[Characterization of liver macrophage subsets in different mouse models of metabolic associated steatohepatitis]

Objective: To characterize the distribution of liver macrophage subsets in metabolic associated steatohepatitis (MASH) mouse models induced by methionine choline-deficient diet (MCD) and a high-fat, high-fructose, and high-cholesterol diet (HFFC), in order to provide a research basis for subsequent macrophage subset studies. Methods: MASH mouse models were induced by feeding an MCD and HFFC diet for four and sixteen weeks, respectively. Real-time fluorescence quantitative reverse transcription PCR (RT qPCR) was used to detect changes in liver inflammation and fat metabolism-related genes in MASH mice. Liver macrophages were isolated by perfusing and digesting mouse livers. Flow cytometry was used to analyze the subpopulations of liver macrophage subsets. Data between different groups was compared using t-test or one-way analysis of variance. Results: The MCD-fed diet led to the inhibition of liver fat synthesis in mice, while the HFFC-fed diet had increased liver fat synthesis in mice. However, both diets led to a decrease in embryonic Kupffer cells (EmKC) that were derived from the livers of mice. The proportion of EmKC in liver macrophages was significantly lower in the HFFC group (73.74%±7.96%) and the MCD group (39.93%±9.03%) than in the normal diet (ND) group (95.14%±1.09%). The proportion of mononuclear macrophages (MDM) in liver macrophages was significantly increased in the HFFC group (19.26%±6.94%) and the MCD group (52.38%±8.38%) compared with the ND group (2.46%±0.53%). The MCD diet led to a greater loss of EmKC and increased recruitment of monocytes. Monocyte-derived Kupffer cells (MoKC) were the main MDM subset in the livers of HFFC diet-fed mice, while lipid-associated macrophages (LAM) and their precursor CCR2+lipid-associated macrophages (C-LAM) were the main MDM subset in MCD diet-fed mice. Conclusion: The recruitment of MDM and the loss of liver EmKC can be induced by both MCD and HFFC diets; however, the composition of MDM subsets varies. The major MDM subset in the HFFC group was MoKC, while the primary MDM subsets in the MCD group were LAM and C-LAM.