Abstract: Objective To observe the effects of macrophage polarization supernatant on the activation of cardiac fibroblasts. Methods Bone marrow cells and cardiac fibroblasts of SD rats were extracted. Bone marrow cells were induced to M1 and M2 by treating with macrophage colony-stimulating factor (M-CSF), and cells were divided into M0 group (no stimulating factor), M1 group (100 μg/L LPS+10 μg/L INF-γ) and M2 group (20 μg/L IL-4). Different macrophages were co-cultured with cardiac fibroblasts, and different macrophage supernatants were collected to culture with cardiac fibroblasts. Immunofluorescence was performed to examine the fibrotic protein expression in cardiac fibroblasts. The mRNA levels of macrophage-specific molecules, fibrosis-related genes and signaling pathways were tested by real-time PCR. The fibrosis-related proteins and the activation of TGFβR and PDGFRs signal pathways were detected by Western blot assay.Results After treatment with M-CSF and stimulating factors, M1 macrophages and M2 macrophages were induced. Compared with the M0 group, the mRNA levels of Col1a1 and Col3a1 and the protein level of α-SMA were significantly decreased in the cardiac fibroblasts treated by the supernatant of M1 macrophage group (P＜0.05), while the mRNA levels of Col1a1 and Col3a1 and the protein levels of CCN2 and α-SMA were significantly increased in the cardiac fibroblasts treated by the supernatant of M2 macrophage group (P＜0.05).The phosphorylated protein level of PDGFRβ was significantly lower in the cardiac fibroblasts treated by the supernatant of M1 macrophage group than those in the cardiac fibroblasts treated by the supernatant of M0 macrophage group (P＜0.01), while phosphorylated PDGFRβ protein levels were significantly higher in the cardiac fibroblasts treated by the supernatant of M2 macrophage group than those in the cardiac fibroblasts treated by the supernatant of M0 macrophage group (P＜0.05). Conclusion M1 macrophage supernatant can inhibit the activation of cardiac fibroblasts, while M2 macrophage supernatant can activate cardiac fibroblasts. The inhibitory effect of M1 macrophages on fibrosis may be related to restraining the activation of PDGFRβ pathway.

Key words: fibrosis, heart, fibroblasts, macrophages, receptor, platelet-derived growth factor beta