Regeneration and activation of liver progenitor cells in liver cirrhosis

Role of HNF4alpha-cMyc interaction in liver regeneration after partial hepatectomy

Background

Hepatocyte nuclear factor 4 alpha (HNF4α) is the master regulator of hepatic differentiation. Recent studies have also revealed the role of HNF4α in hepatocyte proliferation via negatively regulating the expression of proto-mitogenic genes, including cMyc. Here, we aimed to study the interaction between HNF4α-cMyc during liver regeneration after partial hepatectomy (PHX).

Methods

Wild-type (WT), hepatocyte-specific knockout of HNF4α (HNF4α-KO), cMyc (cMyc-KO), and HNF4α-cMyc double knockout (DKO) mice were subjected to PHX to induce liver regeneration. Blood and liver tissue samples were collected at 0h, 24h, 48h, 7D, and 14D after PHX for further analysis.

Results

WT, HNF4α-KO, cMyc-KO and DKO mice regained liver weight by 14 days after PHX. The deletion of cMyc did not affect liver regeneration, which was similar to the WT mice. WT and cMyc-KO mice started regaining liver weight as early as 24 hours after PHX, with a peak proliferation response at 48 hours after PHX. HNF4α- KO and DKO showed a delayed response with liver weight increase by day 7 after PHX. The overall hepatocyte proliferation response by DKO mice following PHX was lower than that of other genotypes. Interestingly, the surviving HNF4α-KO and DKO mice showed re-expression of HNF4α at mRNA and protein levels on day 14 after PHX. This was accompanied by a significant increase in the expression of Krt19 and Epcam, hepatic progenitor cell markers, in the DKO mice on day 14 after PHX.

Conclusion

These data indicate that, in the absence of HNF4α, cMyc contributes to hepatocyte-driven proliferation to compensate for the lost tissue mass. Furthermore, in the absence of both HNF4α and cMyc, HPC-driven proliferation occurs to support liver regeneration.

Uncovering a Novel Functional Interaction Between Adult Hepatic Progenitor Cells, Inflammation and EGFR Signaling During Bile Acids-Induced Injury

Chronic cholestatic damage is associated to both accumulation of cytotoxic levels of bile acids and expansion of adult hepatic progenitor cells (HPC) as part of the ductular reaction contributing to the regenerative response. Here, we report a bile acid-specific cytotoxic response in mouse HPC, which is partially impaired by EGF signaling. Additionally, we show that EGF synergizes with bile acids to trigger inflammatory signaling and NLRP3 inflammasome activation in HPC. Aiming at understanding the impact of this HPC specific response on the liver microenvironment we run a proteomic analysis of HPC secretome. Data show an enrichment in immune and TGF-β regulators, ECM components and remodeling proteins in HPC secretome. Consistently, HPC-derived conditioned medium promotes hepatic stellate cell (HSC) activation and macrophage M1-like polarization. Strikingly, EGF and bile acids co-treatment leads to profound changes in the secretome composition, illustrated by an abolishment of HSC activating effect and by promoting macrophage M2-like polarization. Collectively, we provide new specific mechanisms behind HPC regulatory action during cholestatic liver injury, with an active role in cellular interactome and inflammatory response regulation. Moreover, findings prove a key contribution for EGFR signaling jointly with bile acids in HPC-mediated actions.

Spontaneously Ruptured Hepatocellular Carcinoma: Computed Tomography-Based Assessment

Spontaneously ruptured hepatocellular carcinoma (SRHCC) is an uncommon and life-threatening complication in patients with hepatocellular carcinoma (HCC). It is usually associated with chronic liver disease and has a poor prognosis with a high mortality rate during the acute phase. SRHCC can cause a severe and urgent condition of acute abdomen disease and requires a correct diagnosis to achieve adequate treatment. Clinical presentation is related to the presence of hemoperitoneum, and abdominal pain is the most common symptom (66–100% of cases). Although the treatment approach is not unique, trans-arterial (chemo)embolization (TAE/TACE) followed by staged hepatectomy has shown better results in long-term survival. A multi-phase contrast-enhanced CT (CECT) scan is a pivotal technique in the diagnosis of SRHCC due to its diagnostic accuracy and optimal temporal resolution. The correct interpretation of the main CT findings in SRHCC, such as active contrast extravasation and the sentinel clot sign, is fundamental for a prompt and correct diagnosis. Furthermore, CT also plays a role as a post-operative control procedure, especially in patients treated with TAE/TACE. Therefore, a multi-phase CECT scan should be the diagnostic tool of choice in SRHCC since it suggests an immediate need for treatment with a consequent improvement in prognosis.

Aurora kinase A regulates liver regeneration through macrophages polarization and Wnt/β-catenin signalling

BACKGROUND AND AIMS

Liver regeneration is a complex process regulated by a variety of cells, cytokines and biological pathways. Aurora kinase A (AURKA) is a serine/threonine kinase that plays a role in centrosome maturation and spindle formation during the cell division cycle. The purpose of this study was to further explore the mechanism of AURKA on liver regeneration and to identify new possible targets for liver regeneration.

METHODS

The effect and mechanism of AURKA on liver regeneration were studied using a 70% hepatectomy model. Human liver organoids were used as an in vitro model to investigate the effect of AURKA on hepatocyte proliferation.

RESULTS

AURKA inhibition significantly reduced the level of β-catenin protein by reducing the phosphorylation level of glycogen synthase kinase-3β (GSK-3β), leading to the inhibition of liver regeneration. Further studies showed that AURKA co-localized and interacted with GSK-3β in the cytoplasm of hepatocytes. When phosphorylation of GSK-3β was enhanced, the total GSK-3β level remained unchanged, while AURKA was not affected, and β-catenin protein levels were increased. In addition, AURKA inhibition affected the formation and proliferation of human liver organoids. Furthermore, AURKA inhibition led to the polarization of M1 macrophages and the release of interleukin-6 and Tumour necrosis factor α, which also led to reduced liver regeneration and increased liver injury.

CONCLUSIONS

These results provide more details on the mechanism of liver regeneration and suggest that AURKA is an important regulator of this mechanism.

The bright side of fibroblasts: molecular signature and regenerative cues in major organs

Fibrosis is a pathologic process characterized by the replacement of parenchymal tissue by large amounts of extracellular matrix, which may lead to organ dysfunction and even death. Fibroblasts are classically associated to fibrosis and tissue repair, and seldom to regeneration. However, accumulating evidence supports a pro-regenerative role of fibroblasts in different organs. While some organs rely on fibroblasts for maintaining stem cell niches, others depend on fibroblast activity, particularly on secreted molecules that promote cell adhesion, migration, and proliferation, to guide the regenerative process. Herein we provide an up-to-date overview of fibroblast-derived regenerative signaling across different organs and discuss how this capacity may become compromised with aging. We further introduce a new paradigm for regenerative therapies based on reverting adult fibroblasts to a fetal/neonatal-like phenotype.