Astrocyte-derived extracellular matrix proteins regulate synapse remodeling in stress-induced depression

Area of Science:

• Neuroscience
• Molecular Psychiatry
• Cell Biology

Background:

• Major depressive disorder (MDD) affects multiple brain regions and cell types, with astrocyte dysfunction implicated in depressive behaviors.
• While neuronal mechanisms in MDD are studied, astrocyte-driven molecular pathways remain less explored.
• Chronic social defeat stress in mice models MDD symptoms like anhedonia and anxiety.

Purpose of the Study:

• To investigate the molecular mechanisms by which astrocytes contribute to major depressive disorder (MDD).
• To identify specific gene expression changes in astrocytes following chronic social defeat stress.

Main Methods:

• Male mice underwent chronic social defeat stress to induce MDD-like symptoms.
• Ribosome affinity purification was used to measure astrocyte translating mRNA expression.
• Bioinformatic analyses, electrophysiology, and synaptosome protein analysis were performed.

Main Results:

• Significant alterations in astrocyte mRNA expression were observed in the prefrontal cortex (PFC) of stressed mice.
• Genes related to extracellular matrix (ECM) proteins, cell-cell interactions, and glutamatergic synaptic function were altered.
• Increased expression of secreted protein acidic and rich in cysteine (SPARC) mRNA correlated strongly with depressive phenotypes and was found in synaptosomes.

Conclusions:

• Astrocyte alterations, particularly increased SPARC expression, are linked to stress-induced synaptic dysfunction in MDD.
• Overexpressing SPARC in the PFC partially alleviated stress symptoms, suggesting a protective role.
• Increased SPARC may represent a natural defense mechanism against depression-related synaptic changes.