Background: Multiple neonatal exposures to sevoflurane induce neurocognitive dysfunctions in rodents. The lack of cell-type specific information following sevoflurane exposure limits the mechanistic understanding of these effects. In this study, we tested the hypothesis that sevoflurane exposures alter the atlas of hippocampal cell clusters and have neuronal and non-neuronal cell-type specific effects in mice of both sexes.

Methods: Neonatal mice were exposed to 3% sevoflurane for 2 hours at postnatal days 6, 8, and 10 and analysed for the exposure effects at postnatal day 37. Single-nucleus RNA sequencing was performed in the hippocampus followed by in situ hybridization to validate the results of RNA sequencing. Morris Water Maze test was performed to test neurocognitive function.

Results: We found sex-specific distribution of hippocampal cell types in control mice alongside cell-type- and sex-specific effects of sevoflurane exposure on distinct hippocampal cell populations. There were important changes in male but not in female mice following sevoflurane exposure regarding the proportions of CA1 neurons (control vs sevoflurane, males: 79.9% vs 32.3%; females: 27.3% vs 24.3%), dentate gyrus (males: 4.2% vs 23.4%; females: 36.2% vs 35.8%), and oligodendrocytes (males: 0.6% vs 6.9%; females: 5.9% vs 7.8%). In male but not in female mice, sevoflurane altered the number of significantly enriched ligand-receptor pairs in the CA1, CA3 and dente gyrus trisynaptic circuit (control vs sevoflurane, CA1-CA3: 18 vs 42 in males and 15 vs 21 in females; CA1-dentate gyrus: 21 vs 35 in males and 12 vs 20 in females; CA3-dentate gyrus: 25 vs 45 in males and 17 vs 20 in females), interfered with dentate gyrus granule cell neurogenesis, hampered microglia differentiation, and decreased CA1 pyramidal cell diversity. Oligodendrocyte differentiation was specifically altered in females with increased expressions of Mbp and Mag. In situ hybridization validated the increased expression of common differentially expressed genes.

Conclusions: This single-nucleus RNA sequencing study reveals the hippocampal atlas of mice, providing a comprehensive resource for the neuronal and non-neuronal cell-type- and sex-specific effects of sevoflurane during development.

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Shao-Yong Song et al.
Anesthesiology February 2023