Expression of placental growth factor in regenerating livers after partial hepatectomy in the rat

Background/aims Placental growth factor (PIGF) is known for its role in pathological conditions to protect parenchymal cells of different organs from injury, whereas its presence in the liver and its potential importance in stimulating liver regeneration has never been described. This was investigated in this study using a rat model of partial hepatectomy (PH). Methods The rat model of 70, 80, and 90% PH was used. Liver samples were taken peroperatively, 1 h, 1, 2, 3, and 7 days after surgery. Liver regeneration was evaluated by liver weight/body weight ratio, liver regeneration rate (%), and proliferating cell marker Ki67. The expression of PIGF, vascular endothelial growth factor (VEGF), VEGF receptor 1 (Flt-1 ), VEGF receptor 2 (Flk-1 and hypoxia inducible factor-1α mRNA was measured by quantitative real-time PCR and localized by immunohistochemistry. Results The mRNA expression of PIGF was upregulated immediately after PH. Compared with 70 and 80% PH groups, the 90% PH group had a significantly lower PIGF and hypoxia inducible factor-1α. mRNA expression, in parallel to a delayed liver weight/body weight ratio recovery. Only little differences were observed in VEGF, Flt-1, and Flk-1 mRNA expression among the PH groups. Conclusion This study shows for the first time the PIGF upregulation in regenerating livers, which is related to hypoxia stimulation and liver growth. The swift PIGF upregulation immediately after PH may indicate an important role for the PIGF/Flt-1 pathway in the early stage of liver regeneration.