Transforming growth factor-beta 1 protein, proliferation and apoptosis of oval cells in acetylaminofluorene-induced rat liver regeneration

Administering of 2-acetylaminofluorene (2-AAF) before a two-thirds partial hepatectomy (PHx) results in suppression of hepatocyte proliferation and st imulation of oval cell proliferation, The objectives of this study was to e xamine the oval cell behaviour and associated transforming growth factor-be ta 1 (TGF-beta 1) protein expression by combining 2-AAF with selective hepa tic damage caused by PHx. We also studied the temporal relationship between TGF-beta 1 expression, and proliferation and apoptosis of oval cells. Oval cells emerged from the portal areas and became more numerous with time fan ning out into the periportal and midzonal hepatic parenchyma, Both smooth m uscle actin (SMA) and TGF-beta 1 immunostain revealed that TGF-beta 1-posit ive cells were SMA-positive hepatic stellate cells (HSCs). Coinciding with the proliferation of oval cells, an increase expression of TGF-beta 1 produ ced by SMA-positive HSCs was observed, thereafter apoptosis of oval cells r eached its peak. This result implicated that TGF-beta 1 produced by HSCs is intimately associated with proliferation and apoptosis of oval cells, and plays a role in the cessation of oval cell activation and remodeling of liv er parenchyma in 2-AAF induced liver regeneration.