DOP074 JAK inhibition to target fibroblasts and IBD-related fibrosis
Authors: Su J , Ke B J , van Os B , Zanella G , Voorneveld P W , Hawinkels L J A C , Matteoli G , Barnhoorn M C 
Published: January 2025

Abstract

Background
Intestinal fibrosis is a common complication of inflammatory bowel disease (IBD). Uncontrolled accumulation of extracellular matrix deposited by fibroblasts is thought to be the underlying cause of fibrogenesis. Janus kinases (JAK) inhibitors are a relatively novel therapeutic strategy in IBD which show a robust anti-inflammatory effect. We hypothesize that JAK-inhibitors might not only play a role in IBD by reducing inflammation, but also offer a therapeutic potential to treat intestinal fibrosis. In this study we explored the effects of JAK inhibition on intestinal fibroblasts in vitro and in vivo.

Methods
In vitro studies were performed with human CCD-18Co and primary colonic fibroblasts. Levels of activated JAKs and STATs were detected by western blot after cytokine stimulation and were inhibited using tofacitinib (10uM) or upadacitinib (10uM). For the T cell transfer colitis model, Rag-/- mice (n=5-12 mice/group) were used. After engraftment of donor T cells the severity of colitis was evaluated with the mouse endoscopy score (MEICS) and mice were treated with upadacitinib (20mg/kg, 4x/week intraperitoneal injection). Intestinal fibroblast subsets were analyzed using anti-CD90, anti-αSMA, anti-podoplanin, anti-FAP, anti-PDGFR-α and -β, by flow cytometry. Sirius red staining was performed to measure collagen deposition. Levels of activated JAKs and downstream STATs were detected by immunofluorescent staining.

Results
Re-analysis of our previously published single-cell RNA sequencing data from fibrostenotic tissue of Crohns disease patients identified that a pathogenic subset of activated pro-inflammatory FAP+ fibroblasts was driven by the activation of STAT3 [1]. Inflammatory cytokines activated the JAK-STAT pathway in human fibroblasts and both upadacitinib and tofacitinib strongly inhibited pJAK1, pJAK2, pSTAT1 and pSTAT3 in a concentration dependent manner. Mice treated with upadacitinib showed a significant lower MEICS compared to controls (2.4 vs 5.3, Figure 1). Interestingly, specific intestinal fibroblast subsets, e.g. CD90+PDGFR-β+ fibroblasts were less abundant upon JAK-inhibition. pSTAT3 expression in the colon seemed to change after JAK inhibition. Furthermore, upadacitinib was able to restore the amount and distribution of collagen in the colon.

Conclusion
Our study is the first to describe that the JAK-STAT pathway can be activated in intestinal fibroblasts and JAK-inhibitors including upadacitinib/ tofacitinib suppress this pathway in vitro. Furthermore, human data show activation of the JAK-STAT pathway in FAP+ fibroblasts and in mice, JAK inhibition has an effect on fibroblasts subsets and collagen deposition. This shows the potential of JAK-inhibitors to target more than immune cells.

References
[1]Ke BJ, Abdurahiman S, Biscu F, et al. Intercellular interaction between FAP+ fibroblasts and CD150+ inflammatory monocytes mediates fibrostenosis in Crohn's disease. J Clin Invest. 2024;134(16):e173835. Published 2024 Jul 23. doi:10.1172/JCI173835