Long-term environmental enrichment reduces microglia morphological diversity of the molecular layer of dentate gyrus

Area of Science:

• Neuroscience
• Neuroimmunology
• Cell Biology

Background:

• Microglia, the resident immune cells of the brain, play crucial roles in neural development and function.
• Environmental factors are known to influence brain plasticity and cellular behavior.
• Understanding microglial responses to environmental stimuli is vital for comprehending brain health and disease.

Purpose of the Study:

• To investigate the long-term effects of environmental enrichment on microglial morphology in the dentate gyrus molecular layer.
• To compare microglial phenotypes in standard (impoverished) and enriched environments across different ages.
• To assess the impact of environmental enrichment on microglial diversity and potential functional roles.

Main Methods:

• Three-dimensional reconstruction and morphological analysis of microglia (IBA-1 labeled) from Swiss albino mice housed in standard (SEA) or enriched (EEA) environments.
• Stereological estimation of microglial numbers in the molecular layer of the dentate gyrus.
• Hierarchical cluster analysis and discriminant function analysis for morphological classification.

Main Results:

• Standard environment (SEA) and young enriched environment (EEY) housing revealed two distinct microglial morphological phenotypes in the MolDG.
• Long-term environmental enrichment (EEA) significantly reduced microglial morphological diversity, resulting in a predominant single morphotype.
• Microglia in the EEA exhibited intermediate morphological complexity between the two phenotypes observed in SE mice.

Conclusions:

• Distinct microglial phenotypes in standard environments may indicate specialized physiological roles.
• Long-term environmental enrichment appears to induce adaptive changes in microglial phenotypes.
• These adaptive microglial responses may be associated with enhanced processing of somatomotor and cognitive stimuli.