Inflammatory Bowel Diseases

Environmental enteropathy (EE) is a chronic, subclinical disorder of the small intestine common in low- and middle-income countries (LMICs), where access to sanitation and exposure to enteric pathogens vary greatly by socioeconomic status (SES). Systemic immune cell activation by enteric microbial exposure is a suspected but poorly characterized driver of EE severity. We hypothesised that adults from Low-SES communities would have more severe EE than adults from High-SES communities and that this would be associated with distinct circulating immune cell phenotypes. We enrolled clinically healthy adults from High- (n=26) and Low-SES (n=76) communities in Lusaka, Zambia. Duodenal biopsies from these adults were used for microscopic morphometry assessments, while plasma and stool biomarkers of epithelial damage, intestinal inflammation, microbial translocation, and systemic inflammation were measured by ELISA. Circulating monocyte, neutrophil and T cell phenotypes were characterised in buffy coat cells by flow cytometry. Compared with the High-SES group, adults from Low-SES communities had higher duodenal villus width and crypt depth and lower epithelial surface area, indicative of more severe EE pathology, and higher levels of plasma biomarkers associated with microbial translocation and systemic inflammation. The Low-SES group also had higher expression of activation markers (CD86 and TLR4) and lower expression of HLA-DR on circulating classical monocytes and neutrophils, higher percentages of gut-homing (4{beta}7+) and activated/exhausted (PD-1+) T cells, including gut-homing (4{beta}7+) regulatory T cells. Principal Component Analysis identified key patterns of immune cell phenotypes across SES groups. Confounder-adjusted linear regression models showed that Principal Component 1 (monocyte/neutrophil activation) was inversely associated with duodenal villus height and epithelial surface area across SES groups. These findings indicate that EE severity varies by SES within LMIC and suggest that monocyte and neutrophil activation is linked to greater duodenal remodelling in adults with EE.

Background: Patients receiving anti-TNF treatment for chronic inflammatory disease display impaired antibody responses, but it remains unclear how immune memory formation is affected. We evaluated antibody responses and memory B cells (Bmem) after COVID-19 booster vaccination in inflammatory bowel disease (IBD) patients receiving anti-TNF treatment. Methodology: Blood was sampled at baseline, 1, and 6 months after WH1/BA.5 bivalent or XBB.1.5 monovalent vaccination from 27 IBD patients receiving intravenous anti-TNF and 44 controls. Neutralizing antibodies were measured using an infectious virus assay. SARS-CoV-2 spike receptor binding domain (RBD)-specific serum IgG was quantified by ELISA, and RBD-specific Bmem were immunophenotyped by flow cytometry using recombinant proteins from ancestral, Omicron BA.1, BA.5, XBB.1.5, and JN.1 variants. Results: Serum IgG to vaccine RBD and neutralizing antibodies in patients increased pre to 1 month post-vaccination, but were lower than controls. Ancestral-, BA.5- and XBB.1.5-specific Bmem increased after vaccination but were significantly lower in patients than controls. Within RBD-specific Bmem, frequencies of recently activated CD21lo cells were increased after vaccination, and were higher in patients than controls. Fewer antigen-specific Bmem in patients expressed IgG4, and more expressed IgG3 or IgD following vaccination. Following vaccination, more RBD-specific Bmem recognized multiple viral variants. However, patients had fewer Bmem that could bind to subvariants than controls. Conclusion: Antibody and Bmem responses to COVID-19 booster vaccination in anti-TNF-treated IBD patients displayed reduced capacity, durability and cross-reactivity, suggesting impaired immune memory for protection against breakthrough infection. This supports the recommendation for annual booster vaccination to prevent severe disease and viral spread.

Inflammatory bowel disease (IBD) is a heterogeneous chronic disease driven by dysregulated mucosal immunity and impaired epithelial barrier function. Although biologics have improved disease management, they are frequently associated with systemic immunosuppression and adverse effects, highlighting the need for localized therapeutic strategies that both control inflammation and promote tissue repair. Here, we developed a protein bispecific termed 7A2-IgG4-IL22, composed of a human IgG4-Fc domain displaying an antagonistic anti-human MAdCAM-1 single chain (sc)-Fv and a human interleukin (IL-)22. The anti-MAdCAM-1 scFv retained the functional activity of the parental monoclonal antibody, inhibiting T cell activation, expansion and differentiation from naive precursors. Blockade of the MAdCAM-1 signaling axis also reduced production of pro-inflammatory cytokines relevant to IBD pathogenesis, including IFN{gamma} and TNF. On the epithelial side, the IL-22 cargo induces robust signaling in epithelial cells, promoting the expression of IL-22 response genes associated with antimicrobial defense, mucosal homeostasis, as well as IL-10 and CXCL1 expression. This effect contributes to immune cell trafficking to the intestinal mucosa. Together, this bispecific provides a localized dual-mechanism strategy for restoring intestinal immune homeostasis.

Background & Aims Dynamic cell cycle control is critical for intestinal crypt maintenance and injury responses, yet genetic regulators driving these changes remain poorly defined. As reserve intestinal stem cells (rISCs) are often considered to be slowly-cycling and can resist replication-dependent injury, factors that restrain proliferation may confer cytoprotection. Here, we define SOX9 as a regulator of intestinal stem cell (ISC) cycling and injury resistance. Methods Primary human ISCs were engineered to tune SOX9 levels, visualize cell cycle state, and manipulate cell cycle regulators. Using this system, we tested how SOX9 dosage impacts stemness, differentiation, proliferative recovery after SOX9 washout, and survival after 5-FU-mediated injury. Transcriptional analyses identified candidate links between SOX9 levels and cell cycle control, which were functionally tested using inducible INK4A (CDKN2A) and Cyclin D2 (CCND2) ISC lines. Results SOX9 induction lengthens the cell cycle in a dose-dependent manner largely by elongating G1 phase through the INK4A-Rb pathway. The effects of high SOX9 levels repressing proliferation and stem cell activity are reversible. SOX9 induction protects against 5-FU toxicity. This protection is mimicked by INK4A overexpression or pharmacological G1 phase arrest and repressed by CCND2 induction. Conclusions These findings identify SOX9-mediated G1 elongation as a reversible cytoprotective program that confers key functional properties associated with rISCs: proliferative restraint, retained stem cell potential, and resistance to replication-dependent injury. This positions G1 length as a potential determinant of which crypt cells survive injury to act as reserve stem cells.

Introduction Patients undergoing polypectomy at colonoscopy remain at risk of metachronous neoplasia despite surveillance guided by histopathological features. Mutational profiling of adenomas, including canonical driver mutations in APC, KRAS, and TP53, may offer additional predictive value. This study aimed to determine whether mutational status in index adenomas was associated with metachronous lesion risk. Methods The INCISE cohort included patients aged 50 to 74 years who underwent polypectomy within the Scottish Bowel Screening Programme and subsequent surveillance colonoscopy within 6 years. Targeted next-generation sequencing was performed on formalin-fixed paraffin-embedded polyps. Driver mutation frequency, tumour mutational burden (TMB), and variant allele frequency (VAF) were analysed and correlated with histopathological features and metachronous outcomes using appropriate statistical models. Results A total of 895 adenomas from 723 patients were analysed. In conventional adenomas, as the number of high-risk histopathological features (size >=10mm, villous architecture, and high-grade dysplasia) increased there was a stepwise increase in the proportion of samples with a mutation in KRAS from 13% to 51% (padj<0.001) and TP53 from 8% to 35% (padj<0.001). However, neither mutation frequency (p=0.901), nor median tumour mutation burden (TMB) (2.27 vs 2.15 mut/Mb, p=0.242), in index adenomas was associated with the development of metachronous lesions. Conclusions While classical driver mutations reflect histopathological progression within adenomas, they do not predict metachronous lesion risk post-polypectomy. Targeted mutation profiling alone is insufficient for surveillance risk stratification, highlighting the need for integrated molecular approaches in this setting.

The murine intestine reactivates developmental gene programs following various forms of damage in vivo and in vitro; however, injury response mechanisms used by the human intestine remain unclear. Using adult human small intestinal epithelium-only organoids ("enteroids"), we characterized the early response to eight injury conditions and injury-associated signaling pathways (P53, PGE2, YAP, TGFB) to interrogate whether human developmental genes were activated. P53 activation and decreased proliferation were common features across treatments. Most (7/8) injuries did not activate human development genes. Butyrate is a notable exception given it inhibited P53 and promoted a human developmental transcriptional signature. We observe that P53 induces a human adult gene signature while TGFB and YAP promote a developmental signature. Together our data characterizes various transcriptional responses to injury, supports injury-associated signaling pathways as regulators of human adult and developmental genes, and highlights how our data can be mined to predict injury-specific interventions for epithelial protection.

Intraepithelial lymphocytes expressing the {gamma}{delta} T cell receptor ({gamma}{delta} IEL) continuously survey the intestinal epithelium to promote mucosal host defense. Although {gamma}{delta} IELs migrate in and out of the lateral intercellular space (LIS) between adjacent enterocytes, the molecular mechanisms governing their migratory behavior are incompletely understood. Based on the known role of CD47, or integrin associated protein (IAP), in mediating neutrophil transepithelial migration, we investigated whether CD47 expression reflects a conserved mechanism regulating {gamma}{delta} IEL surveillance behavior. Here, we report that conditional CD47 deletion on intestinal epithelial cells or {gamma}{delta} T cells had no effect on IEL composition. Using intravital imaging, we identified complementary roles for CD47 on {gamma}{delta} IELs and epithelial cells, with epithelial CD47 restricting {gamma}{delta} IEL motility and {gamma}{delta} T-cell-derived CD47 promoting cell migration. Further investigation revealed that both CD47 and CD18 contribute to {gamma}{delta} IEL surveillance behavior, although CD47 regulates {gamma}{delta} IEL migration in a CD18-independent manner.

Importance: Understanding population differences in epidemiology, clinical presentation, and genetic architecture remains a major challenge for all rare genetic disorders. Hirschsprung disease (HSCR), despite being the commonest cause of neonatal intestinal obstruction, has been poorly studied with respect to its significant heterogeneity across U.S. populations. Objective: To characterize self-identified race and ethnicity differences in HSCR incidence, clinical presentation, and genetic architecture in the United States from diverse data sources. Design, Setting, and Participants: We used retrospective, population-based surveillance data from 3 independent US wide sources - (1) The National Birth Defects Prevention Network (NBDPN; 1996-2010), (2) aggregated electronic health record data from Epic COSMOS (1997-2025), and (3) individual level clinical and genomic data from the Hirschsprung Disease Research Collaborative (HDRC; 2011-2025). Statistical analyses of incident HSCR cases identified at birth, across time and geography, in conjunction with clinical phenotypes and genome sequences from unrelated HDRC probands were performed to characterize epidemiologic, phenotypic and genetic heterogeneity in HSCR. Exposures: HSCR cases were identified based on standardized clinical diagnostic criteria, primarily rectal biopsy with histopathologic confirmation of aganglionosis. The disease was defined using ICD-9-CM code 751.3, CDC/BPA code 751.30-751.34. and ICD-10-CM code Q43.1. Patients were classified by self-identified race and ethnicity (SIRE), with primary comparisons conducted between non-Hispanic Blacks/African Americans (Blacks) and non-Hispanic Whites (Whites). Main Outcomes and Measures: HSCR incidence and the frequency of clinical features were estimated overall and by SIRE. We also estimated the individual and total genetic burden of rare pathogenic coding variants and common noncoding regulatory variants at established HSCR genes by population. Results: Overall HSCR incidence in the U.S. was 2.04 per 10,000 live births (95% CI, 1.99-2.09) as previously estimated. We show, Blacks have the highest HSCR incidence (2.83-3.13 per 10 000 live births), in comparison to Whites (1.89-2.02) and Asians (1.54-1.98), a difference not previously ascertained from previous smaller cohorts from limited geographical regions. This difference persists across surveillance times and geography. This incidence difference from NBDPN is consistent with Epic COSMOS, a nation-wide, independent hospital-based data source. Clinically, Blacks are more likely to present with isolated HSCR and with milder manifestations at birth, including chronic severe constipation (CSC). Genetically, the burden of pathogenic coding variants did not differ between Blacks and Whites. However, Blacks had a significantly higher enrichment of two non-coding regulatory variants (rs199582499 and rs28735659) at the SOX10 gene locus, as compared with Whites. Conclusions and Relevance: This study demonstrates, for the first time, that Black HSCR patients in the U.S. have a higher incidence accompanied by milder clinical presentation and distinct noncoding regulatory SOX10 variants as compared to White patients. Nevertheless, Blacks are severely under-represented in U.S. studies of HSCR leading to significant health disparities in their care and management.

Hirschsprung disease (HSCR) is a severe birth defect where ganglia of the enteric nervous system (ENS) are missing from distal bowel. The aganglionic segment is also characterized by increased epithelial permeability and pro-inflammatory immune activation. These problems may sequentially lead to translocation of gut microbes into the colon wall and systemic circulation, resulting in enterocolitis and sepsis. Current HSCR treatment via surgical resection of the aganglionic segment is lifesaving but not curative, often leaving patients with persistent gastrointestinal complications including recurrent risk of enterocolitis. As alternative, we are developing a regenerative medicine strategy based on in situ stimulation of tissue-resident ENS progenitors via rectal administration of the neurotrophic factor GDNF. Here, we report that GDNF-based therapy has pleiotropic gastrointestinal effects in a mouse model of short-segment HSCR, beyond its role in ENS regeneration. Interestingly, we found that these protective effects are not restricted to the aganglionic distal colon, also positively impacting the ENS-containing proximal colon. GDNF treatment reduces bacterial translocation both locally and in peripheral organs, and this is associated with recovery of the key epithelial junction proteins CLDN3, ZO1 and DSG2. Furthermore, multiparameter flow cytometry-based analysis of 55 lymphoid and 17 myeloid cell subtypes revealed that GDNF treatment has global anti-inflammatory effects, preferentially affecting innate over adaptive immunity. Overall, these findings highlight a critical role for GDNF treatment in reestablishing proper epithelial and immune cell homeostasis, offering promising therapeutic avenues not only for HSCR but also potentially for other intestinal disorders with overlapping pathophysiology.

Regulatory T (Treg) cells expressing ROR{gamma}t accumulate in the intestinal mucosa, yet the signals that determine whether they remain suppressive or acquire inflammatory features are incompletely defined. We first reanalyzed human ileal single-cell data and identified Crohns disease-enriched FOXP3 states in which RORC, HIF1A, hypoxia-responsive, inflammatory, and metabolic programs converged. We then deleted Hif1a in ROR{gamma}t-expressing cells and tested acute DSS colitis, T cell transfer colitis, and azoxymethane/DSS-induced colitis-associated colorectal cancer (CAC). {Delta}Hif1a mice were protected in all three settings. In lymphopenic recipients given the same pathogenic naive T cells, changing only the genotype of the cotransferred Treg population enhanced protection, linking the phenotype to regulatory-cell function in vivo. Reanalysis of mouse colonic Treg single-cell ATAC-seq nominated suppressive and mitochondrial programs for cell-intrinsic testing during low HIF1- expression. {Delta}Hif1a ROR{gamma}t Treg produced more IL-10 and less IL-17A and IFN-{gamma}, limited responder-cell proliferation, contained fewer dysfunctional and mitochondrial-reactive-oxygen-species-high mitochondria, favored fusion-associated transcription, and displayed greater basal and maximal oxygen consumption and reserve capacity. During CAC, HIF-1 loss blunted inflammatory ROR{gamma}t Treg accumulation and reduced tumor burden. Human trajectory and gene-regulatory-network analyses further predicted that HIF1A perturbation would oppose selected disease-associated branches. Together, these findings identify HIF-1 as a context-dependent checkpoint that connects hypoxia-responsive transcription to mitochondrial fitness and inflammatory plasticity in intestinal ROR{gamma}t Treg.

Introduction: Illness perceptions, the cognitive and emotional beliefs patients hold about their condition, are key determinants of patient outcomes across a range of chronic health conditions. Although well-studied in several gastrointestinal disorders, their role remains poorly characterized within patients with functional dyspepsia (FD) and chronic nausea and vomiting syndrome (CNVS). This study examined the associations between illness perceptions, gastrointestinal symptoms, mental health, and gastric electrophysiology in these patients. Methods: Patients meeting self-reported Rome IV criteria for FD and/or CNVS underwent body surface gastric mapping (BSGM) using Gastric Alimetry (Alimetry, New Zealand). The standardized protocol included a 30-minute fasting baseline, 482 kCal meal, and a 4-hour postprandial recording, with concurrent symptom logging. From the BSGM data, patients were phenotyped using established rule-based criteria via the Auckland Classification. Illness perceptions were assessed using the Brief Illness Perceptions Questionnaire alongside validated psychological and quality of life metrics. Results: The cohort included 309 patients (80% female; median age= 36, 15-88) who reported highly negative illness perceptions, which were significantly correlated with worse symptomatology, quality of life, and mental health (medium-large effect sizes). Using multivariable analysis, perceived consequences and emotional responses emerged as the most robust predictors of these patient-reported outcomes. Additionally, illness perceptions significantly mediated the relationship between mental health and gastrointestinal symptoms, with large effect sizes. Associations with gastric electrophysiology were limited to BMI-Adjusted Amplitude, which was associated with poorer perceptions of treatment control and greater emotional response to symptoms. Furthermore, the Continuous Phenotype (normal spectral activity, with continuous symptoms) was associated with worse illness perceptions, including higher perceived consequences, symptom identity, concern, and emotional response, whilst the High Frequency Phenotype was associated with lower understanding. Discussion: The way patients perceive their condition is a quantifiable aspect of the illness experience that is associated with symptom burden, mental health, and quality of life in patients with FD and CNVS. The observed associations with gastric electrophysiology suggest that illness perceptions may also vary in relation to underlying patient physiology. These findings support the consideration of illness perceptions as part of multidisciplinary assessment and management, including targeted patient education and clinical interventions to address distressing or maladaptive illness beliefs.

Interactions between intraepithelial lymphocytes (IELs) and the intestinal epithelium are central to mucosal homeostasis and disease. However, mechanistic in vitro studies describing their crosstalk in humans are limited by scarceness of primary material and insufficient knowledge about co-culture requirements. Here, we establish an autologous human duodenal IEL-organoid co-culture system encompassing expandable and bankable IEL and organoid protocols, with co-culture conditions that allow viability of both cell types. This system enables successive interrogation of lympho-epithelial interactions starting from minimal biopsy material. Under baseline conditions, CD45CD8CD103TCR{beta} IELs retain tissue-residency and effector features and induce an epithelial interferon response and chemokine production, without overt epithelial apoptosis. IL-15 and IL-21, essential cytokines involved in IEL-activation in intestinal enteropathies like celiac disease, increases granzyme B expression and interferon-{gamma} secretion but do not trigger epithelial cell death. However, enforcing IEL-epithelial contact using an anti-CD3-anti-Ep-CAM bispecific antibody induces epithelial apoptosis accompanied by increased tumor necrosis factor (TNF) and FAS-ligand (FASLG) secretion. These findings validate the platforms ability to resolve non-destructive and cytotoxic lympho-epithelial interaction and provide a tractable system for studying intestinal inflammation and immune-mediated epithelial cell death.

Modern lifestyle factors have altered gut microbiota composition and function. Bacteria in the Clostridia class modulate mucosal immune responses through various mechanisms including production of secondary bile acids (SBA). Here, we present a novel system to study how the SBA isodeoxycholic acid (isoDCA) regulates host immunity. Through targeted mutagenesis of bile acid epimerization genes, we engineered Ruminococcus gnavus to ablate isoDCA production. Combining R. gnavus (WT or KO) with Peptacetobacter hiranonis created a two-member consortium that toggles isoDCA production on or off while keeping all other variables constant. Using this system, we demonstrate that isoDCA induces colonic lamina propria ROR{gamma}t{square} Foxp3{square} regulatory T cells (pTregs) through a mechanism requiring both the Takeda G protein-coupled receptor 5 (TGR5) and the Farnesoid X receptor (FXR). Engraftment of this isoDCA+ consortium protected against colitis in an adoptive T cell transfer model by reshaping the microbiota and suppressing host inflammation.

Small bowel gastrointestinal stromal tumors (GISTs) are more aggressive than gastric GISTs, yet the biologic basis for this difference remains poorly understood. We hypothesized that differential expression of immune checkpoints contributes to this site-specific behavior. Bulk RNA sequencing of 42 primary GISTs (36 gastric, 6 small bowel) revealed marked upregulation of VTCN1, which encodes the inhibitory checkpoint B7-H4, in small bowel tumors (log2FC = 7.95, adjusted P < 0.001). In contrast, expression of the therapeutically targeted checkpoints PD-L1, PD-1, and CTLA-4 was comparable between sites. Concordantly, B7-H4 enrichment was accompanied by an immunosuppressive tumor microenvironment, characterized by reduced antigen-presenting cells, fewer effector-memory CD8+ T cells, lower granzyme B expression, and suppression of interferon and inflammatory signaling pathways. Notably, the differences in B7-H4 expression were independent of imatinib-treatment status. These findings were corroborated in an external cohort of 77 untreated GISTs, in which VTCN1 was similarly enriched in small bowel tumors. Independent immunohistochemical analysis of a tissue microarray comprising 68 untreated primary GISTs confirmed the pattern, showing median B7-H4 positivity of 78.6% in duodenal, 20.5% in jejunal/ileal, and 0% in gastric tumors, with staining localized to tumor cells rather than stroma. Collectively, these data identify B7-H4 as a site-specific feature of small bowel GISTs and a potential therapeutic target for tumors that have not responded to conventional checkpoint blockade.

CD28 costimulation contributes to pathogenic T cell responses in inflammatory bowel disease (IBD), but current B7-directed blockade also limits CTLA-4 signaling. Using a sensitive NanoBiT split-luciferase screening platform, we identified and optimized CA-23, a small molecule antagonist that directly binds human and mouse CD28 without measurable binding to CD80, CD86, or CTLA-4. CA-23 inhibited CD28-B7 engagement and CD28-dependent T cell activation without agonist activity in human whole blood and peripheral blood mononuclear cells. CA-23 achieved exposure in the colon and mesenteric lymph nodes and reduced disease severity, histologic injury, and pathogenic Th1 and Th17 responses in a T cell transfer model of colitis. In PBMCs from donors with ulcerative colitis or Crohns disease, CA-23 suppressed inflammatory cytokine production and T cell activation to a degree matching or exceeding Abatacept. In human intestinal epithelial-PBMC co-cultures, CA-23 preserved Treg suppressive activity and epithelial barrier integrity, whereas Abatacept reduced Treg function. CA-23 did not alter CD80 or CD86 expression on autologous antigen-presenting cells and showed no substantial off-target activity in the tested selectivity panel. These findings support direct CD28 antagonism as a mechanistically differentiated alternative to B7-directed co-stimulation blockade for suppressing pathogenic T cell responses in preclinical models of IBD. One Sentence SummaryA CD28-selective small molecule blocks pathogenic T cell activation and preserves Treg function unlike Abatacept in IBD models.

Human pluripotent stem cell-derived intestinal organoids hold great promise for disease modeling, drug screening, and regenerative medicine. However, conventional intestinal organoids are predominantly epithelial, small in scale, and lack the multicellular complexity required to recapitulate the pathophysiology of intestinal disorders such as inflammatory bowel disease (IBD) and colorectal cancer (CRC). Here, we report the development of Centimeter-Scale, purely 3D self-organized human intestinal organoids (IOs) from induced pluripotent stem cells (iPSCs) that encompass multiple tissue lineages, including epithelium, mesenchyme, smooth muscle, neurons, immune cells, and vasculature. These organoids achieve functional maturation by day 100+, exhibiting rhythmic peristaltic-like contractions, and by day 147 they display histological structures including lumens, crypt-like architecture, goblet cells, and smooth muscle. Importantly, for the first time, the neuro-muscle lineages arise spontaneously and autonomously in a purely 3D culture system, without any external stimulation (e.g., electrical, chemical, or mechanical), and mature to form functional neuromuscular junctions, driving macroscopically visible peristaltic-like contractions that mimic intestinal motility entirely through in vitro culture, without any xenotransplantation. Single-cell RNA sequencing at day 115 identified 12 cell subtypes across four major lineages, recapitulating the cellular diversity of the developing human intestine. Using this platform, we established an LPS/IFN-{gamma}-induced IBD model that recapitulated key pathological features, including epithelial disruption, immune cell infiltration, and IL-6 elevation. Transcriptomic analysis confirmed activation of the NF-{kappa}B and JAK2-STAT3 pathways, multi-modal cell death, and immune recruitment machinery, all consistent with clinical IBD pathology. Furthermore, we developed intestinal cancer models at 7 and 21 days showing abnormal hyperplasia, and a probiotic co-culture system demonstrating anti-inflammatory efficacy. Together, these results establish Centimeter-Scale intestinal organoids as a physiologically relevant, multicellular platform for modeling intestinal diseases and evaluating therapeutic interventions.

CTLA-4 (haplo)insufficiency displays incomplete penetrance and phenotypic heterogeneity, indicating the involvement of additional disease modifiers beyond the genetic defect. Microbiome analyses reveal a positive association between disease severity and intestinal dysbiosis, highlighting the microbiome as a critical contributor. To investigate this relationship mechanistically, we generated Ctla4/- wildlings harboring a natural microbiota. Unlike specific pathogen free (SPF) counterparts, which remain healthy, Ctla4/- wildlings spontaneously develop disease phenotypes resembling human CTLA-4 haploinsufficiency. Disease onset is followed by reduced microbial diversity and expansion of pathobionts. Integrative immunophenotyping shows that the natural microbiota synergizes with Ctla4 haploinsufficiency to reshape innate and adaptive immune compartments, generating a sustained pro-inflammatory milieu and reduced CTLA-4 expression in the cecum. Furthermore, microbiota-derived metabolites promote inflammatory cytokine production in both murine and human primary T cells via NF-{kappa}B activation. Collectively, Ctla4/- wildlings constitute an effective model for dissecting microbiome-immune crosstalk in CTLA-4 (haplo)insufficiency and for exploring therapeutic strategies.

Background: Transplant arterial injury is an underlying feature of acute organ transplant rejection and is a main cause of late heart transplant failure. The role of the gut microbiota, and especially specific microbial components of this community, in controlling immune responses that cause this aspect of rejection is poorly understood. Methods: We utilized a murine aortic interposition model of transplant arterial injury to investigate the role of the gut commensal bacteria, Akkermansia muciniphila, in controlling immune responses in transplant arteries. Results: Early life treatment of female mice with broad spectrum antibiotics, which delayed colonization of the intestinal tract with bacteria until after weaning, led to the development of dysbiosis in adults that was characterized by the absence of A. muciniphila. This was related to an elevation in systemic levels of CCL2 and a reduction in the immunomodulatory short-chain fatty acid, propionate. When transplant arterial injury was examined, there was more arterial injury indicative of acute rejection and increased intimal thickening reflective of transplant arteriosclerosis in grafts from dysbiotic mice compared to controls. Dysbiosis also increased macrophage accumulation early after transplantation in dysbiotic mice. Notably, restoring A. muciniphila in the gut microbiota of dysbiotic mice through voluntary oral administration in infants ameliorated macrophage-mediated transplant arterial injury. Conclusions: A. muciniphila is an immunomodulatory component of the gut microbiota that protects against vascular injury and pathology in organ transplantation.

Inflammatory bowel disease (IBD) often involves disrupted intestinal epithelial barrier, but therapies specifically targeting this barrier are limited. We found that downregulated AUF1 (HNRNPD) contributes to defective barrier integrity in ulcerative colitis (UC). Compared to controls, its expression level was decreased and inversely correlated with clinical severity. Knocking down AUF1 in human and mouse colonic organoids led to impaired barrier function, with reduced Occludin and upregulated Claudin-2, mimicking characteristic IBD-associated mucosal alterations. Distinct RNA-binding activity of AUF1 protein isoforms contributed to these changes: p37 stabilized Occludin mRNA and blocked microRNA-122/Ago2-mediated repression, whereas p40 promoted Claudin-2 mRNA degradation via ubiquitin-proteasome pathway. Restoring AUF1 expression in organoids enhanced epithelial properties and, when transplanted into mice with established colitis, accelerated mucosal healing and epithelial regeneration in recipient mice and decreased fibrosis. Our study unravelled a post-transcriptional mechanism important for intestinal homeostasis and demonstrated a concept of using engineered organoids for treating IBD.

Introduction: C3 glomerulopathy (C3G) is driven by fluid-phase alternative complement pathway dysregulation, with emerging evidence linking glomerular neutrophil infiltration to disease severity. Neutrophil extracellular traps (NETs) are implicated in other forms of glomerulonephritis. However, their participation in the pathogenesis of C3G remains undefined. Methods: Kidney biopsies from 33 patients with C3G (15 with dense deposit disease [DDD] and 18 with C3 glomerulonephritis [C3GN]) were compared with 15 anti-neutrophil cytoplasmic antibody associated vasculitis (AAV) biopsies as a neutrophil-rich disease control in this retrospective cross-sectional study. Glomerular neutrophils and NETs were identified using immunofluorescence, staining for myeloperoxidase, citrullinated histone H3, peptidyl arginine deiminase-4, and DNA. Supervised machine learning was used to quantify glomerular NET formation, and the data were correlated with kidney function at time of biopsy using linear regression. Results: Intraglomerular NETs were abundant and detected in the majority of glomeruli in C3G biopsies. Compared with AAV, C3G showed a significantly higher fraction of neutrophils forming NETs, despite similar neutrophil counts per glomerulus. NET abundance was similar in DDD and C3GN. In exploratory analyses, a greater proportion of glomeruli containing NETs was associated with lower kidney function (estimated glomerular filtration rate) at biopsy, and this association remained significant after adjustment for age, C3G subtype, and interstitial fibrosis. Conclusions: These observations demonstrate that intraglomerular NETs are a common and prominent observation in C3G and are associated with reduced kidney function at biopsy. These findings raise the possibility that NET deposition in glomeruli is a previously unrecognized driver of glomerular injury in C3G.