Effects of Lipopolysaccharide on Oligodendrocyte Differentiation at Different Developmental Stages: an In Vitro Study

Lipopolysaccharide (LPS) exerts cytotoxic effects on brain cells, especially on those belonging to the oligodendrocyte lineage, in preterm infants. The susceptibility of oligodendrocyte lineage cells to LPS-induced inflammation is dependent on the developmental stage. This study aimed to investigate the effect of LPS on oligodendrocyte lineage cells at different developmental stages in a microglial cell and oligodendrocyte co-culture model. The primary cultures of oligodendrocytes and microglia cells were prepared from the forebrains of 2-day-old Sprague-Dawley rats. The oligodendrocyte progenitor cells (OPCs) co-cultured with microglial cells were treated with 0 (control), 0.01, 0.1, and 1 µg/mL LPS at the D3 stage to determine the dose of LPS that impairs oligodendrocyte differentiation. The co-culture was treated with 0.01 µg/mL LPS, which was the lowest dose that did not impair oligodendrocyte differentiation, at the developmental stages D1 (early LPS group), D3 (late LPS group), or D1 and D3 (double LPS group). On day 7 of differentiation, oligodendrocytes were subjected to neural glial antigen 2 (NG2) and myelin basic protein (MBP) immunostaining to examine the number of OPCs and mature oligodendrocytes, respectively. LPS dose-dependently decreased the proportion of mature oligodendrocytes (MBP+ cells) relative to the total number of cells. The number of MBP+ cells in the early LPS group was significantly lower than that in the late LPS group. Compared with those in the control group, the MBP+ cell numbers were significantly lower and the NG2+ cell numbers were significantly higher in the double LPS group, which exhibited impaired oligodendrocyte lineage cell development, on day 7 of differentiation. Repetitive LPS stimulation during development significantly inhibited brain cell development by impairing oligodendrocyte differentiation. In contrast, brain cell development was not affected in the late LPS group. These findings suggest that inflammation at the early developmental stage of oligodendrocytes increases the susceptibility of the preterm brain to inflammation-induced injury.