Sex-Dependent Gliovascular Interface Abnormality in the Hippocampus following Postnatal Immune Activation in Mice

The neuro-gliovascular unit is a crucial structure for providing a balanced well-functioning environment for neurons and their synapses. Activation of the immune system during the developmental period is believed to affect the gliovascular unit, which may trigger neurodevelopmental and neurological/neuropsychiatric diseases. In this study, we hypothesized that vulnerability of the male brain to a neonatal insult was conditioned by sex-dependent differences in the impairment of the hippocampal gliovascular unit. Male and female C57BL/6J pups received lipopolysaccharide (LPS) (1 mg/kg) or saline on postnatal day (P) 5. Brains were collected at P12 and morphological quantifications of hippocampal fibrillary glial acid protein (GFAP⁺) astrocytes and ionized calcium-binding adaptor molecule 1 protein (Iba1+) microglia were performed by using 3-D image analysis together with measuring the length of CD31⁺ and aquaporin-4 (AQP4⁺) vessels. We found a significant increase in the length of CD31⁺ capillaries in the male LPS group compared to the saline group; however, coverage of capillaries by astrocytic end-feet (AQP4⁺) was significantly reduced. In contrast, there was a significant increase in AQP4⁺ capillary length in female pups 1 week after LPS injection. GFAP⁺ astrocytes via morphological changes in the hippocampus showed significant enhancement in the activity 1 week following LPS injection in male mice. We propose that neonatal inflammation could induce susceptibility to neurodevelopmental disorders through modification of hippocampal gliovascular interface in a sex-dependent manner.