Abstract Background TWEAK (TNF-like weak inducer of apoptosis), a member of the tumor necrosis factor superfamily, has been found to be upregulated in IBD biopsies and to promote chronic inflammation in in vivo murine models. Previous work by our group has identified that TWEAK represses the expression of homeostatic factors in colonic fibroblasts, and it promotes inflammatory fibroblast-monocyte crosstalk. The aim of this study was to translate in vitro observations into a clinical setting by investigating the presence of TWEAK in the healthy and inflamed gut and its correlation with inflammatory fibroblasts. Methods Fresh colonic biopsies were enzymatically digested and processed to extract single cells. Isolated cells were analysed by flow cytometry to characterise the expression and cellular source of TWEAK, as well as changes in structural cell compartments, including inflammatory polarisation in colonic fibroblasts. Flow cytometry was conducted on 31 colonic samples of patients with known IBD (inflamed n=11, noninflamed n=10, remission, n=10) as well as 4 healthy controls with no history of IBD Results We observed an increased number of TWEAK+ myeloid cells (CD45+/CD11b+/TWEAK+) in inflamed segments compared to non-involved sections, or to biopsies from healthy donors or patients in remission (Figure 1A). Similarly, inflamed biopsies showed an increase in CD90+/PDPN+ stromal cells, which is consistent with an expansion in inflammatory fibroblasts (Figure 1B), and highly correlates with the accumulation of TWEAK+ myeloid cells (Figure 1C). Conclusion The accumulation of TWEAK+ myeloid cells in inflamed tissues is concomitant with the expansion of the inflammatory stroma in ulcerative colitis, positioning TWEAK as a potential driver of inflammatory fibroblast polarisation. Understanding the effect of TWEAK in stromal remodelling is of key importance both to understanding intestinal physiology and to developing potential therapeutic strategies in diseases as diverse as inflammatory bowel disease.
Read full abstract