We have observed interferon gamma-treated autologous mesenchymal stem cells (MSC) to rapidly ex vivo expand CD3+CD4+CD25- T cells to >80% CD3+CD4+C25+FoxP3+ T regulatory cells with greater efficiency than naïve MSC and to suppress graft versus host disease and promote long-term survival in murine cardiac allografts using 4-5 times less MSC. In this study, autologous naïve or interferon-gamma activated mesenchymal stem cells were studied for their effect on cynomolgus recipients of MHC-disparate renal allografts. Control animals (n=8) were compared to animals treated with Passage 4 MSC administered on days 0, 5, 11, 18, 28 in the following treatment groups: 1) naïve (n=3, 2 X 10⁶/kg), 2) interferon gamma activated, high dose, (n=6, 0.5 x 10⁶/kg), 3) Interferon gamma activated, low dose (n=2, 0.05 x 10⁶/kg). Sub-therapeutic immunosuppression consisted of thymoglobulin (10 mg/kg) on POD 0, 1,2 and 4, daily FK506 from POD -1 through POD 27-30 and rapamycin from POD 28 through the end of the experiment (target trough levels 8-12 ng/ml). MSC identity was defined as CD45^–CD31^–CD34^– and CD105⁺,CD29⁺CD73⁺. Activated MSC,remained CD45^– but expressed MHC Class II. Potency assays demonstrated activated MSC suppressed T cell proliferation to a greater extent than naïve; 6-day co-culture with CD3+CD4+CD25- sorted T cells led to 78-82% conversion to CD4+CD25+FoxP3+ T regulatory cells vs 63-67% with naïve MSC, and activated MSC suppressed bone marrow derived LPS stimulated macrophage production of TNF and enhanced IL-10 production. Median renal allograft survival was 58, 27, 39, and 34.5 for control and groups 1,2, & 3,respectively. These data show that naïve and activated MSC efficiently and rapidly induced T regulatory cells and macrophage phenotype switching in vitro, however following intravenous administration and distribution neither MSC preparations enhanced renal allograft survival with the immunosuppression and MSC dose regimens tested. Alternative routes of administration with greater control of the targeted microenvironment may better mimic in vitro findings for better efficacy.

CITATION INFORMATION: Patil R, Premanand K, Halliday L, Szilagyi E, Willman M, Yu J, Hickey R, Berman D, Antony A, Pan F, Wang X, McHenry K, Salomon D, Kenyon N, Bartholomew A. Naïve and Interferon-gamma Activated Mesenchymal Stem Cells Differentially Affect Immune Responses In Vitro and In Vivo. Am J Transplant. 2017;17 (suppl 3).

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