American Journal of Transplantation

BackgroundSubclinical kidney allograft acute rejection (SCR) corresponds to "the unexpected histological evidence of acute rejection in a stable patient". The diagnosis of SCR relies on surveillance biopsy. Positron emission tomography (PET/CT) after injection of F18-fluorodeoxyglucose ([18F]FDG) has been proposed as a non-invasive screening approach. In the present multicenter prospective study, we assess the diagnostic yield [18F]FDGPET/CT to rule out SCR in stable KTR at 3 months post KTx. MethodsFrom 01/2021 to 03/2025, we prospectively combined surveillance biopsy and [18F]FDGPET/CT at [~]3 months post transplantation in adult kidney transplant recipients from 4 independent imaging centers. The mean standardized uptake value (mSUV) was measured in kidney cortex and referenced as a ratio to psoas muscle mSUV (mSUVR). ResultsOur multicentric 185-patient cohort was categorized upon Banff-2022: normal (n=158); borderline (n=18); SCR (n=9, including 6 T-cell-mediated rejection and 3 microvascular inflammation). No significant correlation was observed between the mSUVR and ti score (R=0.032, p-value=0.67). The mSUVR reached 2.33 [1.97-2.93], 2.71 [2.50-3.33] and 2.42 [2.27-3.14] in normal, borderline and SCR groups, respectively. In multivariate models stratified by center, the risk of non-normal histology (n=27, including borderline and SCR) increased with donor age (OR=1.05 [1.01-1.1], p=0.02) but not with the mSUVR (OR=4.11 [0.91-18.48], p=0.07). The risk of biopsy-proven SCR (n=9) was not significantly associated with mSUVR. ConclusionsThe mSUVR of [18F]FDG PET/CT does not reliably rule out SCR on surveillance biopsy.

BackgroundThe effects of Banff histological diagnoses on kidney transplant outcome have been well characterized. However, repeated observation of such histological injury across multiple biopsies in kidney transplant recipients remains insufficiently explored. MethodsIn an observational cohort (N=1819 transplantations with 5736 post-transplant biopsies, recurrent event survival models quantified transitions between diagnoses of T-cell mediated rejection (TCMR), antibody-mediated rejection (AMR), DSA-negative C4d-negative microvascular inflammation (MVIDSA-/C4d-), BK polyomavirus nephropathy (BKPyVAN), borderline TCMR (bTCMR), and probable AMR (pAMR), revealing patterns in the disease trajectories. In two observational cohorts (N=1818 transplantations with 5732 biopsies, N=853 transplantations with 975 biopsies), time-dependent cumulative covariates were constructed for TCMR, AMR, MVIDSA-/C4d- and BKPyVAN, enabling estimation of associations of repeated diagnoses with graft failure using multivariable cause-specific Cox models. ResultsThe incidence rate of a diagnosis was most strongly associated with earlier diagnosis of the same type, but associations between different types of diagnoses also occurred. The hazard of kidney graft failure was significantly increased by repeated observation of TCMR in multiple biopsies (HR 7.97, 95% CI 4.94 - 12.86), as well as by repeated AMR (HR 6.19, 95% CI 3.15 - 12.17), repeated MVIDSA-/C4d- (HR 4.53, 95% CI 2.15-9.54) and repeated BKPyVAN (HR 10.90, 95% CI 5.83 - 20.35). The hazard of graft failure was increased more after repeated diagnoses in transplants than after first diagnoses. The effects of repeated TCMR and repeated AMR remained significant even when observed in protocol biopsies in the absence of graft dysfunction. Repeated observation of BKPyVAN was the most detrimental of all diagnoses when observed in indication biopsies, but it was the least harmful when observed in protocol biopsies. ConclusionIncidence of Banff histological diagnoses appears to be affected by earlier diagnoses, especially those of the same type. These repeated observations of a specific diagnosis have an additional effect on the hazard of graft failure, underscoring a critical unmet need for adequate treatment strategies for these recurrent or persistent injury processes. Lay summaryIn two observational cohorts of 1819 and 750 kidney transplant recipients, kidney transplant biopsies were taken at multiple time points after transplantation. Based on the Banff classification for transplant pathology, various post-transplant diseases were diagnosed, often at more than one time point during follow-up. We assessed patterns in the occurrence of diagnoses over time, and related these diagnoses to survival of the kidney grafts using survival models with time-dependent cumulative diagnoses. We found that repeated observation of the same diagnosis was much more common than consecutive observations of different diagnoses. Repeated diagnoses of tissue injury also decreased kidney graft survival more compared to single diagnoses. This indicates that treatment options for patients with repeated or persistent diagnoses are currently inadequate and novel strategies are needed.

BackgroundIn lung transplantation, de novo immunodominant donor-specific anti-HLA antibodies recognizing HLA-DQ antigens (dn-iDSA-DQ) are predominant and can induce chronic lung allograft dysfunction (CLAD). We previously developed a method to measure the active concentration of dn-iDSA-DQ. We aimed to determine whether this new quantitative biomarker is associated with transplantation outcomes. MethodsThis retrospective multicentre cohort study included 90 lung transplant recipients (LTRs) developing dn-iDSA-DQ, evidenced through single antigen flow beads (SAFB) follow-up. We measured the active concentration of dn-iDSA-DQ at the time of their first detection (T0) for all LTRs, and within the 2 years after DSA detection, whenever possible. SAFB dn-iDSA-DQ characteristics and clinical data were retrieved up to 5 years after DSA detection. ResultsWe tested 184 sera with SPR (n=90 at T0, n=94 within the 2 years after DSA detection), among which 63 (34.4%) had a quantifiable concentration of the dn-iDSA-DQ ([&ge;]0.3 nM). The median SAFB mean fluorescence intensity (MFI) of the dn-iDSA-DQ with a concentration [&ge;]0.3 nM was higher (p<0.0001), yet the correlation between SAFB MFI and active concentration was low (r=0.758, p<0.0001). In multivariate analysis, a concentration of the dn-iDSA-DQ [&ge;]0.3 nM at T0 was independently associated with a lower 2-year CLAD-free survival (HR 2.06, p=0.02). A concentration of the dn-iDSA-DQ [&ge;]0.3 nM within the 2 years from DSA detection was associated with a lower graft survival in univariate analysis. ConclusionsActive concentration of dn-iDSA-DQ appears as a valuable biomarker to identify pathogenic DSA at their first detection because of its association with CLAD.

Background: We aimed to identify data-driven FEV1 trajectory phenotypes post-chronic lung allograft dysfunction (CLAD), relate these phenotypes to patient factors and future graft loss, and develop a classification approach for prospective patients. Methods: We studied adult first lung recipients with probable CLAD from two prospective multicenter cohorts: CTOT-20 (n=206) and LTOG (n=1418). FEV1 trajectories over the first nine months post-CLAD were characterized using joint latent class mixed models, jointly modelling time-to-graft loss to account for informative censoring. Models were fit independently in both cohorts and also only among LTOG bilateral recipients. A classification and regression tree (CART) model was derived in LTOG bilateral recipients and applied to CTOT-20 bilateral recipients. Findings: Four distinct early FEV1 trajectory classes were identified in CTOT-20, with large differences in nine month graft loss (72.3%, 31.1%, 2.2%, 0%). In LTOG, similar trajectory patterns were reproduced, with an additional class demonstrating early post-CLAD FEV1 improvement. Among bilateral recipients, trajectory classes showed a clear risk gradient, including a high-risk class with 100% graft loss and a low-risk class with no early graft loss. A CART model incorporating clinical and spirometric variables demonstrated good discrimination in LTOG bilateral recipients (multiclass AUC 0.85) and consistent class assignment and trajectory patterns when applied to CTOT-20. Interpretation: We identified reproducible, clinically meaningful early post-CLAD FEV1 trajectory phenotypes with differential graft loss risk. These phenotypes and a pragmatic classification tool may support risk stratification, trial enrichment, and improved prognostication for patients and clinicians.

BackgroundIron metabolism disorder is highly prevalent before and after heart transplantation (HTx). The impact of pretransplant and posttransplant iron disorder on posttransplant outcomes is unclear. ObjectivePretransplant serum levels of key regulator proteins of iron metabolism (hepcidin, interleukin-6, erythroferrone) were tested for prediction of the composite outcome 1-year posttransplant all-cause mortality (ACM) or [&ge;]moderate acute cellular rejection (ACR). Furthermore, serum levels of these proteins were measured at 1-year posttransplant to explore their posttransplant course and association with ACR. ResultsIn a multicenter cohort including 276 consecutive HTx recipients, patients with or without outcome (n=118/158, respectively) did not differ for pretransplant demographics, mismatch of donor/recipient sex, mismatch of HLA epitopes, and hepcidin or interleukin-6 levels. However, pretransplant erythroferrone levels were higher (1.40 vs. 1.19 ng/mL; p=0.013) and hemoglobin levels were lower (124.5 vs. 127 g/L; p=0.004) among patients with the composite outcome. Pretransplant erythroferrone levels >2.25 ng/ml (4th-quartile) were significantly associated with the composite outcome in multivariable analysis (OR 2.17; 95% CI 1.19-3.94, p=0.011; reference: 1st-3rd quartiles). In adjusted predicted proportions analysis, the incidence of the composite outcome was higher in 4th-quartile patients when compared to 1-3rd -quartiles patients (58.0 vs. 37.7%; p=0.003). At 1-year posttransplant, 80.4% of patients with pretransplant erythroferrone levels >2.25 ng/ml remained high; 88.4% of patients with pretransplant erythroferrone levels [&le;]2.25 ng/ml had high levels posttransplant. In 1-year survivors with high erythroferrone levels and [&ge;]moderate ACR during the first postoperative year, the ratio of the opponent regulators of hepcidin gene expression, erythroferrone to interleukin-6, was higher when compared to those without ACR (1.18 vs. 0.41; p=0.016). Hepcidin levels were not different between these two subgroups indicating disproportionate ERFE increase. ConclusionHigh pretransplant erythroferrone levels predict the composite posttransplant outcome 1-year ACM and ACR. Disproportionately high posttransplant erythroferrone levels are related with [&ge;]moderate acute cellular rejection.

Kidney transplantation faces a critical paradox: while thousands await organs, approximately 30% of potential deceased donor kidneys are discarded for various reasons, including subjective assessments due to the lack of an objective molecular biomarker of preservation quality. Here, we applied novel "top-down" proteoform imaging mass spectrometry across living donor (LD), deceased donor (brain death or cardiac death), and discarded human kidneys to quantify proteoforms correlating with post-transplant kidney function. This approach preserves post-translational modifications and splice variants, revealing molecular tissue variability beyond protein presence. LD kidneys displayed robust metabolic signatures, including L-xylulose reductase and cytochrome oxidase subunits, whereas deceased donor and discarded organs showed elevated cellular stress markers such as alpha-B-crystallin and peroxiredoxin 1. Post-transplant blood proteoform analysis validated tissue findings, demonstrating persistent cellular stress and immune activation in deceased donor recipients compared with physiologic wound healing in LD recipients. Consistent with these molecular predictions, serum creatinine levels were highest in DCD, intermediate in DBD, and lowest in LD recipients. The intersection of tissue proteoform signatures across all marginal tissues identified four proteoforms consistently elevated in deceased and discarded kidneys: ACTG1, acetylated CRYAB, PARK7, and S100A4. Collectively, these proteoforms capture key molecular indicators of graft quality, reflecting oxidative stress, cellular injury, and immune activation pathways. As such, they represent promising point-of-care (POC) biomarker candidates for objective kidney classification, potentially improving donor kidney utilization. Translational statementCurrent methods for evaluating donor kidney quality rely on subjective assessments, contributing to the discard of approximately 30% of potentially viable organs. This study demonstrates that "top-down" proteomics can objectively identify molecular signatures distinguishing high-quality from marginal donor kidneys. Top-down proteomics analyzes intact proteins with their post-translational modifications or cleavage products, termed proteoforms to provide mechanistic insights into graft quality. We identified four proteoforms (ACTG1, acetylated CRYAB, PARK7, and S100A4) to be consistently elevated in deceased and discarded kidneys, reflecting oxidative stress, cellular injury, and immune activation. These molecular markers correlated with post-transplant kidney outcome, as measured by serum creatinine levels and recipient blood proteoforms. As a next step, validation in larger cohorts could establish these proteoforms as point-of-care biomarkers for real-time donor kidney assessment during procurement. This objective molecular stratification could reduce unnecessary organ discards and improve transplant outcomes by matching organ quality with recipient risk profiles.

Immune reconstitution after allogeneic hematopoietic stem cell transplantation is influenced by graft-composition and viral reactivation, but the combined long-term impact on {beta} and {gamma}{delta}T cells remains unclear. We analyzed a cohort of 213 patients receiving either {beta}T cell-depleted grafts (n=146; graft engineering that removes donor {beta}T cells) or T cell-replete grafts (n=67; containing donor T cells). Longitudinal immune phenotyping was integrated with bulk and single-cell TCR repertoire and transcriptomic profiling. CMV reactivation was associated with expansion of CD8+ {beta}T cells across both transplant types and with numerical dominance of V{delta}2- {gamma}{delta}T cells specifically in {beta}T cell-depleted recipients. V{delta}2- {gamma}{delta}T cells underwent early polyclonal expansion followed by repertoire focusing, independent of CMV, whereas {beta}T cells remained clonally restricted. Reduced early V{delta}2+ {gamma}{delta}TCR diversity was associated with EBV reactivation. Single-cell and TCR tracking analyses revealed long-term persistence of donor-derived V{delta}2+ {gamma}{delta}TCRs, whereas V{delta}1+ {gamma}{delta} and {beta}T cell repertoires were predominantly rebuilt de novo. Despite de novo rebuilding, {beta}TCR repertoire diversity diverged by platform at one year: {beta}T cell-depleted recipients exhibited marked (hyper)expansion of {beta}TCR clonotypes and lower diversity than T cell-replete recipients, indicating a durable imprint of graft engineering on {beta}TCR-clonality. Transcriptomic profiling showed that post-transplant T cells predominantly adopted effector programs, with platform-dependent polarization toward cytotoxic signatures in {beta}T cell-depleted recipients and toward AREG-associated tissue-repair signatures in T cell-replete recipients, consistent with wound-healing functions. In conclusion, transplantation platforms imprint durable clonal and transcriptional remodeling of {beta} and {gamma}{delta}T cells, while viral reactivation primarily amplifies expansion without fundamentally reshaping repertoire architecture. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/704768v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@88f136org.highwire.dtl.DTLVardef@944f13org.highwire.dtl.DTLVardef@d3835corg.highwire.dtl.DTLVardef@5548ef_HPS_FORMAT_FIGEXP M_FIG C_FIG

Acute antibody-mediated rejection (aABMR) is an important cause of clinical kidney graft injury and failure. Transcripts associated with NK cell activation in graft biopsies are diagnostic of aABMR, but mechanisms underlying NK cell activation during ABMR remain poorly understood. In contrast to the long-term (> 60 days) survival of complete MHC-mismatched kidney allografts in wild type C57BL/6 mice, B6.CCR5-/- recipients develop high titers of donor-specific antibody (DSA) with allograft rejection between days 18 to 28 post-transplant. This has allowed investigation of mechanisms underlying NK cell activation within kidney allografts during aABMR. DSA titers first became detectable in B6.CCR5-/- (H-2b) recipients of A/J (H-2a) kidney allografts at day 8 and peaked on day 15 post-transplant and was accompanied by a parallel increase in mRNA levels of Rae-1e, a ligand for the NK cell activation receptor NKG2D. A/J kidneys in B6.CCR5-/-NKG2D-/- recipients and A/J.Rae-1e-/- kidneys in B6.CCR5-/- recipients survived >60 days, despite high serum DSA levels. Flow cytometric analysis of allograft infiltrating cells in B6.CCR5-/- recipients on day 15 post-transplant revealed inflammatory monocyte and NK cell infiltration and NK cell activation to proliferate and express CD107a, a marker of cytotoxic function. These features of aABMR were absent or markedly reduced by recipient NKG2D- or donor graft Rae-1e-deficiency. These findings suggest that interference with expression of allograft Rae-1e or recipient NK cell NKG2D abrogates aABMR despite persistently high DSA levels and that aABMR requires coordination between infiltrating NK cell and inflammatory monocyte activation within the kidney allograft.

Background: Kidney transplantation is the preferred treatment strategy for end-stage kidney disease. Deceased donor kidneys usually undergo cold storage until kidney transplantation, leading to cold ischemia injury that may contribute to poor graft outcomes. However, the molecular characterization of potential mechanisms of cold ischemia injury remains incomplete. Results: To bridge this knowledge gap, we leveraged the 10x Visium spatial transcriptomic technology to perform full transcriptome profiling of murine kidneys subject to varying durations of cold ischemia typical in a deceased donor kidney transplant setting. We developed a computational workflow to identify and compare spatiotemporal transcriptomic changes that accompany the injury pathophysiology in a tissue compartment-specific manner. We identified proportional enrichment of oxidative phosphorylation (OXPHOS) genes with increasing duration of cold ischemia injury within the oxygen-lean inner medulla region, suggestive of atypical metabolic presentation. This was distinct in cold ischemia injury tissue compared to warm ischemia-reperfusion kidney injury tissue. Spatiotemporal trends were validated by qPCR and immunofluorescence in a larger cohort of mice. We provide an interactive online browser at https://jef.works/CellCarto-ColdIschemia/ to facilitate exploration of our results by the broader scientific and clinical community. Conclusions: Altogether, our spatiotemporal transcriptomic analysis identified coordinated molecular changes within metabolic pathways such as OXPHOS deep within the cold ischemic kidney, highlighting the need for increased attention to the inner medulla and potential opportunities for new insights beyond those available from superficial biopsy-focused tissue examinations.

BK polyomavirus (BKPyV) is a major complication in kidney transplant recipients (KTR), for whom no specific antiviral therapy is available. Modulation of immunosuppressive therapy results in virus clearance in most KTR with BKPyV DNAemia (controllers), but a significant minority fail to clear the virus (non-controllers). Here, we adapt LIBRA-seq, which links antibody sequence data to antigen specificity, to intact viral capsids of the four BKPyV genotypes to study and compare BKPyV-specific B-cell repertoires in controllers (n=8) versus non-controllers (n=3). Sequences were obtained for 5197 BKPyV-specific antibodies, and predicted antigen specificities were validated by ELISA and neutralizing assays (n=21 antibodies). We show that cross-genotype reactivity results from the recruitment of numerous broadly cross-reactive B-cell clones with preferential binding to the infecting genotype, making up 4,3% to 44,6% of the BKPyV-specific repertoire, while true broadly neutralizing antibodies are rare. The proportions of broadly-specific and isotype switched antibodies, rates of somatic hypermutation and repertoire diversity were comparable in both patient groups, indicating that there is no identifiable deficit in the humoral response mounted by BKPyV non-controllers, and supporting the notion that humoral immunity alone is insufficient to control established BKPyV replication. This work shows that LIBRA-seq can be successfully applied to a non-enveloped virus and provides a framework for analyzing antiviral B-cell repertoires and antibody specificity in clinically relevant settings. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=180 SRC="FIGDIR/small/26345220v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@18ef2b6org.highwire.dtl.DTLVardef@1e0b7a2org.highwire.dtl.DTLVardef@3822fcorg.highwire.dtl.DTLVardef@180deea_HPS_FORMAT_FIGEXP M_FIG C_FIG

The intestinal microbiome influences immune recovery and long-term outcomes after allogeneic hematopoietic stem cell transplantation (allo-SCT). While reduced bacterial diversity and depletion of immunomodulatory microbial metabolites during peri-engraftment have been linked to acute graft-versus-host disease (aGvHD) and mortality, it remains unclear whether microbiome recovery after engraftment and immune reconstitution is better reflected by bacterial diversity or by microbial metabolic output. We aimed to define microbiome recovery in the late post-transplant period and test whether a metabolite-based biomarker improves the prediction of clinical outcomes, including overall survival (OS) and chronic (c) GvHD. In this two-center longitudinal observational study, serial stool samples were collected from pre-transplant baseline to day +100 after allo-SCT in a discovery cohort (n = 20, Technical University Munich University Hospital (TUM)) and an independent validation cohort (n = 100, University Hospital Regensburg (UKR)). Gut microbiome composition was assessed by 16S rRNA gene amplicon sequencing, with metagenomic profiling in selected patients, and stool metabolites were quantified using targeted mass spectrometry. Patients were classified as RECOVERY or NO RECOVERY based on changes in bacterial richness between baseline and the post-transplant period. To capture microbial metabolic output, the previously established Immune-Modulatory Metabolite Risk Index (IMM-RI), comprising butyric, propionic, and isovaleric acids, desaminotyrosine and indole-3-carboxaldehyde, was adapted to the late post-transplant period (IMM-RI post-TX). Bacterial alpha diversity frequently improved by day +100; however, this did not consistently indicate restoration of baseline community structure and was not paralleled by recovery of stool metabolite profiles. Accordingly, RECOVERY status showed a limited association with survival or transplant-related mortality (TRM). In contrast, IMM-RI post-TX low-risk identified patients with preserved butyrate-associated biosynthetic capacity and was significantly associated with improved OS in both cohorts (UKR: HR 0.2052, 95% CI 0.07703 - 0.5466, p < 0.0001). In the validation cohort, IMM-RI post-TX low-risk was significantly associated with reduced relapse-related mortality. Interestingly, stool butyric-, propionic and valeric acid concentrations were increased in cGvHD of the skin, indicating context-dependent metabolite effects. These findings suggest that metabolite profiling outperforms bacterial diversity for predicting outcomes after allo-SCT and support microbial metabolites as promising biomarkers for risk stratification and actionable candidates for precision microbiome interventions after allo-SCT.

IntroductionKidney biopsy reports contain rich information that is clinically actionable and useful for research. However, the narrative format hinders scalable reuse. We here investigated whether open-source large language models (LLMs) can extract relevant, standardized readouts from native kidney biopsy pathology reports. MethodsGerman free-text native kidney biopsy reports were parsed with three open-source LLMs (Llama3 70B, Llama3 8B, MedGemma) to generate structured JSON outputs covering relevant report elements (e.g., diagnosis, glomerular counts, histopathological patterns). Two independent observers manually curated the same report elements; disagreements between the two were resolved by an experienced nephropathologist to create the final ground truth. Performance was assessed using strict and soft matching and summarized accuracy. Inter-rated agreement was quantified using Cohens and Lights Kappa with 95% confidence intervals via 1000-times bootstrapping. ResultsLlama3 70B achieved the highest overall accuracy (93.3% strict, 97.1% soft), followed by MedGemma. These larger models showed near perfect performance for explicit and discrete variables and positivity of immunohistochemistry markers, while accuracy decreased for report elements requiring interpretation (e.g., primary diagnosis, interstitial inflammation in fibrosis vs. non-fibrotic cortex). Human raters showed strong agreement for the primary diagnosis ({kappa} = 0.74, 95% CI 0.64-0.84). Adding Llama3 70B or MedGemma as a third rater increased overall agreement (0.82, 95% CI 0.74-0.89 and 0.78, 95% CI 0.69-0.85, respectively), whereas Llama3 8B reduced it. ConclusionsOpen-source LLMs can accurately transform narrative nephropathology reports into a structured and machine-readable format, potentially supporting scalable retrospective cohort building. While some report elements can be extracted without supervision, interpretation-dependent elements should be supervised by a human observer. Lay SummaryRetrospective data collection from nephropathology reports is essential for building informative cohorts in computational nephropathology research, yet manual processing of narrative reports is time-consuming and limits scalability. In this study, we demonstrate that open-source large language models can reliably extract key diagnostic, quantitative, and descriptive data elements from kidney biopsy reports with high accuracy. While factual and clearly stated report elements can be extracted automatically, findings that require contextual or interpretative judgment still benefit from expert supervision. Overall, this approach substantially reduces manual effort and enables efficient generation of structured datasets from diagnostic routine, facilitating the development of kidney registries and future computational nephropathology research. In addition, such systems could be implemented into the routine diagnostic workflow, to directly transform narrative reports into structured data.

BackgroundKidney volumetry derived from CT has been proposed as a surrogate of renal function in living kidney donor evaluation. However, clinical integration has been limited by reader-dependent workflows and semiautomatic methods susceptible to image quality. PurposeTo evaluate whether fully automated CT-based segmentation of renal cortex, medulla and total parenchymal volume provides reproducible volumetric biomarkers associated with global and split renal function in living kidney donor candidates. Materials and MethodsIn this retrospective single-center study, 461 living kidney donor candidates (2003-2021) underwent contrast-enhanced abdominal CT. A convolutional neural network was trained to automatically segment cortical, medullary, and total parenchymal volumes on arterial-phase images. Segmentation performance was evaluated against manual reference annotations. Volumes were indexed to body surface area. Associations with eGFR, 24-hour creatinine clearance, cystatin C, and tubular clearance were assessed using Spearman correlation coefficient ({rho}), and side-specific volume fractions were compared with scintigraphy -derived split function. ResultsAutomated segmentation achieved excellent agreement with expert reference segmentations (Dice 0.95 for cortex; 0.90 for medulla). eGFR correlated moderately with cortical ({rho} = 0.46) and total parenchymal volume ({rho} = 0.45), and modestly with medullary volume ({rho} = 0.30). Similar associations were observed for other global measures, with the strongest correlation for cortical volume and tubular clearance ({rho} = 0.53). Side-specific volume fractions correlated with scintigraphy-derived split renal function ({rho} = 0.49-0.56; all p < 0.001). ConclusionAutomated CT-based renal subcompartment segmentation provides reproducible volumetric biomarkers within routine donor evaluation. Cortical volume performs comparably to total parenchymal volume and tracks split renal function at the cohort level, suggesting potential utility in donor assessment.

BackgroundTraditional heart transplant registries often lack the granularity required for deep phenotyping and rely on labor-intensive manual abstraction. We describe the methodology and validation of a next-generation, automated, multi-source registry designed to address these limitations. MethodsUtilizing a High-Performance Computing environment, we integrated structured data from Epic data warehouses (Clarity and Caboodle), external molecular diagnostics, and verified UNOS survival records. A custom deterministic rule-based Natural Language Processing (NLP) engine was developed to extract echocardiographic measures, rejection grades, and vasculopathy scores from over 21,000 unstructured clinical reports. ResultsThe Houston Methodist J.C. Walter Jr. Transplant Center Precision Registry and Platform-Heart (TCPR-Heart) captures 1,687 heart transplants (1,636 patients) spanning the years 1984-2025. The TCPR-Heart comprises 1,054 transplants with active clinical follow-up: 555 transplants were extracted and abstracted from our modern electronic health record (EHR) in the decade since deployment, providing access to data throughout the patients course of heart transplant; 427 were legacy active transplants (transplanted pre-2016 with continued follow-up), and 72 were external transplants (transplanted elsewhere but followed at Methodist). Additionally, the registry houses a historic cohort of 633 transplants (last follow-up < June 2016) with limited variables. Automated deep phenotyping successfully generated longitudinal data trends across clinical domains, including immunosuppression strategies, rejection, immunologic HLA data, renal function, metabolic profiles, vasculopathy, graft function, hospitalization burden and survival information. ConclusionThis automated framework unifies clinical, administrative, and molecular data streams. By leveraging an automated, regularly updated registry, we established a scalable, high-fidelity data source as a foundation for further innovations and novel applications based on an expertly curated and validated data source.

ImportanceDonor hospitals in the United States are assigned to a designated organ procurement organization (OPO) responsible for managing deceased donors in the designated donation service area (DSA). Donor hospitals can apply for waivers to work with a different OPO with appropriate justification, and beginning with the 2026 OPO certification cycle, the highest-performing OPOs can bid to work with donor hospitals managed by intermediate- and low-performing OPOs. ObjectiveWe sought to evaluate the impact of donor hospital waivers on organ donation activity. DesignRetrospective cohort study. SettingWe evaluated Organ Procurement and Transplantation Network (OPTN) data from two OPOs (Donor Network West and Honor Bridge), each with a donor hospital (Renown Regional Medical Center and North Carolina Baptist Hospital) in its DSA granted a waiver to work with a different OPO beginning in April 2025. Main OutcomeWe assessed changes in the number of organ donors and organs transplanted pre- and post-granting of a waiver using a difference-in-differences approach based on multilevel mixed-effects models. ResultsAfter switching OPO affiliations, these two donor hospitals had marked and statistically significant increases in the number of donors recovered and organs transplanted, despite stable numbers of reported deaths at each hospital. In multivariable models, switching OPO affiliations was associated with a statistically significant increase in donors recovered and organs transplanted. Conclusion: With eight months of post-waiver data, donor hospitals with granted waivers had significant increases in donation activity driven by improved donor conversion rather than changes in referral patterns or organ yield per donor. Although longer-term data are needed to confirm these findings, CMS and the organ transplant community should feel confident that changing donor hospital-OPO affiliations will not negatively impact donation and may lead to significant increases in donation. These data also counter unfounded concerns that the continued granting of waivers and realignments of donor hospital-OPO affiliations during the 2026 recertification cycle will lead to a collapse of the system of organ donation. KEY POINTSO_ST_ABSQuestionC_ST_ABSDo donor hospitals who request a waiver to change OPO affiliations have changes in organ donation rates? FindingsUsing a difference-in-difference approach, the two donor hospitals who changed OPO affiliations had a significant increase in organ donors and organs transplanted after being granted a waiver. MeaningDonor hospitals that change OPO affiliations have an immediate increase in organ donation activity.

BackgroundCardiac allograft vasculopathy (CAV) is a leading cause of late graft failure and mortality following heart transplantation, with limited therapeutic options. Endothelial cells (ECs), at the interface between the donor graft and host immune system, play a central role in CAV development. However, the molecular mechanisms driving endothelial dysfunction and vascular remodeling in chronic heart transplant rejection remain poorly understood. MethodsTo characterize endothelial alterations associated with CAV, we isolated nuclei from cardiac tissues of four human donor groups: (1) early post-transplant CAV-negative surveillance biopsies, (2) CAV-negative explanted grafts with acute cellular rejection (ACR), (3) late-stage CAV-positive explanted grafts, and (4) naive non-transplanted control hearts. We applied intranuclear cellular indexing of transcriptomes and epitopes (inCITE-seq) to profile endothelial gene expression together with nuclear protein levels of splice factor polypyrimidine tract-binding protein 1 (PTBP1), a key post-transcriptional regulator of endothelial inflammatory responses. Functional relevance of PTBP1 was assessed using endothelial-specific deletion of Ptbp1 in an F1 hybrid murine model of CAV. ResultsIn human CAV, endothelial cells exhibited increased transforming growth factor-{beta} (TGF-{beta}) signaling and reduced oxidative phosphorylation (OxPhos) transcripts. Nuclear PTBP1 protein levels were markedly elevated in CAV endothelium and were associated with TGF-{beta}-responsive transcriptional programs and correlated with clinical indices of cardiac dysfunction. In murine heart transplants, endothelial-specific deletion of Ptbp1 markedly reduced hallmarks of CAV, including neointimal hyperplasia, fibrosis, and lymphocyte activation. At the molecular level, endothelial Ptbp1 deletion prevented suppression of mitochondrial transcripts and preserved mitochondrial content and integrity under hypoxic stress, attenuating interferon signaling in endothelial cells. ConclusionThese findings identify PTBP1 as a central endothelial regulator linking pro-fibrotic stress to mitochondrial dysfunction and immune activation in chronic cardiac allograft rejection. Targeting endothelial PTBP1 may represent a strategy to limit chronic graft injury while minimizing systemic immunosuppression.

0BackgroundA Disintegrin and Metalloprotease 17 (ADAM17) is a key sheddase regulating multiple inflammatory and growth factor-related pathways implicated in diabetic kidney disease (DKD). While cell-specific deletion of ADAM17 has shown renoprotective effects, the impact of global ADAM17 ablation in the context of diabetes remains incompletely understood. MethodsWe investigated the effects of tamoxifen-induced global Adam17 deletion in a murine model of type 1 diabetes induced by streptozotocin. Renal function, structural injury, inflammatory responses, stress-related signalling pathways, and fibrotic remodelling were comprehensively assessed and compared between diabetic Adam17 knockout and control mice. ResultsDespite persistent hyperglycaemia and albuminuria, diabetic Adam17 knockout mice exhibited preservation of glomerular filtration rate and marked attenuation of diabetes-associated renal injury. Global Adam17 deletion reduced mesangial expansion and structural damage, limited macrophage infiltration and chemokine expression, and significantly attenuated fibrotic remodelling. At the molecular level, Adam17 deficiency was associated with selective modulation of stress-related signalling pathways, including reduced activation of the PI3K/Akt axis and partial preservation of mitochondrial stress regulators, without evidence of a generalized suppression of cellular stress responses. ConclusionsOur findings demonstrate that global deletion of ADAM17 confers robust protection against diabetes-induced kidney injury through coordinated attenuation of inflammatory activation, stress-related signalling, and fibrotic progression. These results highlight the context-dependent role of ADAM17 in diabetic kidney disease and support the concept that therapeutic strategies targeting ADAM17-related pathways may require tissue- and disease-specific modulation to achieve renoprotective effects.

Background: Each year around 4,500 people in the UK receive an organ transplant. These surgeries can be life changing and life extending for patients but are also associated with significant costs for the health service. However, by reducing the need for other expensive interventions involved in non-transplant care for organ failure, such as dialysis, some of these costs may be recovered. Methods: We assessed the lifetime costs and benefits associated with transplantation focussing on deceased donor adult transplants for kidneys, livers, hearts, and lungs. We incorporated costs of organ retrieval, surgery, post-transplant secondary care, and medications, as well as impacts on quality and duration of life. These were compared to the cost of managing patients with end-stage organ failure for whom no transplant occurs. Results: Kidney transplants were found to be cost saving with lifetime costs approximately 220,000 GBP lower than alternative treatment. Heart transplants and liver transplants were found to be more cost-effective than thresholds used by NICE for new medicines at approximately 17,000 GBP to 18,000 GBP per quality adjusted life year gained. Lung transplants were the least cost-effective organ transplant with a cost per quality adjusted life year gained of over 50,000 GBP. Conclusions: Although transplants can be costly, not providing a transplant to a patient who needs one also brings significant costs. Kidney transplants can save the health system money by reducing the need for dialysis. Increasing the number of kidney's available for transplant could save the NHS money whilst saving and improving lives.

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Vaccination frequently elicits suboptimal immunogenicity in organ transplant recipients, particularly those on long-term immunosuppressive therapy, highlighting the need for improved understanding of immunosuppression mechanisms and optimized vaccination strategies. This study enrolled a cohort of 132 individuals and observed significantly lower antibody levels in kidney transplant recipients (KTRs) compared to non-transplant controls (non-KTRs). Antibody levels were inversely associated with both the dosage and duration of immunosuppressive therapy. Complementary small animal studies demonstrated that immunosuppressive treatment dosage-dependently and reversibly impaired antibody production, primarily by depleting immune cells, notably B cells. A single shot of adenoviral vector-based vaccines demonstrated enhanced immunogenicity relative to two shots of alum-adjuvanted protein vaccines, inducing potent neutralizing antibodies (NAbs) and a Th1-biased T-cell response even under continuous immunosuppression. The enhanced response was driven by reduced interference from pre-existing antibodies, sustained transgene expression, and the reprogramming of lipid metabolism to activate T and B cells. Our findings advocate for tailored vaccination strategies, positioning adenoviral vectors as a candidate modality for this vulnerable population.