Liver Regeneration: Polyploidy and Cellular Senescence as Potential Regulators

The liver is a highly versatile and resilient organ that is crucial for metabolism, detoxification, digestion, and immune regulation. Its remarkable regenerative capacity is driven primarily by two key cellular processes: hepatocyte polyploidy and cellular senescence. This review explores the complex roles of polyploidy, in which hepatocytes possess multiple chromosome sets, and senescence, characterized by irreversible cell cycle arrest, in maintaining liver homeostasis and facilitating regeneration. Polyploid hepatocytes increase genetic and metabolic diversity, enabling the liver to withstand stress and recover from injury through mechanisms such as compensatory regeneration, depolyploidization, and the fusion of extrinsic stem cells. Concurrently, cellular senescence acts as a protective barrier against uncontrolled cell proliferation and genomic instability while also promoting tissue repair via the senescence-associated secretory phenotype (SASP). The interplay between polyploidy and senescence is regulated by critical molecular pathways, including the Hippo, PI3K/Akt, and p53 signaling pathways, which balance cell proliferation, differentiation, and apoptosis. Additionally, this review discusses the therapeutic potential of targeting these processes to increase liver regeneration, prevent fibrosis, and reduce the risk of hepatocellular carcinoma (HCC). Emerging strategies such as senolytic drugs, stem cell therapies, and cytokine modulation offer promising avenues for treating chronic liver diseases. However, challenges remain in fully understanding the functional distinctions between diploid and polyploid hepatocytes and managing the dual roles of senescence. Future research should focus on molecular insights and targeted interventions to optimize liver health and regenerative outcomes.