Proteomic analysis of the regenerating liver following 2/3 partial hepatectomy in rats

BACKGROUND: Liver regeneration (LR) after 2/3 partial hepatectomy (PH) is one of the most studied models of cell, organ, and tissue regeneration. Although the transcriptional profile analysis of regenerating liver has been carried out by many reserachers, the dynamic protein expression profile during LR has been rarely reported up to date. Therefore, this study aims to detect the global proteomic profile of the regenerating rat liver following 2/3 hepatectomy, thereby gaining some insights into hepatic regeneration mechanism. RESULTS: Protein samples extracted from the sham-operated and the regenerating rat livers at 6, 12, 24, 72, 120 and 168 h after PH were separated by IEF/SDS-PAGE and then analyzed by MALDI-TOF/TOF mass spectrometry. Compared to sham-operated groups, there were totally 220 differentially expressed proteins (including 156 up-regulated, 62 down-regulated, and 2 up/down-regulated ones) identified in the regenerating rat livers, and most of them have not been previously related to liver regeneration. According to the expression pattern analysis combined with gene functional analysis, it showed that lipid and carbohydrate metabolism were enhanced at the early phase of LR and continue throughout the regeneration process. Ingenuity Pathway Analysis indicated that YWHAE protein (one of members of the 14-3-3 protein family) was located at the center of pathway networks at all the timepoints after 2/3 hepatectomy under our experimental conditions, maybe suggesting a central role of this protein in regulating liver regeneration. Additionally, we also revealed the role of Cdc42 (cell division cycle 42) in the termination of LR. CONCLUSIONS: For the first time, our proteomic analysis suggested an important role of YWHAE and pathway mediated by this protein in liver regeneration, which might be helpful in expanding our understanding of LR amd unraveling the mechanisms of LR.

Alterations in DNA repair gene expression and their possible regulation in rat-liver regeneration

Rapidly proliferating tissue may require enhanced DNA repair capacity in order to avoid fixation of promutagenic DNA lesions to mutations. Partial hepatectomy (PH) triggers cell proliferation during liver regeneration (LR). However, little is known on how DNA repair genes change and how they are regulated at the transcriptional level during LR. In the present study, the Rat Genome 230 2.0 array was used to detect the expression profiles of DNA repair genes during LR, and differential expression of selected genes was confirmed by real-time RT-PCR. 69 DNA repair genes were found to be associated with LR, more than half of which distributed in a cluster characterized by a gradual increase at 24-72h and then returning to normal. The expression of base excision repair- and transcription-coupled repair-related genes was enhanced in the early and intermediate phases of LR, whereas the expression of genes related to HR, NHEJ and DNA cross-link repair, as well as DNA polymerases and related accessory factors, and editing or processing nucleases, were mainly enhanced in the intermediate phase. The expression changes of genes in DNA damage response were complicated throughout the whole LR. Our data also suggest that the expression of most DNA repair genes may be regulated by the cell cycle during LR.