DOP65 T-cell derived TGFβ1 remodels the rectum mesenchyme in Crohn’s Disease patients with perianal fistulizing disease
Gudiño, V.(1)*;Cho, J.W.(2);Corraliza, A.M.(1);Caballol, B.(3);Garrido-Trigo, A.(1);Masamunt, M.C.(3);Ordás, I.(3);Ricart, E.(3);Hemberg, M.(2);Panés, J.(3);Salas, A.(1);
(1)Institut d'Investigacions Biomèdiques August Pi i Sunyer IDIBAPS, Inflammatory Bowel Disease Unit, Barcelona, Spain;(2)Evergrande Centre- Brigham and Women’s Hospital, Quantitative models of gene expression, Boston, United States;(3)Hospital Clinic, Inflammatory Bowel Disease Unit, Barcelona, Spain;
Background
Perianal fistulizing disease (PFD) is a complication occurring in about 20% of Crohn’s Disease (CD) patients. It consists of the formation of new epithelised tracks connecting the intestine with the outer perianal region, which dramatically worsens a patient's quality of life. The mechanisms driving fistula formation have not been elucidated and therefore, there are currently no specific treatments for PFD.
Methods
We collected rectum biopsies of CD patients with and without PFD in the absence of rectal inflammation (CD and CD+PFD), and with active rectal inflammation (CDinf and CD+PFDinf) (Fig.1). Rectal tissue samples were processed for RT-qPCR, or histologic analysis, and single-cell RNA sequencing (scRNAseq) for each patient.
Results
Differential expression gene (DEG) analysis of CD4+ and CD8+ T cells comparing CD vs CD+PFD and CDinf vs CD+PFDinf patients, respectively, revealed increased expression of TGFB1 in patients with fistulae. To investigate the main cellular subsets TGFB1 was interacting with, we performed ligand-receptor interaction analysis using CellphoneDB, which indicated that T-cell derived TGFB1 was primary interacting with the stromal compartment (Fig.2). 365 DEG were found in lamina propria (LP) fibroblasts of CD+PFD compared to CD, including TGFβ1-inducible genes such as TFPI2, SERPINE2 and MMPs 1 and 3. These changes were validated by bulk RT-qPCR, underscoring their potential use as PFD biomarkers (Fig.3). Moreover, we also identified a signature of elastin fibre assembly genes dysregulated in CD+PFD fibroblasts, suggesting molecular changes in the formation of elastin fibres in these patients. To determine whether the differentiation of fibroblasts was altered in the context of PFD, we conducted trajectory analysis using RNA velocity. Whilst fibroblasts in CD patients preferentially differentiate towards myofibroblasts, patients with PFD are biased towards LP fibroblasts, indicating an overall structural rearrangement of the mesenchyme in the rectum of patients with PFD, regardless of their inflammatory status (Fig.4). Importantly, analysis of an independent scRNAseq dataset of CD and ulcerative colitis (UC) patients showed higher expression of TGFB1 in T cells of active CD compared to active UC patients, suggesting that these alterations are already present in CD patients before the onset of a fistulizing phenotype and might potentially contribute to explain the absence of PFD in UC patients.
Conclusion
Based on these results, we suggest that the rectum of patients suffering from PFD present cellular and transcriptomic differences compared to CD patients without PFD. These changes are inflammation independent and point towards the TGFβ pathway as the main driver of this complication.