Molecular cartography uncovers evolutionary and microenvironmental dynamics in sporadic colorectal tumors.

Colorectal cancer exhibits dynamic cellular and genetic heterogeneity during progression from precursor lesions toward malignancy. Analysis of spatial multi-omic data from 31 human colorectal specimens enabled phylogeographic mapping of tumor evolution that revealed individualized progression trajectories and accompanying microenvironmental and clonal alterations. Phylogeographic mapping ordered genetic events, classified tumors by their evolutionary dynamics, and placed clonal regions along global pseudotemporal progression trajectories encompassing the chromosomal instability (CIN+) and hypermutated (HM) pathways. Integrated single-cell and spatial transcriptomic data revealed recurring epithelial programs and infiltrating immune states along progression pseudotime. We discovered an immune exclusion signature (IEX), consisting of extracellular matrix regulators DDR1, TGFBI, PAK4, and DPEP1, that charts with CIN+ tumor progression, is associated with reduced cytotoxic cell infiltration, and shows prognostic value in independent cohorts. This spatial multi-omic atlas provides insights into colorectal tumor-microenvironment co-evolution, serving as a resource for stratification and targeted treatments.

Differential pre-malignant programs and microenvironment chart distinct paths to malignancy in human colorectal polyps.

Colorectal cancers (CRCs) arise from precursor polyps whose cellular origins, molecular heterogeneity, and immunogenic potential may reveal diagnostic and therapeutic insights when analyzed at high resolution. We present a single-cell transcriptomic and imaging atlas of the two most common human colorectal polyps, conventional adenomas and serrated polyps, and their resulting CRC counterparts. Integrative analysis of 128 datasets from 62 participants reveals adenomas arise from WNT-driven expansion of stem cells, while serrated polyps derive from differentiated cells through gastric metaplasia. Metaplasia-associated damage is coupled to a cytotoxic immune microenvironment preceding hypermutation, driven partly by antigen-presentation differences associated with tumor cell-differentiation status. Microsatellite unstable CRCs contain distinct non-metaplastic regions where tumor cells acquire stem cell properties and cytotoxic immune cells are depleted. Our multi-omic atlas provides insights into malignant progression of colorectal polyps and their microenvironment, serving as a framework for precision surveillance and prevention of CRC.

The Human Tumor Atlas Network: Charting Tumor Transitions across Space and Time at Single-Cell Resolution.

Crucial transitions in cancer-including tumor initiation, local expansion, metastasis, and therapeutic resistance-involve complex interactions between cells within the dynamic tumor ecosystem. Transformative single-cell genomics technologies and spatial multiplex in situ methods now provide an opportunity to interrogate this complexity at unprecedented resolution. The Human Tumor Atlas Network (HTAN), part of the National Cancer Institute (NCI) Cancer Moonshot Initiative, will establish a clinical, experimental, computational, and organizational framework to generate informative and accessible three-dimensional atlases of cancer transitions for a diverse set of tumor types. This effort complements both ongoing efforts to map healthy organs and previous large-scale cancer genomics approaches focused on bulk sequencing at a single point in time. Generating single-cell, multiparametric, longitudinal atlases and integrating them with clinical outcomes should help identify novel predictive biomarkers and features as well as therapeutically relevant cell types, cell states, and cellular interactions across transitions. The resulting tumor atlases should have a profound impact on our understanding of cancer biology and have the potential to improve cancer detection, prevention, and therapeutic discovery for better precision-medicine treatments of cancer patients and those at risk for cancer.

Reassessment of Exosome Composition.

The heterogeneity of small extracellular vesicles and presence of non-vesicular extracellular matter have led to debate about contents and functional properties of exosomes. Here, we employ high-resolution density gradient fractionation and direct immunoaffinity capture to precisely characterize the RNA, DNA, and protein constituents of exosomes and other non-vesicle material. Extracellular RNA, RNA-binding proteins, and other cellular proteins are differentially expressed in exosomes and non-vesicle compartments. Argonaute 1-4, glycolytic enzymes, and cytoskeletal proteins were not detected in exosomes. We identify annexin A1 as a specific marker for microvesicles that are shed directly from the plasma membrane. We further show that small extracellular vesicles are not vehicles of active DNA release. Instead, we propose a new model for active secretion of extracellular DNA through an autophagy- and multivesicular-endosome-dependent but exosome-independent mechanism. This study demonstrates the need for a reassessment of exosome composition and offers a framework for a clearer understanding of extracellular vesicle heterogeneity.

The pan-ErbB negative regulator Lrig1 is an intestinal stem cell marker that functions as a tumor suppressor.

Lineage mapping has identified both proliferative and quiescent intestinal stem cells, but the molecular circuitry controlling stem cell quiescence is incompletely understood. By lineage mapping, we show Lrig1, a pan-ErbB inhibitor, marks predominately noncycling, long-lived stem cells that are located at the crypt base and that, upon injury, proliferate and divide to replenish damaged crypts. Transcriptome profiling of Lrig1(+) colonic stem cells differs markedly from the profiling of highly proliferative, Lgr5(+) colonic stem cells; genes upregulated in the Lrig1(+) population include those involved in cell cycle repression and response to oxidative damage. Loss of Apc in Lrig1(+) cells leads to intestinal adenomas, and genetic ablation of Lrig1 results in heightened ErbB1-3 expression and duodenal adenomas. These results shed light on the relationship between proliferative and quiescent intestinal stem cells and support a model in which intestinal stem cell quiescence is maintained by calibrated ErbB signaling with loss of a negative regulator predisposing to neoplasia.

MCMICRO: a scalable, modular image-processing pipeline for multiplexed tissue imaging.

Highly multiplexed tissue imaging makes detailed molecular analysis of single cells possible in a preserved spatial context. However, reproducible analysis of large multichannel images poses a substantial computational challenge. Here, we describe a modular and open-source computational pipeline, MCMICRO, for performing the sequential steps needed to transform whole-slide images into single-cell data. We demonstrate the use of MCMICRO on tissue and tumor images acquired using multiple imaging platforms, thereby providing a solid foundation for the continued development of tissue imaging software.

GammaGateR: semi-automated marker gating for single-cell multiplexed imaging.

MOTIVATION: Multiplexed immunofluorescence (mIF) is an emerging assay for multichannel protein imaging that can decipher cell-level spatial features in tissues. However, existing automated cell phenotyping methods, such as clustering, face challenges in achieving consistency across experiments and often require subjective evaluation. As a result, mIF analyses often revert to marker gating based on manual thresholding of raw imaging data. RESULTS: To address the need for an evaluable semi-automated algorithm, we developed GammaGateR, an R package for interactive marker gating designed specifically for segmented cell-level data from mIF images. Based on a novel closed-form gamma mixture model, GammaGateR provides estimates of marker-positive cell proportions and soft clustering of marker-positive cells. The model incorporates user-specified constraints that provide a consistent but slide-specific model fit. We compared GammaGateR against the newest unsupervised approach for annotating mIF data, employing two colon datasets and one ovarian cancer dataset for the evaluation. We showed that GammaGateR produces highly similar results to a silver standard established through manual annotation. Furthermore, we demonstrated its effectiveness in identifying biological signals, achieved by mapping known spatial interactions between CD68 and MUC5AC cells in the colon and by accurately predicting survival in ovarian cancer patients using the phenotype probabilities as input for machine learning methods. GammaGateR is a highly efficient tool that can improve the replicability of marker gating results, while reducing the time of manual segmentation. AVAILABILITY AND IMPLEMENTATION: The R package is available at https://github.com/JiangmeiRubyXiong/GammaGateR.

Inhibition of autocrine HGF maturation overcomes cetuximab resistance in colorectal cancer.

Although amplifications and mutations in receptor tyrosine kinases (RTKs) act as bona fide oncogenes, in most cancers, RTKs maintain moderate expression and remain wild-type. Consequently, cognate ligands control many facets of tumorigenesis, including resistance to anti-RTK therapies. Herein, we show that the ligands for the RTKs MET and RON, HGF and HGFL, respectively, are synthesized as inactive precursors that are activated by cellular proteases. Our newly generated HGF/HGFL protease inhibitors could overcome both de novo and acquired cetuximab resistance in colorectal cancer (CRC). Conversely, HGF overexpression was necessary and sufficient to induce cetuximab resistance and loss of polarity. Moreover, HGF-induced cetuximab resistance could be overcome by the downstream MET inhibitor, crizotinib, and upstream protease inhibitors. Additionally, HAI-1, an endogenous inhibitor of HGF proteases, (i) was downregulated in CRC, (ii) exhibited increased genomic methylation that correlated with poor prognosis, (iii) HAI-1 expression correlated with cetuximab response in a panel of cancer cell lines, and (iv) exogenous addition of recombinant HAI-1 overcame cetuximab resistance in CC-HGF cells. Thus, we describe a targetable, autocrine HAI-1/Protease/HGF/MET axis in cetuximab resistance in CRC.

Anapole-Assisted Low-Power Optical Trapping of Nanoscale Extracellular Vesicles and Particles.

This study addresses the challenge of trapping nanoscale biological particles using optical tweezers without the photothermal heating effect and the limitation presented by the diffraction limit. Optical tweezers are effective for trapping microscopic biological objects but not for nanoscale specimens due to the diffraction limit. To overcome this, we present an approach that uses optical anapole states in all-dielectric nanoantenna systems on distributed Bragg reflector substrates to generate strong optical gradient force and potential on nanoscale biological objects with negligible temperature rise below 1 K. The anapole antenna condenses the accessible electromagnetic energy to scales as small as 30 nm. Using this approach, we successfully trapped nanosized extracellular vesicles and supermeres (approximately 25 nm in size) using low laser power of only 10.8 mW. This nanoscale optical trapping platform has great potential for single molecule analysis while precluding photothermal degradation.

Inhibition of the bone morphogenetic protein pathway suppresses tumor growth through downregulation of epidermal growth factor receptor in MEK/ERK-dependent colorectal cancer.

The bone morphogenetic protein (BMP) pathway promotes differentiation and induces apoptosis in normal colorectal epithelial cells. However, its role in colorectal cancer (CRC) is controversial, where it can act as context-dependent tumor promoter or tumor suppressor. Here we have found that CRC cells reside in a BMP-rich environment based on curation of two publicly available RNA-sequencing databases. Suppression of BMP using a specific BMP inhibitor, LDN193189, suppresses the growth of select CRC organoids. Colorectal cancer organoids treated with LDN193189 showed a decrease in epidermal growth factor receptor, which was mediated by protein degradation induced by leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) expression. Among 18 molecularly characterized CRC organoids, suppression of growth by BMP inhibition correlated with induction of LRIG1 gene expression. Notably, knockdown of LRIG1 in organoids diminished the growth-suppressive effect of LDN193189. Furthermore, in CRC organoids, which are susceptible to growth suppression by LDN193189, simultaneous treatment with LDN193189 and trametinib, an FDA-approved MEK inhibitor, resulted in cooperative growth inhibition both in vitro and in vivo. Taken together, the simultaneous inhibition of BMP and MEK could be a novel treatment option in CRC cases, and evaluating in vitro growth suppression and LRIG1 induction by BMP inhibition using patient-derived organoids could offer functional biomarkers for predicting potential responders to this regimen.

Induction of apically mistrafficked epiregulin disrupts epithelial polarity via aberrant EGFR signaling.

In polarized MDCK cells, disruption of the tyrosine-based YXXΦ basolateral trafficking motif (Y156A) in the epidermal growth factor receptor (EGFR) ligand epiregulin (EREG), results in its apical mistrafficking and transformation in vivo. However, the mechanisms underlying these dramatic effects are unknown. Using a doxycycline-inducible system in 3D Matrigel cultures, we now show that induction of Y156A EREG in fully formed MDCK cysts results in direct and complete delivery of mutant EREG to the apical cell surface. Within 3 days of induction, ectopic lumens were detected in mutant, but not wild-type, EREG-expressing cysts. Of note, these structures resembled histological features found in subcutaneous xenografts of mutant EREG-expressing MDCK cells. These ectopic lumens formed de novo rather than budding from the central lumen and depended on metalloprotease-mediated cleavage of EREG and subsequent EGFR activity. Moreover, the most frequent EREG mutation in human cancer (R147stop) resulted in its apical mistrafficking in engineered MDCK cells. Thus, induction of EREG apical mistrafficking is sufficient to disrupt selective aspects of polarity of a preformed polarized epithelium. This article has an associated First Person interview with the first author of the paper.

Recent Advances in the Study of Extracellular Vesicles in Colorectal Cancer.

There has been significant progress in the study of extracellular vesicles (EVs) since the 2017 American Gastroenterological Association-sponsored Freston Conference "Extracellular Vesicles: Biology, Translation and Clinical Application in GI Disorders." The burgeoning interest in this field stems from the increasing recognition that EVs represent an understudied form of cell-to-cell communication and contain cargo replete with biomarkers and therapeutic targets. This short review will highlight recent advances in the field, with an emphasis on colorectal cancer. After a brief introduction to secreted particles, we will describe how our laboratory became interested in EVs, which led to refined methods of isolation and identification of 2 secreted nanoparticles. We will then summarize the cargo found in small EVs released from colorectal cancer cells and other cells in the tumor microenvironment, as well as those found in the circulation of patients with colorectal cancer. Finally, we will consider the continuing challenges and future opportunities in this rapidly evolving field.

Quantifying and correcting slide-to-slide variation in multiplexed immunofluorescence images.

MOTIVATION: Multiplexed imaging is a nascent single-cell assay with a complex data structure susceptible to technical variability that disrupts inference. These in situ methods are valuable in understanding cell-cell interactions, but few standardized processing steps or normalization techniques of multiplexed imaging data are available. RESULTS: We implement and compare data transformations and normalization algorithms in multiplexed imaging data. Our methods adapt the ComBat and functional data registration methods to remove slide effects in this domain, and we present an evaluation framework to compare the proposed approaches. We present clear slide-to-slide variation in the raw, unadjusted data and show that many of the proposed normalization methods reduce this variation while preserving and improving the biological signal. Furthermore, we find that dividing multiplexed imaging data by its slide mean, and the functional data registration methods, perform the best under our proposed evaluation framework. In summary, this approach provides a foundation for better data quality and evaluation criteria in multiplexed imaging. AVAILABILITY AND IMPLEMENTATION: Source code is provided at: https://github.com/statimagcoll/MultiplexedNormalization and an R package to implement these methods is available here: https://github.com/ColemanRHarris/mxnorm. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Interaction of lncRNA MIR100HG with hnRNPA2B1 facilitates m6A-dependent stabilization of TCF7L2 mRNA and colorectal cancer progression.

BACKGROUND: Epithelial-to-mesenchymal transition (EMT) is a process linked to metastasis and drug resistance with non-coding RNAs (ncRNAs) playing pivotal roles. We previously showed that miR-100 and miR-125b, embedded within the third intron of the ncRNA host gene MIR100HG, confer resistance to cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, in colorectal cancer (CRC). However, whether the MIR100HG transcript itself has a role in cetuximab resistance or EMT is unknown. METHODS: The correlation between MIR100HG and EMT was analyzed by curating public CRC data repositories. The biological roles of MIR100HG in EMT, metastasis and cetuximab resistance in CRC were determined both in vitro and in vivo. The expression patterns of MIR100HG, hnRNPA2B1 and TCF7L2 in CRC specimens from patients who progressed on cetuximab and patients with metastatic disease were analyzed by RNAscope and immunohistochemical staining. RESULTS: The expression of MIR100HG was strongly correlated with EMT markers and acted as a positive regulator of EMT. MIR100HG sustained cetuximab resistance and facilitated invasion and metastasis in CRC cells both in vitro and in vivo. hnRNPA2B1 was identified as a binding partner of MIR100HG. Mechanistically, MIR100HG maintained mRNA stability of TCF7L2, a major transcriptional coactivator of the Wnt/ß-catenin signaling, by interacting with hnRNPA2B1. hnRNPA2B1 recognized the N6-methyladenosine (m6A) site of TCF7L2 mRNA in the presence of MIR100HG. TCF7L2, in turn, activated MIR100HG transcription, forming a feed forward regulatory loop. The MIR100HG/hnRNPA2B1/TCF7L2 axis was augmented in specimens from CRC patients who either developed local or distant metastasis or had disease progression that was associated with cetuximab resistance. CONCLUSIONS: MIR100HG and hnRNPA2B1 interact to control the transcriptional activity of Wnt signaling in CRC via regulation of TCF7L2 mRNA stability. Our findings identified MIR100HG as a potent EMT inducer in CRC that may contribute to cetuximab resistance and metastasis by activation of a MIR100HG/hnRNPA2B1/TCF7L2 feedback loop.

MIRIAM: A machine and deep learning single-cell segmentation and quantification pipeline for multi-dimensional tissue images.

Increasingly, highly multiplexed tissue imaging methods are used to profile protein expression at the single-cell level. However, a critical limitation is the lack of robust cell segmentation tools for tissue sections. We present Multiplexed Image Resegmentation of Internal Aberrant Membranes (MIRIAM) that combines (a) a pipeline for cell segmentation and quantification that incorporates machine learning-based pixel classification to define cellular compartments, (b) a novel method for extending incomplete cell membranes, and (c) a deep learning-based cell shape descriptor. Using human colonic adenomas as an example, we show that MIRIAM is superior to widely utilized segmentation methods and provides a pipeline that is broadly applicable to different imaging platforms and tissue types.

Commentary on the Continued Investigational Status of DBS for Psychiatric Indications.

Behavioral disorders exact a tragic toll on patients, families, and society. Consequently, the search for better treatments is a public health priority. Recent research promises to lead to advances in psychiatric treatment that may include implantation of deep brain stimulation (DBS) devices. In this commentary, the authors discuss how promising results from initial pilot studies of DBS in treatment-resistant depression (TRD) were not validated in 2 randomized, controlled, multicenter trials. Reliance on pilot data may have contributed to the selection of primary efficacy endpoints that were not achieved, and to the underestimation of adverse events and device-related complications. Published data on the population prevalence of affective disorders also may have led sponsors to overestimate the number of patients with TRD who were candidates for DBS therapy. Consequently, a more complete discussion of certain aspects of the depression trials may allow a realistic appraisal of the clinical and ethical situation of DBS therapy for TRD in a US regulatory context. A US regulatory perspective also may clarify the clinical research and reimbursement consequences of the Humanitarian Device Exemption (HDE) approval status of DBS for obsessive-compulsive disorder (OCD). Retrospective analyses akin to failure modes and effects analysis in engineering may clarify unexpected results in the DBS depression trials. Recent research suggests that subject selection in future trials may be augmented by advanced neuroimaging methods. For the present, the noncommercial research status of DBS to treat depression and the HDE status for OCD appear likely to remain in place.

Targeted mobilization of Lrig1+ gastric epithelial stem cell populations by a carcinogenic Helicobacter pylori type IV secretion system.

Helicobacter pylori-induced gastritis is the strongest risk factor for gastric adenocarcinoma, a malignancy preceded by a series of well-defined histological stages, including metaplasia. One microbial constituent that augments cancer risk is the cag type 4 secretion system (T4SS), which translocates the oncoprotein CagA into host cells. Aberrant stem cell activation is linked to carcinogenesis, and Lrig1 (leucine-rich repeats and Ig-like domains 1) marks a distinct population of progenitor cells. We investigated whether microbial effectors with carcinogenic potential influence Lrig1 progenitor cells ex vivo and via lineage expansion within H. pylori-infected gastric mucosa. Lineage tracing was induced in Lrig1-CreERT2/+;R26R-YFP/+ (Lrig1/YFP) mice that were uninfected or subsequently infected with cag+H. pylori or an isogenic cagE- mutant (nonfunctional T4SS). In contrast to infection with wild-type (WT) H. pylori for 2 wk, infection for 8 wk resulted in significantly increased inflammation and proliferation in the corpus and antrum compared with uninfected or mice infected with the cagE- mutant. WT H. pylori-infected mice harbored significantly higher numbers of Lrig1/YFP epithelial cells that coexpressed UEA1 (surface cell marker). The number of cells coexpressing intrinsic factor (chief cell marker), YFP (lineage marker), and GSII lectin (spasmolytic polypeptide-expressing metaplasia marker) were increased only by WT H. pylori In human samples, Lrig1 expression was significantly increased in lesions with premalignant potential compared with normal mucosa or nonatrophic gastritis. In conclusion, chronic H. pylori infection stimulates Lrig1-expressing progenitor cells in a cag-dependent manner, and these reprogrammed cells give rise to a full spectrum of differentiated cells.

Protein kinase A-mediated phosphorylation of naked cuticle homolog 2 stimulates cell-surface delivery of transforming growth factor-α for epidermal growth factor receptor transactivation.

The classic mode of G protein-coupled receptor (GPCR)-mediated transactivation of the receptor tyrosine kinase epidermal growth factor receptor (EGFR) transactivation occurs via matrix metalloprotease (MMP)-mediated cleavage of plasma membrane-anchored EGFR ligands. Herein, we show that the Gαs-activating GPCR ligands vasoactive intestinal peptide (VIP) and prostaglandin E2 (PGE2 ) transactivate EGFR through increased cell-surface delivery of the EGFR ligand transforming growth factor-α (TGFα) in polarizing madin-darby canine kidney (MDCK) and Caco-2 cells. This is achieved by PKA-mediated phosphorylation of naked cuticle homolog 2 (NKD2), previously shown to bind TGFα and direct delivery of TGFα-containing vesicles to the basolateral surface of polarized epithelial cells. VIP and PGE2 rapidly activate protein kinase A (PKA) that then phosphorylates NKD2 at Ser-223, a process that is facilitated by the molecular scaffold A-kinase anchoring protein 12 (AKAP12). This phosphorylation stabilized NKD2, ensuring efficient cell-surface delivery of TGFα and increased EGFR activation. Thus, GPCR-triggered, PKA/AKAP12/NKD2-regulated targeting of TGFα to the cell surface represents a new mode of EGFR transactivation that occurs proximal to ligand cleavage by MMPs.

Murine Intrarectal Instillation of Purified Recombinant Clostridioides difficile Toxins Enables Mechanistic Studies of Pathogenesis.

Clostridioides difficile is linked to nearly 225,000 antibiotic-associated diarrheal infections and almost 13,000 deaths per year in the United States. Pathogenic strains of C. difficile produce toxin A (TcdA) and toxin B (TcdB), which can directly kill cells and induce an inflammatory response in the colonic mucosa. Hirota et al. (S. A. Hirota et al., Infect Immun 80:4474-4484, 2012) first introduced the intrarectal instillation model of intoxication using TcdA and TcdB purified from VPI 10463 (VPI 10463 reference strain [ATCC 43255]) and 630 C. difficile strains. Here, we expand this technique by instilling purified, recombinant TcdA and TcdB, which allows for the interrogation of how specifically mutated toxins affect tissue. Mouse colons were processed and stained with hematoxylin and eosin for blinded evaluation and scoring by a board-certified gastrointestinal pathologist. The amount of TcdA or TcdB needed to produce damage was lower than previously reported in vivo and ex vivo Furthermore, TcdB mutants lacking either endosomal pore formation or glucosyltransferase activity resemble sham negative controls. Immunofluorescent staining revealed how TcdB initially damages colonic tissue by altering the epithelial architecture closest to the lumen. Tissue sections were also immunostained for markers of acute inflammatory infiltration. These staining patterns were compared to slides from a human C. difficile infection (CDI). The intrarectal instillation mouse model with purified recombinant TcdA and/or TcdB provides the flexibility needed to better understand structure/function relationships across different stages of CDI pathogenesis.

Succinate Produced by Intestinal Microbes Promotes Specification of Tuft Cells to Suppress Ileal Inflammation.

BACKGROUND & AIMS: Countries endemic for parasitic infestations have a lower incidence of Crohn's disease (CD) than nonendemic countries, and there have been anecdotal reports of the beneficial effects of helminths in CD patients. Tuft cells in the small intestine sense and direct the immune response against eukaryotic parasites. We investigated the activities of tuft cells in patients with CD and mouse models of intestinal inflammation. METHODS: We used microscopy to quantify tuft cells in intestinal specimens from patients with ileal CD (n = 19), healthy individuals (n = 14), and TNFΔARE/+ mice, which develop Crohn's-like ileitis. We performed single-cell RNA sequencing, mass spectrometry, and microbiome profiling of intestinal tissues from wild-type and Atoh1-knockout mice, which have expansion of tuft cells, to study interactions between microbes and tuft cell populations. We assessed microbe dependence of tuft cell populations using microbiome depletion, organoids, and microbe transplant experiments. We used multiplex imaging and cytokine assays to assess alterations in inflammatory response following expansion of tuft cells with succinate administration in TNFΔARE/+ and anti-CD3E CD mouse models. RESULTS: Inflamed ileal tissues from patients and mice had reduced numbers of tuft cells, compared with healthy individuals or wild-type mice. Expansion of tuft cells was associated with increased expression of genes that regulate the tricarboxylic acid cycle, which resulted from microbe production of the metabolite succinate. Experiments in which we manipulated the intestinal microbiota of mice revealed the existence of an ATOH1-independent population of tuft cells that was sensitive to metabolites produced by microbes. Administration of succinate to mice expanded tuft cells and reduced intestinal inflammation in TNFΔARE/+ mice and anti-CD3E-treated mice, increased GATA3+ cells and type 2 cytokines (IL22, IL25, IL13), and decreased RORGT+ cells and type 17 cytokines (IL23) in a tuft cell-dependent manner. CONCLUSIONS: We found that tuft cell expansion reduced chronic intestinal inflammation in mice. Strategies to expand tuft cells might be developed for treatment of CD.