New research indicates that astrocytes, star-shaped cells that support the function of neurons in the brain, play a key role in depression. The findings, published in Frontiers in Psychiatry, indicate that depression is associated with reduced astrocyte densities in several important brain regions.
“Depression is a common and debilitating condition that many people experience. We are interested in reducing the impact depression has on society, by improving our understanding of how it affects the brain,” said Liam O’Leary of McGill University, the first author of the new study.
The researchers used postmortem analysis to examine astrocytes in the brain. Included in the analysis was 10 male Caucasian adults with depression who had died by suicide and 10 matched controls who had died suddenly without any known inflammatory, psychiatric or neurological disorder.
“The opportunity to work with postmortem human brain samples is a real privilege,” O’Leary explained. “It allows us to measure precisely how the number and structure of brain cells are affected by neurological and psychiatric conditions. By studying the anatomy of the human brain in people who have experienced depression, we have a better chance of understanding how to create better treatments for depression.”
The researchers were particularly interested in three brain regions, the dorsomedial prefrontal cortex, dorsal caudate nucleus and mediodorsal thalamus, which have been implicated in depression.
The postmortem analysis suggested that the depressed individuals tended to have a reduced number of astrocytes. But while the number of astrocytes differed, the cells had a similar structure to psychiatrically healthy individuals.
“Our findings show astrocytes are majorly affected in depression, which is interesting given that no antidepressant treatments have yet been made to affect astrocytes,” O’Leary told PsyPost. The study also indicates “that depression commonly reduces the quantity of astrocytes in many human brain regions, without changing the structure of these cells.”
For more information, watch this video featuring the first author of the study:
Astrocytes are responsible for a variety of functions, such as supplying nutrients, removing metabolic wastes, and modulating the electrical activity of neurons.
“This research indicates that depression may be linked to the cellular composition of the brain,” said co-author Naguib Mechawar in a news release. “The promising news is that unlike neurons, the adult human brain continually produces many new astrocytes. Finding ways that strengthen these natural brain functions may improve symptoms in depressed individuals.”
The researchers were able examine cell density and morphology by staining two astrocyte-specific biomarkers — glial fibrillary acidic protein and vimentin. The method provided “a clear, complete and unprecedented view of the entire microscopic structure of these cells,” O’Leary said.
“Our observations are based on protein levels, and so our observations may alternatively mean that astrocytes have very low protein levels in depression which can no longer be detected. However, as these proteins play central roles for astrocyte activity, this would still imply depression majorly impairs astrocyte function throughout the brain,” he explained.
There is also another caveat: The study was only conducted with tissue samples from male patients. “It remains unknown how age, sex and gender could affect these anatomical differences in depression,” O’Leary said.
The study, “Widespread Decrease of Cerebral Vimentin-Immunoreactive Astrocytes in Depressed Suicides“, was authored by Liam Anuj O’Leary, Claudia Belliveau, Maria Antonietta Davoli, Jie Christopher Ma, Arnaud Tanti, Gustavo Turecki, and Naguib Mechawar.