Oxygen Tension And Indolamine 2,3-dioxygenase Expression Regulate Mesenchymal Stem Cell-mediated Regulatory T Cell Expansion
Rohini Kadle, BS, Johnathan Massie, BS, Trevor Ellison, BS, Sophia Hameedi, N/A, Piul Rabbani, PhD, Bukhtawar Waqas, BS, Daniel Ceradini, MD.
NYU, New York, NY, USA.
PURPOSE: Mesenchymal stem cells (MSCs) have powerful immunosuppressive properties, partially mediated by expansion of regulatory T cells populations (Tregs). We previously showed that priming MSCs with hypoxic and inflammatory conditions enhances their stem-like and immunomodulatory properties, largely through induction of indolamine 2,3-dioxygenase (IDO). We therefore hypothesize that priming MSCs will increase MSC-mediated Treg expansion via an IDO-specific mechanism.
METHODS: We harvested CD4+ T cells from Lewis rat spleens and co-cultured them with MSCs and allogeneic rat endothelial cells (ECs). MSCs were cultured in either hypoxia (5% O2) or normoxia, or primed with inflammatory cytokine IFNy. Flow cytometry for FoxP3 determined %Tregs.
RESULTS: With MSC/CD4+/EC co-culture, %Tregs tripled to 24.13±2.16%, versus CD4+/EC(9.28±1.15%) or CD4+ alone (7.94±1.22%), p<0.0001 for both. When MSCs were physically separated in culture from CD4+/ECs, %Tregs was similar to MSC/CD4+/EC (27.77±1.99% vs 22.6±5.65%). Using hypoxia-primed MSCs, %Tregs more than doubled to 24.13±2.16% vs 11.06±2.19% with normoxic MSCs (p<0.01). When we inhibited IDO, %Tregs significantly decreased to 12.4± 3.10% (p<0.01), almost negating effects of MSCs on Treg proliferation. Priming MSCs with IFNγ had no impact on % Tregs, in normoxia and hypoxia.
CONCLUSION: Addition of autologous MSCs to co-culture increases Treg proliferation, which is potentiated by hypoxia-primed MSCs. MSC-mediated Treg expansion does not require direct contact, indicating a paracrine mechanism. Inhibition of IDO significantly decreases the proliferation of Tregs, implying a key role of IDO. These results further delineate the mechanisms by which MSCs exert their immunomodulatory functions, demonstrating methods to prime MSCs to optimize their immunomodulation.
Back to 2016 Joint Meeting Abstracts