Role of regulatory cells and tissue cytokines in patients with ulcerative colitis: implications for patient-oriented therapy

Ulcerative colitis (UC) is an inflammatory bowel disease that results in a chronic inflammation and ulcers of the mucosa of the colon. In UC, two important issues, specifically related to the prognosis, remain to be clarified. A) Extension of disease greatly influences the prognosis and biological factors involved in the limitation of the disease extent are presently unknown B) Due to increased availability of biological drugs targeting different cytokines, biological therapy need to be optimized on the key cytokine(s) relevant for the inflammatory process. Aim: A) We hypothesized that regulatory T cells might be relevant in limiting the extension of inflammation and that B) UC patients might be stratified according to distinctive cytokine profiles. Methods: In a cross-sectional study, we evaluated the relationship between UC extension and the proportions of CD3+CD4+Foxp3+ and CD3+CD4+LAP+Foxp3-Tregs in the colonic lamina propria (LP) in UC patients undergoing colonoscopy for clinical relapse and controls undergoing colonoscopy for non-inflammatory conditions. The role of these cells in UC extension was also investigated in the murine oxazolone-induced colitis model. B) At the same time, we analyzed tissue cytokine by RTqPCR in endoscopic biopsies from uninvolved and involved tissue of UC patients and controls. Mucosal microbiota analysis was also performed. Results: A) Involved and uninvolved tissue show different and opposite frequency of LP CD3+CD4+Foxp3+ and LP CD3+CD4+LAP+ Tregs with the latter significantly increased in uninvolved vs involved tissue. In mice with oxazolone-induced distal colitis, treatment with α-LAP-depleting antibody was associated with the development of extensive colitis; B) We quantified by RTqPCR TNF-α, IFN-γ, IL-10, IL-6, IL-17, and IL-13 and analyzed the results by r square of the k means for cluster solution. IL-17A and IL-13 mRNA tissue content show classificatory power and their distribution points to the existence of discrete clusters of subjects. Six clusters define the optimal partition of data explaining 91% of the total information present in the data set (R-square=0.91). UC patients were distributed in two clusters characterized by high/low IL-13 mRNA tissue content in the context of high IL-17A mRNA tissue content. The two subsets differ in clinical-pathological characteristics. High IL-13mRNA patients are younger at diagnosis and show higher prevalence of extensive colitis than low IL-13mRNA ones. They also show a more frequent use of steroid/immunosuppressant/anti-TNFα therapy during a one-year follow-up. The two subgroups show a differential enrichment of mucosa associated microbiota genera with prevalence of Prevotella in patients with high IL-13mRNA tissue content and Sutterella and Acidaminococcus in patients with low IL-13mRNA tissue content. Conclusion: A) LP CD3+CD4+LAP+ Tregs efficiently limit the extension of inflammatory lesions. Therapeutic strategy aimed at their expansion may help in containing the spreading of inflammation and possibly in preventing inflammatory relapse. B) Evaluation of IL-13 and IL-17 mRNA content allows the identification of different UC patients’ subsets with associated different clinic phenotypes. Therapeutic options might be optimized according to the patients’ tissue cytokine profile.