Involvement of transforming growth factor-beta in the expression of gicerin, a cell adhesion molecule, in the regeneration of hepatocytes.

Gicerin, an Ig-superfamily cell adhesion molecule, appears transiently in embryonic tissues including those of the nervous, urogenital, respiratory and digestive systems, and it promotes neurite extension, cell migration and epithelialization through its cell adhesive activities. In addition, gicerin also reappears in regenerating tissue after suffering either a traumatic injury or a viral infection. In the present study, we examined the expression pattern of gicerin in the regeneration of hepatocytes. Immunohistochemically, gicerin protein appeared in the regenerating hepatocytes of carbon tetrachloride (CCl4)-induced acute hepatitis, while it was scarcely expressed in the hepatocytes of normal mouse liver. Real-time PCR revealed the up-regulation of gicerin transcription in the regenerating process of CCl4-induced hepatitis. The expression of transforming growth factor (TGF)-beta1 was also increased during the regeneration. Furthermore, the gicerin mRNA expression increased during the process of an in vitro hepatocyte regeneration model using mouse primary hepatocytes and hepa 1-6 cells. To note, the mRNA levels of gicerin in these cells were enhanced by the presence of TGF-beta1. Collectively, these findings suggest that TGF-beta1 may therefore regulate gicerin expression in hepatocytes leading to liver regeneration by cell-cell or cell-ECM interactions.