Oligodendrocyte lineage is severely affected in human alcohol-exposed foetuses

Prenatal alcohol exposure is a major cause of neurobehavioral disabilities. MRI studies in humans have shown that alcohol is associated with white matter microstructural anomalies but these studies focused on myelin abnormalities only after birth. Only one of these studies evaluated oligodendrocyte lineage, but only for a short period during human foetal life. As data are lacking in humans and alcohol is known to impair oligodendrocyte differentiation in rodents, the present study aimed to compare by immunohistochemistry the oligodendrocyte precursor cells expressing PDGFR-alpha and immature premyelinating/mature oligodendrocytes expressing Olig2 in the ganglionic eminences and the frontal cortex of 14 human foetuses exposed to alcohol from 15 to 37 weeks' gestation with age-matched controls. The human brains used in this study were obtained at the time of foetal autopsies for medical termination of pregnancy, in utero or post-natal early death. Before birth, PDGFR-alpha expression was strongly increased in the ganglionic eminences and the cortex of all foetuses exposed to alcohol except at the earliest stage. No massive generation of Olig2 immunoreactive cells was identified in the ganglionic eminences until the end of pregnancy and the density of Olig2-positive cells within the cortex was consistently lower in foetuses exposed to alcohol than in controls. These antenatal data from humans provides further evidence of major oligodendrocyte lineage impairment at specific and key stages of brain development upon prenatal alcohol exposure including defective or delayed generation and maturation of oligodendrocyte precursors.