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Concept

Hépatocyte

Résumé

Les hépatocytes (ou cellules hépatiques) sont des cellules constituant la grande majorité des cellules du foie. Ce sont de véritables usines biochimiques, assurant de nombreuses fonctions métaboliques. Elles servent par exemple au stockage ou à la libération du glucose, dans le cadre de l'hypoglycémie ou de l'hyperglycémie. Cette fonction est activée lorsque le pancréas sécrète soit de l'insuline, soit du glucagon. L'insuline provoque un stockage du glucose alors que le glucagon provoque la libération de celui-ci. Structures Les hépatocytes ont une forme polyédrique de 20-30 µm de côté. Ils sont organisés en travées, appelées travées de Remak. Ils ont la particularité de comporter parfois deux noyaux, alors que la plupart des cellules eucaryotes n'en ont qu'un. Ce sont des cellules polarisées : elles possèdent une face exposée au sang dont elles ne sont séparés que par un endothélium, et sur la face opposée elles constituent un réseau de canalicules biliaires par accolemen

Source officielle

https://fr.wikipedia.org/wiki/H%C3%A9patocyte

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This course is aimed to familiarize students with the 3D organization of a eukaryotic cell, its compartmentalization, how cellular compartments communicate together and how a cell communicates with its environment. The related molecular mechanisms will be discussed.

This course introduces the student to the fudamentals of pharmacology, pharmacokinetics and drug-receptor interactions. It discusses also pharmacogenetics and chronopharmacology, to exemplify the challenges of personalized medicine.

Students will learn essentials of cell and developmental biology, with an emphasis on animal model systems and quantitative approaches.

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Séances de cours associées (16)

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Many liver diseases involve hepatocyte malfunction. In most cases, transplantation of corrected hepatocytes would correct for disease symptoms. Liver donor shortage and hepatocyte inability to proliferate in vitro accentuate this problem. Embryonic stem and induced pluripotent stem cells proliferate indefinitely and have the capacity to differentiate into every cell type of the body. They could thus represent a solution to this organ donor shortage. In this project, we aim to differentiate ES and iPS cells to hepatocytes. First, we consider an approach to select the ES/iPS cell line showing the best potential to generate liver lineage using teratomas as a selection tool. Then we use lentiviral vectors to transduce this selected cell line with essential liver-‐specific development factors to help differentiation efficiency. Next, we developed an in vitro differentiation protocol based on existing protocols and developmental clues of liver development to generate a pool of hepatocyte precursors. Later on, we injected these differentiated cells in mice liver of Fah-‐, Rag2-‐ and Il-‐2rγ-‐deficient mice to check for engraftment and liver marker expression. Our findings show, after checking for hepatocyte-‐ specific markers in the differentiated cells, that our previous selection for the potentially best cell line seems correct. We also find that the transcription factors involved in liver development appear to have a negative effect in vitro on liver differentiation. Applying our protocol to regular ES cells results on the production of late maturity hepatocyte markers, showing correct differentiation and maturation of newly formed hepatocytes. Finally, mouse in vivo liver transplantation of these differentiated cells gives us human albumin expression detectable in blood serum of said mice

2010

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Bioengineering approaches in immunotherapy

Martina Damo

Vaccination has been regarded to as the most attractive immunotherapy for cancer because of its ability to instruct immune cells to recognize and kill tumor cells. Exosomes are one of the most recent discoveries translated from basic biology into experimental vaccine therapy of cancer. Exosomes are 30-150 nm membrane vesicles released by many cell types. In particular, dendritic cell (DC)-derived exosomes (Dexo) inherit the molecules that make DCs able to activate antigen-specific immunity. As a consequence, Dexo have been tested in clinical trials for the vaccination of melanoma and lung carcinoma patients, however resulting in poor therapeutic outcomes due to weak immunogenicity. We therefore developed a protocol for the production of Dexo with improved immunogenic properties by exploiting the physiological ability of DCs to mature into immunostimulatory cells in the presence of antigens and immunogenic signals. We cultured Dexo-producing DCs with a murine melanoma cell lysate, that provided tumor antigens, and poly(I:C), a synthetic nucleic acid analog that provided immunogenic signals. The result was a Dexo vaccine capable of eliciting robust tumor-specific immunity in melanoma-bearing mice, leading to significantly reduced tumor growth and enhanced survival of experimental mice. These data indicate our strategy as a valuable improved alternative to currently available protocols for the production of potent tumor-tailored Dexo vaccines. Healthy tissues are spared from immune aggression via the establishment of immune tolerance to self antigens. The liver has recently been attributed an important role in peripheral tolerogenesis to circulating extracellular antigens, mainly due to the antigen scavenging properties of liver sinusoid endothelial cells. However, even though hepatocytes are the most abundant cell type of the liver and possess enzymatic activities necessary for processing of blood-borne molecules, their ability to take up and induce tolerance to extracellular antigens has yet to be explored. In this thesis we show for the first time in vitro and in vivo that hepatocytes efficiently take up, process and present extracellular antigens on MHC-I complexes inducing CD8+ T cell tolerance. We also show that the negative regulatory PD-1/PD-L1 pathway is involved in hepatocyte-dependent tolerogenesis. Therefore, we propose that hepatocytes are instrumental in the establishment and maintenance of liver-mediated peripheral tolerance towards extracellular antigens reaching the liver through the bloodstream. In addition, this thesis also provides evidence that hepatocytes are capable of directly expressing antigens specific of other peripheral tissues, a process known as promiscuous gene expression. Promiscuous gene expression allows to broaden the pool of self antigens presented to T lymphocytes in central and peripheral lymphoid organs, thus increasing the likelihood of inducing T cell tolerance to self antigens. We describe here for the first time that Deaf1, a transcription factor involved in promiscuous gene expression, is significantly expressed in murine hepatocytes, together with other well characterized peripheral tissue-restricted antigen-coding genes. Even though preliminary, these data further suggest a central role of hepatocytes in peripheral tolerogenesis and confirm the relevance of hepatocyte-targeted approaches as valuable immunotherapy candidates for the treatment of autoimmunity and hepatic chronic infections.

EPFL2016

Chargement

Human Hepatocyte-Derived Induced Pluripotent Stem Cells: MYC Expression, Similarities to Human Germ Cell Tumors, and Safety Issues

Marc Samuel Friedli, Carmen Maria Unzu Ezquerro

Induced pluripotent stem cells (iPSC) are a most promising approach to the development of a hepatocyte transplantable mass sufficient to induce long-term correction of inherited liver metabolic diseases, thus avoiding liver transplantation. Their intrinsic self-renewal ability and potential to differentiate into any of the three germ layers identify iPSC as the most promising cell-based therapeutics, but also as drivers of tumor development. Teratoma development currently represents the gold standard to assess iPSC pluripotency. We analyzed the tumorigenic potential of iPSC generated from human hepatocytes (HEP-iPSC) and compared their immunohistochemical profiles to that of tumors developed from fibroblast and hematopoietic stem cell-derived iPSC. HEP-iPSC generated tumors significantly presented more malignant morphological features than reprogrammed fibroblasts or CD34+ iPSC. Moreover, the protooncogene myc showed the strongest expression in HEP-iPSC, compared to only faint expression in the other cell subsets. Random integration of transgenes and the use of potent protooncogenes such as myc might be a risk factor for malignant tumor development if hepatocytes are used for reprogramming. Nonviral vector delivery systems or reprogramming of cells obtained from less invasive harvesting methods would represent interesting options for future developments in stemcell-based approaches for liver metabolic diseases.

2016

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Bioengineering approaches in immunotherapy

Martina Damo

EPFL2016