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Disrupted host-microbe interactions at the mucosal level are key to the pathophysiology of IBD. This study aimed to comprehensively examine crosstalk between mucosal gene expression and microbiota in patients with IBD. To study tissue-specific interactions, we perform transcriptomic (RNA-seq) and microbial (16S-rRNA-seq) profiling of 697 intestinal biopsies (645 derived from 335 patients with IBD and 52 from 16 non-IBD controls). Mucosal gene expression patterns in IBD are mainly determined by tissue location and inflammation, whereas the mucosal microbiota composition shows a high degree of individual specificity. Analysis of transcript-bacteria interactions identifies six distinct groups of inflammation-related pathways that are associated with intestinal microbiota (adjusted P < 0.05). An increased abundance of Bifidobacterium is associated with higher expression of genes involved in fatty acid metabolism, while Bacteroides correlates with increased metallothionein signaling. In patients with fibrostenosis, a transcriptional network dominated by immunoregulatory genes is associated with Lachnoclostridium bacteria in non-stenotic tissue (adjusted P < 0.05), while being absent in CD without fibrostenosis. In patients using TNF-α-antagonists, a transcriptional network dominated by fatty acid metabolism genes is linked to Ruminococcaceae (adjusted P < 0.05). Mucosal microbiota composition correlates with enrichment of intestinal epithelial cells, macrophages, and NK-cells. Overall, these data demonstrate the presence of context-specific mucosal host-microbe interactions in IBD, revealing significantly altered inflammation-associated gene-taxa modules, particularly in patients with fibrostenotic CD and patients using TNF-α-antagonists. This study provides compelling insights into host–microbe interactions that may guide microbiota-directed precision medicine and fuels the rationale for microbiota-targeted therapeutics as a strategy to alter disease course in IBD. Here, through parallel profiling of the mucosal transcriptome and microbiome of intestinal biopsies derived from patients with IBD and from non-IBD controls, the authors characterize interactions between gene expression and microbiota composition associated with traits of patients with inflammatory bowel diseases. Peer Review Information:Nature Communications thanks Robert Häsler, and the other, anonymous, reviewers for their contribution to the peer review of this work. A peer review file is available. [ABSTRACT FROM AUTHOR]

Fatigue is a common and clinically challenging symptom in patients with inflammatory bowel diseases (IBD), occurring in ~ 50% of patients with quiescent disease. In this study, we aimed to investigate whether fatigue in patients with clinically quiescent IBD is reflected by circulating inflammatory proteins, which might reflect ongoing subclinical inflammation. Ninety-two (92) different inflammation-related proteins were measured in plasma of 350 patients with clinically quiescent IBD. Quiescent IBD was defined as clinical (Harvey-Bradshaw Index < 5 or Simple Clinical Colitis Activity Index < 2.5) and biochemical remission (C-reactive protein < 5 mg/L and absence of anemia) at time of fatigue assessment. Leukemia inhibitory factor receptor (LIF-R) concentrations were inversely associated with severe fatigue, also after adjustment for confounding factors (nominal P < 0.05). Although solely LIF-R showed weak ability to discriminate between mild and severe fatigue (area under the curve [AUC] = 0.61, 95%CI: 0.53–0.69, P < 0.05), a combined set of the top seven (7) fatigue-associated proteins (all P < 0.10) was observed to have reasonable discriminative performance (AUC = 0.82 [95%CI: 0.74–0.91], P < 0.01). Fatigue in patients with IBD is not clearly reflected by distinct protein signatures, suggesting there is no subclinical inflammation defined by the studied inflammatory proteins. Future studies are warranted to investigate other proteomic markers that may reflect fatigue in clinically quiescent IBD. [ABSTRACT FROM AUTHOR]

Single-cell RNA sequencing (scRNA-seq) has revolutionized the study of the cellular landscape of organs. Most single-cell protocols require fresh material, which limits sample size per experiment, and consequently, introduces batch effects. This is especially true for samples acquired through complex medical procedures, such as intestinal mucosal biopsies. Moreover, the tissue dissociation procedure required for obtaining single cells is a major source of noise; different dissociation procedures applied to different compartments of the tissue induce artificial gene expression differences between cell subsets. To overcome these challenges, we have developed a one-step dissociation protocol and demonstrated its use on cryopreserved gut mucosal biopsies. Using flow cytometry and scRNA-seq analysis, we compared this one-step dissociation protocol with the current gold standard, two-step collagenase digestion, and an adaptation of a recently published alternative, three-step cold-active Bacillus licheniformus protease digestion. Both cell viability and cell type composition were comparable between the one-step and two-step collagenase dissociation, with the former being more time-efficient. The cold protease digestion resulted in equal cell viability, but better preserves the epithelial cell types. Consequently, to analyze the rarer cell types, such as glial cells, larger total biopsy cell numbers are required as input material. The multi-step protocols affected cell types spanning multiple compartments differently. In summary, we show that cryopreserved gut mucosal biopsies can be used to overcome the logistical challenges and batch effects in large scRNA-seq studies. Furthermore, we demonstrate that using cryopreserved biopsies digested using a one-step collagenase protocol enables large-scale scRNA-seq, FACS, organoid generation and intraepithelial lymphocyte expansion. [ABSTRACT FROM AUTHOR]

OBJECTIVES:Genetic susceptibility is known to make a major contribution to the pathogenesis of ulcerative colitis (UC). Recently, three studies, including a genome-wide association study (GWAS), reported novel UC risk loci.METHODS:The top-20 single-nucleotide polymorphisms (SNPs) from the first UC-GWAS were genotyped, as part of the study's replication phase, in 561 UC cases and 728 controls from our Dutch UC study sample. We genotyped eight SNPs identified in two more studies, in these individuals, and replicated all significantly associated SNPs in an additional 894 UC cases and 1,174 controls from our Dutch UC study sample. A combined analysis for all patients (n=1,455) and controls (n=1,902) was performed. Dose–response models were constructed with the associated risk alleles.RESULTS:We found 12 SNPs tagging ten loci, including HLA-DRA, IL10, IL23R, JAK2, S100Z, ARPC2, and ECM1, to be associated with UC. We identified 10q26, flagged by the UC-GWAS but not confirmed in its replication phase, as a UC locus and found a trend toward association for GAS7. No association with disease localization or severity was found. The dose–response models show that individuals carrying 11 or more risk alleles have an odds ratio of 8.2 (confidence interval 3.0–22.8) for UC susceptibility.CONCLUSIONS:We confirmed the association of multiple loci with UC in the Dutch population and found evidence for association of 10q26 and a trend suggesting association for GAS7. Genetic models show that multiple risk loci in an individual increase the risk for developing UC. [ABSTRACT FROM AUTHOR]

A correction to the article "Genetic Analysis in A Dutch Study Sample Identifi es More Ulcerative Colitis Susceptibility Loci and Shows Their Additive Role in Disease Risk" that was published in the previous issue is presented.