Extracellular vesicles (EVs) released during cell stress, or demise, can contain a barcode of the cell origin, including specific
microRNAs (
miRNAs). Here, we tested the hypothesis that during early
alcoholic steatohepatitis (ASH) development, hepatocytes (HCs) release EVs with an
miRNA signature that can be measured in circulation. A time-course experiment showed that after 2 weeks of intragastric infusion, a time point that results in isolated steatosis, there was no increase of blood EVs. After 4 weeks of infusion, mice developed features of early ASH accompanied by a marked increase in the level of EVs in blood (P < 0.05), as well as in
culture media of isolated HCs (P < 0.001) and hepatic macrophages (P < 0.001), with HCs being the predominant source of EVs. The transcriptome analysis of HC-EVs from ASH mice detected differentially expressed
miRNAs, including nine significantly up-regulated and four significantly down-regulated
miRNAs. Target prediction and pathway analyses of the up-regulated
miRNAs identified 121 potential target genes involved in inflammatory and
cancer pathways, such as
nuclear factor kappa B,
EGF, Wnt, and
B-cell lymphoma 2. Three
miRNAs, let7f, miR-29a, and miR-340, were increased in blood EVs from ASH mice (P < 0.05), but not in blood EVs from three other models of chronic liver injury, including bile duct
ligation,
nonalcoholic steatohepatitis, and obese mice, as well as EVs released from hepatocytes exposed to
ethanol. Blood EV level (P < 0.01) and three
miRNAs (P < 0.05) were significantly increased in patients with ambulatory mild ALD as compared to nonalcoholics.
CONCLUSION: Damaged hepatocytes from ASH mice are a key EV source with a specific
miRNA cargo, which are specific for ASH-related liver injury. These findings uncover EVs as a potentially novel diagnostic for ASH. (Hepatology 2017;65:475-490).