IL-34 Inhibits Acute Rejection of Rat Liver Transplantation by Inducing Kupffer Cell M2 Polarization.

ABSTRACT

BACKGROUND: Recent studies have demonstrated that IL-34 is implicated in the regulation of macrophage functions. However, the effect of IL-34 on Kupffer cells (KCs) in acute rejection (AR) of liver transplantation remains unclear. METHODS: IL-34 expression was detected in graft and serum from allotransplantation and syngeneic transplantation groups. The adeno-associated virus-expressing IL-34 was used to assess the effect of IL-34 on AR of rat liver transplantation. The effect of IL-34 on KC polarization was evaluated by in vitro and in vivo assays. Kupffer cells in donors were depleted by clodronate treatment before transplantation, and the nontreated KCs or lipopolysaccharide-treated KCs were transferred into recipients during liver transplantation. RESULTS: IL-34 expression levels in grafts and serum were decreased in the allotransplantation group compared with the syngeneic transplantation group. Adeno-associated virus-expressing IL-34 treatment induced KC M2 polarization in vivo and inhibited the AR of rat liver transplantation. Moreover, we found that IL-34 switched the phenotype of KCs from M1 to M2 by activating the PI3K/Akt pathway in vitro. In addition, the results of KC deletion and adaptive transfer experiments showed that the AR inhibition induced by IL-34 was M2 KC-dependent. CONCLUSIONS: IL-34 plays an important role in KC M2 polarization-dependent AR inhibition of rat liver transplantation.