miR-155 and miR-21 as Diagnostic and Therapeutic Biomarkers for Ulcerative Colitis: There Is Still a Long Way to Go

(1) Elucidating the role of miRNAs (miRs) in ulcerative colitis may provide new insights into disease pathogenesis, diagnosis, treatment, and monitoring We aimed to investigate whether plasma levels of miR-21-5p and miR-155-5p may be used to differentiate between patients with organic disease such as ulcerative colitis (UC) and Clostridioides difficile infection (CDI), and patients with functional disease such as irritable bowel syndrome with diarrhea (IBS-D). (2) Serological samples were collected to quantify miR-155 and -21 expression, which was carried out through quantitative real-time polymerase chain reaction (qRT-PCR), from 84 patients: 34 with acute UC (group 1), 17 with CDI (group 2), and 33 with IBS-D (control group). (3) In this study, we found that the expression levels of miR-155-5p were almost the same for the two conditions and the control group (UC: 4.22 ± 1.61, CDI: 3.94 ± 1.62, IBS-D: 4.26 ± 1.26), with no significant differences either for ΔCt- or for ΔΔCt-derived parameters (p = 0.74 and p = 0.73, respectively). For miR-21, ΔCt levels presented significantly higher values among the ulcerative colitis group (p < 0.01), but the most important expression fold change was noticed in patients with CDI (UC:4.11 ± 8,46, CDI: 4.94 ± 9.68, IBS-D: 2.83 ± 5.41). (4) Circulating miR-155 and miR-21 were upregulated in UC, CDI, and IBS-D, but differentiation was not possible among them. But their involvement in the pathogenesis of the three diseases makes them suitable for improving the accuracy of diagnosis and facilitating the development of personalized treatment strategies.