A Semi-Automated and Unbiased Microglia Morphology Analysis Following Mild Traumatic Brain Injury in Rats.

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• Mild traumatic brain injury (mTBI) impacts millions annually.
• Microglia, the brain's immune cells, change morphology with activation.
• Morphological states (ramified, hypertrophic, ameboid, rod-like) reflect microglia activation levels.

Purpose of the Study:

• To quantify microglial morphological changes following mTBI.
• To classify microglia states using quantitative morphological features.
• To establish an unbiased method for assessing mTBI-induced neuroinflammation.

Main Methods:

• Utilized the Closed-Head Impact Model of Engineered Rotational Acceleration (CHIMERA) in Sprague-Dawley rats.
• Collected brain tissue 4 days post-mTBI for Iba-1 staining.
• Employed MicrogliaMorphology ImageJ plugin and R package to quantify 27 morphological features.
• Applied k-means clustering for microglia state classification.

Main Results:

• CHIMERA injury significantly altered microglial morphology compared to sham controls.
• A notable increase in hypertrophic (activated) microglia was observed.
• A decrease in ramified (inactive) microglia was detected post-mTBI.

Conclusions:

• mTBI induces significant shifts in microglia morphology, indicating activation.
• The study provides a quantitative, semi-automated method for microglia classification.
• Findings contribute to understanding neuroinflammation after mTBI and potential classification strategies.