Adipose Tissue Macrophages in Metabolic Dysfunction-Associated Steatohepatitis Secrete Extracellular Vesicles That Activate Liver Fibrosis in Obese Male Mice.

BACKGROUND & AIMS: Given the need for effective interventions in metabolic dysfunction-associated steatohepatitis (MASH), understanding the role of adipose tissue macrophage (ATM)-derived small extracellular vesicles (sEVs) is important. We aimed to evaluate the contribution of MASH-ATM-sEVs to the development of liver fibrosis in obese male mice.

METHODS

Using flow cytometry and nanoparticle tracking analysis, we characterized MASH-ATMs and their secreted sEVs. We assessed the fibrogenic effects of sEVs from MASH-ATMs or anti-inflammatory macrophages on stellate cells in vitro and in mice in vivo. In addition, we isolated Dicer knockdown microRNA (miRNA)-depleted sEVs from MASH-ATMs and cotreated stellate cells with MASH-ATM-sEVs and miR-155 or miR-34a antagomirs.

RESULTS

MASH-ATMs exhibited a pro-inflammatory and lipid-associated phenotype, secreting sEVs enriched in the fibrogenic miRNAs, miR-155 and miR-34a, which also down-regulate Pparg. In vitro, MASH-ATM-sEVs induced hepatic stellate cell activation and fibrogenesis and exacerbated liver fibrosis when administered to obese mice. In addition, anti-inflammatory macrophage sEVs mitigated fibrosis both in vitro and in vivo. miRNA-free Dicer knockdown-MASH-ATM-sEVs were without effects and cotreatment with miR-155/miR-34a antagomirs blocked the effects of MASH-ATM-sEVs to induce hepatic stellate cell activation.

CONCLUSIONS

This study demonstrated the role of MASH-ATM-sEVs in promoting liver fibrosis in obesity. Identification of the fibrogenic miRs, miR-155, and miR-34a, within MASH-ATM-sEVs, highlights the mechanistic importance of extrahepatic signals in MASH. These findings showed the therapeutic potential of modulating macrophage phenotypes and their sEV cargo to ameliorate MASH.