Yes-associated protein promotes the proliferation and differentiation of liver progenitor cells during liver fibrosis.

Liver fibrosis is closely related to the proliferation and differentiation of liver progenitor cells (LPCs). Yes-associated protein (YAP) is a key effector molecule of the Hippo signaling pathway and plays an important role in regulating cell proliferation and liver homeostasis. However, its role in LPCs proliferation and differentiation during liver fibrosis are not well understood. Using immunohistochemistry, immunofluorescence staining, quantitative PCR and Western blotting, we discovered that LPCs expansion and enhanced YAP expression in LPCs in either choline-deficient, ethionine-supplemented (CDE) diet or 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet-induced fibrotic mice, as well as in patients with liver fibrosis. By injecting adeno-associated virus vectors under the transcriptional control of Lgr5 promoter, we found that targeted knockdown of YAP in LPCs attenuated the CDE/DDC diet-induced ductular reaction and liver fibrosis. Using EdU incorporation and Cell Counting Kit-8 assays, we demonstrated that YAP can modulate LPCs proliferation. Importantly, spleen transplantation of YAP-overexpressing LPCs improved their ability to differentiate into hepatocytes and alleviated carbon tetrachloride-induced liver fibrosis. Collectively, our findings indicate that LPCs expansion and differentiation during liver fibrosis could be modulated by YAP, further suggesting the possibility of manipulating YAP expression in LPCs as a potential treatment for chronic liver diseases.

YAP affects the efficacy of liver progenitor cells transplantation in CCl4-induced acute liver injury.

The liver is a highly regenerative organ. During acute liver injury, the remaining hepatocytes rapidly proliferate to restore liver parenchyma and liver function. However, hepatocytes-driven regeneration is compromised in severe liver injury; instead, liver progenitor cells (LPCs) proliferate and differentiate into hepatocytes or cholangiocytes to restore mass and function of liver. The Hippo signaling pathway is of vital importance in liver regeneration, and Yes-associated protein (YAP) is the key component of the Hippo pathway. The therapeutic role of YAP has been well studied in hepatocytes-driven liver regeneration. However, the role of LPCs transplantation in acute liver injury has not been defined. Here, we investigated the therapeutic effect of splenic-transplantation of LPCs in CCl4-induced acute liver injury and explored the role of YAP during the procedure. LPCs isolated from choline-deficient, ethionine-supplemented diet (CDE) model were infected with GFP-YAP cDNA lentiviral vector, GFP-YAP shRNA lentiviral vector, and GFP lentiviral vector as control, respectively. At 48 h after CCl4 injection, PBS (control group), GFP lentiviral vector-infected LPCs (GFP-LPC group), GFP-YAP cDNA lentiviral vector-infected LPCs (YAP-LPC group) and GFP-YAP shRNA lentiviral vector-infected LPCs (sh-YAP-LPC group) were injected into spleens in CCl4-treated mice. Histological and serological analyses were performed to evaluate pathology and liver function. The effect of LPCs on the proliferation of hepatocytes and inflammation was investigated. We demonstrated that intra-splenic transplantation of LPCs alleviates CCl4-induced acute liver injury and YAP signaling acts a key role during the procedure. Further studies suggested that LPCs alleviate acute liver injury by promoting pre-existing hepatocytes proliferation rather than differentiating into hepatocytes. Furthermore, intra-splenic transplantation of LPCs attenuates inflammation, which facilitates tissue repair in acute liver injury. In conclusion, LPCs transplantation is a potential treatment for acute liver injury and YAP is a prospective therapeutic target in acute liver injury.

Dissecting the single-cell transcriptomeunderlying chronic liver injury.

Chronic liver disease (CLD) is currently a major health problem worldwide, which is accompanied by chronic liver injury and lack of clinically effective treatment; however, systematic characterization of chronic liver injury procedures at single-cell resolution is lacking. In the present study, we established chronic liver injury mouse models and conducted single-cell RNA sequencing (scRNA-seq), including choline-deficient, ethionine-supplemented (CDE) and 3,5-diethoxycarbonyl 1,4-dihydrocollidinen (DDC) mouse models. We captured in total 16,389 high-quality cells and identified 12 main cell types in scRNA-seq data. Macrophages and endothelial cells are the largest cell populations in our dataset. Transcriptional trajectory analysis revealed different expression patterns of cells between CDE and DDC models and identified potential liver injury markers, such as Ets1, Gda, Itgam, and Sparc. Differential analysis identified 25 and 152 differentially expressed genes in CDE and DDC macrophages, respectively. In addition, 413 genes were detected to exclusively express in specific pseudotime states of macrophages. These genes were found to participate in immune-related biological processes. Further cell-cell communication analysis found extensive receding of cell-cell interactions between different cell types in the liver injury process, especially in the DDC model. Our study characterized the single-cell transcriptional landscape in the process of chronic liver injury, promoting the understanding of the underlying molecular mechanisms and providing candidate clinical strategy for effective intervention of chronic liver diseases.