Mesenchymal stem cells alleviate acute kidney injury by down-regulating C5a/C5aR pathway activation

Acute kidney injury (AKI) leads to serious renal damage, and early inhibition of inflammation is necessary for its treatment. C5a/C5aR signaling activation promotes inflammatory response in tissue injury. Anti-inflammatory activity of mesenchymal stem cells (MSCs) makes it possible to alleviate AKI by controlling the C5a/C5aR signaling activation.

Ischemia reperfusion (I/R)-induced AKI models in wild-type and C5aR KO mice were used. In addition, human bone marrow MSCs (hBM-MSCs) or C5aR antagonist were injected in this model. All animals were killed at 72 h after reperfusion. In vitro, the LPS-activated macrophage line RAW264.7 cells were co-cultured with or without hBM-MSCs in the presence of recombinant C5a or not for indicated time points. After that, C5aR expression, the inflammatory factor production, and NF-κB translocation in RAW264.7 cells were measured.

hBM-MSC treatment and C5a/C5aR signaling blockade or C5aR-deficiency exhibited similar attenuated effects on I/R-induced AKI, macrophages infiltration, and the pro-inflammatory cytokines TNF-α and IL-1β expression in renal tissues in mice. Moreover, hBM-MSC administration led to a significant reduction in C5a levels in serum and C5aR expression in the kidney tissues in mice after I/R. In vitro, upon co-culture with hBM-MSCs, both C5aR expression and the secretion of pro-inflammatory factors TNF-α, IL-6, and nitric oxide in LPS-activated macrophages were markedly reduced. Accordingly, recombinant complement C5a accelerated LPS-induced NF-κB translocation and pro-inflammatory factors expression in macrophages, but the addition of hBM-MSCs reversed these C5a-induced effects.

The present study indicates that hBM-MSCs alleviate AKI via suppressing C5a/C5aR-NF-κB pathway activation.