TNF-a/IL-1ß-licensed mesenchymal stromal cells promote corneal allograft survival via myeloid cell-mediated induction of Foxp3+ regulatory T cells in the lung.

Mesenchymal stromal cells (MSCs) have shown promise as a therapy for immune-mediated disorders, including transplant rejection. Our group previously demonstrated the efficacy of pretransplant, systemic administration of allogeneic but not syngeneic MSCs in a rat cornea transplant model. The aim of this study was to enhance the immunomodulatory capacity of syngeneic MSCs. In vitro, MSCs licensed with TNF-¿/IL-1ß (MSCsTNF-¿/IL-1ß) suppress syngeneic lymphocyte proliferation via NO production. In vivo, when administered post-transplantation, nonlicensed syngeneic MSCs improved graft survival from 0 to 50% and MSCsTNF-¿/IL-1ß, in an NO-dependent manner, improved survival to 70%. Improved survival was associated with increased CD4+CD25+forkhead box P3+ regulatory T (Treg) cells and decreased proinflammatory cytokine expression in the draining lymph node. MSCsTNF-¿/IL-1ß demonstrated a more potent immunomodulatory capacity compared with nonlicensed MSCs, promoting an immune-regulatory CD11b+B220+ monocyte/macrophage population and significantly expanding Treg cells in the lungs and spleen. Ex vivo, we observed that lung-derived myeloid cells act as intermediaries of MSC immunomodulatory function. MSC-conditioned myeloid cells suppressed stimulated lymphocyte proliferation and promoted expansion of Treg cells from naive lymphocytes. This work illustrates how syngeneic MSC therapy can be enhanced by licensing and optimization of timing strategies and further highlights the important role of myeloid cells in mediating MSC immunomodulatory capacity.-Murphy, N., Treacy, O., Lynch, K., Morcos, M., Lohan, P., Howard, L., Fahy, G., Griffin, M. D., Ryan, A. E., Ritter, T. TNF-¿/IL-1ß-licensed mesenchymal stromal cells promote corneal allograft survival via myeloid cell-mediated induction of Foxp3+ regulatory T cells in the lung.This study was supported by a Science Foundation Ireland Investigator Award (grant number 12/IA/1624; NM, OT, KL, MM, PL, MDG, TR). This work was also supported by grants from the Health Research Board of Ireland (grant number HRA_POR/2013/341) (NM, MDG, TR), a Science Foundation Ireland Starting Investigator Grant (grant number 15/SIRG/3456; AR), by the EU FP7 Collaborative Health Project VISICORT (grant number 602470; NM, 691 PL, MDG, TR) and the European Regional Development Fund. The authors wish to acknowledge the advice, assistance and technical expertise of Ms. Georgina Shaw NUI Galway. All flow cytometry experiments were performed in the NUI Galway Flow Cytometry Core Facility which is supported by funds from NUI Galway, Science Foundation Ireland, the Irish Government’s Programme for Research in Third Level Institutions, Cycle 5 and the European Regional Development Fund. The authors acknowledge the facilities as well as the scientific and technical assistance of the National Centre for Biomedical Engineering Science Genomics Facility at the National University of Ireland Galway, a facility that is funded by National University of Ireland Galway and the Irish Government’s Programme for Research in Third Level Institutions, Cycles 4 and 5, National Development Plan 2007–2013.peer-reviewe