Trending Topics in Gastroenterology | GastroAGI

Single-Dose PCSK9 Base Editing Achieves Durable LDL Reduction : NEJM | May 2026

Introduction Hypercholesterolemia remains a major driver of atherosclerotic cardiovascular disease despite the availability of statins, PCSK9 inhibitors and RNA-based therapies. Lifelong treatment adherence and incomplete LDL reduction continue to limit long-term risk modification in high-risk populations. Problem Statement Whether in vivo gene editing can safely achieve durable suppression of PCSK9 and sustained LDL cholesterol reduction after a single treatment remains a major unanswered question in cardiovascular therapeutics. Summary This first-in-human phase 1 study evaluated VERVE-102, an investigational liver-directed base-editing therapy designed to permanently inactivate PCSK9 following a single intravenous infusion. VERVE-102 uses a lipid nanoparticle platform delivering messenger RNA encoding an adenine base editor together with guide RNA targeting PCSK9. The therapeutic strategy is based on naturally occurring loss-of-function PCSK9 variants associated with lifelong low LDL cholesterol levels and reduced cardiovascular risk. The study demonstrated clear dose-dependent reductions in circulating PCSK9 and LDL cholesterol levels across escalating dose cohorts. At the highest dose level, LDL cholesterol fell by more than 60%, with substantial absolute LDL reductions sustained throughout follow-up. Importantly, lipid lowering appeared durable over time, with maintained reductions extending beyond one year in available participants. These findings strongly support the feasibility of permanent in vivo gene editing as a potentially transformative “one-and-done” lipid-lowering strategy. Safety outcomes were encouraging in this early-phase trial. No dose-limiting toxicities were observed, and most adverse events consisted of mild infusion-related reactions or transient liver enzyme elevations. No major safety signal directly related to gene editing emerged during follow-up. The study represents a major milestone in clinical base-editing therapeutics. Unlike CRISPR nuclease-based approaches that create double-stranded DNA breaks, adenine base editing introduces targeted nucleotide changes without generating double-strand cleavage, theoretically reducing genomic instability risks. Clinically, the implications are substantial. Patients with familial hypercholesterolemia or premature coronary artery disease often require lifelong multidrug lipid-lowering therapy, and treatment adherence remains a persistent challenge. Durable single-dose gene editing could fundamentally alter preventive cardiology. The work also reflects the rapid convergence of lipid biology, RNA therapeutics and precision genome engineering. Following the success of siRNA therapies targeting PCSK9, permanent genomic suppression now appears technically achievable in humans. Importantly, the study focused on patients at particularly high cardiovascular risk, including those with heterozygous familial hypercholesterolemia. These populations may derive the greatest benefit from sustained LDL reduction over decades. The findings additionally raise broader questions regarding future management paradigms for chronic cardiometabolic disease. Gene editing may eventually transition cardiovascular prevention from chronic pharmacotherapy toward definitive molecular intervention. Nevertheless, several critical uncertainties remain. Long-term durability, rare off-target editing effects, immunogenicity and very late safety outcomes require extended observation before broader implementation can be considered. Cost, accessibility and ethical considerations surrounding permanent somatic gene editing will also become increasingly important as these technologies move toward larger clinical trials and potential commercialization. The study additionally reinforces the growing therapeutic relevance of hepatocyte-directed gene editing platforms, which may eventually expand beyond lipid disorders into multiple inherited and metabolic liver diseases. Overall, this phase 1 trial demonstrates that single-dose in vivo PCSK9 base editing with VERVE-102 can produce substantial, durable LDL cholesterol reduction with an encouraging early safety profile, marking a major advance toward permanent gene-editing therapies for cardiovascular disease prevention.

Pediatric Single-Cell Liver Atlas Reveals Distinct Age-Dependent Immune and Fibrotic Signatures : Hepatol Commun | May 2026

Introduction Liver development during childhood involves dynamic metabolic, immune and stromal maturation processes that differ substantially from adult liver biology. However, most hepatic single-cell reference atlases and mechanistic studies have focused predominantly on adult tissue. This gap is particularly important because pediatric liver diseases frequently display unique inflammatory, cholestatic and fibrotic phenotypes distinct from adult disorders. Problem Statement The lack of a comprehensive pediatric liver single-cell reference map limits understanding of age-specific hepatic biology and hampers accurate interpretation of cellular mechanisms underlying pediatric liver diseases such as Intestinal Failure-Associated Liver Disease. Summary This study generated a high-resolution single-cell RNA sequencing atlas of the normal pediatric liver and leveraged it to characterize disease-associated cellular programs in pediatric intestinal failure-associated liver disease. The investigators analyzed more than 42,000 cells from healthy pediatric livers and compared them with adult hepatic single-cell datasets, revealing important age-related differences in immune and stromal cell populations. One of the most striking findings was the distinct phenotype of pediatric Kupffer-like macrophages, which demonstrated heightened expression of immune activation genes including IL1B, CCL3 and CCL4 compared with adult counterparts. These findings suggest that the healthy pediatric liver exists in a more immunologically activated baseline state than adult liver tissue. Functional validation further supported this concept, with pediatric liver myeloid populations demonstrating enhanced IL-1β secretion following stimulation. The study is highly important because it challenges the assumption that adult liver reference datasets can adequately model pediatric hepatic biology. Age-dependent immune signatures appear sufficiently distinct that reliance on adult comparators alone may obscure critical disease-relevant pathways in childhood liver disorders. Using the pediatric atlas as a disease reference framework, the authors subsequently analyzed pediatric IFALD biopsies and identified fibrosis-associated transcriptional programs that would likely have been missed using adult reference tissue alone. Kupffer-like cells in IFALD showed increased expression of inflammatory and fibrosis-linked genes such as LY96, implicating innate immune activation in early pediatric fibrogenesis. Interestingly, mesenchymal populations within IFALD adopted transcriptional profiles more closely resembling adult fibrotic liver states than healthy pediatric tissue, suggesting premature activation of pro-fibrogenic remodeling programs during disease progression. The work has major translational implications for pediatric hepatology. Single-cell atlases tailored to developmental stage may become increasingly important for understanding disease heterogeneity, biomarker discovery and therapeutic targeting in pediatric liver disorders. The findings also reinforce the emerging concept that immune ontogeny strongly influences tissue-specific disease behavior. Pediatric hepatic macrophages appear functionally distinct rather than simply quantitatively different from adult populations, potentially contributing to unique inflammatory responses, fibrosis patterns and regenerative behavior in childhood liver disease. Methodologically, the study demonstrates the growing power of single-cell transcriptomics for resolving age-dependent cellular ecosystems. Beyond hepatology, developmental atlases are likely to become foundational tools across pediatric translational medicine. The atlas may additionally provide an important framework for future investigation of pediatric cholestatic disorders, metabolic liver diseases, immune-mediated hepatitis and transplant immunobiology, where developmental immune context may critically shape disease expression and therapeutic response. From a fibrosis perspective, the study also highlights how early-life inflammatory signaling may prime mesenchymal activation pathways differently than in adults. Understanding these developmental fibrogenic programs could eventually facilitate age-specific antifibrotic therapeutic approaches. Overall, this study establishes a foundational single-cell atlas of the healthy pediatric liver and demonstrates that pediatric hepatic immune and stromal biology differ substantially from adult liver tissue. The findings provide a critical developmental reference framework for mechanistic investigation of pediatric liver diseases and emphasize the importance of age-specific precision hepatology approaches.

Hereditary Pancreatitis Plasticity Accelerates KRAS-Driven Carcinogenesis : Gut | May 2026

Introduction Chronic Pancreatitis is a well-established risk factor for Pancreatic Ductal Adenocarcinoma, particularly in hereditary pancreatitis syndromes where lifetime cancer risk is markedly elevated. However, the biologic mechanisms linking chronic pancreatic inflammation to early malignant transformation remain incompletely understood. Increasing evidence suggests that inflammatory stress-induced epithelial plasticity may create a permissive environment for oncogenic KRAS-driven tumorigenesis. Problem Statement The mechanisms through which hereditary chronic pancreatitis cooperates with oncogenic KRAS Mutation during early pancreatic carcinogenesis remain poorly defined, particularly regarding epithelial cell plasticity, inflammatory signaling and stromal-immune interactions. Summary This mechanistic study combined a humanized hereditary pancreatitis mouse model carrying the pathogenic CPA1 p.N256K mutation with the established KrasG12D pancreatic cancer model to investigate how chronic inflammatory injury promotes early pancreatic neoplasia. Mice harboring both hereditary pancreatitis and oncogenic Kras mutations demonstrated striking acceleration of pancreatic remodeling, fibrosis and metaplastic lesion formation compared with Kras-mutant controls alone. The findings strongly support the concept that chronic inflammatory stress creates a biologically permissive microenvironment for KRAS-driven carcinogenesis. A major finding was the extensive epithelial plasticity induced by the CPA1 mutation across both acinar and ductal compartments. Acinar cells underwent prominent acinar-to-ductal metaplasia (ADM), an early premalignant reprogramming process increasingly recognized as a central initiating event in pancreatic cancer development. These metaplastic acinar cells demonstrated strong activation of endoplasmic reticulum stress pathways and inflammatory transcriptional programs. The study additionally identified a distinct inflammatory ductal cell phenotype termed “iDucts,” characterized by inflammatory signaling activation and altered intercellular communication. Single-cell transcriptomic analyses revealed highly dynamic multicellular interaction networks involving ductal cells, fibroblasts and granulocytes that collectively sustained pancreatic inflammation and early neoplastic progression. Importantly, the work highlights that chronic pancreatitis-associated carcinogenesis is not driven solely by epithelial mutations, but rather by coordinated interactions among stressed epithelial cells, inflammatory immune populations and activated stromal fibroblasts. These findings reinforce the concept of pancreatic cancer as a disease emerging from chronic inflammatory ecosystem remodeling rather than isolated oncogenic transformation alone. Mechanistically, CPA1 mutation-induced endoplasmic reticulum stress appears particularly important. Persistent protein misfolding stress within acinar cells likely promotes maladaptive regenerative responses, inflammatory cytokine release and dedifferentiation toward duct-like phenotypes vulnerable to KRAS-mediated transformation. The study is also notable because it models hereditary chronic pancreatitis using a clinically relevant humanized mutation rather than experimentally induced acute injury models. This provides a more biologically faithful framework for understanding the exceptionally high pancreatic cancer risk observed in hereditary pancreatitis patients. Clinically, the findings support intensified surveillance strategies in hereditary pancreatitis populations and further emphasize the importance of targeting inflammatory and stromal signaling pathways during early pancreatic carcinogenesis. The identified inflammatory ductal phenotypes and cell-cell communication networks may additionally represent future therapeutic or biomarker targets for pancreatic cancer interception. Overall, this translational study demonstrates that hereditary pancreatitis-associated epithelial plasticity, inflammatory remodeling and multicellular signaling networks cooperate with oncogenic KRAS to accelerate early pancreatic carcinogenesis. The work provides important mechanistic insight into how chronic pancreatic injury drives malignant transformation and advances understanding of inflammation-associated pancreatic cancer initiation.

Autophagic HIF-1α Degradation Extends Mammalian Lifespan : Nat Aging | May 2026

Introduction Hypoxia-Inducible Factor 1-alpha is a master regulator of cellular adaptation to hypoxia, coordinating metabolic reprogramming, angiogenesis and stress responses. Although transient HIF-1α activation is protective during acute hypoxic stress, chronic HIF-1α accumulation has increasingly been linked to inflammation, mitochondrial dysfunction, senescence and age-related tissue injury. This landmark study explored why certain tissues age more slowly than others and identified a previously unrecognized autophagy-mediated mechanism regulating hypoxia-associated aging. Problem Statement The molecular mechanisms underlying differential organ aging rates remain poorly understood. In particular, how chronically hypoxic tissues avoid long-term HIF-1α–mediated cellular stress and whether these protective pathways can be therapeutically transferred to other organs has remained unclear. Summary Using cross-tissue molecular aging analyses, investigators identified the intervertebral disc (IVD) as an unusually slow-aging tissue despite its chronically hypoxic microenvironment. Mechanistic studies revealed that nucleus pulposus cells within the IVD possess a unique ability to selectively degrade HIF-1α through optineurin-mediated autophagy, thereby uncoupling persistent hypoxia from sustained HIF-1α accumulation. This selective autophagic degradation pathway prevented chronic cellular stress signaling, reduced senescence-associated injury and preserved tissue homeostasis despite prolonged hypoxic exposure. The findings challenge the traditional assumption that hypoxia necessarily results in persistent HIF-1α stabilization and instead demonstrate that regulated HIF-1α turnover may be critical for healthy aging under hypoxic conditions. Building upon this biologic mechanism, investigators developed a novel small-molecule autophagy-targeting compound termed HATC designed to promote selective autophagic degradation of HIF-1α across tissues. Systemic administration of HATC in aged mice substantially reduced HIF-1α accumulation in multiple organs and produced broad geroprotective effects. Remarkably, weekly HATC treatment ameliorated numerous age-related pathologies while significantly extending both median and maximum lifespan. Median lifespan increased by approximately 14%, while maximal lifespan improved by roughly 12%. Treated animals additionally demonstrated improvements across multiple physiologic aging phenotypes, suggesting enhancement of overall healthspan rather than isolated survival prolongation. Mechanistically, the study positions chronic HIF-1α accumulation as a potentially central driver of mammalian aging biology. Persistent HIF-1α signaling may promote metabolic dysfunction, inflammatory activation and cellular stress responses that progressively impair tissue integrity with age. Selective autophagic degradation therefore represents a targeted strategy for restoring cellular homeostasis without globally suppressing adaptive hypoxia signaling. The work is particularly important because it introduces a new therapeutic paradigm within geroscience: selective degradation of aging-associated signaling proteins through engineered autophagy tethering rather than conventional enzymatic inhibition. This strategy may allow highly specific modulation of pathogenic pathways while minimizing broader physiologic disruption. Overall, this groundbreaking study identifies optineurin-mediated autophagic degradation of HIF-1α as a key endogenous longevity mechanism in slowly aging tissues and demonstrates that pharmacologic transfer of this pathway can extend mammalian lifespan. The findings establish HIF-1α-directed autophagy modulation as a highly promising emerging strategy in translational aging biology and geroprotective therapeutics.

Microvillar Contacts Govern PD-1 Checkpoint Signaling : Sci Immunol | May 2026

Introduction Programmed Cell Death Protein 1 blockade has revolutionized cancer immunotherapy, yet the precise spatial and temporal mechanisms by which PD-1 suppresses T-cell activation remain incompletely understood. Although PD-1 signaling is known to inhibit T-cell receptor (TCR) activation through recruitment of phosphatases such as SHP2, how checkpoint signaling is physically organized at the immune synapse has remained unclear. This mechanistic study identifies nanoscale microvillar contacts as critical hubs for early PD-1–mediated immune regulation. Problem Statement The cellular architecture governing integration of PD-1 inhibitory signaling with TCR activation has not been fully resolved. Furthermore, current checkpoint-blocking antibodies may paradoxically induce inhibitory signaling under certain conditions, potentially limiting therapeutic efficacy. Summary Using advanced fluorescence imaging and nanoscale spatial analyses, investigators demonstrated that PD-1 signaling is initiated within dynamic microvillar close contacts formed during T-cell interaction with target cells. These specialized nanoscale membrane protrusions function as highly organized signaling hubs where PD-1 and TCR pathways are integrated during the earliest phases of immune synapse formation. PD-1 signaling began immediately as microvillar contacts formed and selectively shortened the duration of TCR signaling without substantially altering signal amplitude. Mechanistically, PD-1 directly recruited SHP2 to microvillar contacts, thereby suppressing proximal TCR activation. In parallel, PD-1 indirectly reduced T-cell activation by limiting cell spreading, decreasing formation of additional close contacts and reducing overall TCR engagement efficiency. Importantly, the inhibitory effects of PD-1 were particularly pronounced in settings of low-affinity or low-density antigen presentation, suggesting that checkpoint signaling preferentially suppresses weaker antitumor immune responses. These findings provide mechanistic insight into why poorly immunogenic tumors may be especially vulnerable to PD-1–mediated immune escape. One of the most clinically significant observations involved the behavior of the PD-1 blocking antibody Nivolumab. Surprisingly, investigators found that Fc receptor–mediated trapping of nivolumab-bound PD-1 within microvillar contacts paradoxically induced inhibitory signaling rather than fully blocking checkpoint activity. This unintended agonistic effect promoted persistent SHP2 recruitment and residual immune suppression despite therapeutic antibody binding. The authors subsequently engineered modified antibodies designed to prevent PD-1 trapping at microvillar contacts. These engineered variants eliminated agonistic signaling effects and demonstrated improved checkpoint blockade efficacy, highlighting an important new principle in immunotherapy antibody design. The findings suggest that spatial organization and membrane dynamics may critically influence checkpoint inhibitor performance beyond simple receptor occupancy. Conceptually, the study reframes immune checkpoint signaling as a highly localized nanoscale process occurring within transient microvillar structures rather than diffuse immune synapses. This model provides a new mechanistic framework explaining how inhibitory and activating immune signals are integrated with extraordinary spatial precision during T-cell target recognition. Overall, this landmark study identifies microvillar close contacts as central regulators of PD-1 checkpoint biology and reveals that antibody-mediated PD-1 trapping may inadvertently preserve inhibitory signaling. These findings may guide development of next-generation immune checkpoint inhibitors with improved spatial dynamics, enhanced antitumor activity and reduced functional resistance.

Autophagy Modulation in Cancer: Therapeutic Promise and Complexity : Nat Rev Drug Discov | May 2026

Introduction Autophagy is a highly conserved cellular homeostatic mechanism that enables recycling of intracellular components, removal of damaged organelles and adaptation to metabolic stress. In cancer biology, autophagy has emerged as a paradoxical process with context-dependent tumor-suppressive and tumor-promoting roles. Increasingly, modulation of autophagy is being explored as a therapeutic strategy across multiple stages of oncogenesis and anticancer treatment. Problem Statement Despite intense therapeutic interest, targeting autophagy in cancer remains highly challenging because autophagy exerts divergent effects depending on tumor type, disease stage, immune context and treatment setting. Furthermore, currently available pharmacologic autophagy inhibitors lack specificity and may adversely affect normal tissues and antitumor immune responses. Summary This comprehensive review outlines the multifaceted role of autophagy across cancer initiation, progression, immune regulation and therapeutic resistance. In early carcinogenesis, defective autophagy promotes genomic instability, oxidative stress, chronic inflammation and accumulation of damaged cellular components, thereby facilitating malignant transformation. These observations support the tumor-suppressive role of basal autophagy during early oncogenesis. Conversely, once tumors are established, proficient autophagic activity often becomes advantageous for malignant cells. Tumor cells exploit autophagy to survive hypoxia, nutrient deprivation, oxidative stress and therapeutic pressure within hostile tumor microenvironments. Autophagy additionally supports mitochondrial fitness, metabolic plasticity and adaptation to cytotoxic therapies, thereby contributing to tumor persistence and treatment resistance. The review highlights growing evidence that autophagy strongly influences anticancer immunity. Depending on context, autophagy may either enhance or impair immune-mediated tumor elimination. In some settings, autophagy facilitates antigen presentation, immunogenic cell death and T-cell activation, thereby supporting immunosurveillance. Conversely, autophagic pathways may also protect tumor cells from immune-mediated cytotoxicity and contribute to resistance against immune checkpoint blockade. Importantly, the authors emphasize that healthy immune cells themselves depend heavily on autophagy for maturation, survival and effector function. Cytotoxic T lymphocytes, dendritic cells and other immune effectors require intact autophagic machinery to sustain antitumor responses. This creates major therapeutic complexity because indiscriminate systemic autophagy inhibition could simultaneously impair both tumor survival and immune-mediated tumor control. The review further discusses current pharmacologic strategies targeting autophagy, including lysosomal inhibitors such as hydroxychloroquine, upstream kinase modulators and novel selective autophagy-targeting agents. However, most clinically available inhibitors remain relatively nonspecific and incompletely suppress autophagic flux. Variable pharmacodynamic activity, compensatory resistance pathways and systemic toxicity have limited clinical success thus far. A major conceptual advance emphasized throughout the review is that autophagy should no longer be viewed as a binary therapeutic target. Instead, future approaches will likely require precision modulation tailored to tumor genotype, metabolic state, immune microenvironment and treatment timing. Context-specific strategies integrating autophagy modulation with chemotherapy, radiotherapy, targeted therapy or immunotherapy may ultimately prove most effective. Overall, this state-of-the-art review positions autophagy as one of the most biologically complex therapeutic vulnerabilities in oncology. The authors underscore that successful clinical translation will require highly selective, context-aware approaches capable of exploiting tumor-specific autophagic dependencies while preserving protective homeostatic and immune functions in normal tissues.

Hepatocyte CCL9 Drives Fibrogenic Immune Signaling : Hepatology | Apr 2026

Introduction Liver Fibrosis results from persistent hepatic injury, chronic inflammation and activation of hepatic stellate cells (HSCs). Chemokine-mediated immune recruitment is central to fibrogenesis, yet many inflammatory pathways governing hepatocyte–immune–stromal interactions remain incompletely characterized. This mechanistic study investigated the role of hepatocyte-derived Ccl9, the murine homolog of human CCL15, in regulating hepatic inflammation and fibrosis progression. Problem Statement Although inflammatory chemokines are known contributors to liver injury, the specific role of hepatocyte-derived Ccl9 in coordinating immune cell recruitment, macrophage polarization and direct stellate cell activation during fibrosis has remained unclear. Summary Using multiple murine fibrosis models including carbon tetrachloride exposure, bile duct ligation and diet-induced steatohepatitis, investigators demonstrated marked upregulation of Ccl9 expression within fibrotic livers. Injured hepatocytes represented the primary cellular source of Ccl9, while the transcription factor Myc was identified as a major upstream regulator driving its induction during hepatic injury. Functional studies using hepatocyte-specific Ccl9 knockout mice showed substantial attenuation of fibrosis and liver injury across all experimental models. Ccl9 deletion reduced inflammatory infiltration, hepatic macrophage accumulation and neutrophil recruitment, supporting a central role for hepatocyte-derived chemokine signaling in orchestrating fibrogenic inflammation. Similar antifibrotic effects were achieved using Ccl9-neutralizing antibodies, highlighting potential translational therapeutic relevance. Mechanistically, Ccl9 promoted recruitment and activation of inflammatory macrophages through the Ccr1 receptor pathway. Importantly, Ccl9 shifted macrophage polarization toward a proinflammatory M1 phenotype and amplified inflammatory cytokine signaling within injured liver tissue. Beyond immune modulation, the study demonstrated that Ccl9 directly activated hepatic stellate cells through a distinct intracellular signaling cascade. Specifically, Ccl9–Ccr1 signaling recruited Myh9 and enhanced Wnt pathway activation via Myh9-mediated ubiquitination of Gsk3β, thereby promoting stellate cell activation and extracellular matrix production. This dual role — simultaneously amplifying inflammatory immune signaling and directly stimulating fibrogenic stellate pathways — positions Ccl9 as a particularly important upstream mediator of fibrosis progression. The findings are especially notable because they identify hepatocytes not merely as passive injury targets but as active immunoregulatory drivers of fibrogenesis through chemokine secretion. The study also strengthens the growing concept that fibrosis progression depends on tightly integrated hepatocyte–immune–mesenchymal signaling networks rather than isolated stellate cell activation alone. Overall, this translational work identifies the hepatocyte-derived Ccl9/Ccr1 axis as a major promoter of liver fibrosis progression through coordinated immune recruitment, macrophage polarization and direct HSC activation. The data support therapeutic targeting of Ccl9 signaling as a potentially promising antifibrotic strategy across diverse chronic liver diseases.

B-Cell Dysfunction and TLS Biology in iCCA : Gut | May 2026

B-Cell Dysfunction and TLS Biology in iCCA : Gut | May 2026 Introduction Intrahepatic Cholangiocarcinoma is characterised by a highly desmoplastic and immunosuppressive tumour microenvironment (TME), contributing to poor responsiveness to systemic therapies and immune checkpoint inhibitors. While T-cell biology in iCCA has been extensively investigated, the role of tumour-infiltrating B lymphocytes and tertiary lymphoid structures (TLS) remains poorly defined. This study comprehensively dissected the phenotypic, transcriptional and functional characteristics of B cells within iCCA and evaluated their relationship with chemoimmunotherapy response. Problem Statement The immunological contribution of B cells in iCCA is incompletely understood. Whether B cells exert antitumour immunity, become functionally suppressed by the TME, or predict response to immunotherapy remains unclear. Identification of B-cell–mediated immune pathways could open new avenues for biomarker development and therapeutic modulation. Summary Using multimodal single-cell technologies, high-dimensional flow cytometry, transcriptomics, imaging mass cytometry and ex vivo coculture systems, the investigators demonstrated that iCCA harbours a profoundly dysfunctional B-cell compartment. B cells were enriched predominantly in peritumoural regions rather than within tumour cores, where they frequently organised into mature tertiary lymphoid structures associated with improved disease-free survival. In contrast, intratumoural B cells were sparse, immature and functionally suppressed. Single-cell RNA sequencing identified multiple B-cell subpopulations with marked suppression of B-cell receptor signalling, differentiation pathways, inflammatory programs and humoral immune responses within tumours. Tumour-infiltrating B cells demonstrated downregulation of activation-associated genes including CD79B, MYC, CD69 and FOS, alongside increased stress-response signatures. Flow cytometry further confirmed depletion of memory B cells, plasmablasts and activated B-cell subsets within tumours, with enrichment of dysfunctional double-negative and immature phenotypes. Functionally, patients with iCCA displayed impaired systemic humoral immunity, including reduced circulating IgM, IgA, IgE and later-stage class-switched immunoglobulin subclasses, suggesting defective B-cell maturation and class-switch recombination. Tumour-associated B cells expressed increased immunosuppressive cytokines including IL-10 and TGF-β while exhibiting reduced effector cytokines such as IL-6 and IL-12. Mechanistically, extensive ligand–receptor interactome analyses revealed that both tumour cells and cancer-associated fibroblasts actively induce B-cell dysfunction through IL-6 and TGF-β–dependent signalling pathways. Ex vivo coculture experiments confirmed that iCCA cells and fibroblasts suppress B-cell maturation, reduce BAFFR expression and promote expansion of exhausted and atypical B-cell subsets. Importantly, combined blockade of IL-6R and TGF-β signalling restored B-cell activation, differentiation and memory/plasmablast generation, highlighting a therapeutically targetable immune axis. The study additionally demonstrated important predictive implications during chemoimmunotherapy with durvalumab, gemcitabine and cisplatin. Responders exhibited higher frequencies of circulating BAFFR-positive B cells, increased BAFF levels and emergence of hyperexpanded B-cell clonotypes. Elevated BAFFR expression correlated with improved progression-free and overall survival, suggesting that B-cell activation status may function as a clinically relevant predictive biomarker for immunotherapy responsiveness in iCCA. Overall, this landmark translational study establishes that iCCA is characterised by profound B-cell immunosuppression orchestrated by tumour-stromal interactions. The findings position B cells, BAFFR signalling and TLS maturation as potential biomarkers and therapeutic targets, supporting future strategies aimed at restoring B-cell function and enhancing chemoimmunotherapy efficacy in biliary tract cancers.

Gut-Derived Ammonia Drives CD8 T-Cell–Mediated MASH : J Clin Invest | May 2026

Introduction Metabolic Dysfunction-Associated Steatohepatitis is increasingly recognized as a multisystem disorder involving complex interactions between metabolism, intestinal microbiota, immune activation and fibrosis. Although gut dysbiosis has long been implicated in MASH progression, the precise microbial metabolites and immune pathways driving hepatic injury remain incompletely defined. This translational study investigated how ammonia-producing intestinal bacteria modulate hepatic immune injury and evaluated the therapeutic potential of the glycine-based tripeptide DT-109. Problem Statement The mechanisms linking intestinal microbial dysbiosis to hepatic immune-mediated injury in MASH remain poorly understood. In particular, whether gut-derived ammonia directly contributes to hepatic inflammation and cytotoxic immune activation beyond its established role in cirrhosis-associated encephalopathy has remained unclear. Summary Using integrated human, murine and non-human primate MASH models, this study identified a major expansion of the ammonia-producing bacterium Clostridium perfringens within the intestinal microbiome during MASH progression. Elevated intestinal ammonia levels were associated with impaired intestinal barrier integrity, increased systemic exposure to microbial products and heightened hepatic immune activation. Mechanistically, gut-derived ammonia promoted FosB-dependent upregulation of chemokine CCL5 within hepatic CD8+ T cells, driving enhanced cytotoxic T-cell activity and liver injury. Functional experiments using microbiota transplantation and genetically modified ammonia-deficient C. perfringens mutants confirmed a causal relationship between bacterial ammonia production and MASH severity. The study therefore establishes ammonia not merely as a metabolic waste product but as an active immunomodulatory mediator within the gut–liver axis. Therapeutically, DT-109 demonstrated significant efficacy across both murine and non-human primate models. Treatment reduced intestinal C. perfringens abundance, lowered ammonia production, restored intestinal barrier function and attenuated hepatic CD8+ T-cell dysregulation. These improvements translated into reduced steatohepatitis severity and amelioration of inflammatory liver injury. The findings suggest that modulation of microbial ammonia metabolism may represent a novel therapeutic strategy for MASH distinct from traditional metabolic-targeted approaches. Overall, this study identifies a previously unrecognized microbiota–ammonia–CD8 T-cell axis contributing to MASH pathogenesis and positions DT-109 as a promising microbiome-directed immunometabolic therapy. The work further reinforces the emerging concept that intestinal microbial metabolites actively shape hepatic immune injury and may provide tractable therapeutic targets in progressive steatotic liver disease.

circPLCE1 Loss Drives Fibrosis in Crohn’s Disease : Gut | May 2026

Introduction Intestinal fibrosis is a major complication of Crohn’s Disease and remains a leading cause of bowel strictures, obstruction and repeated surgery. Current anti-inflammatory therapies have limited efficacy once fibrotic remodeling becomes established, highlighting the urgent need for mechanistic antifibrotic targets. Emerging evidence suggests that fibroblast metabolic reprogramming is central to organ fibrosis, although its contribution to intestinal fibrogenesis in Crohn’s disease has remained incompletely understood. Problem Statement The metabolic pathways that sustain activated intestinal fibroblasts and extracellular matrix deposition in Crohn’s disease are poorly characterized. In particular, the role of the Pentose phosphate pathway and its upstream regulatory networks in intestinal fibrosis has not previously been defined. Summary Using integrated metabolomics, single-cell RNA sequencing and spatial transcriptomics from paired strictured and non-strictured intestinal tissue, this study identified marked activation of the pentose phosphate pathway (PPP) within intestinal fibroblasts during Crohn’s-associated fibrosis. The investigators demonstrated that xylulokinase (XYLB)-mediated generation of xylulose-5-phosphate promoted extracellular matrix synthesis through epigenetic enhancement of collagen transcription. This established PPP activation as a direct driver of fibroblast profibrotic activity rather than merely a metabolic bystander phenomenon. Mechanistically, the study identified downregulation of the circular RNA circPLCE1 as a central upstream regulator of this metabolic reprogramming. Reduced circPLCE1 expression enhanced PPP activation, increased glycolytic flux and elevated nicotinamide adenine dinucleotide phosphate production, collectively promoting fibroblast activation and intestinal fibrosis both in vitro and in murine fibrosis models. Importantly, circPLCE1 directly interacted with the catalytic domain of XYLB, competitively inhibiting its enzymatic activity. Loss of circPLCE1 therefore restored XYLB function and led to accumulation of xylulose-5-phosphate, driving sustained fibrogenic signaling. Fibroblast-specific circPLCE1 knockdown in vivo significantly aggravated intestinal fibrosis, confirming the biological importance of this regulatory axis. The study further linked metabolic rewiring to epigenetic collagen regulation, reinforcing the emerging concept that immunometabolic pathways are central to chronic fibrostenotic disease progression in Crohn’s disease. Overall, these findings identify a novel circPLCE1–XYLB–Xu5P metabolic axis governing intestinal fibrogenesis and position fibroblast PPP modulation as a promising antifibrotic therapeutic strategy in Crohn’s disease. The work also expands understanding of how non-coding RNAs regulate stromal cell metabolism and tissue remodeling in chronic intestinal inflammation.