P1.05: Human Intestinal Transplant: is IL-22 stimulation of Intestinal Stem Cells a new partner for immunosuppressive therapies?

Acute cellular rejection (ACR) is leading cause of graft loss and death in intestinal transplant (ITx) patients. ACR promotes intestinal injury, disruption of the mucosal barrier, organ dysfunction and bacterial translocation. Epithelial regeneration is critical to reverse the situation. The intestinal stem cell (ISC) provides signals supporting normal epithelial maintenance. It has been shown that innate lymphoid cells 3 (ILC3), potent producers of IL-22 after intestinal injury, increase proliferation and expansion of the ISC in an IL-22-dependent fashion. Therefore, we aimed to evaluate the immunological status during the ACR focusing on the axis ILC3/IL-22/IL22R/ISC. To do this, lamina propria cells of biopsies were isolated from ITx [Non-rejection (NR)=17; Mild rejection (MR)=4] and non-transplant patients (NITx)=7. Enrichment of ILCs and CD4 population was done using MACS technology. ILC3 were determined by flow cytometry. CD4 T cells were isolated and the expression levels of functional markers of Th1 (Tbet, IFN-γ), Th2 (GATA3, IL-13), Th22/17 (RORC, IL-22, IL-17A), Tregs (Foxp3, TGF-β) were evaluated by qPCR. Total levels of IL-22 in biopsies [NR=5 and Moderate rejection (MoR)=6] were measured by qPCR. ISC IL-22R+ were detected by immunohistochemical staining [NR=13; MR=9, MoR=12, Severe rejection (SR)=5]. The results showed that during ACR the expression of Tbet, GATA3, RORC, Foxp3 were significantly decreased (P=0.05). Although the total percentage of ILC3s was not impaired (P=0.47); a reduction of ILC3 NCR+/NCR- ratio was observed. ISC IL-22R+ number was similar in all groups studied (P=0.21) while IL-22R expression showed a trend to be increased (P=0.06). Levels of IL-22 in ITxMoR were lower than in NRITx patients with normal biopsies (P=0.063) and NITx biopsies. In conclusion, during rejection CD4 population (TH1, TH2, TH17/22, Tregs) and ILC3/IL-22/IL-22R axis are affected. In this context ISC number not only is unaffected, but also is able to increase IL-22R expression. Finally, the variation in the ILC3 NCR+/NCR- ratio observed during ACR could explained, in part, the impairment in the epithelial regeneration observed during this process. Thus, our findings reveal that IL-22 can potentially be uses as a new therapeutic approach to be used in conjunction with immunosuppressants in order to promote mucosal regeneration. Due to the small number of patients evaluated, this preliminary study is currently being extended with a larger population.