P038 Notch pathway in fibrosis: a new anti-fibrotic therapy in Crohn's disease?

Abstract Background Fibrosis represent the main complications related to Crohn's disease (CD). Notch signalling mediate fibrogenic process, including epithelial-mesenchymal transition (EMT) and fibroblast senescence but its role in CD fibrosis is currently unknown. Previous studies have shown a high expression of NOTCH4, NOTCH3, DLL3 and DLL4 in CD fibrotic tissue. DLL4 mainly activates transcription factors involved in EMT, and macrophages could act as a possible source of DLL4 (Edo, et al., 2022. JCC (i200)).The general aim of the present study is to determine the possible potential of Notch pathway as a therapeutic target in intestinal fibrosis associated with CD. Specifically, we pretend: to analyze the localization of NOTCH3/4 receptors in the intestinal tissue of patients with CD complicated; to study the relevance of NOTCH3/4 receptors in the EMT; to study the relevance of Notch pathway in the senescence of intestinal fibroblast. Methods We have analyzed in intestinal samples from CD patients with complicated lesions: the localization of NOTCH3/4 receptors by IH and the protein expression of senescence markers (BCL2 and P53) by WB. We carry out in vitro studies and analyze: the protein expression of HES1 (effector Notch pathway) and EMT markers in DLL4-HT29 treated cells transfected with miNOTCH3 or miNOTCH4; and the protein expression of senescence proteins in HSIF fibroblasts treated with DLL4 or DLL3. Results NOTCH3 was located preferentially in muscular areas -muscularis mucosa, endothelium and muscularis externa- with a striking staining of infiltrated cells in the mucosa of the unaffected area. NOTCH4 is found more specifically in the crypts of the mucosa, as well as in cells of the lamina propria of the unaffected mucosa. The expression of senescence proteins in the tissue showed elevated levels of BCL2 and P53, compared to the unaffected tissue of the same patient. DLL4 increased the protein expression of EMT markers in HT29 cells, and NOTCH4 silencing significantly reverted the expression of these EMT markers. NOTCH3 silencing produced no significant changes after DLL4-HT29 treatment. DLL3, and not DLL4, produced in intestinal fibroblasts a significant increase in the protein expression levels of BCL2, and P53, compared to the vehicle (Figure). Conclusion NOTCH pathway is involved in the regulation of key cellular functions and processes essential for the pathogenesis of intestinal fibrosis in CD patients. DLL4-NOTCH4 interaction triggers transcription factors involved in mesenchymal epithelial transition in colonic epithelial cells, while DLL3 seems to have a more relevant role in activation of senescence in fibroblasts.