Review: regulation of liver regeneration by pro-inflammatory cytokines

The liver has tremendous regenerative capacity. This distinguishes it from other vital organs (e.g. the brain, heart and lungs) that cannot replace functional tissue once it has been destroyed. Although hepatocytes rarely proliferate in the healthy adult liver, virtually all surviving hepatocytes replicate at least once after 70% partial hepatectomy. Therefore, partial liver resection has been used to characterize mechanisms that regulate liver regeneration. Residual hepatocytes up-regulate both proliferative and liver-specific gene expression in order to preserve tissue specific function. In addition, hepatocyte proliferation is tightly co-ordinated to complement regenerative responses in hepatic non-parenchymal cells (e.g. endothelia, biliary epithelia, stellate and Kupffer cells), so that the entire organ can be reconstituted within days. Studies with neutralizing antibodies to tumour necrosis factor-alpha (TNF) clearly demonstrate that, after partial hepatectomy, TNF promotes liver cell proliferation. The present review focuses on the regulation of the hepatocyte proliferative response by pro-inflammatory cytokines.