Macrophages contribute to liver repair after monocrotaline-induced liver injury via SDF-1/CXCR4.

Monocrotaline (MCT) administration induces liver injury in rodents that mimics the pathology of human sinusoidal obstruction syndrome. MCT-induced SOS models are used to investigate the mechanism of injury and optimize treatment strategies. However, the processes underlying liver repair are largely unknown. Specifically, the role of macrophages, the key drivers of liver repair, has not been elucidated. The current study aimed to examine the role of macrophages in the repair of MCT-induced liver injury in male C57/BL6 mice. Maximal liver injury occurred at 48 h post-MCT treatment, followed by repair at 120 h post-treatment. Immunofluorescence analysis revealed that CD68 macrophages were recruited to the injured regions after MCT treatment. This was associated with the decreased expression of genes related to a pro-inflammatory macrophage phenotype and the increased expression of those associated with a reparative macrophage phenotype during the repair phase. The results also revealed that stromal cell-derived factor-1 (SDF-1) and its receptor C-X-C chemokine receptor-4 (CXCR4) were upregulated, and CD68 macrophages were co-localized with CXCR4 expression. Treatment of mice with AMD3100, a CXCR4 antagonist, delayed liver repair and increased the expression of genes related to a pro-inflammatory macrophage phenotype. In contrast, SDF-1 treatment stimulated liver repair and increased the expression of genes related to a reparative macrophage phenotype. The results suggested that macrophages accumulate in the liver and repair damaged tissue after MCT treatment, and that the SDF-1-CXCR4 axis is involved in this process.