Fas and Fas-ligand Expression in Hepatocytes during Regeneration after Partial Hepatectomy in Rats

The regenerative response after partial hepatectomy stops suddenly when liver mass has been restored. In this resulation, arrest of hepatocyte proliferation in addition to elimination of excess hepatocytes would appear to be necessary. To determine whether excess hepatocytes are eliminated by Fas-mediated apoptosis, we examined expression of Has and Fas-ligand in hepatocytes using immunohistochemical staining ofter 70% partial hepatectomy. In addition, apoptotic hepatocytes were identified using in situ DNA end-labeling. Fas-positive, Fas-ligand-positive, and apoptotic hepatocytes ware detected only rarely in the uninjured liver. Fas-positive hepatocytes increased somewhat on day 3 follwing hepatectomy and signficantly increased somewhat on day 4, markedly on day 6, and then desreased on day 14. According to these findings, apoptosis began to occur in hepatocytes 1 day after initial expression of Fas and its ligand. These apoptotic changes may be explained by the consideration that some abruptly regenerated hepatocytes of Fas and its ligand may indicate paracrine or autocrine mechanisms of cell elimination executed by the hepatocytes themselves.

Fas

Fas-ligand

Apoptosis

Hepatocyte

Liver regeneration