Analyses of Jagged1 and Notch1 in Hepatocyte Culture: Differentiation and Proliferation Conditions affect receptor and ligand of Notch Pathway.

The Jagged/Notch signaling pathway controls cell fate determination and differentiation, and its dysfunction is associated with human pathologies, including Alagille syndrome. Our previous studies have shown that Notch‐ and Jagged ‐ siRNA treated rat liver reduces the ability in proliferation and regeneration following partial hepatectomy. To determine the putative role of the transmembrane receptor Notch and its ligand Jagged in cell‐cell interaction and proliferation of hepatocytes, we analyzed expression of Jagged1 and Notch1 in the primary cultures of rat hepatocytes. Rat hepatocytes were cultured in the presence or absence of HGF, EGF, TGFalpha, Dexamethason or Matrigel. Real‐time PCR was performed to detect levels of Notch‐1, Jagged‐1 and target genes like Hes‐1. Protein levels of Notch and Jagged were detected by Western Blot analyses. Our results show that expression of receptor, ligand and target gene of Notch‐pathway depend on different culture conditions. Stimulating hepatocytes in proliferation increases expression of Notch, Jagged or Hes, whereas differentiated hepatocytes express low levels of Jagged and HES. Interestingly, there is a clear difference of receptor and ligand expression in normal liver and fresh isolated hepatocytes. The above results indicate that cell‐cell interaction via Jagged/Notch signaling pathway varies as a result of cell proliferation and differentiation. We have shown that expression of Notch pathway players depend on factors, which are involved in liver regeneration. This supports our hypothesis that this pathway can regulate differentiation and proliferation of hepatocytes during liver regeneration.