OBJECTIVE To explore the ameliorative effect of ursolic acid on carbon tetrachloride-induced acute liver injury in mice,and the feasibility of multispectral optoacoustic tomography(MSOT)for characteristic structural and functional imaging of liver tissues.METHODS Kunming mice were randomly divided into the normal control group,model group,model+ursolic acid 30,60 mg·kg-1 groups and model+bifendate 5.625 mg·kg-1 group,with 14 mice in each.Each group was given the corresponding drug once daily for 7 days.An acute liver injury model was established in mice by intraperitoneal injection of 0.2％carbon tetrachloride in olive oil solution after the last administration.Blood was collected,liver tissues were taken 24 h after modeling,and the liver index was calculated,8 mice from each group and the levels of serum glutamic pyruciv transaminase(GPT)and glutamic oxaloacetic transaminase(GOT),as well as superoxide dismutase(SOD)activity and malondialdehyde(MDA)content in liver tissues were measured.The enzyme-linked immunosorbent assay(ELISA)method was used to detect the level ofα-glutathione S-transferase(α-GST)in serum.The histopathological changes of the liver were observed under a light microscope.The remaining 6 mice in each group underwent MSOT technique was used for characteristic structural and functional imaging of liver tissue.Levels of oxygenated hemoglobin(HbO2)and deoxygenated hemoglobin(Hb)were analyzed,oxygen saturation was calculated,and the extent of liver injury was assessed by examining the intrahepatic distribution of indocyanine green(ICG).RESULTS Compared with the normal group,the levels of GPT,GOT and α-GST in serum,content of MDA in liver tissues and the liver index in the model control group were significantly increased while the activity of SOD in liver tissues were significantly decreased.Compared with the model group,ursolic acid in each dose group significantly reduced the liver index of mice,lowered the serum levels of GPT and GOT as well as the level of α-GST,decreased the content of MDA in liver tissues,and elevated the activity of SOD in liver-injured mice.Hematoxylin-eosin staining showed that significant steatosis and hepatocyte necrosis and inflammatory cell infiltration in hepatocytes of mice in the model group.Ursolic acid significantly attenuated the degree of hepatocellular lesions and markedly reduced steatosis in mice.MSOT imaging showed that the HbO2 level and oxygen saturation were significantly lower while the Hb level was remarkably higher in the liver of mice in the model group.In each administration group,the level of HbO2 significantly increased,the level of Hb was significantly decreased,oxygen saturation was significantly increased in the liver of model mice and the accumulation of ICG dye probe was atten-uated in the body after hepatocyte injury.CONCLUSION Ursolic acid can elevate the hepatic oxygen saturation,improve the metabolism of ICG,reduce the degree of hepatic necrosis in mice,and help protect against carbon tetrachloride-induced hepatic injury in mice.The mechanism is probably related to the inhibition of oxidative stress.

OBJECTIVE To explore the ameliorative effect of ursolic acid on carbon tetrachloride-induced acute liver injury in mice,and the feasibility of multispectral optoacoustic tomography(MSOT)for characteristic structural and functional imaging of liver tissues.METHODS Kunming mice were randomly divided into the normal control group,model group,model+ursolic acid 30,60 mg·kg-1 groups and model+bifendate 5.625 mg·kg-1 group,with 14 mice in each.Each group was given the corresponding drug once daily for 7 days.An acute liver injury model was established in mice by intraperitoneal injection of 0.2％carbon tetrachloride in olive oil solution after the last administration.Blood was collected,liver tissues were taken 24 h after modeling,and the liver index was calculated,8 mice from each group and the levels of serum glutamic pyruciv transaminase(GPT)and glutamic oxaloacetic transaminase(GOT),as well as superoxide dismutase(SOD)activity and malondialdehyde(MDA)content in liver tissues were measured.The enzyme-linked immunosorbent assay(ELISA)method was used to detect the level ofα-glutathione S-transferase(α-GST)in serum.The histopathological changes of the liver were observed under a light microscope.The remaining 6 mice in each group underwent MSOT technique was used for characteristic structural and functional imaging of liver tissue.Levels of oxygenated hemoglobin(HbO2)and deoxygenated hemoglobin(Hb)were analyzed,oxygen saturation was calculated,and the extent of liver injury was assessed by examining the intrahepatic distribution of indocyanine green(ICG).RESULTS Compared with the normal group,the levels of GPT,GOT and α-GST in serum,content of MDA in liver tissues and the liver index in the model control group were significantly increased while the activity of SOD in liver tissues were significantly decreased.Compared with the model group,ursolic acid in each dose group significantly reduced the liver index of mice,lowered the serum levels of GPT and GOT as well as the level of α-GST,decreased the content of MDA in liver tissues,and elevated the activity of SOD in liver-injured mice.Hematoxylin-eosin staining showed that significant steatosis and hepatocyte necrosis and inflammatory cell infiltration in hepatocytes of mice in the model group.Ursolic acid significantly attenuated the degree of hepatocellular lesions and markedly reduced steatosis in mice.MSOT imaging showed that the HbO2 level and oxygen saturation were significantly lower while the Hb level was remarkably higher in the liver of mice in the model group.In each administration group,the level of HbO2 significantly increased,the level of Hb was significantly decreased,oxygen saturation was significantly increased in the liver of model mice and the accumulation of ICG dye probe was atten-uated in the body after hepatocyte injury.CONCLUSION Ursolic acid can elevate the hepatic oxygen saturation,improve the metabolism of ICG,reduce the degree of hepatic necrosis in mice,and help protect against carbon tetrachloride-induced hepatic injury in mice.The mechanism is probably related to the inhibition of oxidative stress.

Liver regenerative medicine can use functional liver cells to repair or replace damaged liver tissue and it is expected to be rapidly developed as an alternative treatment to liver transplantation. However, regenerative medicine requires cells with stable proliferation ability and liver cell characteristics. Liver organoids are derived from adult stem cells or pluripotent stem cells. They can be proliferated in large quantities and cultured for a long time in vitro, meanwhile maintain genetic stability, and simulate the structural and functional characteristics of organs in the body, providing a new strategy for liver regeneration. This article reviews liver organoids and their research progress in liver regenerative medicine, and discusses their application potential and existing limitations.