Granulocyte Colony-Stimulating Factor Attenuates Renal Ischemia-Reperfusion Injury by Inducing Myeloid-Derived Suppressor Cells
Authors: Yan Ji-Jing , Ryu Jung-Hwa , Piao Honglin , Hwang Ju Hee , Han Dongkyu , Lee Sun-Kyung , Jang Joon Young , Lee Joongyub , Koo Tai Yeon , Yang Jaeseok 
Published: March 2020

Significance Statement
Myeloid-derived suppressor cells are innate suppressors that play an immunoregulatory role in autoimmunity, transplantation, and antitumor immunity; however, their effects on renal ischemia-reperfusion injury remain unclear. The authors showed that granulocyte colony-stimulating factor (G-CSF) increased renal infiltration of myeloid-derived suppressor cells after ischemia-reperfusion injury. When given before ischemia-reperfusion, G-CSF subsequently attenuated acute tissue injury, renal apoptosis, and renal inflammation; when given after ischemia-reperfusion, G-CSF facilitated renal recovery and attenuated renal fibrosis. They also showed that granulocytic myeloid-derived suppressor cells played a role in the beneficial effects induced by G-CSF via arginase-1 and reactive oxygen species. These findings elucidate protective roles of G-CSF–induced myeloid-derived suppressor cells against ischemia-reperfusion injury and indicate that human studies investigating the therapeutic potential of myeloid-derived suppressor cells and G-CSF in renal ischemia-reperfusion injury are warranted.

Background
Granulocyte colony-stimulating factor (G-CSF) can increase populations of myeloid-derived suppressor cells, innate immune suppressors that play an immunoregulatory role in antitumor immunity. However, the roles of myeloid-derived suppressor cells and G-CSF in renal ischemia-reperfusion injury remain unclear.

Methods
We used mouse models of ischemia-reperfusion injury to investigate whether G-CSF can attenuate renal injury by increasing infiltration of myeloid-derived suppressor cells into kidney tissue.

Results
G-CSF treatment before ischemia-reperfusion injury subsequently attenuated acute renal dysfunction, tissue injury, and tubular apoptosis. Additionally, G-CSF treatment suppressed renal infiltration of macrophages and T cells as well as renal levels of IL-6, MCP-1, IL-12, TNF-α, and IFN-γ, but it increased levels of IL-10, arginase-1, and reactive oxygen species. Moreover, administering G-CSF after ischemia-reperfusion injury improved the recovery of renal function and attenuated renal fibrosis on day 28. G-CSF treatment increased renal infiltration of myeloid-derived suppressor cells (F4/80−CD11b+Gr-1int), especially the granulocytic myeloid-derived suppressor cell population (CD11b+Ly6GintLy6Clow); splenic F4/80−CD11b+Gr-1+ cells sorted from G-CSF–treated mice displayed higher levels of arginase-1, IL-10, and reactive oxygen species relative to those from control mice. Furthermore, these splenic cells effectively suppressed in vitro T cell activation mainly through arginase-1 and reactive oxygen species, and their adoptive transfer attenuated renal injury. Combined treatment with anti–Gr-1 and G-CSF showed better renoprotective effects than G-CSF alone, whereas preferential depletion of myeloid-derived suppressor cells by pep-G3 or gemcitabine abrogated the beneficial effects of G-CSF against renal injury.

Conclusions
G-CSF induced renal myeloid-derived suppressor cells, thereby attenuating acute renal injury and chronic renal fibrosis after ischemia-reperfusion injury. These results suggest therapeutic potential of myeloid-derived suppressor cells and G-CSF in renal ischemia-reperfusion injury.