Objective To investigate the effects of interleukin(IL)-34 on the polarization and migration ability of macrophages derived from human peripheral blood monocytes.Methods The CD14+monocytes were isolated from human peripheral blood monocytes by immunomagnetic bead sorting,and the purity of CD14+monocytes was detected by flow cytometry.The CD14+monocytes were divided into M1 type group,IL-34-M1 type group,M2 type group and IL-34-M2 type group.The cells in the M1 type group and IL-34-M1 type group were added granulocyte-macrophage colony stimulating factor(GM-CSF)to induce for 5 days,and half of the fluid was changed,and then the interferon-γ,lipopolysaccharides,IL-6 and GM-CSF were added for another 4-day induction;the cells in the M2 type group and IL-34-M2 type group were added macrophage colony stimulating factor(M-CSF)to induce for 5 days,and half of the fluid was changed,and M-CSF,IL-4,IL-6,and IL-13 were added for another 4-day induction.The cells in IL-34-M1 group and IL-34-M2 group were co-induced with IL-34 at the beginning of induction and on the 5th day of induction.On the 9th day of induction,the proportion of CD14+CD86+cells(M1 type macrophages)and CD14+CD163+cells(M2 type macrophages)in each group was detected by flow cytometry,and the migration ability of cells in the M2 type group and IL-34-M2 type group was detected by the Transwell chamber experiments.Results High purity CD14+monocytes were obtained through magnetic bead sorting,with a CD14 positive rate of(96.77± 2.72)％,which could be used for macrophage induction.The proportion of CD14+CD86+cells in the M1 type group and IL-34-M1 type group was(43.20±7.59)％and(27.87±2.06)％,respectively.The proportion of CD14+CD163+cells in the M2 type group and IL-34-M2 type group was(47.70±4.49)％and(58.95±3.65)％,respectively;the proportion of CD14+CD86+cells in the IL-34-M1 type group was significantly lower than that in the M1 type group(P＜0.05),while the proportion of CD14+CD163+cells in the IL-34-M2 type group was significantly higher than that in the M2 type group(P＜0.05).The number of migrating cells of macrophages in the M2 type group and IL-34-M2 type group was 97.8±9.0 and 205.6±21.9,respectively;the number of migrating cells of macrophages in the IL-34-M2 type group was significantly higher than that in the M2 type group(P＜0.05).Conclusion IL-34 can inhibit the polarization of macrophages derived from human monocytes cells towards M1 type,promote the polarization of macrophages towards M2 type,and enhance the migration ability of M2 type macrophages.

Background: Interleukin-34 (IL-34) is an important immunomodulatory factor that plays a crucial role in a variety of autoimmune diseases. Aims: To investigate the expression of IL-34 in primary biliary cholangitis (PBC) and its influence on intrahepatic inflammation and bile duct damage. Methods: Liver tissues were obtained from 26 PBC patients and 10 hepatic hemangioma patients without PBC. Expression and localization of IL-34 were detected by immunohistochemistry. In animal experiment, Poly I:C intraperitoneal injection was used to construct PBC model in wild-type and IL-34-knockout C57BL/6 mice (WT-PBC group and IL-34KO-PBC group). Subsequently, the intrahepatic inflammation and bile duct damage were evaluated pathologically, and the expressions of IL-34 and associated cytokines in liver tissues were detected by real-time PCR and Western blotting. Results: Expression of IL-34 in liver tissues of PBC patients and PBC model mice was significantly higher as compared with those of the controls (all P<0.05). No morphological changes in hepatic pathological evaluation were observed in IL-34KO mice receiving intraperitoneal saline injection. In IL-34KO-PBC mice, the portal area inflammation and biliary epithelial cell damage were more severe than those in WT-PBC mice (all P<0.05). Expressions of proinflammatory cytokine interleukin-1β (IL-1β) and monocyte chemotactic protein-1 (MCP-1) in liver tissues of IL-34KO-PBC mice were significantly increased than those of WT-PBC mice, whereas expressions of antiinflammatory cytokine IL-10 and CD163, the surface marker of M2 macrophages, were significantly reduced (all P<0.05). Conclusions: IL-34 expression is increased in liver tissues of PBC patients and animals. It might reduce the portal area inflammation and bile duct damage via modulating cytokines expression and driving macrophages polarization to the M2 phenotype. IL-34 might act as a self-rescue factor which negatively regulates hepatic immune microenvironment and prevents disease progression.