Exosome-Mediated Intercellular Communication between Hepatitis C Virus-Infected Hepatocytes and Hepatic Stellate Cells

Abstract

Fibrogenic pathways in the liver are principally regulated by activation of hepatic stellate cells (HSC). Fibrosis is associated with chronic hepatitis C virus (HCV) infection, although the mechanism is poorly understood. HSC comprise the major population of nonparenchymal cells in the liver. Since HCV does not replicate in HSC, we hypothesized that exosomes secreted from HCV-infected hepatocytes activate HSC. Primary or immortalized human hepatic stellate (LX2) cells were exposed to exosomes derived from HCV-infected hepatocytes (HCV-exo), and the expression of fibrosis-related genes was examined. Our results demonstrated that HCV-exo internalized to HSC and increased the expression of profibrotic markers. Further analysis suggested that HCV-exo carry miR-19a and target SOCS3 in HSC, which in turn activates the STAT3-mediated transforming growth factor ␤ (TGF-␤) signaling pathway and enhances fibrosis marker genes. The higher expression of miR-19a in exosomes was also observed from HCV-infected hepatocytes and in sera of chronic HCV patients with fibrosis compared to healthy volunteers and non-HCV-related liver disease patients with fibrosis. Together, our results demonstrated that miR-19a carried through the exosomes from HCV-infected hepatocytes activates HSC by modulating the SOCS-STAT3 axis. Our results implicated a novel mechanism of exosome-mediated intercellular communication in the activation of HSC for liver fibrosis in HCV infection.IMPORTANCE HCV-associated liver fibrosis is a critical step for end-stage liver disease progression. However, the molecular mechanisms for hepatic stellate-cell activation by HCV-infected hepatocytes are underexplored. Here, we provide a role for miR-19a carried through the exosomes in intercellular communication between HCVinfected hepatocytes and HSC in fibrogenic activation. Furthermore, we demonstrate the role of exosomal miR-19a in activation of the STAT3-TGF-␤ pathway in HSC. This study contributes to the understanding of intercellular communication in the pathogenesis of liver disease during HCV infection. KEYWORDS hepatitis C virus, exosomes, miRNAs, liver fibrosis, hepatic stellate cells, microRNA H epatitis C virus (HCV) is a positive-sense, single-stranded RNA virus with a genome size of 9.6 kb that encodes several structural and nonstructural proteins. About 170 million people are infected with HCV worldwide. Chronic HCV infection often results in the development of fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). HCVassociated liver fibrosis is a key pathological process leading to liver cirrhosis and HCC (1, 2), although the underlying mechanisms of disease progression remain unclear. Hepatic stellate cells (HSC) are involved in the pathogenesis of liver fibrosis (3). Liver injury is characterized by a phenotypic and functional transformation of normally

Decoding the role of extracellular vesicles in liver diseases

“…73 In addition, Dreux et al 74 showed that exosomes mediate the transfer of viral RNA from HCV-permissive cells to non-permissive plasmacytoid dendritic cells, which subsequently activates innate immunity. Furthermore, Devhare et al 75 demonstrated that exosomes from HCV-infected hepatocytes activate human HSCs, which is crucial for fibrogenic activation in HCV patients. Additionally, this study showed that miR-19a was highly enriched in EVs isolated from HCV-infected hepatocytes and in sera of chronic HCV patients with fibrosis.…”

“…Uptake of miR-19a into HSCs results in HSC activation through the depletion of suppressor of cytokine signaling (SOCS) 3 and subsequently activates a signaling cascade involving signal transducer and activator of transcription 3 (STAT3), transforming growth factor β1 (TGF-β1), and SMAD family member 3 (SMAD3). 75 …”

Hepatitis C virus–induced tumor‐initiating cancer stem–like cells activate stromal fibroblasts in a xenograft tumor model

“…A number of mechanisms are reported to activate HSCs during HCV infection . We have recently shown that chemokine (C‐C motif) ligand 5 is induced in macrophages during exposure to HCV and that microRNA‐19a carried through the exosomes from HCV‐infected hepatocytes activates HSCs . In this study, we demonstrated that HCV‐infected hepatocytes recruit activated fibroblasts, in part, by secretion of TGF‐β.…”

Hepatitis C Virus Manipulates Humans as its Favorite Host for a Long‐Term Relationship

“…TGF‐β, a multifunctional cytokine, secreted in conditioned medium from HCV‐infected human hepatocytes, activates fibrosis‐related markers in HSCs, further suggesting its role in fibrosis activation. Exosomes are extracellular vesicles which are considered important mediators of cell‐cell communication by delivering the information they carry to neighboring cells . In the liver, exosomes carrying miRNAs may take part in fibrosis by modulating epigenetic regulation of HSCs .…”

“…Exosome‐mediated intercellular transfer of connective tissue growth factor is also implicated in fine‐tuning of liver fibrosis. Exosomes carrying miR‐19a shuttle from HCV‐infected hepatocytes to HSCs and target SOCS3 to induce the STAT3/TGF‐β1 axis for fibrogenic activation …”