Induction of indoleamine 2,3-dioxygenase by pre-treatment with poly(I:C) may enhance the efficacy of MSC treatment in DSS-induced colitis

Mesenchymal stem cells (MSCs) have been used experimentally for treating inflammatory disorders, partly owing to their immunosuppressive properties. The goal of the study was to determine whether TLR ligands can enhance the therapeutic efficacy of bone marrow-derived MSCs for the treatment of inflammatory bowel disease. Mice (C57BL6) were administered with 4% dextran sulfate sodium (DSS) in drinking water for 7 days and injected with MSCs on days 1 and 3 following DSS ingestion. Our results demonstrated that among various TLR ligands, MSCs treated with polyinosinic-polycytidylic acid [poly(I:C)], which is a TLR3 ligand, more profoundly induced IDO, which is a therapeutically relevant immunosuppressive factor, without any observable phenotype change in vitro. The poly(I:C)-treated MSCs attenuated the pathologic severity of DSS-induced murine colitis when injected i.p. but not i.v. In summary, preconditioning MSCs with poly(I:C) might improve their efficacy in treating DSS-induced colitis, and this effect at least partly depends on the enhancement of their immunosuppressive activity through increasing their production of IDO.