Human olfactory bulb neurogenesis study sheds light on depression.


A new study from researchers at the Douglas Institute and McGill University, suggests that the integration of new neurons in the adult brain is a phenomenon more generally compromised in the brains of depressed patients.  This new finding confirms that neurogenesis in the human olfactory bulb is a marginal phenomenon in adults. These findings shed light on the special features of the human brain.  The opensource study is published in the journal Frontiers in Neuroanatomy.

Previous studies have shown the existence of neurogenesis in the adult brain, the process through which new neurons are produced and integrated throughout the course of life, mainly in two brain regions, the hippocampus and the olfactory bulb (OB). So far, however, this knowledge has relied mainly on studies in rodents. In humans, although neurogenesis in the adult hippocampus is no longer a matter of debate, the presence of neurogenesis in the OB has remained controversial.

Now, the current study based on post-mortem brain samples from the Douglas-Bell Canada Brain Bank, shows the presence of only a few immature cells within each olfactory tract, which is the migration path to the OB. However, the comparison of brain tissue from healthy people with samples from depressed, suicidal individuals, suggests that migration and maturation of these cells is affected in depressed patients.

Previous studies involving animals and humans has suggested that neuronal proliferation or survival might be altered in depression, the team state the current study is the first evidence implicating changes in neuronal maturation and migration in the disorder.

The team surmise that given that the phenomenon of neurogenesis in the adult hippocampus has already been implicated in depression, these new data findings is an important step towards understanding depression.

Source:  Douglas Institute (CIUSSS de l’Ouest-de-l’île-de-Montréal) 

Cellular composition and characterization of doublecortin-immunoreactive (DCX-IR) cells in the human olfactory tract (OT) and subventricular zone (SVZ).  (J-K) DCX-IR multipolar cells were present in both lateral and medial regions. DCX-IR processes were generally aligned parallel to the tract, particularly in medial OT regions. (L-M) Occasionally, DCX-IR multipolar cells possessed bulbous, growth cone-like tips.  Increased doublecortin (DCX) expression and incidence of DCX-immunoreactive multipolar cells in the subventricular zone-olfactory bulb system of suicides.  Mechawar et al 2015.

Cellular composition and characterization of doublecortin-immunoreactive (DCX-IR) cells in the human olfactory tract (OT) and subventricular zone (SVZ). (J-K) DCX-IR multipolar cells were present in both lateral and medial regions. DCX-IR processes were generally aligned parallel to the tract, particularly in medial OT regions. (L-M) Occasionally, DCX-IR multipolar cells possessed bulbous, growth cone-like tips. Increased doublecortin (DCX) expression and incidence of DCX-immunoreactive multipolar cells in the subventricular zone-olfactory bulb system of suicides. Mechawar et al 2015.

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