Urinary exosomal microRNAs as predictive biomarkers for persistent psychotic-like experiences

Psychotic-like experiences (PLEs), psychotic symptoms occurring in adolescence without underlying illness, affect 5-17% of the general population. While most PLEs are transient, persistence is a robust risk factor for subsequent psychiatric disorders like schizophrenia and depression. Identifying biomarkers for persistent PLEs is crucial for early intervention. Exosomal microRNAs (miRNAs), short non-coding RNAs regulating gene expression, are found in various body fluids and are promising biomarkers for psychiatric disorders. Their presence in easily accessible urine samples, potentially reflecting brain pathophysiology, makes them particularly attractive for adolescent studies. This study hypothesized that urinary exosomal miRNA expression profiles could predict the persistence of PLEs in adolescents.

Existing literature highlights the prevalence and impact of PLEs, with persistence significantly increasing the risk of developing serious mental illnesses. Meta-analyses consistently show a substantial percentage of adolescents experiencing PLEs, and longitudinal studies demonstrate a clear link between persistent PLEs and later-onset psychiatric disorders. However, few biological markers have been identified to predict PLE persistence. While exosomal miRNAs have gained attention as potential biomarkers for various psychiatric conditions, their role in PLEs remained unexplored prior to this study.

This study used a population-based biomarker subsample (pb-TTC) of the Tokyo Teen Cohort Study (TTC). 345 adolescents (mean age 13.5 years) underwent PLE assessments at baseline (age 13) and follow-up (age 14) using semi-structured interviews by experienced psychiatrists, based on self-reported questionnaires including the Adolescent Psychotic-Like Symptom Screener (APSS). Four groups were defined: no-experience, remitted, incident, and persistent PLEs. Urine samples were collected at baseline. Exosomes were isolated from urine using a miRCURY Exosome Cell/Urine/CSF Kit, and RNA was extracted using a miRNeasy Micro kit. Next-generation sequencing (NovaSeq 6000) quantified miRNA expression. Differential expression analysis (edgeR) compared persistent and remitted PLE groups, and logistic regression models were built to predict persistent PLEs using differentially expressed miRNAs. Five-fold cross-validation assessed model robustness. Pathway enrichment analysis (DIANA-mirPath v.3) explored the functions of identified miRNAs.

The study included 15 adolescents with persistent PLEs and 15 age- and sex-matched adolescents with remitted PLEs in the miRNA analysis. Of 2631 miRNAs, 427 were expressed above a threshold in at least three subjects. Six miRNAs (hsa-miR-486-5p, hsa-miR-199a-3p, hsa-miR-144-5p, hsa-miR-451a, hsa-miR-143-3p, and hsa-miR-142-3p) showed significant differential expression (FDR < 5%, >2-fold change) between the groups, all downregulated in the persistent PLE group. A logistic regression model using these six miRNAs achieved an AUC of 0.853 in predicting persistent PLEs. Five-fold cross-validation yielded an average AUC of 0.847 (95% CI: 0.690-0.994), demonstrating good predictive performance and lack of overfitting. Pathway enrichment analysis revealed associations with pathways relevant to schizophrenia and major depressive disorder, including dopaminergic synapse and ECM-receptor interaction. Three of the six miRNAs (hsa-miR-144-5p, hsa-miR-451a, and hsa-miR-143-3p) have previously been linked to schizophrenia or major depressive disorder.

This study's findings provide compelling evidence that urinary exosomal miRNAs can accurately predict the persistence of PLEs in adolescents. The high predictive accuracy of the six-miRNA model (AUC > 0.8) suggests a significant potential for these miRNAs as novel biomarkers. The identified miRNAs and their associated pathways (dopaminergic synapse, ECM interaction) align with known biological mechanisms in schizophrenia and other psychiatric disorders, strengthening the relevance of these findings. This research contributes significantly to early detection and intervention strategies for individuals at high risk of developing these serious mental illnesses.

This study identified a panel of six urinary exosomal microRNAs that effectively predicts the persistence of psychotic-like experiences in adolescents. The model demonstrates high accuracy and robustness, suggesting a potential for these miRNAs as novel biomarkers for assessing the risk of developing serious psychiatric disorders. Future research should validate these findings in larger, independent cohorts and investigate the functional roles of these miRNAs in the pathophysiology of PLEs and the transition to psychosis.

The study's relatively small sample size is a key limitation. While statistical methods like the Benjamini-Hochberg procedure and cross-validation mitigated this to some extent, replication in larger, independent cohorts is crucial to validate the findings. Further research is needed to explore the functional relationship between urinary exosomal miRNAs and PLEs and to evaluate predictive performance over longer time periods.