Effects of Alcohol Abuse on Proliferating Cells, Stem/Progenitor Cells, and Immature Neurons in the Adult Human Hippocampus

In animal studies, impaired adult hippocampal neurogenesis is associated with behavioral pathologies including addiction to alcohol. We hypothesize that alcohol abuse may have a detrimental effect on the neurogenic pool of the dentate gyrus in the human hippocampus. In this study we investigate whether alcohol abuse affects the number of proliferating cells, stem/progenitor cells, and immature neurons in samples from postmortem human hippocampus. The specimens were isolated from deceased donors with an on-going alcohol abuse, and from controls with no alcohol overconsumption. Mid-hippocampal sections were immunostained for Ki67, a marker for cell proliferation, Sox2, a stem/progenitor cell marker, and DCX, a marker for immature neurons. Immunoreactivity was counted in alcoholic subjects and compared with controls. Counting was performed in the three layers of dentate gyrus: the subgranular zone, the granular cell layer, and the molecular layer. Our data showed reduced numbers of all three markers in the dentate gyrus in subjects with an on-going alcohol abuse. This reduction was most prominent in the subgranular zone, and uniformly distributed across the distances from the granular cell layer. Furthermore, alcohol abusers showed a more pronounced reduction of Sox2-IR cells than DCX-IR cells, suggesting that alcohol primarily causes a depletion of the stem/progenitor cell pool and that immature neurons are secondarily affected. These results are in agreement with observations of impaired adult hippocampal neurogenesis in animal studies and lend further support for the association between hippocampal dysfunction and alcohol abuse.