The overlap of these miRNAs in the blood of UC and CD patients suggests a generalized inflammatory status common to both

diseases as well as other autoimmune diseases. The first papers published on miRNA expression patterns in IBD patients were performed in tissue samples [22-25]. We small molecule library screening have found seven miRNAs expressed specifically in the mucosa of aCD. None of these miRNAs have been described previously in the mucosa of aCD patients. One tissue miRNA of aCD, miR-140-3p, coincided with one of the miRNAs expressed exclusively in the blood of CD patients (aCD and iCD together). Previous studies have demonstrated that miR-140-3p was down-regulated in tumour samples of colorectal cancer [42] and could regulate the expression of a membrane protein (CD38) through the activation of TNF-α and NF-κB [43]. We believe that miR-140-3p should be explored specifically in the blood of aCD to gain an understanding of its role in the pathogenesis of CD and to confirm the mucosa and serum correlation. We hypothesized that miR-140-3p could be used as a biomarker of active disease. In contrast to the serum findings, we found five tissue miRNAs that were able to distinguish aUC from iUC. None of these tissue miRNAs have been described previously for aUC patients. In contrast, Fasseu et al. described

a decreased expression of miR-196b in the mucosa of BIBW2992 clinical trial iUC patients [23]. None of the mucosa miRNAs found exclusively in aUC coincided with mucosa miRNAs in aCD, which suggests the possibility of using tissue miRNAs expression patterns to distinguish both pathologies. The available evidence indicates that miRNA expression in plasma and serum appears to reflect the extrusion of miRNAs from distant tissues or organs or disease pathways [11-13, 20]. In this regard, the results of Wu et al. did not identify

the same expression patterns in mucosa and peripheral blood. Mirabegron They hypothesized that the peripheral blood miRNAs of their study possibly identified the expression in circulating white blood cells [19]. Our results do not show an exact correlation between the miRNA expression profiles of the serum and mucosa of the same patients. We believe that this dissimilarity may be because of the small number of patients, who were extremely heterogeneous, and the treatments employed during the disease could cause epigenetic changes with an impact on the miRNA expression profiles. Nevertheless, we have shown throughout the discussion that some of our serum miRNAs have been found previously in the mucosa under the same conditions. The most surprising finding was that miR-127-3p was shown to be the miRNA with increased expression in both UC and CD patients. Similar to our findings, Fasseu et al.