New research provides further evidence that astrocytes, a specialized subtype of star-shaped brain cells, may play an important role in depression.
Scientists at McGill University in Canada carried out a post-mortem of 10 men with depression who died of suicide and another 10 men who died suddenly by other means. Looking at three different brain regions — dorsomedial prefrontal cortex, dorsal caudate nucleus, and mediodorsal thalamus — they discovered that the brains of depressed people had significantly fewer Vimentin-Immunoreactive (VIR-IM) astrocytes.
"We found a reduced number of astrocytes, highlighted by staining the protein vimentin, in many regions of the brain in depressed adults," Naguib Mechawar, senior study author and a Professor at the Department of Psychiatry at McGill University, said in a statement. "These star-shaped cells are important because they support the optimal function of brain neurons. Our findings confirm and extend previous research implicating astrocytes in the pathology of depression."
Astrocytes, named after their star-shaped tendrils, are the most common cells of the human brain. Since they don’t send electrical impulses themselves, they were once assumed to be passive scaffolding structures that did little more than provide physical and nutritional support for neurons. However, it’s now known that this glial cell type help to strongly modulate many aspects of neuronal activity and can influence neural circuits, allowing them to play a diverse range of roles, such as controlling brain energy metabolism, as well as the secretion or absorption of neurotransmitters.
Previous research has hinted at this possible link between astrocytes and depression, but these new findings from the post-mortems provide some of the most direct evidence yet. That said, the study does contain a number of limitations, namely the small sample size that only involved males. Equally, the study only found a correlation between depression and a loss of VIR-IM astrocytes without looking for the actual causation.
Much of this relationship between astrocytes and depression remains hazy, but it does open the door to future research and, even further down the line, possible new treatments for depression. For example, if more studies back up this idea, scientists could investigate treatments that target the loss of astrocytes.
"This research indicates that depression may be linked to the cellular composition of the brain. 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,” continues Mechawar.
"Our study provides a strong rationale for developing drugs that counteract the apparent loss of astrocytes in depression," adds Liam O'Leary, who worked on this project as a PhD student at McGill. "No antidepressants have yet been developed to target these cells directly, although the leading theory for the rapid antidepressant action of ketamine, a relatively new treatment option, is that it corrects for astrocyte abnormality."