Blood-Based miRNA Biomarkers as Correlates of Brain-Based miRNA Expression

Area of Science:

• Neuroscience
• Epigenetics
• Molecular Biology

Background:

• Peripheral samples (blood, saliva) are used in neurological/neuropsychiatric research, but linking peripheral biomarkers to brain pathology is challenging.
• Understanding the relationship between peripheral blood and brain epigenetic activity is crucial for biomarker development.

Purpose of the Study:

• To investigate correlations between microRNA (miRNA) expression in peripheral blood mononuclear cells (PBMCs) and various brain regions in baboons (Papio hamadryas).
• To explore the potential of blood-based miRNA profiling as a proxy for brain miRNA activity.

Main Methods:

• Pilot study using next-generation sequencing on PBMCs and 14 brain regions from two groups of baboons (4 and 6 animals each).
• Analysis included identifying expressed miRNAs, calculating pairwise and averaged correlations, principal component analysis, and linear mixed effects modeling.
• Hierarchical clustering was used to identify co-expression patterns and enriched cell types.

Main Results:

• 362 miRNAs were identified in brain samples; 39-44 showed nominal correlations between peripheral blood and mean brain expression.
• Averaged across tissue types, significant correlations (P < 2.2 × 10^-16) were found between PBMCs and brain regions (r = 0.47-0.57).
• miRNA expression differed between blood and brain, but most variance was due to miRNA type (>70%); blood-derived miRNAs were enriched in immune cells and targeted MYC.

Conclusions:

• Despite differentiation between tissue types, significant correlated patterns exist between blood and brain miRNAs.
• Blood-based miRNA profiling shows potential utility for indirectly assessing brain miRNA activity.
• Findings have implications for understanding neuroinflammation and c-Myc-mediated processes.