p16Ink4a-positive hepatocytes accumulate in zone 3 during CCl4-induced liver injury, exhibit senescent characteristics, drive liver fibrosis through activation of the LIFR signaling pathway via CTF1/LIF ligands, and their selective elimination ameliorates fibrosis through suppression of hepatic stellate cell activation.
Key Findings
Background
p16Ink4a-positive hepatocyte (p16h) populations correlate with severity of fibrosis in human cirrhotic patients.
A 'robust correlation' was observed between the severity of fibrosis in human cirrhotic patients and the population of hepatocytes expressing elevated levels of p16Ink4a.
This correlation in human patients served as the initial observation motivating the study's mechanistic investigations.
p16h hepatocytes were proposed as potential 'initiators of fibrogenic processes in response to liver injury' based on this human data.
Results
p16h hepatocytes accumulate specifically in zone 3 of the liver in the CCl4-induced hepatitis model.
A CCl4-induced hepatitis model was employed to promote fibrogenic processes.
p16h hepatocytes were observed to accumulate in zone 3 of the liver following CCl4 treatment.
These p16h cells manifested 'numerous senescent characteristics' upon accumulation.
Results
Accumulation of p16h hepatocytes strongly correlates with the severity of liver fibrosis in the CCl4 model.
The accumulation of p16h cells was 'strongly correlated with the severity of liver fibrosis' in the CCl4-induced model.
This finding paralleled the correlation observed in human cirrhotic patient data.
The senescent characteristics of p16h hepatocytes were associated with their pro-fibrogenic role.
Results
Selective elimination of p16h hepatocytes ameliorates CCl4-induced liver fibrosis.
Selective elimination of p16h hepatocytes was shown to ameliorate CCl4-induced liver fibrosis.
The amelioration of fibrosis occurred 'presumably through the suppression of hepatic stellate cell activation.'
This finding establishes a causal role for p16h hepatocytes in driving fibrosis rather than merely correlating with it.
Results
Single-cell transcriptomic analysis revealed that murine and human hepatocytes upregulate CTF1 or LIF, ligands of the LIFR signaling pathway, in the context of senescence.
Single-cell transcriptomic analysis was conducted on both murine and human hepatocytes.
Senescent hepatocytes upregulated Ctf1 (cardiotrophin-1) or Lif (leukemia inhibitory factor), both ligands of the LIFR signaling pathway.
This finding identified the LIFR family pathway as a key senescence-associated secretory mechanism in hepatocytes.
Both murine and human data were consistent in showing upregulation of these LIFR ligands.
Results
Administration of LIFR ligands enhances phosphorylation of STAT3, and LIFR inhibition rescues the fibrogenic phenotype in hepatic stellate cells induced by senescent hepatocyte secreted factors.
Administration of LIFR ligands (CTF1 or LIF) was demonstrated to enhance phosphorylation of STAT3.
A LIFR inhibitor 'rescued the fibrogenic phenotype in hepatic stellate cells induced by secreted factors from senescent hepatocytes.'
This identifies the LIFR-STAT3 signaling axis as the mechanistic link between senescent hepatocytes and hepatic stellate cell activation.
The finding offers 'potential therapeutic insights for the management of liver fibrosis.'