Serum and mucosal Serpin E1 concentration correlates with endoscopic activity in inflammatory bowel disease - potential new activity marker

Abstract Background Inflammatory bowel disease (IBD) is characterized by an unregulated immune response generating unbalance cytokine homeostasis. Analysis of patient-specific cytokine profiles may open new therapeutic targets or identify biomarkers that distinguish responders from non-responders before initiating therapy. Therefore, the aim of the present study was to determine cytokine profile of IBD patients and identify cytokines with predictive potential. Methods Blood and biopsy samples were obtained from 79 clinically active IBD patients and 28 controls without IBD. Inclusion criteria included change of therapy or initiation of new treatment for IBD patients. Organoid culture (OC) was generated from 5 clinically active IBD patients and 5 controls. Cytokine Array was used to analyse cytokine expression patterns. Total protein and mRNA were isolated from biopsies and from OCs. Protein levels were measured by ELISA and gene expression by qRT-PCR in serum, mucosa and in OCs. Results Pro-inflammatory cytokines were not detected in control samples, whereas in IBD biopsies the cytokine profiles enabled the discrimination between inflamed or non-inflamed areas. The mucosal expression of Serpin E1 was detected in all inflamed biopsy samples, whereas it was below the detection limit in healthy subjects. In responders Serpin E1 gene expressions were significantly (p<0.001) lower than in non-responders. On the other hand, we were not able to detect significant changes between responders and non-responders in gene expression of TNF-α, IL-1β, IL-6 and TGF-β. In responders, mucosal Serpin E1 concentration significantly decreased (p<0,05) after the initiation of therapy compared to non-responders. Serum and mucosal Serpin E1 concentrations were significantly higher in patients with endoscopically and clinically active disease compared to inactive (endoscopic: p<0.0001, clinical: p<0.05). Correlation analysis revealed that serum Serpin E1 level correlates with disease activity (p<0.01). In OCs the level and expression of Serpin E1 was lower in healthy organoids compared to OCs generated from inflamed samples. Conclusion Our results suggest that serum and mucosal Serpin E1 expression reflects endoscopic activity in IBD, which could be used to follow-up disease activity and possibly therapeutic response. Organoids mimicked the expression of Serpin E1 in the original biopsies suggesting that OCs can be used to study the effect of Serpin E1 inhibition.