Paired related homeobox protein 1 regulates PDGF-induced chemotaxis of hepatic stellate cells in liver fibrosis

The roles of ETS transcription factors in liver fibrosis

E26 transformation specific or E twenty-six (ETS) protein family consists of 28 transcription factors, five of which, named ETS1/2, PU.1, ERG and EHF, are known to involve in the development of liver fibrosis, and are expected to become diagnostic markers or therapeutic targets of liver fibrosis. In recent years, some small molecule inhibitors of ETS protein family have been discovered, which might open up a new path for the liver fibrosis therapy targeting ETS. This article reviews the research progress of ETS family members in the development liver fibrosis as well as their prospect of clinical application.

The paired-related homeobox protein 1 promotes cardiac fibrosis via the Twist1-Prrx1-tenascin-C loop

Cardiac fibrosis is a common pathology in the advanced stage of cardiovascular diseases, which leads to cardiac systolic and diastolic dysfunction. It is important to prevent cardiac fibrosis during myocardial injury. The transcription factor Prrx1 is involved in cancer-associated fibrosis and other organ fibrosis. However, the role and mechanism of Prrx1 in cardiac fibrosis deserves further exploration. We identified that overexpressed Prrx1 promoted the proliferation and migration of cardiac fibroblasts, and transform cardiac fibroblasts to myofibroblasts in vitro. We demonstrated that the expression of Prrx1 is upregulated in TGF-β1-treated fibroblasts. And silencing Prrx1 could attenuate cardiac fibrosis induced by TGF-β1 in vitro. In addition, a Twist1-paired-related homeobox 1 (Prrx1)-tenascin-C (TNC) positive feedback loop (PFL) combined with Twist1, Prrx1, and TNC activated fibroblasts, which was the mechanism the Prrx1 in cardiac fibrosis. In conclusion, our findings showed that the deficiency of Prrx1 attenuated cardiac fibrosis in vitro and reveal a novel Twist1-Prrx1-TNC PFL in the regulation of cardiac fibrosis.

A novel tumor-homing TRAIL variant eradicates tumor xenografts of refractory colorectal cancer cells in combination with tumor cell-targeted photodynamic therapy

Multidrug resistance (MDR), which is common in colorectal cancer (CRC), induces high mortality in patients. Due to its robust and selective apoptosis induction in some CRC cells with MDR, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is attractive as a novel tool for CRC therapy. However, TRAIL is limited by its poor tumor-homing ability and inefficient apoptosis induction in CRC cells expressing low levels of death receptor (DR). Here, the tumor-homing RGR peptide (CRGRRST) was fused to TRAIL to produce RGR-TRAIL. Compared with TRAIL, RGR-TRAIL showed greater cell binding and cytotoxicity in CRC cells. In addition, RGR-TRAIL exerted significantly enhanced tumor uptake and growth suppression in mice bearing CRC tumor xenografts. Notably, RGR-TRAIL eradicated all tumor xenografts of DR-overexpressing COLO205 cells. However, TRAIL only showed mild tumor growth suppression under the same conditions, indicating that RGR fusion significantly increased the antitumor effect of TRAIL in DR-overexpressing CRC cells by improving tumor homing. Nevertheless, RGR fusion did not significantly enhance the antitumor effect of TRAIL in HT29 cells expressing low levels of DR. We found that DR expression in HT29 cells was enhanced by epidermal growth factor receptor (EGFR)-targeted photodynamic therapy (PDT). Moreover, both the in vitro and in vivo antitumor effects of RGR-TRAIL were significantly improved by combination with PDT. HT29 tumor xenografts (∼20%) were even eradicated by combination therapy. These results indicate that it is valuable to further evaluate the combination therapy of RGR-TRAIL and tumor-targeted PDT for clinical therapy of CRC with MDR.

The Effects of Irisin on the Interaction between Hepatic Stellate Cell and Macrophage in Liver Fibrosis

BACKGRUOUND

Hepatic stellate cells (HSCs) are the central players interacting with multiple cell types in liver fibrosis. The crosstalk between HSCs and macrophages has recently become clearer. Irisin, an exercise-responsive myokine, was known to have a potentially protective role in liver and renal fibrosis, especially in connection with stellate cells. This study investigated the effects of irisin on the interaction between HSCs and macrophages.

METHODS

Tamm-Horsfall protein-1 (THP-1) human monocytes were differentiated into macrophages, polarized into the inflammatory M1 phenotype with lipopolysaccharide. Lieming Xu-2 (LX-2) cells, human HSCs, were treated with conditioned media (CM) from M1 macrophages, with or without recombinant irisin. HSCs responses to CM from M1 macrophages were evaluated regarding activation, proliferation, wound healing, trans-well migration, contractility, and related signaling pathway.

RESULTS

CM from M1 macrophages significantly promoted HSC proliferation, wound healing, transwell migration, and contractility, but not activation of HSCs. Irisin co-treatment attenuated these responses of HSCs to CM. However, CM and irisin treatment did not induce any changes in HSC activation. Further, irisin co-treatment alleviated CM-induced increase of phopho-protein kinase B (pAKT), matrix metalloproteinase-9 (MMP-9), and tissue inhibitor of metalloproteinases-1 (TIMP-1).

CONCLUSION

These findings suggested that irisin may play a protective role in the pathogenesis of liver fibrosis, especially when working in the crosstalk between HSCs and macrophages.

Time and phenotype-dependent transcriptome analysis in AAV-TGFβ1 and Bleomycin-induced lung fibrosis models

We have previously established a novel mouse model of lung fibrosis based on Adeno-associated virus (AAV)-mediated pulmonary overexpression of TGFβ1. Here, we provide an in-depth characterization of phenotypic and transcriptomic changes (mRNA and miRNA) in a head-to-head comparison with Bleomycin-induced lung injury over a 4-week disease course. The analyses delineate the temporal state of model-specific and commonly altered pathways, thereby providing detailed insights into the processes underlying disease development. They further guide appropriate model selection as well as interventional study design. Overall, Bleomycin-induced fibrosis resembles a biphasic process of acute inflammation and subsequent transition into fibrosis (with partial resolution), whereas the TGFβ1-driven model is characterized by pronounced and persistent fibrosis with concomitant inflammation and an equally complex disease phenotype as observed upon Bleomycin instillation. Finally, based on an integrative approach combining lung function data, mRNA/miRNA profiles, their correlation and miRNA target predictions, we identify putative drug targets and miRNAs to be explored as therapeutic candidates for fibrotic diseases. Taken together, we provide a comprehensive analysis and rich data resource based on RNA-sequencing, along with a strategy for transcriptome-phenotype coupling. The results will be of value for TGFβ research, drug discovery and biomarker identification in progressive fibrosing interstitial lung diseases.

Metabolic Reprogramming of Liver Fibrosis

Liver fibrosis is an excessive and imbalanced deposition of fibrous extracellular matrix (ECM) that is associated with the hepatic wound-healing response. It is also the common mechanism that contributes to the impairment of the liver function that is observed in many chronic liver diseases (CLD). Despite the efforts, no effective therapy against fibrosis exists yet. Worryingly, due to the growing obesity pandemic, fibrosis incidence is on the rise. Here, we aim to summarize the main components and mechanisms involved in the progression of liver fibrosis, with special focus on the metabolic regulation of key effectors of fibrogenesis, hepatic stellate cells (HSCs), and their role in the disease progression. Hepatic cells that undergo metabolic reprogramming require a tightly controlled, fine-tuned cellular response, allowing them to meet their energetic demands without affecting cellular integrity. Here, we aim to discuss the role of ribonucleic acid (RNA)-binding proteins (RBPs), whose dynamic nature being context- and stimuli-dependent make them very suitable for the fibrotic situation. Thus, we will not only summarize the up-to-date literature on the metabolic regulation of HSCs in liver fibrosis, but also on the RBP-dependent post-transcriptional regulation of this metabolic switch that results in such important consequences for the progression of fibrosis and CLD.

Epithelial Mesenchymal Transition and its transcription factors

Epithelial–mesenchymal transition or EMT is an extremely dynamic process involved in conversion of epithelial cells into mesenchymal cells, stimulated by an ensemble of signaling pathways, leading to change in cellular morphology, suppression of epithelial characters and acquisition of properties such as enhanced cell motility and invasiveness, reduced cell death by apoptosis, resistance to chemotherapeutic drugs etc. Significantly, EMT has been found to play a crucial role during embryonic development, tissue fibrosis and would healing, as well as during cancer metastasis. Over the years, work from various laboratories have identified a rather large number of transcription factors (TFs) including the master regulators of EMT, with the ability to regulate the EMT process directly. In this review, we put together these EMT TFs and discussed their role in the process. We have also tried to focus on their mechanism of action, their interdependency, and the large regulatory network they form. Subsequently, it has become clear that the composition and structure of the transcriptional regulatory network behind EMT probably varies based upon various physiological and pathological contexts, or even in a cell/tissue type-dependent manner.

Single-cell and bulk transcriptomics of the liver reveals potential targets of NASH with fibrosis

Fibrosis is characterized by the excessive production of collagen and other extracellular matrix (ECM) components and represents a leading cause of morbidity and mortality worldwide. Previous studies of nonalcoholic steatohepatitis (NASH) with fibrosis were largely restricted to bulk transcriptome profiles. Thus, our understanding of this disease is limited by an incomplete characterization of liver cell types in general and hepatic stellate cells (HSCs) in particular, given that activated HSCs are the major hepatic fibrogenic cell population. To help fill this gap, we profiled 17,810 non-parenchymal cells derived from six healthy human livers. In conjunction with public single-cell data of fibrotic/cirrhotic human livers, these profiles enable the identification of potential intercellular signaling axes (e.g., ITGAV-LAMC1, TNFRSF11B-VWF and NOTCH2-DLL4) and master regulators (e.g., RUNX1 and CREB3L1) responsible for the activation of HSCs during fibrogenesis. Bulk RNA-seq data of NASH patient livers and rodent models for liver fibrosis of diverse etiologies allowed us to evaluate the translatability of candidate therapeutic targets for NASH-related fibrosis. We identified 61 liver fibrosis-associated genes (e.g., AEBP1, PRRX1 and LARP6) that may serve as a repertoire of translatable drug target candidates. Consistent with the above regulon results, gene regulatory network analysis allowed the identification of CREB3L1 as a master regulator of many of the 61 genes. Together, this study highlights potential cell-cell interactions and master regulators that underlie HSC activation and reveals genes that may represent prospective hallmark signatures for liver fibrosis.

COL6A3 expression in adipose tissue cells is associated with levels of the homeobox transcription factor PRRX1

Fibrillar collagen COL6α3 in adipose tissue has been associated with obesity, inflammation, insulin resistance and cancer. We here aimed to identify novel transcriptional regulators of COL6A3 expression. Based on a transcriptome dataset of adipose tissue, we identified strong correlations for 56 genes with COL6A3 mRNA, including targets of TGF-β/SMAD signaling. Among the identified candidates, the homeobox transcription factor PRRX1 showed a particularly striking co-expression with COL6A3, validated across several different cohorts, including patients with extreme obesity, insulin sensitive and resistant obesity (subcutaneous and omental), after profound fat loss (subcutaneous), and lean controls (subcutaneous). In human and mouse adipose cells, PRRX1 knockdown reduced COL6A3 mRNA and PRRX1 overexpression transactivated a reporter construct with the endogenous human COL6A3 promoter. Stable PRRX1 overexpression in 3T3-L1 cells induced Col6a3 mRNA threefold specifically after adipogenic induction, whereas TGF-β1 treatment upregulated Col6a3 mRNA also in the preadipocyte state. Interestingly, pro-inflammatory stimulus (i.e., TNF-α treatment) decreased PRRX1-mediated Col6a3 transactivation and mRNA expression, supporting a role for this mechanism in the regulation of adipose tissue inflammation. In conclusion, we identified the homeobox factor PRRX1 as a novel transcriptional regulator associated with COL6A3 expression, providing new insight into the regulatory mechanisms of altered adipose tissue function in obesity and insulin resistance.

Dynamic analysis of m6A methylation spectroscopy during progression and reversal of hepatic fibrosis

Aim: To dynamically analyze the differential m6A methylation during the progression and reversal of hepatic fibrosis. Materials & methods: We induced hepatic fibrosis in C57/BL6 mice by intraperitoneal injection of CCl4. The reversal model of hepatic fibrosis was established by stopping drug after continuous injection of CCl4. Dynamic m6A methylation was evaluated using MeRIP-Seq in the progression and reversal of hepatic fibrosis at different stages. Result: During the hepatic fibrosis, differential m6A methylation was mainly enriched in processes associated with oxidative stress and cytochrome metabolism, while differential m6A methylation was mainly enriched in processes associated with immune response and apoptosis in the hepatic fibrosis reversal. Conclusion: m6A methylation plays an important role in the progression and reversal of hepatic fibrosis.

Astrocytic NDRG2 is critical in the maintenance of neuropathic pain

Activation of astrocytes and abnormal synaptic glutamate metabolism are closely associated with the induction and maintenance of neuropathic pain (NP), but the exact mechanism underlying this association remains unclear. N-myc downstream-regulated gene 2 (NDRG2), a novel tumor-suppressor protein and stress-response gene, is involved in the pathogenesis of several neurodegenerative diseases. However, its role in nociceptive transduction has rarely been investigated. Here, we found that NDRG2, which was mainly expressed in the astrocytes in the central nervous system (CNS), was increased in the spinal cord of a spinal nerve ligation (SNL) rat model for NP. Suppression of NDRG2 by intrathecal injection of an NDRG2-RNAi-adenovirus significantly alleviated SNL-induced mechanical and thermal hypersensitivity, as well as elevated astrocytic glutamate transporter 1 (GLT-1) expression and downregulated pro-inflammatory cytokine levels, in the spinal dorsal horn of rats on Day 10 after SNL. Furthermore, in lipopolysaccharide (LPS)-stimulated primary astrocytic cultures derived from neonatal rats, inhibition of NDRG2 significantly reversed both the LPS-induced activation of astrocytes and decreased expression of GLT-1. By contrast, overexpression of NDRG2 by an adenoviral vector carrying NDRG2 resulted in astrocytic activation, aberrant glutamatergic neurotransmission, and spontaneous nociceptive responses in rats. Intrathecal injection of AG490, which is an inhibitor of the Janus tyrosine kinase and signal transducer and activator of the transcription 3 (JAK/STAT3) signaling pathway, significantly attenuated both mechanical and thermal hyperalgesia, as well as inhibited reactive astrocytes and restored normal expression levels of astrocytic GLT-1, in the spinal dorsal horn of NDRG2-overexpression rats. In conclusion, spinal astrocytic NDRG2 is critical in the maintenance of NP. Moreover, NDRG2 modulates astrocytic activation and inflammatory responses via regulating GLT-1 expression through the JAK/STAT3 signaling pathway. Our findings suggested that NDRG2 could be a novel therapeutic target for the treatment of NP.

Cytochrome P4501B1 in bone marrow is co-expressed with key markers of mesenchymal stem cells. BMS2 cell line models PAH disruption of bone marrow niche development functions

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants that are metabolized to carcinogenic dihydrodiol epoxides (PAHDE) by cytochrome P450 1B1 (CYP1B1). This metabolism occurs in bone marrow (BM) mesenchymal stem cells (MSC), which sustain hematopoietic stem and progenitor cells (HSPC). In BM, CYP1B1-mediated metabolism of 7, 12-dimethylbenz[a]anthracene (DMBA) suppresses HSPC colony formation within 6 h, whereas benzo(a)pyrene (BP) generates protective cytokines. MSC, enriched from adherent BM cells, yielded the bone marrow stromal, BMS2, cell line. These cells express elevated basal CYP1B1 that scarcely responds to Ah receptor (AhR) inducers. BMS2 cells exhibit extensive transcriptome overlap with leptin receptor positive mesenchymal stem cells (Lepr+ MSC) that control the hematopoietic niche. The overlap includes CYP1B1 and the expression of HSPC regulatory factors (Ebf3, Cxcl12, Kitl, Csf1 and Gas6). MSC are large, adherent fibroblasts that sequester small HSPC and macrophage in the BM niche (Graphic abstract). High basal CYP1B1 expression in BMS2 cells derives from interactions between the Ah-receptor enhancer and proximal promoter SP1 complexes, boosted by autocrine signaling. PAH effects on BMS2 cells model Lepr+MSC niche activity. CYP1B1 metabolizes DMBA to PAHDE, producing p53-mediated mRNA increases, long after the in vivo HSPC suppression. Faster, direct p53 effects, favored by stem cells, remain possible PAHDE targets. However, HSPC regulatory factors remained unresponsive. BP is less toxic in BMS2 cells, but, in BM, CYP1A1 metabolism stimulates macrophage cytokines (Il1b > Tnfa> Ifng) within 6 h. Although absent from BMS2 and Lepr+MSC, their receptors are highly expressed. The impact of this cytokine signaling in MSC remains to be determined.

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BMS2 and Lepr+MSC cells co-express CYP1B1 and 12 functional niche activity markers.

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CYP1B1 mRNA in BMS2 cells depends on activation of SP1 coupled to an AhR enhancer unit.

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DMBA metabolism by CYP1B1 activates p53 gene targets in BMS2 cells far more than BP.

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HSPC suppression by CYP1B1 generation of PAHDE requires rapid, non-genomic targets.

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BMS2 and Lepr+MSC share receptors activated by BP stimulation of macrophage cytokines.

Expression of hepatic stellate cell activation-related genes in HBV-, HCV-, and nonalcoholic fatty liver disease-associated fibrosis

Liver fibrosis is a manifestation of chronic liver injury. It leads to hepatic dysfunction and is a critical element in the pathogenesis of cirrhosis and hepatocellular carcinoma. The activation of hepatic stellate cells (HSC) plays a central role in liver fibrogenesis of different etiologies. To elucidate the molecular mechanism of this phenomenon, it is important to analyze the changes in gene expression that accompany the HSC activation process. In this study, we isolated quiescent and activated HSCs from control mice and mice with CCl₄-induced liver fibrosis, respectively, and performed RNA sequencing to compare the differences in gene expression patterns between the two types of HSCs. We also reanalyzed public gene expression data for fibrotic liver tissues isolated from patients with HBV infection, HCV infection, and nonalcoholic fatty liver disease to investigate the gene expression changes during liver fibrosis of these three etiologies. We detected 146 upregulated and 18 downregulated genes in activated HSCs, which were implicated in liver fibrosis as well. Among the overlapping genes, seven transcription factor-encoding genes, ARID5B, GATA6, MITF, PBX1, PLAGL1, SOX4, and SOX9, were upregulated, while one, RXRA, was downregulated. These genes were suggested to play a critical role in HSC activation, and subsequently, in the promotion of liver fibrosis. We undertook the RNA sequencing of quiescent and activated HSCs and analyzed the expression profiles of genes associated with HSC activation in liver fibrotic tissues from different liver diseases, and also aimed to elucidate the changes in gene expression patterns associated with HSC activation and liver fibrosis.

TWEAK promotes hepatic stellate cell migration through activating EGFR/Src and PI3K/AKT pathways

Activated human hepatic stellate cells (HSCs) showed enhanced ability of migration compared with quiescent HSCs, which is pivotal in liver fibrogenesis. The aim of the present study was to investigate the effects of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) on the migration of activated HSCs and to explore the relevant potential mechanisms. Human HSCs LX-2 cells were cultured with TWEAK. TNFRSF12A-downexpressing lentiviruses were used to infect LX-2 cells. The specific matrix metalloproteinases inhibitor BB94, the Src family kinase inhibitor, Dasatinib, and the specific inhibitor of phosphoinositide 3-kinase (PI3K), LY294002 were used to treat LX-2 cells combined with TWEAK. Cell migration and invasion was tested by the transwell assay. The expression of EGFR/Src, PI3K/AKT, and matrix metallopeptidase 9 (MMP9) was identified by real-time polymerase chain reaction or western blotting. The result showed TWEAK promoted HSC migration and collagen production. BB94 significantly attenuated the migration of LX-2 induced by TWEAK. Dasatinib inhibited the ability of cell migration stimulated by TWEAK. TWEAK upregulated the phosphorylation of epidermal growth factor receptor (EGFR) and Src. The phosphorylation of PI3K and AKT was significantly activated by TWEAK stimulation. Inhibition of PI3K/AKT reduced the expression of MMP9 induced by TWEAK. The present study, for the first time, demonstrated that TWEAK promoted HSC migration through the activation of EGFR/Src and PI3K/AKT pathways, and showed a novel potential mechanism of HSC migration regulated by TWEAK.

Identification of potential platelet-derived growth factor receptor α inhibitors by computational screening and binding simulations

Platelet-derived growth factor receptor α (PDGFRα) is considered as a promising target for the treatment of fibrotic diseases. In this study, two types of pharmacophore model, which generated by ligand-based and receptor-based method, were put forward to identify novel chemical entities as PDGFRα inhibitors. It was found that some pharmacophore characteristics established by the two approaches overlap each other. In order to elucidate detailed interactions, representative molecules were selected to predict the conformations and binding modes of the molecules by molecular docking method. The calculation results of binding free energy illustrated that the van der Waals energy and nonpolar solvation were the most prominent contribution to the interactions between the inhibitors and PDGFRα. To further verify the accuracy of the docking results and the stability of the complexes system, the binding modes of two potent PDGFRα inhibitors were examined by 100 ns molecular dynamics simulations. Herein, we reported the basic structural requirements of PDGFRα inhibitors for the first time through molecular docking and molecular dynamics simulations. Subsequently, the two pharmacophore models were used for virtual screening to query potential active molecules from Food and Drug Administration approved database. The hit molecules here might provide additional scaffolds for further optimization of PDGFRα inhibitors.

Insulin receptor substrate 2 (IRS2) deficiency delays liver fibrosis associated with cholestatic injury

Insulin receptor substrate 2 (IRS2) is a key downstream mediator of insulin and insulin-like growth factor 1 (IGF1) signalling pathways and plays a major role in liver metabolism. The aim of this study was to investigate whether IRS2 had an impact on the hepatic fibrotic process associated with cholestatic injury. Bile duct ligation (BDL) was performed in wild-type (WT) and Irs2-deficient (IRS2KO) female mice. Histological and biochemical analyses, together with fibrogenic and inflammatory responses were evaluated in livers from mice at 3, 7 and 28 days following BDL. We also explored whether activation of human hepatic stellate cells (HSCs) induced by IGF1 was modulated by IRS2. IRS2KO mice displayed reduced disruption of liver histology, such hepatocyte damage and excess deposition of extracellular matrix components, compared with WT mice at 3 and 7 days post-BDL. However, no histological differences between genotypes were found at 28 days post-BDL. The less pro-inflammatory profile of bile acids accumulated in the gallbladder of IRS2KO mice after BDL corresponded with the reduced expression of pro-inflammatory markers in these mice. Stable silencing of IRS2 or inhibition of ERK1/2 reduced the activation of human LX2 cells and also reduced induction of MMP9 upon IGF1 stimulation. Furthermore, hepatic MMP9 expression was strongly induced after BDL in WT mice, but only a slight increase was found in mice lacking IRS2. Our results have unravelled the signalling pathway mediated by IGF1R–IRS2–ERK1/2–MMP9 as a key axis in regulating HSC activation, which might be therapeutically relevant for targeting liver fibrosis.

Summary: IRS2 is a key mediator of IGF1R signalling in hepatic stellate cell activation in cholestatic liver injury.

Transcriptional regulation of Hepatic Stellate Cell activation in NASH

Non-alcoholic steatohepatitis (NASH) signified by hepatic steatosis, inflammation, hepatocellular injury, and fibrosis is a growing cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma. Hepatic fibrosis resulting from accumulation of extracellular matrix proteins secreted by hepatic myofibroblasts plays an important role in disease progression. Activated hepatic stellate cells (HSCs) have been identified as the primary source of myofibroblasts in animal models of hepatotoxic liver injury; however, so far HSC activation and plasticity have not been thoroughly investigated in the context of NASH-related fibrogenesis. Here we have determined the time-resolved changes in the HSC transcriptome during development of Western diet- and fructose-induced NASH in mice, a NASH model recapitulating human disease. Intriguingly, HSC transcriptional dynamics are highly similar across disease models pointing to HSC activation as a point of convergence in the development of fibrotic liver disease. Bioinformatic interrogation of the promoter sequences of activated genes combined with loss-of-function experiments indicates that the transcriptional regulators ETS1 and RUNX1 act as drivers of NASH-associated HSC plasticity. Taken together, our results implicate HSC activation and transcriptional plasticity as key aspects of NASH pathophysiology.

Transcriptome analysis reveals differentially expressed genes between human primary bone marrow mesenchymal stem cells and human primary dermal fibroblasts

Stromal cells have been widely used in biomedical research and disease modeling studies in vitro. The most commonly used types of stromal cells are mesenchymal stem cells and fibroblasts. Their cellular phenotypes and differentiation capabilities are quite similar and there are no specific distinction criteria. In order to identify transcriptomic differences between these 2 cell types, we performed next-generation RNA sequencing. Using the global gene expression profile and pathway analysis, we showed that human primary bone marrow mesenchymal stem cells and human primary dermal fibroblasts have different molecular signatures. We also identified critical transcription factors that are differentially expressed between these cells. We then proposed that homeobox genes and some other sequence-specific transcription factors are not only responsible for transcriptional differences, but also discriminate bone marrow mesenchymal stem cells and dermal fibroblasts at the transcriptional level.

Cellular crosstalk mediated by platelet-derived growth factor BB and transforming growth factor β during hepatic injury activates hepatic stellate cells

Apoptotic hepatocytes release factors that activate hepatic stellate cells (HSCs), thereby inducing hepatic fibrosis. In the present study, in vivo and in vitro injury models were established using acetaminophen, ethanol, carbon tetrachloride, or thioacetamide. Histology of hepatotoxicant-induced diseased hepatic tissue correlated with differential expression of fibrosis-related genes. A marked increase in co-staining of transforming growth factor β receptor type II (TGFRIIβ) – desmin or α-smooth muscle actin – platelet-derived growth factor receptor β (PDGFRβ), markers of activated HSCs, in liver sections of these hepatotoxicant-treated mice also depicted an increase in Annexin V – cytokeratin expressing hepatocytes. To understand the molecular mechanisms of disease pathology, in vitro experiments were designed using the conditioned medium (CM) of hepatotoxicant-treated HepG2 cells supplemented to HSCs. A significant increase in HSC proliferation, migration, and expression of fibrosis-related genes and protein was observed, thereby suggesting the characteristics of an activated phenotype. Treating HepG2 cells with hepatotoxicants resulted in a significant increase in mRNA expression of platelet-derived growth factor BB (PDGF-BB) and transforming growth factor β (TGFβ). CM supplemented to HSCs resulted in increased phosphorylation of PDGFRβ and TGFRIIβ along with its downstream effectors, extracellular signal-related kinase 1/2 and focal adhesion kinase. Neutralizing antibodies against PDGF-BB and TGFβ effectively perturbed the hepatotoxicant-treated HepG2 cell CM-induced activation of HSCs. This study suggests PDGF-BB and TGFβ as potential molecular targets for developing anti-fibrotic therapeutics.