Project description:Hepatic stellate cells (HSC) constitute the most important fibrogenic cell type during liver fibrosis. To analyse the different phenotypes of quiescent and activated cells, cells of 5 animals were transdifferentiated in a well established in vitro transdifferentiaition assay and compared to freshly seeded, quiescent HSC. Gene expression profiling of quiescent and in vitro activated HSC revealed well known and new marker genes upregulated upon HSC activation. ltbp1 (latent transforming growth factor beta binding protein 1) is a crucial factor controlling the secretion and bioactivation of TGFß1. Using the data comparing quiescent and activated HSC, we were able to qualify the subtle but reproducible differences in gene expression observed when comparing activated ltbp1-deficient and activted wt HSC. ltbp1-deficient HSC showed a less fibrogenic phenotype after 6 days of in vitro transdifferentiation compared to the wt counterparts. The microarray data was indepently confirmed in vivo using an experimental model for the induction of liver fibrosis (ligation of the common bile duct). ltbp1-/- mice, after 4 weeks of bile obstruction, showed markedly reduced signs of liver fibrosis. Keywords: gene expression profiling, analysyis of a fibrogenic cell type in the liver and the influence of ltbp1-k.o.
Project description:Unveiling the regulatory pathways maintaining hepatic stellate cells (HSC) in a quiescent (q) phenotype is essential to develop new therapeutic strategies to treat fibrogenic diseases. To uncover the miRNA-mRNAs regulatory interactions in qHSCs, HSCs were FACS-sorted from healthy livers and activated HSCs were generated in vitro. MiRNA Taqman array analysis showed HSCs expressed a low number of miRNA, from which 46 were down-regulated and 212 up-regulated upon activation. Computational integration of miRNA and gene expression profiles revealed that 66% of qHSCs miRNAs correlated with more than 6 altered targeted mRNAs (17,28±10,7 targets/miRNA), whereas aHSC-associated miRNAs had an average of 1,49 targeted genes. Interestingly, interaction networks generated by miRNA-targeted genes in qHSCs were associated with key HSCs activation processes. Next, selected miRNAs were validated in healthy and cirrhotic human livers and miR-192 was chosen for functional analysis. Down-regulation of miR-192 in HSC was found to be an early event during fibrosis progression in mouse models of liver injury. Moreover, mimic assays for miR-192 in HSCs revealed its role in HSC activation, proliferation and migration. Together, these results uncover the importance of miRNAs in the maintenance of qHSC phenotype and form the basis for understanding the regulatory networks in HSCs. Transcriptomic profile derived from four quiescent hepatic stellate (QHSC), four activated hepatic stellate (AHSC), three liver sinusoidal endothelial (LSEC) and two hepatocytes cells (HEP).
Project description:The molecular determinants of a healthy human liver cell phenotype remain largely uncharacterized. In addition, the gene expression changes associated with activation of primary human hepatic stellate cells, a key event during fibrogenesis, remain poorly characterized. Here, we provide the transriptomic profile underpinning the healthy phenotype of human hepatocytes, liver sinusoidal endothelial cells (LSECs) and quiescent hepatic stellate cells (qHSCs) as well as activated HSCs (aHSCs) We assess the transcriptome for purified, non-cultured human hepatocytes, liver sinusoidal cells (LSECs) and quiescent hepatic stellate cells (qHSCs) as well as culture-activated HSCs (aHSCs). Hepatocytes (n=2 donors), LSECs (n=3), qHSCs (n=3) and in vitro activated HSCs (n=3; from the same donors as the qHSCs and LSECs) were used for this study.
Project description:Liver fibrosis is characterized by the excessive formation and accumulation of matrix proteins as a result of wound healing in the liver. A main event during fibrogenesis is the activation of the liver resident quiescent hepatic stellate cell (qHSC). Recent studies suggest that reversion of the activated HSC (aHSC) phenotype into a quiescent-like phenotype could be a major cellular mechanism underlying fibrosis regression in the liver, thereby offering new therapeutic perspectives for the treatment of liver fibrosis. The goal of the present study is to identify experimental conditions that can revert the activated status of human HSCs and to map the molecular events associated with this phenotype reversion by gene expression profiling Transcriptomic profiling of primary human quiescent HSCs (qHSCs), in vitro activated HSCs (aHSCs) and in vitro reverted HSCs (rHSCs). The cell types come from different donors (This is detailed in the original manuscript.).
Project description:Normal and cirrhotic LSECs can influence hepatic stellate cells (HSCs) differently. This project aims to determine the set of proteins secreted by LSECs from healthy and cirrhotic livers, and identify the protein(s) that promote HSC activation.
Project description:Contrasting chromatin accessibility between activated and quiescent hepatic stellate cells to identify key gene networks for the activation process.
Project description:Contrasting transcript expression between activated and quiescent hepatic stellate cells to identify key gene networks for the activation process.
Project description:Gene expression was determined in primary rat hepatic stellate cells during the in vitro activation process in freshly isolated (4h), quiescent (1d), early activated (3d) and fully activated (7d) hepatic stellate cells. The cells were isolated from the liver using density centrifugation and cultured on plastic in DMEM containing serum for the indicated time. RNA was isolated using the Qiagen Rneasy Mini Kit. The Affymetrix Gene Chip Rat Gene 2.0 ST was used for gene expression analysis performed by the genomic core facility of the EMBL (Heidelberg, Germany). All experiments were performed three times with independent animals.
Project description:Cell reprogramming enables dedifferentiation to generate induced pluripotent stem cells or transdifferentiation to produce desired terminally differentiated cell types. However, the concept of forced reprogramming has not been extended to converting the activation status of specialized cell types such as hepatic stellate cell (HSC) which, once activated, plays a central role in promoting liver fibrosis. We identified miR-15a as a key driver to reprogram activated HSC back toward quiescence, partly by directly targeting Wisp1, to generate what we designate as induced quiescent-like HSC (iqHSC). iqHSCs had a morphologic, transcriptional, and functional phenotype similar to that of truly quiescent HSCs. Finally, performing cell therapy with iqHSCs attenuated hepatic inflammation and fibrosis in mouse models of liver injury induced by toxin, biliary obstruction, or diet.
Project description:Under conditions of the liver exposed to chronic insults such as viral infection, excess deposition of fat, regurgitation of bile acids etc., hepatic stellate cells (HSCs) change from quiescent to activated states and proliferate. During this process, HSCs secrete collagen and metalloproteinases. Involvement of collagen in sustaining activated HSC (aHSC) survival was postulated, although the precise mechanisms underlying the survival and apoptosis of aHSCs is still controversial. In this study, we compared the expression profiles between quiescent and activated HSCs to clarify the mechanisms of apoptosis for exploration of novel anti-fibrosis modalities.