Introdution: Acute-on-chronic liver failure (ACLF) is an acutely decompensated cirrhosis syndrome with a high short-term mortality rate. In China, hepatitis B virus (HBV) infection is the main cause of chronic liver disease (CLD). Immune dysregulation is thought to be involved in the progression from CLD to ACLF, which involves systemic inflammation and exacerbation of the innate immune system resulting in multiple organ failures and immunosuppression. Macrophages perform as one of the most important undertakers of hepatic innate immunity, but the understanding of the roles of macrophages in the pathogenesis and immunoregulation of ALCF is limited. Here, we explored the macrophage remodeling during CLD-ACLF process with the single-cell RNA sequencing (scRNA-seq) technology.

Methods: 4738 intrahepatic macrophages from 2 healthy donors (HDs), 5 CLD and 5 ACLF patients as well as 1732 peripheral blood monocytes from 2 ACLF and 1 CLD patients were analyzed by scRNA-seq. Intrahepatic macrophage sub-populations derived from scRNA-seq were confirmed by immunohistochemistry (IHC) and immunofluorescence (IF). Fatty acid (FA) metabonomic was used to qualitative and quantitative analyzed the intrahepatic free FA during ACLF.

Results: ACLF patients exhibited more intrahepatic macrophages than those of CLD patients and HDs. Increase of APOE+TREM2+ anti-inflammation macrophage subpopulation and exhaustion of SPP1+ M2-like macrophage subpopulation and Kupffer cells (KCs) were the main features of intrahepatic macrophages of ACLF patients. Not the proliferation of the intrahepatic macrophages but the monocyte-derived macrophages (MoMFs) migration into liver was the reason for intrahepatic macrophages expansion in ACLF. Multiple FAs were increased in ACLF liver, which resulted in pro-inflammatory macrophages transformation into anti-inflammatory macrophages and contributed to immunosuppression during ACLF.

Conclusions: During ACLF, KCs were replaced by the MoMFs. Intrahepatic macrophages were transformed from pro-inflammatory states to anti-inflammatory states, which was regulated by increased free FAs in the ACLF liver. TREM2 and intrahepatic FAs may be the potential target for ACLF treatment.