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Sunil Chauhan, Masahiro Omoto; Mechanisms of Mesenchymal Stem Cell-Mediated Promotion of Regulatory T cell Function. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1856.
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© ARVO (1962-2015); The Authors (2016-present)
Mesenchymal stem cells (MSC) and regulatory T cells (Tregs) have been shown to exert critical immunomodulatory function in various ocular inflammatory disorders, including corneal transplant rejection and autoimmune dry eye disease. Interactions between MSC and Tregs are complex, and mediated by soluble or cell surface molecules. The purpose of this study was to investigate whether direct cell-to-cell contact between MSC and Tregs is necessary for the maximal enhancement of Treg function.
Naïve Balb/c mice were used to generate bone marrow-derived MSC (CD45-CD34-SCA1+CD29+), and to isolate CD4+CD25+ Tregs (purity: >95% Foxp3+) from spleen and lymph nodes. MSC and purified Tregs were co-cultured with or without transwells (1 um pore size). After 72h of co-culture, cells were immunostained for Treg markers (CD4+CD25+Foxp3+) and the frequency of Foxp3hi expressing Tregs was analyzed using flow cytometry. MSC surface expression of CD80 was investigated using flow cytometry. Effect of blockade of MSC-expressed CD80 on Treg expression of Foxp3 was analyzed in a co-culture assay using CD80 blocking antibodies.
Tregs co-cultured in direct cell-to-cell contact with MSC showed increased (2-fold) frequencies of Foxp3hi population (62%) compared to those Tregs that were cultured in a transwell with MSC (37%) or without MSC (23%). Flow cytometric analysis of CD80 surface-stained MSC showed a substantial right shift of whole population compared to isotype antibody stained MSC. In the MSC-Tregs co-culture assay, functional blockade of MSC membrane-expressed CD80 led to a significant reduction (40%, p<0.02) in Foxp3 expression by Tregs.
Our data demonstrate that direct cell-to-cell interaction between MSC and Tregs is essential for maximal enhancement of Treg function, which in part is mediated by MSC membrane-expressed CD80 molecule.
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