Abstract: Objective To explore the correlation between the number of macrophages and neutrophil extra cellular traps (NETs) in thrombi of patients with acute ischemic stroke (AIS), and to compare the NET-degrading and clearing abilities of macrophages in different polarization states. Methods Immunohistochemical staining was performed to detect CD16⁺ macrophages, CD163⁺ macrophages and citrullinated histone 3(CitH3) in AIS thrombi. Thrombi were co-cultured with macrophages, and the CitH3 concentration in the supernatant was measured to evaluate the NET-degrading and clearing capacities of different macrophage subtypes. Results All 30 thrombi showed positive expression of CD16 macrophages, CD163 macrophages and CitH3. The numbers of both CD16⁺ and CD163⁺ macrophages were positively correlated with the percentage of CitH3-positive area (CD16: r=0.538, P＜0.05; CD163: r=0.641, P＜0.001). After co-culture, the CitH3 concentration was significantly lower in both the M1- and M2- macrophage groups than in the blank control group (M1: t=-3.981, P＜0.001; M2: t=-2.057, P＜0.05). The concentration of CitH3 was lower in the M1 group than in the M2 group (t=-2.125, P＜0.05). Conclusions Both M1 and M2 macrophage infiltration are correlated with NET content in AIS thrombi, and their abilities to clear and degrade NETs are different.

Key words: acute ischemic stroke, neutrophil extra cellular traps, macrophages, thrombus