# p16Ink4a‐Positive Hepatocytes Drive Liver Fibrosis Through Activation of LIFR Family Pathway

## TL;DR

Older livers show more fibrosis, and a type of aged liver cell called p16high hepatocytes seems to drive this process by activating a specific signaling pathway.

## Contribution

The study identifies p16high hepatocytes as key drivers of liver fibrosis through the LIFR signaling pathway.

## Key findings

- p16high hepatocytes accumulate in zone 3 and correlate with fibrosis severity.
- Eliminating p16high hepatocytes reduces liver fibrosis by suppressing stellate cell activation.
- CTF1/LIF from p16high hepatocytes activate the LIFR pathway, promoting fibrosis.

## Abstract

As organs undergo the process of aging, they exhibit signs of progressive fibrosis, a hallmark of aging that is observed in various organs, including the liver, kidneys, and lungs. Liver fibrosis is a particularly deleterious outcome of the healing processes that occur during the repair of chronic liver injury. It is widely accepted that the majority of these injuries are initially triggered by hepatocytes. Indeed, elderly patients have been shown to be more prone to developing liver fibrosis following hepatic injury. However, the mechanisms by which aging promotes fibrotic processes remain to be elucidated. The preceding observation, indicating a robust correlation between the severity of fibrosis in human cirrhotic patients and the population of hepatocytes expressing elevated levels of p16Ink4a (p16h), proposes that p16h hepatocytes might serve as initiators of fibrogenic processes in response to liver injury. In this study, we employed a CCl4‐induced hepatitis model to promote a fibrogenic process and observed the accumulation of p16h hepatocytes in zone 3. These p16h cells manifest numerous senescent characteristics, and their accumulation has been strongly correlated with the severity of liver fibrosis. Selective elimination of p16h hepatocytes has been shown to ameliorate CCl4‐induced liver fibrosis, presumably through the suppression of hepatic stellate cell activation. Single‐cell transcriptomic analysis revealed that murine and human hepatocytes up‐regulated Ctf1 or Lif, the ligands of the LIFR signaling pathway. The administration of LIFR ligands has been demonstrated to enhance the phosphorylation of STAT3, and the LIFR inhibitor rescued the fibrogenic phenotype in hepatic stellate cells induced by secreted factors from senescent hepatocytes. This finding offers potential therapeutic insights for the management of liver fibrosis.

This study found that, following the long‐term CCl4 treatment, p16high hepatocytes appeared in zone 3, spatially co‐localizing with fibrotic areas. A specific cluster of p16high hepatocytes upregulated CTF1/LIF expression which induced HSC activation and further liver fibrosis, as revealed by single cell transcriptomic analysis. The transcriptomic signatures of mouse p16high hepatocytes exhibited a significantly enrichment in a subset of human hepatocytes derived from liver cirrhotic patients, as opposed to those from healthy donors.