Role of Myeloid-Derived Suppressor Cells in Glucocorticoid-Mediated Amelioration of FSGS.

The mechanism by which glucocorticoids alleviate renal inflammatory disorders remains incompletely understood. Here, we report that the efficacy of glucocorticoids in ameliorating FSGS depends on the capacity to expand myeloid-derived suppressor cells (MDSCs). After glucocorticoid treatment, the frequency of CD11b(+)HLA-DR(-)CD14(-)CD15(+) MDSCs in peripheral blood rapidly increased in patients with glucocorticoid-sensitive FSGS but remained unchanged in patients with glucocorticoid-resistant FSGS. The frequency of CD11b(+)Gr-1(+) MDSCs in mouse peripheral blood, bone marrow, spleen, kidney-draining lymph nodes (KDLNs), and kidney also increased after glucocorticoid treatment. The induced MDSCs from glucocorticoid-treated mice strongly suppressed T cells, dendritic cells, and macrophages but induced regulatory T cells in spleen, KDLNs, and kidney. Moreover, glucocorticoid treatment suppressed doxorubicin-induced T cell proliferation, dendritic cell and macrophage infiltration, and proinflammatory cytokine production, whereas this protective effect was largely abolished by depleting MDSCs using anti-Gr-1 antibody. Finally, the adoptive transfer of induced MDSCs into the doxorubicin-treated mice not only confirmed the protective role of MDSCs in doxorubicin-induced renal injury but also showed that the transferred MDSCs rapidly migrated into the lymphocyte-accumulating organs, such as the spleen and KDLNs, where they suppressed T cell proliferation. Taken together, these results demonstrate that glucocorticoid treatment ameliorates FSGS by expanding functional MDSCs and that this rapid elevation of MDSCs in peripheral blood may serve as an indicator for predicting the efficacy of glucocorticoid treatment.