| 【Background and aim】Liver regeneration（LR）refers to the process by which the liver regains its original size after suffering from injury or resection.During LR,the remaining hepatocytes are stimulated by various signaling pathways and proliferate rapidly.LR is relevant in clinical scenarios.For example,LR happens after hepatectomy of liver cancer and the living donor liver transplant.However,unsuccessful LR in these settings results in complications such as small for size syndrome（SFSS）,which deteriorates the prognosis of patients.Therefore,an incisive investigation of the LR process is clinical significant.Translationally controlled tumor protein（TCTP）,which is also called as P23,P21,fortilin,or histamine releasing factor（HRF）,is highly-conserved and extensively-expressed among various kinds of cells and tissues.TCTP is a multifunctional protein,which plays a role in cell growth,development,apoptosis,malignant transformation DNA repair,immune response and anaphylactic reaction.One of the most important functions of TCTP is its proliferation promoting activity.It has been reported that the downregulation of Drosophila TCTP（d TCTP）decreases the number of proliferative cell and organ size.Moreover,TCTP’s proliferation-regulation activity remains conserved among different kinds of species.It has been documented that d TCTP knockout-induced cell proliferation defects can be rescued by both Arabidopsis TCTP（At TCTP）and human TCTP（h TCTP）.Despite very few studies demonstrated that TCTP is involved in LR,the specific role and underlying mechanism by which TCTP regulates LR have not been illustrated at present.Therefore,the present study aims to determine the role and mechanism of TCTP in LR.【Methods】1.First,wild-type C57BL/6 mice were subjected to a 70%partial hepatectomy（PHx）to induce LR.The dynamic changes of TCTP were measured by real-time quantitative PCR,Western Blot and immunohistochemical staining.2.PHx was performed on TCTP+/-（homozygous is embryonically lethal）and TCTP+/+mice.The effect of TCTP on LR was preliminarily studied by comparing some indicators of LR between the two kinds of mice,such as the recovery of liver weight/body weight ratio and liver function,hepatocyte proliferation,the expression of proliferation-related molecular,lipid metabolism and lymphoid infiltration.3.RNA sequencing was used to initially explore the pathways through which TCTP affects LR.Thereafter,in vitro LR model,TCTP knock-down hepatocytes,mass spectrum,immunofluorescence co-localization,co-immunoprecipitation and other analysis were used to determine the pathways involved in TCTP’s impact on LR.4.To preliminarily observe the relationship between serum TCTP and human LR,ELISA was used to measure the changes of serum TCTP in patients with hepatic hemangioma after hepatectomy,and the correlation analysis between the changes of TCTP and the changes of liver function indexes was conducted.【Results】1.TCTP mRNA level began to rise at 2 hours post-PHx,peaked at 12 hours,and then dropped to its horizontal level at 48 hours.However,TCTP protein started to ascend at 12hours post-PHx,reached its peak at 48 hours,and descended to its baseline in 96 hours.2.The liver-to-body weight ratio and liver function of TCTP+/+mice recovered in about one week post-PHx.However,the recovery of liver-to-body weight ratio and liver function of TCTP+/-mice were hampered during LR.Hepatocytes in the control group entered the cell cycle and proliferated rapidly on post-operative day two（POD2）,whereas hepatocytes in TCTP+/-mice showed significant proliferation on POD4,and the proliferation intensity was lower than that in the control group.The mRNA levels of IL-6,TNF-α,HGF,cyclinD1 and cyclinA2,which are associated with cell cycle initiation,in the liver of TCTP+/-mice were significantly lower than those in the control group.The LR of TCTP+/-mice was accompanied by abnormal lipid metabolism and lymphocyte infiltration.3.Results of RNA sequencing indicated that TCTP can regulate the PI3K/AKT signaling pathway.Results of mass spectrum,immunofluorescence co-localization,co-immunoprecipitation and other analysis showed that TCTP could interact with mTORC2,one of the upstream molecules of AKT.Therefore,this study demonstrated that the TCTP/mTORC2/AKT pathway can promote LR.4.During the first 5 days after human hepatectomy,the level of serum TCTP continued to rise.In addition,the rising speed of TCTP was positively correlated with the recovery speed of ALT and AST,but not with the recovery speed of ALB.【Conclusions】1.TCTP was highly induced at the early state of LR.2.TCTP affects the recovery of liver-to-body weight ratio and liver function,cell cycle initiation,lipid metabolism and inflammatory response.3.TCTP regulates the phosphorylation of AKT by interacting with mTORC2,which subsequently promotes LR.4.Serum TCTP was increased and correlated with ALT and AST recovery during LR in humans. |
