Microglia play a critical role in the long-term sequelae of early life stress

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Childhood abuse and neglect are major risk factors for the development of numerous childhood psychopathologies that in many cases linger as chronic mental illnesses that are refractory to treatment in adulthood. The molecular mechanisms by which early life stress (ELS) modifies vulnerability to stress and cognition in humans are currently poorly understood. However, similar observations in rodents and nonhuman primates suggest that at least some aspects of this process are conserved and can be further studied in animal models. Here we present preliminary data that suggest that ELS impairs hippocampal function in adulthood by down regulating expression of genes, such as the lipopolysaccharide binding protein (LBP), that are necessary to support microglia-mediated synaptic pruning during a critical period of development. Abnormal synaptic pruning leads to the establishment of inefficient wiring grid that persists into adulthood and affects complex behavior. This hypothesis is consistent with a growing body of work showing that microglia cells play an essential role in synaptic pruning and that exposure to ELS is associated with increased spine density in limbic areas that persist into adulthood. In addition, the ability of glucocorticoids to suppress microglia activity in vivo and in vitro makes them a likely cellular target for ELS. These findings provide the first evidence to suggest that some of the developmental consequences of ELS are mediated by impairing microglia function and synaptic pruning in the mouse. We predict that similar dysregulation of MG function will be confirmed in children and adolescents and that our mouse model will generate novel strategies to diagnose and treat psychopathologies caused by exposure to ELS in humans. .