*Purpose: Mesenchymal stem cells (MSCs) typically exhibit unique regenerative and immunomodulatory properties when exposed to proinflammatory cytokines. Invariant natural killer T (iNKT) cells are known to modulate the acquired immune system by producing Th1, Th2, and Th17 cytokines. We previously reported that iNKT cell stimulation by ɑ-galactosylceramide (αGalCer) led to the induction of de novo generation of Tregs in murine thymocyte culture system. Here, we tested the hypothesis that MSCs exhibit more effective immunomodulatory activity in coexistence with activated iNKT cells.

*Methods: MSCs from mouse adipose tissues and murine splenocytes were co-cultured in the presence or absence of αGalCer on culture plates. It has been reported that only NKT cells were activated by αGalCer in mouse spleen cells. To investigate further, MSCs and splenocytes were also plated in the lower and upper chambers, respectively, of a trans-well dish, and cultured in the presence or absence of αGalCer. The mRNA expression levels of indoleamine 2,3-dioxygenase (IDO) and programmed cell death 1 ligand 1 (PD-L1) in MSCs were measured by real-time polymerase chain reaction. The proportion of Tregs were analyzed by flow cytometry. The concentration of interferon (IFN)-γ in the culture supernatants was measured using the Cytometric Bead Array.

*Results: When co-cultured with splenocytes in the presence of αGalCer, the mRNA expression of IDO and PD-L1 was increased in MSCs (Fig.1) in both the culture plates and trans-well plates. These results suggest that the immunomodulatory activity of MSCs was induced by soluble factors secreted from activated iNKT cells. The concentration of IFN-γ in culture supernatants was increased and Tregs were significantly expanded in the co-culture in the presence of αGalCer, but not in its absence (Fig.2).

*Conclusions: By co-culture with iNKT cells stimulated with ɑ-galactosylceramide, MSCs exhibit more effective immunomodulatory activity, including induction of expression of various immunoregulatory molecules and expansion of regulatory T cells.

« Back to 2022 American Transplant Congress