Novel in vitro biomarkers for hepatotoxicity: exosomal miR-122

Introduction: In vitro models for liver disease suffer from the lack of well-established and sensitive biomarkers of cellular damage. MicroRNAs (miRNAs; small noncoding RNAs) represent potential biomarkers for the detection of drug-induced liver injury in vivo and in vitro. Altered physiological state caused by disease or tissue damage results in altered release of exosomal- or protein-bound miRNAs, detectable in body fluids and cell culture media.

Materials and Methods: Here, we exposed 3D-HepaRG cultures to methotrexate (MTX) and acetaminophen (APAP) and used q-RT-PCR to investigate miRNAs as potentially sensitive markers of hepatotoxicity in vitro, with a specific focus on the exosomal release. We investigated three miRNAs, miR-122-5p and miR-192-5p, both associated with hepatic damage, and miR-34a-5p, involved with apoptosis. Metabolic activity, urea and albumin release were assessed to confirm key hepatocellular characteristics of 3D-HepaRG.

Results: The 3D-HepaRG model was able to metabolise testosterone, produced urea and albumin. APAP treatment increased exosomal release of all three tested miRNAs, while MTX increased miR-122-5p release only. Absolute quantification of miR-122-5p corroborated the release of this miRNA by both treatments.

Discussion: Exosomes could be efficiently isolated from 3D-HepaRG, characterized, and used for miRNA extraction and quantification. We identified that total extracellular and exosomal-miR-122-5p release occurred at concentrations lower than those leading to MTX-induced apoptosis/necrosis, which corroborate previous findings using other hepatotoxic compounds.

Conclusion: Our results demonstrate the suitability of 3D-HepaRG combined with exosomal miRNA measurement for the detection of hepatotoxicity in vitro. Specifically, exosomal-miR-122-5p is a sensitive marker of APAP- and MTX-induced in vitro damage.