P118 Induction of ETS1 and senescence associated secretory phenotype in human intestinal fibroblasts

Abstract Background Fibrosis is a complication commonly present in Crohn’s disease (CD) patients with a structuring (B2) or penetrating (B3) behaviour, with no available treatment. This process is characterized by an excessive extracellular matrix deposition, mainly associated with a dysregulated function of myofibroblasts. We analyse here, the expression of markers of senescence in human intestinal fibroblasts. Methods Human small intestinal fibroblasts (HSIF; P10760, Innoprot, Spain) were treated during 48h with 2µg/mL of DLL4, 20ng/ml of TNFα, 2ng/ml of IL-1β, 5ng/ml of TGFβ1, and 100ng/ml of. In some cases, fibroblasts were treated with 20nM of siRNA to ETS1 gene (siETS21) or negative control (NC). Gene expression profiles were analysed by RT-qPCR. Results Treatment of fibroblasts with IL-1β significantly increased the mRNA expression of a) different senescence-associated secretory phenotype (SASP) factors (IL-1α, IL-1β, IL-8, and Serpine1); b) a metalloprotease ADAM12 and the chitinase CHI3L1 and c) the transcription factor related to senescence ETS proto-oncogene 1 (ETS1), all compared with vehicle treatment. Treatment with PDGF significantly increased the mRNA expression of ADAM12, ETS1, PTEN and the transcription factor, E2F5, while it induced a non-significant increase in the expression of senescence markers such as P16, P21, P53 and MCL1. Treatment with TGFβ1 did not significantly alter the expression of markers reported above and it only significantly increased the expression of IGFBP3 gene, another SASP factor. Both DLL4 and TNFα failed to significantly modify the expression of any of the above markers. Finally, a cellular model of depletion of ETS1 showed that siETS1 fibroblasts in basal conditions exhibited decreased levels of IL-8 and BCL2. Conclusion In human primary intestinal fibroblasts, treatment with IL1b increased the expression of senescence associated secretory phenotype while treatment with PDGF increased the expression of markers involved in cell cycle arrest. The induction of ETS1 by both treatments and the involvement of this transcription factor regulating gene expression in basal conditions, suggest a relevant role for ETS1 in the activation of intestinal fibroblasts