Exabis Library

Innate Lymphoid Cells (ILC) develop from Common Lymphoid Precursors in the bone marrow, and ILC precursors (ILCP) migrate to mucosa where they mature, promote homeostasis, and provide a potent, antigen-non-specific sources of cytokines. Deciphering what local stimuli drive the final stages of ILCP maturation in these tissues remains a pressing question, as ILC frequencies can become dysregulated during chronic infection and inflammatory diseases. For example, Type-1 innate lymphoid cells (ILC1) are enriched in the mucosa of patients with active inflammatory bowel disease (IBD) and the impact of this accumulation remains elusive.

Here, we develop and use co-cultures of both murine and human iPSC-derived gut and lung organoids with ILCP and with mature ILC isolated from IBD patients’ intestinal biopsies.

Harnessing these versatile models, we demonstrate that epithelial cells provide a complex niche capable of supporting the final maturation of all helper-like ILC1, ILC2, and ILC3. Notably, organoid identity was sufficient to robustly recapitulate tissue-specific ILC imprints and frequencies, even in the absence of microbial stimuli, other cell types, or cytokine supplementation.

In addition, we show that that ILC1 drive expansion of the epithelial stem cell crypt through p38γ phosphorylation, driving a potentially pathological proliferative feedback loop between β-catenin and Cd44v6. We harnessed this model to elucidate that this phenotype was unexpectedly regulated by ILC1-derived TGFβ1. We further show that human gut ILC1 also secrete TGFβ1, and drive CD44v6 expression in both HIO epithelium and mesenchyme. As TGFβ1 is a master regulator of fibrosis, the leading indicator for surgery in IBD, we next characterised the ability of ILC1 to regulate matrix remodelling using a functionalized, synthetic hydrogel system. We show that ILC1 drive both matrix stiffening and degradation, which we posit occurs through a balance of MMP9 degradation and TGFβ1-induced fibronectin deposition.

Taken together, our work provides unprecedented insight into in situ ILC maturation, which we show to be driven by epithelial signals, and into ILC function. We also report that intestinal ILC1 modulate epithelial and matrix remodelling, which may drive either wound healing in homeostasis, but may tip toward pathology when enriched in IBD.
Moreover, our work introduces a modular organoid platform, which provides exquisite control over both environmental stimuli and host genetics, making it a powerful tool for dissecting the interactions between complex mucosal tissues and rare cell subtypes in development and disease.

Extracellular RNAs (exRNAs) are RNA species present outside of the cells in which they were transcribed. They are found in human serum, though the exact role of circulating exRNAs remains to be established, especially in inflammatory bowel diseases (IBD). Besides their potential help in our pathophysiological understanding of disease, they might serve as liquid biopsies or non-invasive biomarkers.  We characterised exRNAs in serum from IBD patients, and questioned their potential in separating ulcerative colitis (UC) from Crohn’s disease (CD).

We carried out SILVER-seq (Small Input Liquid Volume Extracellular RNA-sequencing) on serum droplets (5-7ml) from a cross-sectional cohort of 26 IBD patients (15 UC, 11 CD) with active endoscopic disease (Mayo endoscopic sub score  or Simple Endoscopic Score for Crohn’s disease ) (Table 1). Normalization and differential expression were done using DESeq2 R package, co-expression network analyses performed using WGCNA (FDR adjusted p ≤0.05). Using randomized generalized linear modelling (RGLM), a diagnostic exRNA marker was designed to separate UC from CD samples (15 UC, 11 CD). 

We detected 60,675 exRNAs in serum from IBD patients, capturing 76.1% of all genes expressed in intestinal tissue, and including highly abundant intestinal genes (e.g MUC2) and intestinal barrier genes (e.g claudin 8, occludin and RETNLB). Co-expression network analysis identified 69 clusters of which 1 significantly correlated with the distinction between CD and UC (FDR p=0.003, r=-0.70). One of the hub genes within this module (consisting of 148 genes, upregulated in UC) was GNA12 (p=2.3E-4, r=0.66 for correlation with the module eigengene), encoding for a membrane bound GTPase that plays a key role in tight junction assembly and has previously been identified as UC-specific SNP in GWAS (Figure 1). Serum GNA12 expression was not associated with faecal calprotectin (p=0.55, r=0.12), disease duration (p=0.24, r=0.25), age (p=0.43, r=0.16) or gender (p=1.0), but did correlate with other UC-specific genes including TNFRSF14 (p=0.04, r=0.4), HNF4A (p=0.04, r=-0.4) and CAMK2A (p=0.004, r=0.54). Through machine learning within the UC-specific module (containing 148 genes), we identified an 8-gene exRNA panel, including GNA12, that could accurately discriminate between UC and CD patients (accuracy 96.2%).

Figure 1: Visualisation of the identified exRNA network including GNA12

Liquid biopsies are a novel non-invasive tool in IBD biomarker development. Although larger in-depth studies are required to further validate, explore and characterise the potential of serum exRNAs in the field of IBD, the current pilot project identified a new non-invasive tool to accurately distinguish CD from UC patients.