Abstract Background Homozygous or compound heterozygous variants in RNU4ATAC, which transcribes a non-coding RNA component of the minor spliceosome, have been associated with a spectrum of disorders, collectively known as RNU4ATAC-related spliceosomeopathies. The phenotypic spectrum of RNU4ATAC-related disease is characterized by dysmorphic features, growth delay, neurological and skeletal features, whose severity ranges from the microcephalic osteodysplastic primordial dwarfism type 1 (MOPD1) to the milder Roifman syndrome. Objectives To characterize the clinical spectrum and evaluate long-term outcomes of RNU4ATAC-related diseases. Methods We evaluated the phenotypic features of four novel patients with deleterious RNU4ATAC variants, diagnosed by means of whole genome sequencing. Same features were evaluated in previously published cases, identified by literature research on PubMed. Results We identified four novel cases with deleterious compound heterozygous variants in RNU4ATAC, which were not restricted to the 5’ stem-loop, including three adult patients. Reported cases expand the clinical spectrum of RNU4ATAC-related disorders, highlighting renal disease, autoimmunity and systemic inflammation as possibly more frequent yet previously under-recognized features. Immunological investigations reveal enhanced HLA-DR and PD-1 expression in T cells from tested patients, suggesting T cell activation and exhaustion. Reevaluation of all previously published cases confirms the strong correlation of RNU4ATAC variants located exclusively at the 5’ stem-loop with severe lethal disease falling under MOPD1. Genotypes carrying at least one variant that spares the 5′ stem-loop are associated with a milder phenotype and later onset. Conclusion Homozygous or compound heterozygous RNU4ATAC variants affecting the 5’ stem-loop region are associated with severe phenotypes and adverse disease courses. In contrast, genotypes sparing the critical 5′ stem-loop region of RNU4ATAC can cause a complex phenotype that is not necessarily dominated by dysmorphic features or growth failure, but rather by immunodeficiency and immune dysregulation.

Kidney fibrosis is characterized by excessive deposition of extracellular matrix, which is ultimately disrupting normal renal architecture. Despite its clinical relevance, no targeted antifibrotic therapies are currently available. Myofibroblasts, primarily derived from pericytes and resident fibroblasts, are key effectors of fibrosis due to their high extracellular matrix production. Here, we tested the hypothesis that ferroptosis induction would enable the targeted elimination of activated kidney fibroblasts. We found that kidney fibroblasts exhibit marked sensitivity to ferroptotic cell death upon exposure to the ferroptosis inducer RAS-selective lethal 3 (RSL3), an effect further amplified by transforming growth factor-β stimulation. In tissue slice cultures of murine fibrotic kidneys, RSL3 eliminated myofibroblasts without causing overt damage to other cell types. Extending these findings in vivo, we applied a postischemia/reperfusion model of kidney fibrosis and demonstrated that repeated low-dose systemic administration of RSL3 significantly reduced the activated fibroblast population without inducing appreciable injury to parenchymal cells. These results provide proof-of-principle that the ferroptosis susceptibility of activated fibroblasts may offer a potential strategy for the selective depletion of profibrotic effector cells in kidney fibrosis.NEW & NOTEWORTHY This study reveals ferroptosis, a pharmacologically inducible form of cell death, as a novel mechanism to eliminate activated fibroblasts, the main drivers of kidney fibrosis. Due to their high ferroptosis sensitivity, these cells are selectively depleted by RSL3 in vitro, in kidney tissue slice cultures, and in fibrotic kidneys in vivo. These findings highlight ferroptosis induction as a promising antifibrotic strategy in kidney disease.

Abstract Autosomal dominant polycystic kidney disease (ADPKD) exhibits substantial interpatient variability in disease course and therapeutic response, but the cellular basis for this variability remains poorly understood. Here, we combine single-nucleus RNA sequencing of human cyst epithelia with machine learning–based histological analysis of >1,800 cysts to resolve three epithelial cyst types—proximal tubule–like, collecting duct–like, and mixed. These cyst types display distinct injury states, metabolic programs, and stromal microenvironments, including a mixed-cyst niche enriched for CCL2-associated inflammatory signaling. Expression of key therapeutic targets was highly cell-type specific with CFTR enriched in proximal-like epithelia, whereas AVPR2 expression was confined to AQP2-positive collecting duct–like cells. Cyst-type composition varied widely across patients and in an orthologous mouse model ( Pkd1 RC/RC ) in which the burden of AQP2-positive cysts correlated with responsiveness to tolvaptan. These findings identify cyst-type heterogeneity as a major determinant of molecular pathway activation and predictability of therapeutic response in ADPKD.

Sepsis-associated acute kidney injury (SA-AKI) remains a frequent and life-threatening complication of sepsis, yet its pathophysiology is still not fully understood, owing to the complex interplay of immune, vascular and parenchymal responses. Closing this knowledge gap is essential for developing urgently needed targeted therapies. Although bulk and single-cell transcriptomics, as well as proteomic approaches, have advanced our understanding of the molecular mechanisms involved in SA-AKI, they lack the spatial context required to fully interpret tissue heterogeneity and microenvironmental changes. The integration of high-resolution spatial transcriptomics with single-cell RNA sequencing and other multi-omics approaches offers a novel lens through which to dissect the cellular and molecular architecture of septic kidneys. In SA-AKI, discrete inflammatory, vascular and tubular niches can cause substantial functional impairment even though global histological changes may be much milder. Integrative spatial transcriptomics localizes pathological signalling and how it is transmitted across immune, endothelial and epithelial cells. By resolving niche-specific crosstalk, these approaches might highlight druggable pathways and lead to the identification of clinical biomarker candidates. These insights, in turn, facilitate the identification of mechanistic endotypes that align more closely with prognosis than with conventional staging. Importantly, translation into clinical trials will require standardized endotype definitions, endotype validation and standardized sampling strategies, as well as scalable analytical pipelines to enable endotype identification at the bedside.

BACKGROUND AND HYPOTHESIS:Women exhibit a lower cardiovascular risk and longer life expectancy compared with men in the general population. However, this advantage is diminished in dialysis and transplant patients, suggesting greater excess risk, i.e. risk above the general population, in women with kidney failure. Yet, data on excess risk in chronic kidney disease (CKD) populations, using those without CKD as the reference, are lacking. METHODS:In this retrospective cohort study, we analyzed de-identified, patient-level data from electronic medical records within the TriNetX database. Adults aged 18-90 years with an eGFR ≥15 mL/min/1.73 m2 without maintenance dialysis or kidney transplantation were included. Primary outcomes were all-cause mortality and cardiovascular composite outcome. Analyses were adjusted for age, sociodemographic factors, cardiovascular risk factors, laboratory measurements, medications and history of CVD, using multivariable Cox proportional hazards models. RESULTS:Of 328 431 eligible individuals, 43 830 were women with CKD, 45 173 men with CKD, 127 383 women without CKD and 112 045 men without CKD. In individuals without CKD, women displayed a reduced risk of all-cause mortality [hazard ratio (HR) 0.53; 95% confidence interval (CI) 0.49-0.58] and cardiovascular events (HR 0.70; 95% CI 0.68-0.71) compared with men. However, this risk reduction in women compared with men was significantly attenuated in individuals with CKD both for all-cause mortality (HR 0.73; 95% CI 0.69-0.77) and for cardiovascular events (HR 0.80; 95% 0.78-0.82). Consequently, CKD conferred significantly greater excess risk of mortality and cardiovascular events in women compared with men, consistent across different levels of kidney function, age and systolic blood pressure. CONCLUSIONS:The cardiovascular and survival advantage observed in women compared with men in the general population is significantly reduced in individuals with CKD, confining an increased excess risk in women with CKD.

T-cell–mediated rejection (TCMR) remains a major cause of kidney transplant failure, despite being considered treatable. Its impact reflects a limited understanding of the underlying molecular mechanisms and their clinical consequences. To address this, we induced acute TCMR in mouse kidney transplants and profiled molecular changes using single-nucleus RNA sequencing (snRNA-seq), spatial transcriptomics and immunofluorescence. Results were compared with human snRNA-seq data from TCMR and stable allografts, as well as single-cell deconvolution analysis of bulk transcriptomic data from kidney transplant biopsies. Here we show that TCMR induces injured epithelial cell states in mouse kidney allografts, particularly in proximal tubules and thick ascending limbs. Spatial transcriptomics of these injured epithelial states demonstrated heterogeneous localization, interactions with immune cells and cellular microenvironments. Cross-species analysis confirmed similar severely injured epithelial states in human samples, whose abundances correlated with transplant survival and persisted despite TCMR resolution. Collectively, our results identify epithelial injury cell states as a determinant of outcome after TCMR. T-cell–mediated rejection (TCMR) remains a major cause of kidney transplant failure with incompletely understood mechanisms. Here the authors use single-nucleus RNA sequencing, spatial transcriptomics and immunofluorescence to show that injured kidney epithelial cell states associate with poor transplant outcomes after T-cell–mediated rejection.

Background: Mineralocorticoid receptor antagonists (MRAs) are the guideline-recommended fourth-line therapy for resistant hypertension. However, resistant hypertension is particularly common in individuals with overweight or obesity. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) induce substantial weight loss and reduce cardiovascular and renal events in randomized trials, with modest reductions in blood pressure. Whether GLP-1RAs provide benefit as an alternative fourth-line therapeutic strategy in patients with resistant hypertension and overweight or obesity is unknown. We compared the effectiveness of GLP-1RAs and MRAs as fourth-line therapy in this population. Methods: In this retrospective multicenter cohort study using the TriNetX US Collaborative Network, adults with overweight or obesity and resistant hypertension (uncontrolled blood pressure despite ACE-inhibitors/angiotensin receptor blockers, calcium antagonists and diuretics) initiating fourth-line therapy between June 2017 and March 2025 were identified. Patients initiating GLP-1RAs (semaglutide or tirzepatide) were compared with those initiating MRAs (spironolactone or eplerenone). The primary outcome was major adverse cardiovascular events (MACE). Secondary outcomes included all-cause mortality, cardiovascular events, kidney outcomes, and blood pressure changes. Propensity score matching balanced baseline characteristics. Outcomes were analyzed using Kaplan–Meier estimates and Cox proportional hazards models. Findings: Among 213,309 eligible patients, 22,694 initiated GLP-1RAs and 5673 initiated MRAs. After propensity score matching, 4,153 patients remained in each group. During a median follow-up of 1.4 years, GLP-1RA therapy was associated with lower risks of MACE (HR 0.63, 95%CI 0.52-0.78), all-cause mortality (HR 0.34, 95%CI 0.21-0.55), cardiovascular events (HR 0.74, 95%CI 0.59-0.92), major adverse kidney events (HR 0.64, 95%CI 0.46-0.88), and acute kidney injury (HR 0.62, 95%CI 0.46-0.83) compared with MRAs. Systolic blood pressure reductions at 12 weeks were similar (−5.7 (95%CI -4.0 to -7.4) mmHg vs −6.3 (95%CI -4.7 to -8.0) mmHg). Interpretation: Among overweight or obese adults with resistant hypertension, GLP-1RA initiation was associated with lower cardiovascular and kidney risk compared with MRAs despite similar blood pressure reductions. Randomized trials are needed to determine whether GLP-1RAs should be incorporated into treatment strategies for resistant hypertension in patients with obesity.

Mehr als 70 Jahre nach der ersten erfolgreichen Organtransplantation zwischen eineiigen Zwillingen steht die Transplantationsmedizin auch heute vor wichtigen Herausforderungen: Wie können die vielen Menschen, die auf eine neue Niere, Leber, Lunge oder ein neues Herz warten, schneller ein passendes Organ erhalten? Wie kann das Überleben auf der Warteliste verlängert werden? Wie gewährleistet man nach der Transplantation ein langfristiges Organüberleben bei hoher Lebensqualität? Die verschiedenen Disziplinen der Transplantationsmedizin widmen sich Tag für Tag diesen Herausforderungen. Ziel dieses Übersichtsbeitrags ist es, praktizierenden Ärztinnen und Ärzten einen Überblick über den aktuellen Stand und die mittelfristigen Perspektiven der Transplantationsmedizin zu geben. Hierfür hat sich ein interdisziplinäres Team von Transplantationsexperten aus dem größten Transplantationszentrum Deutschlands zusammengetan, um in kompakter Form und organübergreifend die aktuellen Innovationen und Zukunftsperspektiven der Transplantationsmedizin zusammenzufassen. Konkret gehen wir auf neue Bridging-Strategien zur Verbesserung des Überlebens auf der Warteliste ein und diskutieren Möglichkeiten zur Erweiterung des Spenderpools. Auch erläutern wir die Perspektiven zur Konditionierung explantierter Spenderorgane durch Maschinenperfusionsstrategien und stellen aktuelle Entwicklungen in der personalisierten Transplantationsnachsorge vor.

More than 70 years after the first successful organ transplant between identical twins, transplantation medicine still faces significant challenges today: How can the large number of people waiting for a new kidney, liver, lung, or heart receive a suitable organ more quickly? How can survival on the waiting list be extended? How can long-term graft survival with high quality of life be ensured after transplantation? The various disciplines of transplantation medicine are working daily to address these challenges. The goal of this overview article is to provide practicing physicians with an overview of the current state and medium-term perspectives of transplantation medicine. For this purpose, an interdisciplinary team of transplantation experts from the largest transplant center in Germany has come together to summarize the current innovations and future perspectives of transplantation medicine in a compact and organ-overarching format. Specifically, new bridging strategies to improve survival on the waiting list will be discussed and possibilities for expanding the donor pool explored. Future perspectives on conditioning explanted donor organs using machine perfusion strategies will also be addressed and current developments in personalized post-transplant care summarized.

Introduction In the kidney, epithelial cells of medullary collecting ducts (MCD) are exposed to a harsh microenvironment characterized by hyperosmolality, hypoxia, and oxidative stress. Still, under physiological conditions, they show no apparent signs of cellular injury. We hypothesized that the study of transcription factors (TFs) enriched in MCD cells might identify pathways of stress resilience. Methods We generated single-cell expression data from mouse kidneys and predicted in silico candidate TFs with MCD-enriched expression and activity. To investigate the transcriptomic effects of perturbing these candidate TFs, we devised a single-cell CRISPR interference (CRISPRi) screen in mouse inner medullary collecting duct (IMCD3) cells. Results We found that perturbation of interleukin enhancer-binding factor 2 (Ilf2), Krueppel-like factor 5 (Klf5), and JunB proto-oncogene (Junb), significantly impacted IMCD3 cells’ gene expression programs, including genes involved in proliferation, apoptosis, and stress-related intracellular signaling, highlighting these TFs as potential regulators of cell-specific resilience. We then focused on Ilf2, validated its impact on gene expression signatures by RNA sequencing, and identified a further role of Ilf2 in the splicing of genes involved in epithelial cellular dynamics and stress responses. Loss of Ilf2 function in IMCD3 cells resulted in nuclear atypia, reduced proliferative capacity, and increased cell death in response to osmotic stress. Ilf2 was upregulated in mouse kidneys during the repair phase following ischemia-reperfusion injury (IRI), as were Ilf2-regulated transcripts and splicing events, suggesting that Ilf2 might serve as a post-ischemic signal to facilitate epithelial stress resilience. Conclusions Our approach nominates novel pathways of cellular resilience in kidney tubular cells and highlights Ilf2 as a potential target for kidney protection. Translational Statement We identify Ilf2 as a transcriptional regulator promoting the stress resilience of renal epithelial cells. Our study provides mechanistic insights into the endogenous mechanisms that protect kidney epithelia from the adverse microenvironment of the renal medulla. Furthermore, Ilf2 activation might constitute a broader mechanism to preserve kidney epithelial integrity under injurious conditions. ### Competing Interest Statement The authors have declared no competing interest. German Research Foundation (DFG) Research Training Group GRK 2318 (B4) M-BM-^V Project ID 318905415 DFG Research Unit 2841 DFG project 547091997

Rationale & Objectives:The cardiovascular-kidney-metabolic (CKM) syndrome is defined as the intricate interplay among metabolic risks, chronic kidney disease (CKD) and the cardiovascular system. The deteriorating CKM syndrome contributes to untimely morbidity and mortality. We aim to characterize gender- and age-related disparities in the prevalence of CKM syndrome over the last 2 decades. Study Design:A cross-sectional population-based survey. Setting & Participants:A total of 32,848 US adults participating in the NHANES survey from 1999 to 2020. Exposures:Gender, age (18-44, 45-64, and ≥65), and period (1999-2002, 2003-3008, 2009-2014, and 2015-2020). Outcomes:Prevalence of CKM stages. Analytical approach:Sample weights and Taylor series linearization method were applied to estimate prevalence and standard errors representative of the noninstitutionalized US adult population. For trend analysis across cycles, survey-weighted logistic regression was employed. Results:Young women aged < 45 years were classified more often, but with decreasing prevalence, in stages without CKM defining factors (22.7% of women vs 13.5% of men) and more often in stages with cardiovascular organ damage (13.4% of women vs 6.5% of men). Elderly women were increasingly classified in stages with cardiovascular organ damage over the last 20 years, reaching the same prevalence as men in the most recent period (25.3 % [95% CI, 20.0 %-30.6 %] of women vs 30.5 [95% CI, 25.7-35.3%] of men aged > 65 years). Limitations:NHANES data allow for assessing CKM stages with cardiovascular organ damage mainly based on self-reporting during interviews. Conclusions:We demonstrate an increasing proportion of women in advanced CKM stages over the last 20 years. Whereas the overrepresentation of younger women in the low-risk stages almost disappeared, elderly women in the last period showed almost the same risk of being in stages with cardiovascular organ damage as elderly men. Our analysis highlights an urgent need of preventive measures especially tailored to women.

Mutations in the transcription factor TFAP2A are linked to congenital anomalies of the kidney and urinary tract in humans. While Tfap2a knockout (KO) in mouse collecting ducts leads to tubular epithelial abnormalities, its precise molecular functions in kidney tubules remain unclear. To investigate Tfap2a-dependent gene regulatory networks in the mouse kidney collecting ducts, we employed conditional KO (Hoxb7-Cre; Tfap2afl/fl) models combined with transcriptomics. Histomorphological and physiological assessments of Tfap2a-KO mice revealed progressive postnatal dilation of the outer medullary collecting ducts. Integrating bulk and single-nucleus RNA sequencing with in silico motif mapping in ATAC-seq datasets demonstrated that Tfap2a is highly expressed and active in normal collecting duct principal cells. Comparative transcriptomics between 3-month-old Tfap2a-KO and control mice identified dysregulated genes associated with cell adhesion and WNT signaling, including Alcam and Wnt9b. These changes were confirmed by in situ hybridization. Ourfindings reveal that Tfap2a regulates medullary collecting duct diameter by orchestrating a transcriptional network involving Wnt9b and Alcam, providing insights into its role in kidney structural integrity.

Cardiovascular-kidney-metabolic (CKM) syndrome is staged to reflect increasing cardiometabolic risk. Substantial heterogeneity exists within stage 2, which includes individuals with metabolic risk factors or chronic kidney disease (CKD) without established cardiovascular disease and affect nearly half of US adults. This study aimed to develop and validate a sex-specific, clinically pragmatic model to subdivide CKM stage 2 into lower-risk (stage 2a) and higher-risk (stage 2b) subgroups We analyzed participants aged ≥18 years with CKM syndrome stage 2 from the 1999-2018 NHANES cycles linked to the US National Death Index. Participants were assigned to development and validation cohorts comprising five survey cycles each. Predictor variables were selected using modified LASSO-regression and Cox-regression model, with cardiovascular mortality as the primary outcome. Model performance was assessed using time-dependent area under the receiver operating characteristic curve (AUC) and the C-statistics. TriNetX database with patient-level data from medical records was analyzed to provide clinical validation using major adverse cardiovascular events (MACE) as the outcome. Stage 2b in women was defined by the presence of at least two of the following: age ≥66 years, CKD, diabetes, or hypertension (AUC 0.79; C-index 0.78). In men stage 2b required at least two of the following: age ≥61 years, CKD, diabetes, or current smoking (AUC 0.73; C-index 0.72). Discrimination was preserved in external validation (women: AUC 0.70, C-index 0.69; men: AUC 0.75, C-index 0.68) with significantly distinct 10-year absolute risk difference of cardiovascular death (women: 4.9% [95% CI 2.2-7.5]; men: 8.5% [95% CI 5.0-12.0]). In TriNetX database, 10-year MACE risk increased from 11.3% to 24.6% in women and from 13.1% to 30.8% in men from stage 2a to stage 2b. Subdividing CKM stage 2 into stages 2a and 2b identifies clinically meaningful differences in cardiovascular risk and may support targeted preventive strategies.