Protocol for the nationwide registry of patients with polycystic kidney disease: japanese national registry of PKD (JRP).

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are major genetic polycystic kidney diseases that can progress to end-stage kidney disease (ESKD). Longitudinal data on the clinical characteristics associated with clinical outcomes in polycystic kidney disease (PKD), including the development of ESKD and cardiovascular disease (CVD) are lacking in Japan. To address this unmet need the authors are establishing a novel, web-based, Nationwide Cohort Registry Study-the Japanese Registry of PKD (JRP). METHODS: The JRP is a prospective cohort study for ADPKD (aim to recruit n = 1000 patients), and both a retrospective and prospective study for ARPKD (aim to recruit n = 100). In the prospective registry, patients will be followed-up for 10 years every 6 months and 12 months for patients with ADPKD and ARPKD, respectively. Data collection will be recorded on Research Electronic Data Capture (REDCap) starting on April 1, 2024, with recruitment ending on March 31, 2029. (jRCT 1030230618). RESULTS: Data to be collected include: baseline data, demographics, diagnostic and genetic information, radiological and laboratory findings, and therapeutic interventions. During follow-up, clinical events such as development of ESKD, hospitalization, occurrence of extra kidney complications including CVD events, and death will be recorded, as well as patient-reported health-related quality of life for patients with ADPKD. CONCLUSIONS: The JRP is the first nationwide registry study for patients with ADPKD and ARPKD in Japan, providing researchers with opportunities to advance knowledge and treatments for ADPKD and ARPKD, and to inform disease management and future clinical practice.

Transcription factor Nrf2 activation regulates NETosis, endothelial injury, and kidney disease in myeloperoxidase-positive antineutrophil cytoplasmic antibody-associated vasculitis.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic autoimmune disease pathologically characterized by vascular necrosis with inflammation. During AAV development, activated neutrophils produce reactive oxygen species (ROS), leading to the aberrant formation of neutrophil extracellular traps (NETs) via NETosis and subsequent fibrinoid vascular necrosis. Nuclear factor-erythroid 2-related factor 2 (Nrf2) functions as an intracellular defense system to counteract oxidative stress by providing antioxidant properties. Herein, we explored the role of Nrf2 in the pathogenesis of AAV. The role and mechanism of Nrf2 in ANCA-stimulated neutrophils and subsequent endothelial injury were evaluated in vitro using Nrf2 genetic deletion and Nrf2 activator treatment. In corresponding in vivo studies, the role of Nrf2 in ANCA-transfer AAV and spontaneous AAV murine models was examined. Pharmacological activation of Nrf2 in vitro suppressed ANCA-induced NET formation via the inhibition of ROS. In contrast, NET formation was enhanced in Nrf2-deficient neutrophils. Furthermore, Nrf2 activation protected endothelial cells from ANC-induced NETs-mediated injury. In vivo, Nrf2 activation ameliorated glomerulonephritis in two AAV models by upregulating antioxidants and inhibiting ROS-mediated NETs. Furthermore, Nrf2 activation restrained the expansion of splenic immune cells, including T lymphocytes and limited the infiltration of Th17 cells into the kidney. In contrast, Nrf2 genetic deficiency exacerbated vasculitis in a spontaneous AAV model. Thus, the pathophysiological process in AAV may be downregulated by Nrf2 activation, potentially leading to a new therapeutic strategy by regulating NETosis.

Human iPSC-derived renal collecting duct organoid model cystogenesis in ADPKD.

In autosomal dominant polycystic kidney disease (ADPKD), renal cyst lesions predominantly arise from collecting ducts (CDs). However, relevant CD cyst models using human cells are lacking. Although previous reports have generated in vitro renal tubule cyst models from human induced pluripotent stem cells (hiPSCs), therapeutic drug candidates for ADPKD have not been identified. Here, by establishing expansion cultures of hiPSC-derived ureteric bud tip cells, an embryonic precursor that gives rise to CDs, we succeed in advancing the developmental stage of CD organoids and show that all CD organoids derived from PKD1-/- hiPSCs spontaneously develop multiple cysts, clarifying the initiation mechanisms of cystogenesis. Moreover, we identify retinoic acid receptor (RAR) agonists as candidate drugs that suppress in vitro cystogenesis and confirm the therapeutic effects on an ADPKD mouse model in vivo. Therefore, our in vitro CD cyst model contributes to understanding disease mechanisms and drug discovery for ADPKD.

Inhibition of Toll-like receptor 4 and Interleukin-1 receptor prevent SARS-CoV-2 mediated kidney injury.

Acute kidney injury (AKI) is a common and severe complication of the coronavirus disease 2019 (COVID-19). Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) directly affects the glomerular and tubular epithelial cells to induce AKI; however, its pathophysiology remains unclear. Here, we explored the underlying mechanisms and therapeutic targets of renal involvement in COVID-19. We developed an in vitro human kidney cellular model, including immortalized tubular epithelial and endothelial cell lines, demonstrating that SARS-CoV-2 directly triggers cell death. To identify the molecular targets in the process of SARS-CoV-2-mediated cell injury, we performed transcriptional analysis using RNA sequencing. Tubular epithelial cells were more prone to dying by SARS-CoV-2 than endothelial cells; however, SARS-CoV-2 did not replicate in renal cells, distinct from VeroE6/transmembrane protease serine 2 cells. Transcriptomic analysis revealed increased inflammatory and immune-related gene expression levels in renal cells incubated with SARS-CoV-2. Toll-like receptor (TLR) 3 in renal cells recognized viral RNA and underwent cell death. Furthermore, analysis of upstream regulators identified several key transcriptional regulators. Among them, inhibition of the interleukin-1 receptor (IL-1R) and TLR4 pathways protects tubular epithelial and endothelial cells from injury via regulation of the signal transducer and activator of transcription protein-3/nuclear factor-kB pathway. Our results reveal that SARS-CoV-2 directly injures renal cells via the proinflammatory response without viral replication, and that IL-1R and TLR4 may be used as therapeutic targets for SARS-CoV-2 mediated kidney injury.

Public support for patients with intractable diseases in Japan: impact on clinical indicators from nationwide registries in patients with autosomal dominant polycystic kidney disease.

BACKGROUND: Clinical practice guidelines recommend antihypertensive and tolvaptan therapies for patients with autosomal dominant polycystic kidney disease (ADPKD) in Japan. However, tolvaptan therapy may pose an economic burden. The Japanese Ministry of Health, Labour and Welfare supports patients with intractable diseases. This study aimed to confirm the impact of the intractable disease system in Japan on the clinical treatment of ADPKD. METHODS: We analyzed the data of 3768 patients with ADPKD having a medical subsidy certificate from the Japanese Ministry of Health, Labour and Welfare in 2015-2016. The following quality indicators were use: the adherence rate to the 2014 clinical practice guideline for polycystic kidney disease (prescription rates of antihypertensive agents and tolvaptan in this cohort) and the number of Japanese patients with ADPKD nationwide started on renal replacement therapy in 2014 and 2020. RESULTS: Compared with new applications from 2015 to 2016, the prescription rates of antihypertensives and tolvaptan for the indicated patients at the 2017 renewal application increased by 2.0% (odds ratio = 1.41, p = 0.008) and 47.4% (odds ratio = 10.1, p > 0.001), respectively. These quality indicators improved with antihypertensive treatment, especially in patients with chronic kidney disease stages 1-2 (odds ratio = 1.79, p = 0.013) and in those aged < 50 years (odds ratio = 1.70, p = 0.003). The number of patients with ADPKD who were started on renal replacement therapy in Japan decreased from 999 in 2014 to 884 in 2020 in the nationwide database (odds ratio = 0.83, p < 0.001). CONCLUSIONS: The Japanese public intractable disease support system contributes to improvement of ADPKD treatment.

Transcriptional dynamics of granulocytes in direct response to incubation with SARS-CoV-2.

Severe coronavirus disease 2019 (COVID-19) is characterized by acute respiratory distress syndrome and multiple organ dysfunction, in which the host immune response plays a pivotal role. Excessive neutrophil activation and subsequent superfluity of neutrophil extracellular traps (NETs) can lead to tissue damage, and several studies have shown the involvement of neutrophils in severe COVID-19. However, the detailed responses of each neutrophil subset to SARS-CoV-2 infection has not been fully described. To explore this issue, we incubated normal-density granulocytes (NDGs) and low-density granulocytes (LDGs) with different viral titers of SARS-CoV-2. NDGs form NETs with chromatin fibers in response to SARS-CoV-2, whereas LDGs incubated with SARS-CoV-2 display a distinct morphology with condensed nuclei and moderate transcriptional changes. Based on these transcriptional changes, we suggest that AGO2 possibly plays a role in LDG regulation in response to SARS-CoV-2.

Cystic Kidney Diseases That Require a Differential Diagnosis from Autosomal Dominant Polycystic Kidney Disease (ADPKD).

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary cystic kidney disease, with patients often having a positive family history that is characterized by a similar phenotype. However, in atypical cases, particularly those in which family history is unclear, a differential diagnosis between ADPKD and other cystic kidney diseases is important. When diagnosing ADPKD, cystic kidney diseases that can easily be excluded using clinical information include: multiple simple renal cysts, acquired cystic kidney disease (ACKD), multilocular renal cyst/multilocular cystic nephroma/polycystic nephroma, multicystic kidney/multicystic dysplastic kidney (MCDK), and unilateral renal cystic disease (URCD). However, there are other cystic kidney diseases that usually require genetic testing, or another means of supplementing clinical information to enable a differential diagnosis of ADPKD. These include autosomal recessive polycystic kidney disease (ARPKD), autosomal dominant tubulointerstitial kidney disease (ADTKD), nephronophthisis (NPH), oral-facial-digital (OFD) syndrome type 1, and neoplastic cystic kidney disease, such as tuberous sclerosis (TSC) and Von Hippel-Lindau (VHL) syndrome. To help physicians evaluate cystic kidney diseases, this article provides a review of cystic kidney diseases for which a differential diagnosis is required for ADPKD.

Soluble Interleukin-2 Receptor Predicts Treatment Outcome in Patients With Autoimmune Tubulointerstitial Nephritis. A Preliminary Study.

Background: Autoimmune tubulointerstitial nephritis (TIN) is characterized by immune-mediated tubular injury and requires immunosuppressive therapy. However, diagnosing TIN and assessing therapeutic response are challenging for clinicians due to the lack of useful biomarkers. Pathologically, CD4+ T cells infiltrate to renal tubulointerstitium, and soluble interleukin-2 receptor (sIL-2R) has been widely known as a serological marker of activated T cell. Here, we explored the usefulness of serum sIL-2R to predict the treatment outcome in patients with autoimmune TIN. Methods: Study Design: Single-center retrospective observational study. Participants: 62 patients were diagnosed of TIN from 2005 to April 2018 at Hokkaido University Hospital. Among them, 30 patients were diagnosed with autoimmune TIN and treated with corticosteroids. We analyzed the association between baseline characteristics including sIL-2R and the change of estimated glomerular filtration rate (eGFR) after initiation of corticosteroids. Results: The serum sIL-2R level in patients with autoimmune TIN was significantly higher than that in chronic kidney disease patients with other causes. Mean eGFR in autoimmune TIN patients treated with corticosteroids increased from 43.3 ± 20.4 mL/min/1.73 m2 (baseline) to 50.7 ± 19.9 mL/min/1.73 m2 (3 months) (ΔeGFR; 22.8 ± 26.0%). Multivariate analysis revealed that higher sIL-2R (per 100 U/mL, ß = 1.102, P < 0.001) level was independently associated with the renal recovery. In ROC analysis, sIL-2R had the best area under the curve value (0.805) and the cutoff point was 1182 U/mL (sensitivity = 0.90, 1-specificity = 0.45). Conclusions: Our study showed that elevated serum sIL-2R levels might become a potential predictive marker for therapeutic response in autoimmune TIN.

Recombinant thrombomodulin ameliorates autoimmune vasculitis via immune response regulation and tissue injury protection.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is characterized by necrotizing vasculitis with the presence of pathogenic ANCA. ANCA can potentially cause neutrophil activation and induce neutrophil extracellular traps (NETs), resulting in endothelial damage as well as activation of autoreactive B cells and alternative complement pathway. Recombinant thrombomodulin (rTM) protects the endothelium from vascular injury during disseminated intravascular coagulation, thus we hypothesized that rTM ameliorates necrotizing vasculitis in AAV. In this study, rTM was administered in an experimental AAV rat model. Treatment of experimental AAV rats with rTM improved pulmonary hemorrhage and glomerulonephritis, with a suppression of ANCA production and NETs formation. In addition, in vitro experiments showed that rTM bound to neutrophils via Mac-1 (macrophage-1 antigen) and inhibited ANCA-induced NETs formation accompanied by a suppression of histone citrullination, leading to a protection of the endothelium from NETs toxicity. Additionally, rTM affected lymphocytes leading to the inhibition of pro-inflammatory cytokine/chemokin in PBMC during the antibody production process, which might indirectly be involved in the reduction of pathogenic ANCA. Our data revealed that the rTM could ameliorate autoimmune vasculitis through a combination of different biological mechanisms.

A case report dysregulated neutrophil extracellular traps in a patient with propylthiouracil-induced anti-neutrophil cytoplasmic antibody-associated vasculitis.

RATIONALE: Neutrophil extracellular traps (NETs) are immune defence systems that release extracellular chromatin and myeloid granules including myeloperoxidase (MPO) to kill pathogens. An experimental animal study recently demonstrated that disordered NETs induced by propylthiouracil (PTU) could contribute to the production of MPO anti-neutrophil cytoplasmic antibody (ANCA) and the development of ANCA-associated vasculitis (AAV). However, the role of dysregulated NETs in the pathogenesis of human AAV remains unclear. PATIENT CONCERNS: We report a 19-year-old woman with Graves' disease on PTU presented fever, polyarthralgia, and lung hemorrhage with high titer of MPO-ANCA. This patient had a variety of atypical ANCAs and disordered NETs in vitro. DIAGNOSES: A diagnosis of PTU-induced AAV (PTU-AAV). INTERVENTIONS: The PTU was discontinued and she was treated with immunosuppressants and plasmapheresis for reducing pathogenic autoantibodies. OUTCOMES: Clinical manifestations including fever, polyarthralgia, and lung hemorrhage were on remission with a decrease of dysregulated NETs. LESSONS: The clinical course of this PTU-AAV case indicated that dysregulated NETs would play a role in the development of ANCA and the pathogenesis of AAV.

The presence of anti-neutrophil extracellular trap antibody in patients with microscopic polyangiitis.

OBJECTIVE: Although ANCA is the major autoantibody in patients with ANCA-associated vasculitis, previous studies have suggested the presence of anti-neutrophil extracellular trap (NET) antibody in patients with microscopic polyangiitis (MPA), one type of ANCA-associated vasculitis. In this study, we aimed to determine the prevalence and pathogenic role of anti-NET antibody (ANETA) in MPA. METHODS: We examined the presence or absence of ANETA in sera obtained from 19 MPA patients by indirect immunofluorescence. We compared the clinical parameters, including age, sex, MPO-ANCA, creatinine, CRP, MPO-DNA complexes and vasculitis activity, in ANETA-positive and ANETA-negative MPA patients. We investigated the serum NET induction and degradation abilities of ANETA-positive and ANETA-negative MPA patients with reference to healthy controls (n = 8). Furthermore, we assessed the relationship between ANETA and the effect of IgG depletion on the serum NET degradation ability. RESULTS: ANETA was present in 10 of the 19 MPA patients. There was no significant difference in the clinical parameters in ANCA-positive and ANCA-negative MPA patients. Although the NET induction ability was higher and the NET degradation ability was lower in MPA sera than those in healthy controls, these abilities were not different between ANETA-positive and ANETA-negative MPA sera. Interestingly, the NET degradation ability in some sera with ANETA was markedly increased by IgG depletion. CONCLUSION: Some MPA patients produce ANETA and some ANETA possess an inhibitory function against the serum NET degradation ability. Although further studies are needed, ANETA is worthy of attention in order to understand the pathophysiology of MPA.

Initial experience with the use of tris-acryl gelatin microspheres for transcatheter arterial embolization for enlarged polycystic liver.

PURPOSE: To assess the safety and effectiveness of transcatheter arterial embolization (TAE) with tris-acryl gelatin microspheres for patients with symptomatic enlarged polycystic liver disease (PCLD). MATERIALS AND METHODS: This prospective study was approved by our hospital's institutional review board and planned for patients with symptoms related to enlarged PCLD, such as distended abdomen, gastrointestinal obstruction and abdominal pain. Hemi-hepatic embolization with tris-acryl gelatin microspheres was performed in the hepatic artery supplying the hepatic lobe that showed the predominant presence of cysts. Each patient underwent an assessment of liver function, a questionnaire survey about symptoms, measurement of the estimated volume of the whole liver before and after TAE, and an assessment of complications associated with TAE. RESULTS: Five patients (four females, one male; mean age 52.6 ± 9.1 years) were treated. All five patients successfully completed TAE. The left lobe was treated in three patients and the right in two. After TAE, post-embolization syndrome and transient elevation of white blood cells, aspartate aminotransferase, and alanine aminotransferase occurred in all patients, but none developed hepatic insufficiency or severe complications. The mean whole liver volume was 7406 ± 2323 mL before TAE, and 6995 ± 2139 mL (95.1 ± 5.2% of the pre-therapeutic value) at 3 months and 6855 ± 2246 mL (93.3 ± 9.7%) at 12 months after TAE. Three of the five patients reported an improvement of clinical symptoms within 12 months after TAE. CONCLUSION: TAE with microspheres can be a safe and effective treatment for symptomatic enlarged PCLD.

The Diagnostic and Clinical Utility of the Myeloperoxidase-DNA Complex as a Biomarker in Otitis Media With Antineutrophil Cytoplasmic Antibody-associated Vasculitis.

OBJECTIVE: This prospective study aimed to evaluate the diagnostic and clinical utility of the myeloperoxidase (MPO)-DNA complex as a NETosis-derived product in the middle ear fluid of patients with otitis media with antineutrophil cytoplasmic antibody-associated vasculitis (OMAAV). STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS: Twenty-two patients diagnosed with OMAAV. INTERVENTION: Collection of the fluid samples from middle ear. MAIN OUTCOME MEASURE: The levels of the MPO-DNA complex in the fluid samples were quantified using an enzyme-linked immunosorbent assay. RESULTS: Patients with both systemic and localized forms of OMAAV showed significantly higher levels of the MPO-DNA complex compared to the controls (p < 0.001 and p = 0.002, respectively). In particular, they showed significantly higher levels of MPO-DNA complex compared to the controls, regardless of serum antineutrophil cytoplasmic antibody status (p < 0.001 and p < 0.001, respectively) or immunosuppressive therapy (p < 0.001 and p < 0.001, respectively) at the time of sampling. An optical density cutoff value of 0.16 at 405 nm according to the receiver operating characteristic curve showed a sensitivity of 86.4%, specificity of 95.5%, positive predictive value of 95.0% and negative predictive value of 87.5% for the diagnosis of OMAAV. Significant positive correlations were observed between the levels of MPO-DNA complex and the values for air conduction - (r = 0.49, p = 0.022) and bone conduction - pure tone average thresholds (r = 0.45, p = 0.035). CONCLUSIONS: The detection and quantification of the MPO-DNA complex in the otitis media fluid may aid in providing a definite diagnosis as well as predicting the activity and severity of OMAAV.

Detection of Autoreactive Type II NKT Cells: A Pilot Study of Comparison Between Healthy Individuals and Patients with Vasculitis.

NKT cells are defined as T cells that recognize hydrophobic antigens presented by class I MHC-like molecules, including CD1d. Among CD1d-restricted NKT cells, type I and type II subsets have been noted. CD1d-restricted type I NKT cells are regarded as pro-inflammatory cells in general. On the contrary, accumulated evidence has demonstrated an anti-inflammatory property of CD1d-restricted type II NKT cells. In our earlier study using a rat model with vasculitis, we demonstrated the pro-inflammatory function of CD1d-restricted type II NKT cells and identified that one such cell recognized P518-532 of rat sterol carrier protein 2 (rSCP2518-532 ), which appeared on vascular endothelial cells presented by CD1d. Based on this evidence, we attempted to detect human CD1d-restricted type II NKT cells in peripheral blood using hSCP2518-532 , the human counterpart of rSCP2518-532, together with a CD1d tetramer in flow cytometry. First, we determined the binding of hSCP2518-532 to CD1d. Next, we detected CD3-positive hSCP2518-532 -loaded CD1d (hSCP2518-532 /CD1d) tetramer-binding cells in peripheral blood of healthy donors. The abundance of TGF-ß-producing cells rather than TNF-α-producing cells in CD3-positive hSCP2518-532 /CD1d tetramer-binding cells suggests the anti-inflammatory property of SCP2-loaded CD1d (SCP2/CD1d) tetramer-binding type II NKT cells in healthy individuals. Furthermore, we compared cytokine profile between healthy individuals and patients with vasculitis in a pilot study. Interestingly, the percentage of TGF-ß-producing cells in SCP2/CD1d tetramer-binding type II NKT cells in vasculitic patients was significantly lower than that in healthy controls despite the greater number of these cells. Although further studies to clarify the mechanism and significance of this phenomenon are needed, SCP2/CD1d tetramer-binding type II NKT cells in peripheral blood should be examined in more detail to understand the pathophysiology of vasculitides in humans. © 2018 International Society for Advancement of Cytometry.

Anti-neutrophil extracellular trap antibody in a patient with relapse of anti-neutrophil cytoplasmic antibody-associated vasculitis: a case report.

BACKGROUND: Neutrophil extracellular traps (NETs) are web-like DNA decorated with antimicrobial proteins, such as myeloperoxidase (MPO), which are extruded from activated neutrophils. Although NETs are essential in innate immunity, an excessive formation of NETs has adverse effects, e.g., induction of anti-neutrophil cytoplasmic antibody (ANCA), to the hosts. Since ANCA can induce NET formation in the primed neutrophils, a positive feedback loop can be formed between NETs and ANCA, which is called "ANCA-NETs vicious cycle." CASE PRESENTATION: A 79-year-old Japanese woman developed hydralazine-induced pauci-immune necrotizing crescentic glomerulonephritis with MPO-ANCA. Although the illness improved after cessation of hydralazine, MPO-ANCA-associated vasculitis relapsed 16 months later. Remission was achieved 5 months after beginning of administration of prednisone. In order to determine the involvement of ANCA-NETs vicious cycle in this patient, we examined NET degradation and induction activities in sera obtained at the disease onset (Serum A; MPO-ANCA, 107 IU/ml), at relapse (Serum B; MPO-ANCA, 195 IU/ml), at 3 months after treatment (Serum C; MPO-ANCA, 4.5 IU/ml), and at remission (Serum D; MPO-ANCA, 2.4 IU/ml). NET degradation activity was low in the all sera. NET induction activity was high in Sera A, B, and C but not in D. Additionally, we demonstrated the presence of anti-NET antibody (ANETA) in Sera B and C but not in A or D. CONCLUSIONS: The collective findings suggest NET induction potential of ANETA in the present patient and that the ANETA could contribute to the enhancement of NETs resulting in amplification of the ANCA-NETs vicious cycle.

Elevated Level of Myeloperoxidase-Deoxyribonucleic Acid Complex in the Middle Ear Fluid Obtained From Patients With Otitis Media Associated With Antineutrophil Cytoplasmic Antibody-associated Vasculitis.

OBJECTIVE: The purpose was to explore the presence of myeloperoxidase (MPO)-deoxyribonucleic acid (DNA) complex as a surrogate marker of neutrophil extracellular traps (NETs) in the middle ear fluid, and to clarify the correlation between its quantifiable level and hearing outcome in patients with otitis media associated with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS: Nine AAV patients presenting with otitis media. INTERVENTION: Collection of the fluid samples from middle ear. MAIN OUTCOME MEASURE: The quantifiable levels of MPO-DNA complex using an enzyme-linked immunosorbent assay. RESULTS: The quantifiable levels of MPO-DNA complex in patients with AAV were significantly higher than those in controls (p < 0.001). In particular, both ANCA-positive and -negative cases indicated higher levels of MPO-DNA complex compared with the controls (p = 0.004 and p = 0.006, respectively). The significant negative correlations were observed between the level of MPO-DNA complex and the functional hearing values for air (r = -0.82, p = 0.009) and bone conduction (r = -0.73, p = 0.028), respectively. CONCLUSION: This analysis is the first to reveal the presence of elevated levels of MPO-DNA complex in the middle ear fluid, suggesting the pathogenic role of NETs in otitis media associated with AAV. NETs may be a valuable biomarker for use in clinical decision-making and predicting hearing outcome, regardless of ANCA status.

Measurement of NET formation in vitro and in vivo by flow cytometry.

Neutrophil extracellular traps (NETs) are extracellular chromatin fibers adorned with antimicrobial proteins, such as myeloperoxidase (MPO), which are extruded from activated neutrophils. NETosis is the metamorphosis of neutrophils with NET formation that follows decondensation of DNA and rupture of the plasma membrane. Although NETs play important roles in innate immunity, excessive formation of NETs can be harmful to the hosts. Until now, various methods for evaluation of NETs have been reported. Although each has a virtue, the gold standard has not been established. Here we demonstrate a simple, objective, and quantitative method to detect NETs using flow cytometry. This method uses a plasma membrane-impermeable DNA-binding dye, SYTOX Green. SYTOX Green-positive cells were detected in human peripheral polymorphonuclear cells exposed to a NET inducer, phorbol 12-myristate 13-acetate (PMA). The number of SYTOX Green-positive cells was increased depending on the exposure duration and concentrations of PMA. Furthermore, co-localization of MPO and plasma membrane-appendant DNA of SYTOX Green-positive cells was demonstrated. Moreover, a NET inhibitor, diphenylene iodonium, could significantly reduce the number of SYTOX Green-positive cells induced by PMA. The collective evidence suggests that SYTOX Green-positive cells include neutrophils that formed NETs. The established method could detect neutrophils that underwent NETosis but not early apoptosis with equivalence in quantification to another well-used image analysis, which is based on fluorescent staining. Additionally, NETs that were formed in vivo were also detectable by this method. It is conceivable that the established method will bring us better understanding of the relation between NETosis and human diseases. © 2017 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of ISAC.