patients in the dysmorphic red blood cell group, patients in the isomorphic red blood cell group had a significantly lower estimated glomerular filtration rate (eGFR) [10.41 mL/min (IQR 5.84-17.06) versus 12.53 (6.81-29.26); P = 0.026], higher Birmingham Vasculitis Activity Score [16 (IQR 12-18) versus 14 (10-18); P = 0.005] and more often received plasma exchange [40.0% versus 23.7% (P = 0.019)] at diagnosis. Kidney biopsies revealed a higher proportion of patients with glomerular basement membrane fracture in the isomorphic red blood cell group [46.3% versus 22.9% (P = 0.033)]. Furthermore, patients with predominant urinary isomorphic red blood cells were more likely to progress to end-stage kidney disease [63.5% versus 47.4% (P = 0.028)] and had a higher risk of death [31.3% versus 19.7% (P = 0.077)]. The end-stage kidney disease-free survival was lower in patients in the isomorphic red blood cell group (P = 0.024). However, urine isomorphic red blood cells ≥ 70% could not predict the presence of end-stage kidney disease in multivariate Cox analysis.

CONCLUSION

Myeloperoxidase-anti-neutrophil cytoplasmic antibody associated vasculitis patients with predominant urinary isomorphic red blood cells at diagnosis had more severe clinical manifestations and a higher risk of poor renal outcomes. In this respect, urinary isomorphic red blood cells could be viewed as a promising biomarker of ANCA_MPO vasculitis severity and progression.

Identification and validation of immune-associated NETosis subtypes and biomarkers in anti-neutrophil cytoplasmic antibody associated glomerulonephritis

Background

NETosis is a new form of cell death, marked by DNA chromatin release from dead neutrophils. While it aids in microbe defense, it may worsen inflammation in autoimmune diseases, causing tissue harm. The impact of NETosis on Anti-neutrophil Cytoplasmic Antibody-associated Glomerulonephritis (ANCA-GN) remains unexplored and requires investigation.

Methods

First, a weighted gene co-expression network analysis (WGCNA) was conducted to uncover differential expression of neutrophil extranuclear trap-associated genes (DE-NETs) in ANCA-GN. The NETosisScore model was established through the single sample gene set enrichment analysis (ssGSEA), which categorized all patients into high-risk and low-risk groups. The accuracy of model was assessed by ROC curve. The biological function of various subgroups was explored through Gene Set Variation Analysis (GSVA), while the abundance of immune cell infiltration was measured with CIBERSORT. Furthermore, the key NETosis-related genes (NRGs) were identified using three machine learning algorithms, and their relationship with renal function was analyzed through the NephroseqV5 database. Through the application of qPCR and immunohistochemical staining techniques, the mRNA and protein expression levels of NRGs were determined in patients with ANCA-GN and control.

Results

A NETosisScore model was developed from 18 DE-NETs using the ssGSEA algorithm. The model's ability to predict ANCA-GN patients with a ROC AUC of 0.921. The high-risk group in ANCA-GN showed enrichment of immune-related pathways and greater infiltration of immune cells, as revealed by KEGG enrichment analysis and CIBERSORT. Using three machine learning algorithms, we identified six NRGs. Significant positive correlations were found between NRGs and CCR, macrophages, T-cell co-inhibition, and TIL. Further KEGG analysis revealed that the functions of NRGs may be closely related to the toll-like receptor signaling pathway. The levels of NRGs increased as kidney function declined and were positively correlated with Scr (serum creatinine) and negatively correlated with GFR (glomerular filtration rate), qPCR analysis showed increased expression of most NRGs in ANCA-GN patients. Furthermore, immunohistochemical staining confirmed higher expression of all NRGs in ANCA-GN patients.

Conclusion

NETosisScore model accurately predicts high-risk patients in ANCA-GN with enriched immune pathways, 6 NRGs identified as potential biomarkers.

Longitudinal monitoring of circulating immune cell phenotypes in anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is a necrotizing multiorgan autoimmune disease that affects small- to medium-sized blood vessels. Despite the improvements in treatments, half of the patients with AAV still experience disease relapses. In this review, we focus on peripheral leukocyte properties and phenotypes in patients with AAV. In particular, we explore longitudinal changes in circulating immune cell phenotypes during the active phase of the disease and treatment. The numbers and phenotypes of leukocytes in peripheral blood were differs between AAV and healthy controls, AAV in active versus inactive phase, AAV in treatment responders versus non-responders, and AAV with and without severe infection. Therefore, biomarkers detected in peripheral blood immune cells may be useful for longitudinal monitoring of disease activity in AAV.