Effect of human umbilical cord blood stem cell transplantation on oval cell response in 2-AAF/CCL4 liver injury model: experimental immunohistochemical study

Troglitazone inhibits hepatic oval cell proliferation by inducing cell cycle arrest through Hippo/YAP pathway regulation

Hepatic oval cells have strong proliferation and differentiation capabilities and are activated when chronic liver injury occurs or when liver function is severely impaired. Peroxisome proliferation-activated receptors (PPARs) are ligand-dependent, sequence-specific nuclear transcription factors. PPARγ is closely related to liver diseases (such as liver cancer, liver fibrosis and non-alcoholic fatty liver disease). As the main effector downstream of the Hippo signaling pathway, YAP can activate the hepatic progenitor cell program, and different expression or activity levels of YAP can determine different liver cell fates. We found that troglitazone (TRO), a classic PPARγ activator, can inhibit the growth of hepatic oval cells, and flow cytometry results showed that TRO inhibited the growth of WB-F344 cells by arresting the cells in the G_0/1 phase. Western blot results also confirmed changes in G_0/1 phase-related protein expression. Further experiments showed that PPARγ agonists induced hepatic oval cell proliferation inhibition and cell cycle G_0/1 phase arrest through the Hippo/YAP pathway. Our experiment demonstrated, for the first time, the relationship between PPARγ and the Hippo/YAP pathway in liver oval cells and revealed that PPARγ acts as a negative regulator of liver regeneration by inhibiting the proliferation of oval cells.

CK19 and OV6 Expressions in the Liver of 2-AAF/CCl4 Rat Model

BACKGROUND: Liver regeneration on a chronic liver injury with rat model research is urgent to study the pathology of human chronic diseases. 2-Acetylaminofluorene (2-AAF) and Carbon Tetrachloride (CCl4) can be applied to study about liver regeneration by liver stem cells, known as oval cells. The use of 2-AAF and CCl4 (2-AAF/CCl4) to induce chronic liver injury can lead severe hepatocyte damages and extensive fibrosis. AIM: to observed the OV6 and CK19 expression in the liver of 2AAF/CCl4 rat model. METHODS: In this research, a high dose of 2-AAF (10mg/kg) was applied and combined repeatedly with CCl4 (2ml/kg) for 12 weeks. An immunohistochemistry (IHC) procedure by using OV6 and CK19 antibodies was also applied to examine the regeneration of oval cells. Both antibodies expressions were then examined semi-quantitatively according to the expressions percentage of each sample based on the liver zone. We have observed the OV6 and CK19 expressions in every zone, including in portae hepatis area.   RESULTS: The results showed that OV6 and CK19 with the highest expression in the zone I. A significant difference between OV6 and CK19 expressions was revealed in healthy (control group) and 2-AAF/CCl4 groups (both indicating p=0.045). Moreover, a ductular reaction was also found in Zone I and II of the 2-AAF/CCl4. CONCLUSIONS: We conclude that 2-AAF/CCl4 induced chronic rat liver injury model, could be utilized to investigate the oval cells with OV6 and CK19 expression.