IL-27 Modulates Mesenchymal Stem Cell Immunoplasticity for Enhanced Lupus Nephritis Therapy via the JAK1–STAT1–IDO Axis and Tryptophan Metabolic Orchestration

Lupus nephritis is recognized as a common and severe complication of systemic lupus erythematosus, without an optimal therapeutic strategy currently available. While mesenchymal stem cells (MSCs) hold therapeutic promise, their efficacy varies substantially, likely due to their plasticity and capacity to adopt pro-inflammatory (MSC1) or anti-inflammatory (MSC2) functional states in response to different microenvironments. Here, we report for the first time that IL-27, via JAK1-STAT1 signaling, up-regulates indoleamine 2,3-dioxygenase (IDO) in MSCs, driving MSC differentiation toward an IDO-positive MSC2 phenotype with low immunogenicity. These IDO-positive MSC2 cells produce kynurenine and kynurenic acid, the metabolites of tryptophan, which bind to the intracellular aryl hydrocarbon receptor. This interaction stimulates an increase in the anti-inflammatory factor TSG-6 and induces the differentiation of regulatory T cells. Notably, IL-27-conditioned MSC2 demonstrated superior therapeutic efficacy compared to conventional MSCs in a murine lupus nephritis model. In conclusion, this study revealed that IL-27 is a critical modulator of MSC immune plasticity and presented a novel therapeutic strategy utilizing IL-27-enhanced MSC2 for autoimmune diseases.