Abstract Background We recently identified, using scRNA-seq data from inflammatory bowel disease (IBD) biopsies, a novel epithelial cell population characterized by the expression of several non-intestinal keratins (including KRT17, KRT6B, and KRT14) emerging in the inflamed mucosa of patients with ulcerative colitis (UC)¹. Here, we aimed to further characterize the significance of KRT17+ cells in IBD. Methods KRT17 expression in whole biopsies was assessed by bulk RNA-seq. Fixed intestinal samples underwent histological evaluation and spatial transcriptomics analysis by CosMx. In addition, protein expression of KRT17, mucin 2 (differentiation marker), p40 (squamous epithelium marker) and MPO (neutrophil marker) was analyzed by immunostaining. Predicted cell–cell interactions were inferred using LIANA on an in-house scRNAseq dataset. Published RNA-seq datasets from organoid cultures2,3 and psoriatic skin samples4 were mapped onto our epithelial dataset to infer functional features of KRT17+ cells. Results In healthy colon, KRT17 protein was not detected, while in IBD mucosa patches of Krt17+ cells with a heterogeneous phenotype were often present (Fig. 1A). In areas with better preserved epithelial architecture, sparse KRT17+ cells with a columnar morphology were observed, while ulcerated regions were frequently covered by cuboidal KRT17+ cells (Fig. 1B). We observed KRT17+ cells with similar morphology in the epithelialized perianal fistula of fistulizing Crohn’s Disease (CD) (Fig. 1C). Mucin 2 expression was attenuated in these areas (Fig. 1B), consistent with a reduced differentiation. Unlike conventional squamous epithelium, KRT17+ epithelium was p40− (Fig. 1B). KRT17 mRNA positively correlated with inflammatory status in both UC and CD (Fig. 1D). Intracellular neutrophils were frequently observed in KRT17+ cells, as well as within crypt abscesses surrounded by KRT17+ epithelium (Fig. 1E). Notably, based on scRNA-seq receptor-ligand interaction analysis, KRT17+ cells were among the top predicted interacting partners of neutrophils in IBD mucosa (Fig. 1F). Enrichment analysis of publicly available data on organoid cultures stimulated with several cytokines identified IL17A as a potential upstream regulator of KRT17+ cells in our epithelial dataset (Fig. 1G). Consistently, the KRT17+ population aligned more closely with psoriatic keratinocytes, which are driven by IL17A-dependent signaling (Fig. 1H). Conclusion Our findings suggest that the KRT17+ population may contribute to the re-epithelialization process during active inflammation, then diminishing as inflammation resolves. Interactions between KRT17+ cells and neutrophils may support this process, potentially through activation of an IL17-driven pathway. References: 1.Dotti I, Melón-Ardanaz E, Sanzo Á, et al. DOP38 A rare KRT17+ population emerges from the epithelium in the inflamed intestinal mucosa of patients with Ulcerative Colitis. J Crohns Colitis. 2024;18(Suppl 1). 2.Pavlidis P, Tsakmaki A, Treveil A, Li K, et al. Cytokine responsive networks in human colonic epithelial organoids unveil a molecular classification of inflammatory bowel disease. Cell Rep. 2022;40(13):111439. 3.Pavlidis P, Tsakmaki A, Pantazi E, Li K, et al. Interleukin-22 regulates neutrophil recruitment in ulcerative colitis and is associated with resistance to ustekinumab therapy. Nat Commun. 2022;13(1):5820. 4.Ma F, Plazyo O, Billi AC, et al. Single cell and spatial sequencing define processes by which keratinocytes and fibroblasts amplify inflammatory responses in psoriasis. Nat Commun. 2023;14(1):3455. Conflict of interest: Dr. Dotti, Isabella: I declare no conflicts of interest Veny, Marisol: Nothing to declare Sanzo Machuca, Angela: No conflicts. Gudiño, Victoria: No conflicts. Moro Buendia, Marc: None Robbins, Lisseth: No conflict of interest Melón-Ardanaz, Elisa: No conflict of interest Carrasco, Antonio: No conflict of interest Lopez-Prades, Sandra: No conflict of interest Cuatrecasas, Míriam: No conflict of interest Ricart Gomez, Elena: E. Ricart has received support for congress and conference attendance, speaker fees, research support or consulting fees from MSD, Abbvie, Ferring, Janssen, Otsuka, Pfizer, Takeda, Faes Farma, Galapagos/Alphasigma, Kern Pharma, Lilly, J & J, Dr Falk Pharma, and Fresenius-Kabi. Salas, Azucena: Grant: Takeda, Roche, Nestle, Pfizer, Genentech, AbbVie, GSK, Scipher Medicine, Alimentiv, Inc, Boehringer Ingelheim and Agomab. Personal Fees: Lilly, Johnson & Johnson, Genentech, GSK, Pfizer, Galapagos, AdBio Partners, HotSpot Therapeutics, Alimentiv, Nestle, GoodGut and Agomab.
Dotti et al. (Thu,) studied this question.