Minimizing the risk of small-for-size syndrome after liver surgery

Gut Microbiota and Liver Regeneration: A Synthesis of Evidence on Structural Changes and Physiological Mechanisms

Liver regeneration (LR) is a unique biological process with the ability to restore up to 70% of the organ. This allows for the preservation of liver resections for various liver tumors and for living donor liver transplantation (LDLT). However, in some cases, LR is insufficient and interventions that can improve LR are urgently needed. Gut microbiota (GM) is one of the factors influencing LR, as the liver and intestine are intimately connected through the gut-liver axis. Thus, healthy GM facilitates normal LR, whereas dysbiosis leads to impaired LR due to imbalance of bile acids, inflammatory cytokines, microbial metabolites, signaling pathways, etc. Therefore, GM can be considered as a new possible therapeutic target to improve LR. In this review, we critically observe the current knowledge about the influence of gut microbiota (GM) on liver regeneration (LR) and the possibility to improve this process, which may reduce complication and mortality rates after liver surgery. Although much research has been done on this topic, more clinical trials and systemic reviews are urgently needed to move this type of intervention from the experimental phase to the clinical field.

Acute liver steatosis signals the chromatin for regeneration via MIER1

During liver regeneration, especially after a hepatectomy, hepatocytes experience significant lipid accumulation. These transiently accumulated lipids are generally believed to provide substrates for energy supply or membrane biomaterials for newly generated hepatocytes. Remarkably, a recent study found that acute lipid accumulation during regeneration can act as a signal for chromatin remodeling to regulate regeneration. Chen, Y.H., et al. identified MIER1 (mesoderm induction early response protein 1) as a crucial inhibitor of liver regeneration through in vivo CRISPR screening. MIER1 binds to and restrains cell cycle genes' expression. During liver regeneration, acute lipid accumulation suppresses MIER1 translation via the EIF2S pathway, resulting in transient down-regulation of MIER1 protein, which promotes cell cycle gene expression and liver regeneration. Interestingly, the researchers also found that the dynamic regulation of MIER1 was impaired in fatty and aging livers with chronic steatosis, while of knockout of MIER1 in these animals improved their regenerative capacity. In conclusion, this study provides valuable insights into the complex mechanisms underlying liver regeneration and highlights the potential therapeutic applications of targeting MIER1 for improving liver regeneration in disease states associated with impaired lipid homeostasis.

Ten-eleven translocation-2-mediated macrophage activation promotes liver regeneration

BACKGROUND

The remarkable regenerative capacity of the liver enables recovery after radical Hepatocellular carcinoma (HCC) resection. After resection, macrophages secrete interleukin 6 and hepatocyte growth factors to promote liver regeneration. Ten-eleven translocation-2 (Tet2) DNA dioxygenase regulates pro-inflammatory factor secretion in macrophages. In this study, we explored the role of Tet2 in macrophages and its function independent of its enzymatic activity in liver regeneration.

METHODS

The model of liver regeneration after 70% partial hepatectomy (PHx) is a classic universal model for studying reparative processes in the liver. Mice were euthanized at 0, 24, and 48 h after PHx. Enzyme-linked immunosorbent assays, quantitative reverse transcription-polymerase chain reaction, western blotting, immunofluorescence analysis, and flow cytometry were performed to explore immune cell infiltration and liver regenerative capability. Molecular dynamics simulations were performed to study the interaction between Tet2 and signal transducer and activator of transcription 1 (Stat1).

RESULTS

Tet2 in macrophages negatively regulated liver regeneration in the partial hepatectomy mice model. Tet2 interacted with Stat1, inhibiting the expression of proinflammatory factors and suppressing liver regeneration. The Tet2 inhibitor attenuated the interaction between Stat1 and Tet2, enhanced Stat1 phosphorylation, and promoted hepatocyte proliferation. The proliferative function of the Tet2 inhibitor relied on macrophages and did not affect hepatocytes directly.

CONCLUSION

Our findings underscore that Tet2 in macrophages negatively regulates liver regeneration by interacting with Stat1. Targeting Tet2 in macrophages promotes liver regeneration and function after a hepatectomy, presenting a novel target to promote liver regeneration and function.