Daiki Aomura

Kidney proximal tubules (PT) utilize endocytosis to maintain body homeostasis. Effective PT repair mechanisms after acute kidney injury (AKI) are crucial to avoid the transition to chronic kidney disease (CKD). Cultured PT cells are often utilized to study these processes, but studies demonstrate loss of functional transporter expression in nearly all available cell lines. Here, we describe acquisition and culture of human PT cells isolated from the kidneys of brain‐dead donors (bddPTC) not suitable for transplantation and designated to research. The kidney cortex was digested, and the cells filtered through strainers were cultured. After passage 1, the cells were labeled for CD10 and CD13, and bddPTC were isolated via fluorescence‐activated sorting. bddPTC strongly expressed the brush border transport receptor megalin and aquaporin‐1 in bddPTC. Functionally, uptake of the megalin ligand myoglobin was greater in bddPTC than HK2, a human PT cell line. Pretreatment with the megalin inhibitor cilastatin, megalin‐targeted small interfering RNA, and endocytosis inhibitors reduced myoglobin uptake in bddPTC. Vascular cell adhesion protein 1, a marker for failed repair of PT after injury, was highly expressed in bddPTC. We provide reproducible means by which bddPTC may be used to study functional assessment and perhaps failed repair of PT.

Background/Objectives: Personalized treatment approaches are increasingly recognized as essential in the management of anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV), given the substantial heterogeneity in disease severity and patient characteristics. Kidney biopsy has the potential to serve as an effective tool for personalized treatment decision-making in patients with AAV. This study aimed to investigate the association of kidney biopsy with intensive immunosuppressive therapy and clinical outcomes in patients with AAV and kidney impairment. Methods: In this retrospective study, propensity score overlap weighting was applied to compare intensive immunosuppressive therapy and clinical outcomes (ESKD, death, combined ESKD and death, and infectious complications) between patients with AAV who underwent kidney biopsy and those who did not. Results: Out of 74 patients with AAV, 38 underwent kidney biopsy. Overlap weight analysis revealed that kidney biopsy was significantly associated with intensive immunosuppressive therapy (risk difference [RD], 28.9%; 95% confidence interval [CI], 0.017 to 0.562). Kidney biopsy was not associated with combined ESKD and death (RD, −0.2%; 95% CI, −0.302 to 0.298), death (RD, −3.8%; 95% CI, −0.264 to 0.189), ESKD (RD, −7.3%; 95% CI, −0.353 to 0.207), and infectious complications (RD, −25.9%; 95% CI, −0.537 to 0.020). Conclusions: In this observational cohort, kidney biopsy was associated with intensification of immunosuppressive therapy. However, after adjustment using overlap weighting, no statistically significant difference in clinical outcomes was detected, and the reduced effective sample size limited statistical power. These findings should be interpreted cautiously, as causal inference regarding the prognostic impact of kidney biopsy remains limited.

The proximal tubule (PT) of the kidney is a highly metabolic organ that regulates systemic homeostasis through ketogenesis and gluconeogenesis. Peroxisome proliferator‐activated receptor alpha (PPARα), a nuclear receptor controlling fatty acid oxidation (FAO) and homeostasis, is expressed in the PT and is activated by fasting. Although the activation of systemic PPARα is essential for renal and systemic energy metabolism, the role of PPARα in PT has not been established. In this study, kidney PT‐specific PPARα knockout mice ( Ppara ^∆KPT ) were generated, and the metabolic changes caused by 48 h of fasting were compared between Ppara ^∆KPT mice and controls. In Ppara ^∆KPT mice, renal FAO and ketogenesis were severely impaired, leading to lipid accumulation in the kidney after 48 h of fasting. The increase in the renal expression of gluconeogenesis‐associated genes due to fasting was insufficient in Ppara ^∆KPT mice, causing a decrease in serum glucose levels and liver glycogen content. Fasting caused hepatic micro‐steatosis and significantly increased the expression of genes linked to FAO and ketogenesis in the liver of Ppara ^∆KPT mice, as well as those associated with lipolysis in the white adipose tissue. These activities likely compensate for the impaired kidney FAO and ketogenesis in Ppara ^∆KPT mice and show that PPARα in PT regulates renal and systemic lipid and glucose metabolism during fasting. PPARα in PT may be a critical component in systemic lipid and glucose homeostasis during fasting.

Background and Aims: Hepatitis C virus (HCV) infection remains a global public health concern, with many carriers remaining undiagnosed because of its asymptomatic nature. Although Japan was previously considered to be on track for national HCV elimination by 2030, recent global modeling studies and updated elimination dashboards indicate that Japan is currently not on track. This underscores the importance of locally coordinated efforts to detect residual cases. Micro‐elimination has recently emerged as a pragmatic and scalable approach by targeting defined populations or geographic areas. The Nagawa Project sought to identify HCV positive individuals through community‐wide screening and directing viremic cases to appropriate direct‐acting antiviral (DAA) therapy. The present study describes the implementation and outcomes of this cohort‐based HCV micro‐elimination strategy. Methods: All 5027 adult residents of Nagawa town, Japan, aged ≥ 20 years were prospectively targeted for HCV antibody testing through routine health check‐ups, outpatient visits, and mailed invitations between June 2021 and March 2024. HCV Antibody positive individuals underwent additional HCV core antigen testing to confirm viremia. Results: A total of 3121 residents (62.1%) underwent HCV antibody testing. Testing rates were significantly higher in early‐stage elderly (65–74 years; 73.7%) residents than in both adult (20–64 years; 54.5%) ( p < 0.001) and late‐stage elderly (≥ 75 years; 66.7%) ( p < 0.001) residents. Twenty‐eight individuals (0.897%) were HCV antibody positive, with three cases (0.096%) confirmed as viremic. Antibody positivity was significantly higher in late‐stage elderly residents (1.91%; p < 0.001 vs. adult and p = 0.031 vs. early‐stage elderly residents). Two viremic individuals received DAA therapy and achieved a sustained virological response. After adjusting for age and sex by propensity score matching, no significant difference in overall survival was observed between HCV antibody positive and negative individuals. Conclusion: The Nagawa Project illustrates the success of a locally coordinated HCV micro‐elimination approach. It offers a practical framework for identifying and managing residual HCV infections, contributing to progress toward Japan's alignment with the World Health Organization's 2030 HCV elimination goals.

Key Points: CKD caused after acute cardiorenal syndrome is distinct from CKD due to kidney injury from the ischemia-reperfusion injury model. A cardiac-specific protein, cysteine-and-glycine–rich protein 3, transits plasma after heart injury and is partially responsible for distinct CKD. The cardiac-specific protein, cysteine-and-glycine–rich protein 3, is taken up in the proximal tubular epithelial cells, and interference with this uptake prevents specific changes. Background: The heart and kidney are bidirectionally interacting organs. Because heart and kidney diseases are among the most common human diseases, investigating disease-causing interactions is important. Here, we identified a new role for cardiac-derived cardiac LIM protein, also known as cysteine-and-glycine–rich protein 3 (CSRP3), in acute cardiorenal syndrome. Methods: Mice, both wild-type and genetically altered to remove CSRP3 from the myocardium, were subjected to a model of acute cardiorenal syndrome, cardiac arrest and cardiopulmonary resuscitation (CA/CPR), or ischemia-reperfusion injury. Recombinant CSRP3 was administered to mice subjected to ischemia-reperfusion injury, and CSRP3 uptake in the kidney was inhibited by pharmacologic means. Results: We found that CSRP3 transits plasma after CA/CPR, and we determined a kidney disease–modifying mechanism in which CSRP3 underwent megalin-dependent endocytosis in the renal proximal tubule and subsequently drove kidney fibrosis. Administration of CSRP3 to mice experiencing kidney injury exclusive of heart injury reproduced the kidney phenotype observed in CA/CPR mice. Genetic deletion of cardiac CSRP3 or proximal tubule megalin ameliorated cardiac arrest–induced chronic kidney injury. Translationally relevant pharmacologic megalin inhibition also ameliorated CSRP3-mediated kidney phenotypic change, and administration of CSRP3 caused transcriptional change in the kidney. Conclusions: We describe the endocrine role of cardiac CSRP3 in a previously unknown heart–kidney interaction, which directs specific kidney dysfunction and renovascular remodeling after cardiac injury. These investigations elucidate a novel facet of the intricate coupling between the heart and kidney after acute cardiorenal syndrome.

Background/Objectives: Kidneys are fatty acid (FA)-consuming organs that use adenosine triphosphate (ATP) for tubular functions, including endocytosis for protein reabsorption to prevent urinary protein loss. Peroxisome proliferator-activated receptor α (PPARα) is a master regulator of FA metabolism and energy production, with high renal expression. Although polyunsaturated fatty acids (PUFAs) are essential nutrients that are natural PPARα ligands, their role in tubular protein reabsorption remains unclear. As clinical PUFA deficiency occurs in humans under various conditions, we used a mouse model that mimics these conditions. Methods: We administered a 2-week intraperitoneal protein-overload (PO) treatment to mice that had been continuously fed a PUFA-deficient diet. We compared the phenotypic changes with those in mice fed a standard diet and those in mice fed a PUFA-deficient diet with PUFA supplementation. Results: In the absence of PO, the PUFA-deficient diet induced increased lysosomal autophagy activation; however, other phenotypic differences were not detected among the diet groups. In the PO experimental condition, the PUFA-deficient diet increased daily urinary protein excretion and tubular lysosomes; suppressed adaptive endocytosis activation, which was probably enhanced by continuous autophagy activation; and worsened FA metabolism and PPARα-mediated responses to PO, which disrupted renal energy homeostasis. However, these changes were attenuated by PUFA supplementation at the physiological intake level. Conclusions: PUFAs are essential nutrients for the tubular adaptive reabsorption response against urinary protein loss. Therefore, active PUFA intake may be important for patients with kidney disease-associated proteinuria, especially those with various PUFA deficiency-inducing conditions.

Background: In cell‐free and concentrated ascites reinfusion therapy (CART), filtration membrane obstruction during the ascites processing step is an important clinical problem. A novel membrane designed polyether sulfone filter (n‐PES) was developed to reduce filter membrane obstruction. However, no clinical studies have compared the performance of n‐PES filters with that of conventional filters. Therefore, we aimed to assess whether n‐PES filters reduce membrane obstruction compared to conventional polyethylene (PE) filters during CART ascites processing.Methods: This was a single‐center, retrospective, observational, controlled cohort study. We compared ascites processing records from the drop‐type with adjustable concentrator CART (DC‐CART) sessions that used n‐PES filters with those that used conventional PE filters. The primary outcome was the occurrence rate of membrane obstruction. Propensity score matching was used to assemble DC‐CART sessions with comparable baseline ascites characteristics.Results: Among the 173 DC‐CART sessions, 31 sessions using n‐PES filters and 31 using PE filters with similar propensity scores were included in the analysis. The rate of filter membrane obstruction was significantly lower in the n‐PES group than in the PE group (p = 0.049). Additionally, the total treatment time was significantly shorter for the n‐PES group (p = 0.006). No sessions experienced issues with the processing procedure.Conclusion: This is the first study to demonstrate that an n‐PES filter reduces the incidence of filter membrane obstruction in clinical CART sessions using human ascites. The n‐PES filter may reduce the burden on the medical staff performing CART.

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) can occasionally trigger thrombotic microangiopathy (TMA). Cytomegalovirus (CMV) may be reactivated during intensive immunosuppressive therapy for AAV and cause TMA. Therefore, we aimed to evaluate the clinical features of and the association between vascular endothelial injury markers and TMA due to CMV in patients with AAV. A 61-year-old female was diagnosed with AAV and severe kidney injury. Immunosuppressive therapy gradually improved her symptoms and laboratory findings. However, 2 weeks after induction therapy initiation, she exhibited altered consciousness, a significant decrease in platelet count, and hemolytic anemia, resulting in a TMA diagnosis. Plasma exchange did not improve TMA findings and routine screening test revealed CMV infection. Ganciclovir injection improved the infection and TMA findings. Consequently, we diagnosed her with CMV-induced TMA. Both AAV and CMV may induce severe vascular endothelial injury, potentially leading to TMA development. CMV-induced TMA should be considered when TMA develops during induction therapy against AAV. Moreover, of the three serum markers of vascular injury—serum sulfatides, soluble thrombomodulin, and pentraxin 3—serum sulfatides may be associated with the development of TMA, and a high level of soluble thrombomodulin may be associated with the development of CMV viremia during the clinical course of AAV.

Sulfatides are a type of sulfated glycosphingolipid that are secreted with lipoproteins into the serum. These molecules are involved in the inflammatory pathway of vessels in addition to coagulation and platelet aggregation. Previous studies have proposed that sulfatides play a pivotal role in regulating inflammation-related disorders. Systemic vasculitis (SV) diseases are generally caused by autoimmune diseases and often involve kidney vasculitis, which may lead to rapidly progressive kidney dysfunction and end-stage kidney disease. Our earlier pilot study revealed that the level of serum sulfatides (SSs) was significantly decreased in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV), a representative disease-causing SV with kidney involvement (SVKI), especially in patients exhibiting active crescentic findings on kidney biopsy. To further explore the clinical significance of an association between SS and SVKI, we analyzed and compared the SS level of patients with various SVKI diseases in this retrospective cohort study. Among patients admitted to our hospital between 2008 and 2021, we ultimately enrolled 26 patients with IgA vasculitis (IgAV), 62 patients with AAV, and 10 patients with anti-glomerular basement membrane disease (GBM) as examples of SVKI diseases, as well as 50 patients with IgA nephropathy (IgAN) and 23 donors for living kidney transplantation as controls. The mean ± standard deviation SS level in the donor, IgAN, IgAV, AAV, and GBM groups was 8.26 ± 1.72, 8.01 ± 2.21, 6.01 ± 1.73, 5.37 ± 1.97, and 2.73 ± 0.99 nmol/mL, respectively. Analysis of patients in the SVKI disease group showed that those with the crescentic class kidney biopsy finding exhibited a significantly lower SS level than did those with other class biopsy features. Additionally, the SS level had a higher detection ability for SVKI patients with crescentic class kidney biopsy findings (area under the receiver operating characteristic curve 0.90, 95% confidence interval 0.82–0.99) than did several other predictor candidates. Our results indicate that the SS level is decreased in more severe SVKI diseases and may be associated with active glomerular lesions in SVKI kidney biopsy samples.

We aim to elucidate factors to aid in the prediction of cytomegalovirus viremia during the treatment of anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). We conducted a single-center, retrospective, observational study of 35 patients with newly diagnosed AAV. Factors associated with the development of CMV viremia were investigated via a logistic regression analysis. The CMV antigenemia test was performed in 25 patients (71%), of whom 15 (60%) were diagnosed with CMV viremia. Of these 15 patients, 5 developed a CMV infection. The total protein, hemoglobin, platelet count and lymphocyte counts at the time of the CMV antigenemia test were significantly lower in patients who developed CMV viremia. In addition, total protein, hemoglobin, platelet count and lymphocyte count also presented significantly decreasing trends in the following order: patients who did not develop CMV viremia, patients who developed CMV viremia without any symptoms, and patients who developed CMV infection. All patients with CMV recovered. In conclusion, the total protein, hemoglobin, platelet count and lymphocyte count may be useful markers for the prediction of CMV viremia and infection after the start of induction of immunosuppressive therapy for patients with AAV.