ABSTRACT
<p><b>OBJECTIVE</b>To investigate the changes of oval cell proliferation rate in the rat 2-acetylaminofluorene/partial hepatectomy (2-AAF/PH) model.</p><p><b>METHODS</b>Livers were collected from 2-AAF/PH rats at different time points after hepatectomy. Paraffin sections were investigated by double immunofluorescent staining with confocal microscopy for oval cell marker epithelial cell adhesion molecule and proliferative index proliferating cell nuclear antigen, or epithelial cell adhesion molecule and alpha-smooth muscle actin. Deposition of matrix in liver tissue was detected by sirius red staining.</p><p><b>RESULTS</b>Response of ductular oval cells could be observed in portal area at 2 days after PH, and the number of oval cells reached its peak at 9 days and then gradually declined. Oval cell proliferation rate decreased from (91.3 +/- 1.6)% at 2 days after PH to (53.6 +/- 4.4)% at 12 days (P < 0.01). In addition, oval cells infiltrating into liver parenchyma were closely associated with activated hepatic stellate cells and extracellular matrix.</p><p><b>CONCLUSIONS</b>Oval cell proliferation rate starts decreasing before its number reaches a peak in 2-AAF/PH model. Hepatic stellate cells probably tightly regulate oval cell number through secreting several factors and producing extracellular matrix.</p>