Microglia maintain the normal structure and function of the hippocampal astrocyte network

Area of Science:

• Neuroscience
• Cell Biology
• Neuroimmunology

Background:

• Microglia-neuron interactions are well-studied, but their influence on astrocyte function is less understood.
• Astrocytes play key roles in regulating neuronal structure and function.
• Microglia are the primary immune cells in the central nervous system.

Purpose of the Study:

• To investigate the role of microglia in regulating astrocyte structure and function in the mouse hippocampus.
• To determine how microglia influence synaptic transmission and plasticity.
• To explore microglia-astrocyte interactions in different functional states.

Main Methods:

• Microglia depletion using a CSF1R antagonist (PLX5622).
• Assessment of astrocyte syncytial isopotentiality and dye coupling.
• Measurement of connexin (Cx) 30 and 43 expression.
• Evaluation of synaptic transmission and long-term potentiation (LTP).
• Microglia priming with lipopolysaccharide (LPS).

Main Results:

• Microglia depletion disrupted astrocyte syncytial isopotentiality and dye coupling, associated with decreased Cx30/43 expression.
• Synaptic transmission was reduced at baseline and after LTP in the absence of microglia.
• Priming microglia enhanced CA3-CA1 synaptic transmission and Homer1 expression.
• Astrocyte network function was unaffected by microglia priming, suggesting state-dependent effects.

Conclusions:

• Microglia are essential for the homeostatic regulation of astrocyte networks and synaptic transmission.
• Microglia modulate synaptic plasticity and strength through astrocyte-dependent and independent mechanisms.
• These findings reveal novel roles for microglia in brain function and disease.