Translational analysis of miRNA-mRNA regulatory networks in male rat and human prefrontal cortex following chronic opioid self-administration

Opioid use disorder (OUD) is a chronic condition driven by neuroadaptations that promote continued drug use. Identifying molecular mechanisms supporting these adaptations remains a major challenge. An understudied area that merits further investigation is the expression of microRNAs (miRNAs) in the brain during OUD. miRNAs are small noncoding RNAs that regulate post-transcriptional gene expression and have a putative role in opioid-induced phenotypes. Opioids impart unique regulation of miRNAs in the brain, dependent on brain region, drug dose, and exposure protocol. However, unbiased measurement of opioid-associated miRNA profiles in key brain regions known to regulate drug-seeking phenotypes, such as the prefrontal cortex (PFC) is limited. The PFC is a critical component of the mesolimbic system that is adversely affected by opioids. To address this knowledge gap, we used a preclinical protocol of self-administration (SA) of the opioid heroin to model chronic volitional opioid use in male rats. We hypothesized that chronic heroin SA induces reproducible alterations in miRNA expression. Using small RNA sequencing, we identified 15 significant miRNAs associated with chronic heroin SA in the rat PFC. Among six fully conserved candidates, three miRNAs, let-7 g-3p, miR-10a-5p, and miR-323-5p, were prioritized for targeted validation across an independent biological cohort using qPCR as a focused sampling of conserved candidates spanning distinct miRNA families and complementary predicted regulatory profiles. While preclinical studies provide insight into miRNA regulation following opioids, measurement of human PFC miRNAs in OUD remains sparse. Therefore, we used miRNA target prediction tools and a published human OUD transcriptomic dataset to examine pathways potentially regulated by these conserved opioid-responsive miRNAs. Our findings suggest conserved miRNA-mRNA regulatory axes may contribute to opioid-induced pathology in the PFC.