Traumatic Brain Injury Leads to Alterations in Contusional Cortical miRNAs Involved in Dementia

Area of Science:

• Neuroscience
• Molecular Biology
• Pathology

Background:

• Traumatic brain injury (TBI) is a known risk factor for Alzheimer's disease (AD), accelerating its onset.
• Post-mortem studies show amyloid-β plaques and tau aggregates in TBI patients, but underlying mechanisms remain unclear.

Purpose of the Study:

• To investigate if focal TBI induces changes in microRNA (miRNA) expression.
• To determine if these miRNA alterations affect genes involved in neurodegeneration and AD pathology.

Main Methods:

• Experimental TBI was induced in rats using the controlled cortical impact (CCI) model.
• miRNA arrays were performed on brain extracts from injured and control rats.
• Quantitative PCR (qPCR) confirmed miRNA expression changes.
• Gene expression of amyloid and tau-related proteins (BACE1, GSK3β) was analyzed.

Main Results:

• Significant alterations in miRNA expression were observed in and around the TBI contusion compared to the contralateral side.
• miR-9 was upregulated, while miR-29b, miR-34a, miR-106b, miR-181a, and miR-107 were downregulated.
• These miRNA changes correlated with altered expression of BACE1 and GSK3β.
• Increased neuroinflammation (TNF-α), glial activation, neuronal loss, and tau phosphorylation were noted.

Conclusions:

• Focal TBI induces specific miRNA expression changes.
• These miRNA alterations are associated with the regulation of genes critical to AD pathogenesis, including amyloid and tau pathways.
• The findings suggest that secondary injury cascades following TBI impact miRNA regulation, contributing to AD dementia development.