Astrocytes require perineuronal nets to maintain synaptic homeostasis in mice

Area of Science:

• Neuroscience
• Cell Biology
• Extracellular Matrix Research

Background:

• Perineuronal nets (PNNs) are extracellular matrices ensheathing fast-spiking inhibitory neurons.
• PNNs play a crucial role in stabilizing synapses and modulating synaptic plasticity.

Purpose of the Study:

• To investigate the structural and functional relationship between PNNs, astrocytes, and synapses in the adult mouse somatosensory cortex.
• To elucidate the role of PNNs and astrocytes in regulating synaptic transmission and their alterations in neurological disorders.

Main Methods:

• Immunohistochemistry and high-resolution microscopy to visualize PNNs, synapses, and astrocytic components.
• Analysis of PNN degradation models and mouse models of Alzheimer's disease and epilepsy.

Main Results:

• Synaptic terminals of fast-spiking interneurons are localized within specific holes in PNNs.
• These PNN holes contain tripartite synapses, including astrocytic processes expressing Kir4.1, glutamate, and GABA transporters.
• PNN degradation leads to altered astrocytic coverage and impaired glutamate and potassium uptake, causing extrasynaptic glutamate spillage.
• Disruption of PNNs and astrocyte-neuron interactions is observed in Alzheimer's disease and epilepsy models.

Conclusions:

• PNNs and astrocytes cooperatively maintain synaptic signal containment under physiological conditions.
• The coordinated function of PNNs and astrocytes is critical for normal brain function and is compromised in neurological diseases.