Reduced Glial Cell Density and Neuronal Size in the Anterior Cingulate Cortex in Major Depressive Disorder

TLDR

Glial cells outnumber neurons in the cortex and are essential for neuronal function, and prior studies have linked reduced neuronal size in schizophrenia and suggest reduced glial density in mood disorders. The study aimed to compare glial cell density, neuronal density, and neuronal size in the anterior cingulate cortex across schizophrenia, major depressive disorder, bipolar disorder, and controls using postmortem tissue. The authors used the nucleator and optical disector to quantify glial cell density, neuronal density, and neuronal size in layer 6 of area 24b from 60 postmortem brains across four diagnostic groups. In layer 6 of the anterior cingulate cortex, major depressive disorder showed a 22 % reduction in glial cell density and a 23 % reduction in neuronal size, schizophrenia.

Abstract

Glial cells are more numerous than neurons in the cortex and are crucial to neuronal function. There is evidence for reduced neuronal size in schizophrenia, with suggestive evidence for reduced glial cell density in mood disorders. In this investigation, we have simultaneously assessed glial cell density and neuronal density and size in the anterior cingulate cortex in schizophrenia, major depressive disorder, and bipolar disorder.We examined tissue from area 24b of the supracallosal anterior cingulate cortex in 60 postmortem brain specimens from 4 groups of 15 subjects, as follows: major depressive disorder, schizophrenia, bipolar disorder, and normal controls. Glial cell density and neuronal size and density were examined in all subjects using the nucleator and the optical disector.Glial cell density (22%) (P =.004) and neuronal size (23%) (P =.01) were reduced in layer 6 in major depressive disorder compared with controls. There was some evidence for reduced glial density in layer 6 (20%) (P =.02) in schizophrenia compared with controls, before adjusting for multiple layerwise comparisons, but there were no significant changes in neuronal size. There was no evidence for differences in glial density or neuronal size in bipolar disorder compared with controls. Neuronal density was similar in all groups to that found in controls.These findings suggest that there is reduced frontal cortical glial cell density and neuronal size in major depressive disorder.