The roles of transforming growth factor-β, Wnt, Notch and hypoxia on liver progenitor cells in primary liver tumours

Primary liver tumours have a high incidence and mortality. The most important forms are hepatocellular carcinoma and intrahepatic cholangiocarcinoma, both can occur together in the mixed phenotype hepatocellular-cholangiocarcinoma. Liver progenitor cells (LPCs) are bipotential stem cells activated in case of severe liver damage and are capable of forming both cholangiocytes and hepatocytes. Possibly, alterations in Wnt, transforming growth factor-, Notch and hypoxia pathways in these LPCs can cause them to give rise to cancer stem cells, capable of driving tumourigenesis. In this review, we summarize and discuss current knowledge on the role of these pathways in LPC activation and differentiation during hepatocarcinogenesis

Advances in hepatic stem/progenitor cell biology

The liver is famous for its strong regenerative capacity, employing different modes of regeneration according to type and extent of injury. Mature liver cells are able to proliferate in order to replace the damaged tissue allowing the recovery of the parenchymal function. In more severe scenarios hepatocytes are believed to arise also from a facultative liver progenitor cell compartment. In human, severe acute liver failure and liver cirrhosis are also both important clinical targets in which regeneration is impaired, where the role of this stem cell compartment seems more convincing. In animal models, the current state of ambiguity regarding the identity and role of liver progenitor cells in liver physiology dampens the enthusiasm for the potential use of these cells in regenerative medicine. The aim of this review is to give the basics of liver progenitor cell biology and discuss recent results vis-à-vis their identity and contribution to liver regeneration

HDAC inhibitors in experimental liver and kidney fibrosis

Histone deacetylase (HDAC) inhibitors have been extensively studied in experimental models of cancer, where their inhibition of deacetylation has been proven to regulate cell survival, proliferation, differentiation and apoptosis. This in turn has led to the use of a variety of HDAC inhibitors in clinical trials. In recent years the applicability of HDAC inhibitors in other areas of disease has been explored, including the treatment of fibrotic disorders. Impaired wound healing involves the continuous deposition and cross-linking of extracellular matrix governed by myofibroblasts leading to diseases such as liver and kidney fibrosis; both diseases have high unmet medical needs which are a burden on health budgets worldwide. We provide an overview of the potential use of HDAC inhibitors against liver and kidney fibrosis using the current understanding of these inhibitors in experimental animal models and in vitro models of fibrosis

P311, Friend, or Foe of Tissue Fibrosis?

P311 was first identified by the group of Studler et al. (1993) in the developing brain. In healthy, but mainly in pathological tissues, P311 is implicated in cell migration and proliferation. Furthermore, evidence in models of tissue fibrosis points to the colocalization with and the stimulation of transforming growth factor β1 by P311. This review provides a comprehensive overview on P311 and discusses its potential as an anti-fibrotic target

Next generation of ALDH substrates and their potential to study maturational lineage biology in stem and progenitor cells

High aldehyde dehydrogenase (ALDH) activity is a feature of stem cells from normal and cancerous tissues and a reliable universal marker used to isolate them. There are numerous ALDH isoforms with preferred substrate specificity variably expressed depending on tissue, cell type, and organelle and cell status. On the other hand, a given substrate may be metabolized by several enzyme isoforms. Currently ALDH activity is evidenced by using Aldefluor, a fluorescent substrate likely to be metabolized by numerous ALDH isoforms. Therefore, isolation techniques based on ALDH activity detection select a heterogeneous population of stem or progenitor cells. Despite active research in the field, the precise role(s) of different ALDH isoforms in stem cells remains enigmatic. Understanding the metabolic role of different ALDH isoform in the control of stem cell phenotype and cell fate during development, tissue homeostasis, or repair, as well as carcinogenesis, should open perspectives to significant discoveries in tissue biology. In this perspective, novel ALDH substrates are being developed. Here we describe how new substrates could be instrumental for better isolation of cell population with stemness potential and for defining hierarchy of cell populations in tissue. Finally, we speculate on other potential applications

Modelling fatty liver disease with mouse liver-derived multicellular spheroids

Chronic liver disease can lead to liver fibrosis and ultimately cirrhosis, which is a significant health burden and a major cause of death worldwide. Reliable in vitro models are lacking and thus mono-cultures of cell lines are still used to study liver disease and evaluate candidate anti-fibrotic drugs. We established functional multicellular liver spheroid (MCLS) cultures using primary mouse hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells and Kupffer cells. Cell-aggregation and spheroid formation was enhanced with 96-well U-bottom plates generating over ±700 spheroids from one mouse. Extensive characterization showed that MCLS cultures contain functional hepatocytes, quiescent stellate cells, fenestrated sinusoidal endothelium and responsive Kupffer cells that can be maintained for 17 days. MCLS cultures display a fibrotic response upon chronic exposure to acetaminophen, and present steatosis and fibrosis when challenged with free fatty acid and lipopolysaccharides, reminiscent of non-alcoholic fatty liver disease (NAFLD) stages. Treatment of MCLS cultures with potential anti-NAFLD drugs such as Elafibranor, Lanifibranor, Pioglitazone and Obeticholic acid shows that all can inhibit steatosis, but only Elafibranor and especially Lanifibranor inhibit fibrosis. Therefore, primary mouse MCLS cultures can be used to model acute and chronic liver disease and are suitable for the assessment of anti-NAFLD drugs

Cell Cycle Phase-Specific Surface Expression of Nerve Growth Factor Receptors TrkA and p75NTR

[EN]Expression of the nerve growth factor (NGF) receptors TrkA and p75NTR was found to vary at the surface of PC12 cells in a cell cycle phase-specific manner. This was evidenced by using flow cytometric and microscopic analysis of cell populations labeled with antibodies to the extracellular domains of both receptors. Differential expression of these receptors also was evidenced by biotinylation of surface proteins and Western analysis, using antibodies specific for the extracellular domains of TrkA and p75NTR. TrkA is expressed most strongly at the cell surface in M and early G1 phases, whereas p75NTR is expressed mainly in late G1, S, and G2 phases. This expression reflects the molecular and cellular responses to NGF in specific phases of the cell cycle; in the G1 phase NGF elicits both the anti-mitogenic effect, i.e., inhibition of the G1 to S transition, and the differentiation response whereas a survival effect is provoked elsewhere in the cell cycle. A model is proposed relating these responses to the surface expression of the two receptors. These observations open the way for novel approaches to the investigation of the mechanism of NGF signal transduction

Design, construction and testing of a COC 3D flow-over flow-through bioreactor for hepatic cell culture

In this poster, we present the joint development efforts for a 3D microfluidic bioreactor for hepatic cell cultures. Cyclic Olefin Copolymer (COC) was selected for constructing the bioreactor, since the material has good chemical resistance, low adsorption and good optical properties, including low auto-fluorescence. A downside of COC is that it is much more difficult to structure than more traditional microfluidic materials, such as PDMS, PMMA, … Two parallel approaches were developed for structuring the COC. In a first approach, mechanical micro-milling of the channels allows for extremely fast manufacturing of new design variations, at the expense of difficulties in scalability to mass-production and a channel surface that requires post-processing to achieve sufficient optical quality. In a second approach, hot embossing using epoxy molds allows for direct structuring of optical grade channels and is scalable to mass production, at the expense of longer cycle time in the development of new channel designs. To facilitate the handling of the bioreactor, a holder was designed to provide the fluidic connections to a pump,ensuring medium exchange and sampling to down-stream sensors connected to the outlets. The design of the bioreactor was intended to maintain and expose pre-formed hepatic co-culture spheroids to toxicants for more than a week. Once seeded, spheroids rest on a polycarbonate membrane with 12 µm pore size, allowing the medium to flow-through, while flow-over is maintained to avoid an excess pressure on the cells. In a single bioreactor, 9 wells are connected to a common inlet to provide the cells with fresh culture medium or test compounds. On a first cell culture trial, it was possible to visually detect the spheroids in the wells after seeding, however, after 1 week of culture there was no possibility to accurately detect the presence and viability of the cells. In the framework of HeMiBio, significant progress has been made towards producing a 3D COC-based bioreactor for hepatic cell culture, and most technological hurdles in producing prototype reactors have been overcome. Further testing is needed to see which improvements to the reactor or the flow conditions should be made to ensure cell viability

EpCAM and the biology of hepatic stem/progenitor cells

Epithelial cell adhesion molecule (EpCAM) is a transmembrane glycoprotein, which is frequently and highly expressed on carcinomas, tumor-initiating cells, selected tissue progenitors, and embryonic and adult stem cells. During liver development, EpCAM demonstrates a dynamic expression, since it can be detected in fetal liver, including cells of the parenchyma, whereas mature hepatocytes are devoid of EpCAM. Liver regeneration is associated with a population of EpCAM-positive cells within ductular reactions, which gradually lose the expression of EpCAM along with maturation into hepatocytes. EpCAM can be switched on and off through a wide panel of strategies to fine-tune EpCAM-dependent functional and differentiative traits. EpCAM-associated functions relate to cell–cell adhesion, proliferation, maintenance of a pluripotent state, regulation of differentiation, migration, and invasion. These functions can be conferred by the full-length protein and/or EpCAM-derived fragments, which are generated upon regulated intramembrane proteolysis. Control by EpCAM therefore not only depends on the presence of full-length EpCAM at cellular membranes but also on varying rates of the formation of EpCAM-derived fragments that have their own regulatory properties and on changes in the association of EpCAM with interaction partners. Thus spatiotemporal localization of EpCAM in immature liver progenitors, transit-amplifying cells, and mature liver cells will decisively impact the regulation of EpCAM functions and might be one of the triggers that contributes to the adaptive processes in stem/progenitor cell lineages. This review will summarize EpCAM-related molecular events and how they relate to hepatobiliary differentiation and regeneration