Deficit of perineuronal net induced by maternal immune activation mediates the cognitive impairment in offspring during adolescence.

Maternal immune activation (MIA) during pregnancy is considered a risk factor for neurodevelopment in the offspring, resulting in behavioral abnormalities. Furthermore, adolescence is a vulnerable period for developing different psycho-cognitive deficits. Here, we aimed to observe the cognitive consequences of prenatal MIA exposure in adolescents and explored the underlying mechanisms. We divided dams into CON and MIA groups after inducing a mouse model of MIA using lipopolysaccharide (120 μg/kg) on gestational day 15. Open field (OF), elevated plus maze (EPM), and novel object recognition (NOR) tests were performed on postnatal day (PD) 35-37. The expression of hippocampal Wisteria floribunda agglutinin (WFA) perineuronal net (PNN), parvalbumin (PV), glial fibrillary acidic protein (GFAP), and ionized calcium-binding adapter molecule-1(Iba-1) were evaluated using immunofluorescence, and the expression of matrix metalloprotein-9 (MMP-9) in the hippocampus was assessed using the western blot. Following the infusion of chondroitinase ABC (ChABC) into CA1 in the offspring from the CON group on PD 30, they were divided into ChABC and Sham groups. OF, EPM, and NOR were performed on PD 35-37. Compared to the CON group, decreased exploration time of the novel object and preference ratio were observed in the MIA group. Meanwhile, the MIA group presented significantly decreased WFA PNN in CA1, increased Iba-1 microglia, and MMP-9 in the hippocampus. Additionally, the density of PV neurons and GFAP astrocytes was comparable between both groups. After digesting the PNN, the exploration time of novel object and preference ratio decreased in the ChABC group compared to the Sham group. Conclusively, the PNN deficit in CA1 caused by prenatal MIA might, at least partially, induce cognitive impairment in adolescents. Microglia and MMP-9 may also be potential candidates for PNN deficit after MIA.