Brain Resident Ly6Chi Monocytes Are Necessary for Maintaining Adult Hippocampal Neurogenesis

Adult hippocampal neurogenesis (AHN) is crucial to various brain functions. Neurodegeneration, neuroinflammation and stress can impair AHN, contributing to the development of neurological and psychiatric disorders. Stress is known to extensively affect both the brain and peripheral immune system. However, the cellular and molecular mechanisms underlying stress-induced impairments in AHN remain unclear. In this study, we found that, unlike neuroinflammatory conditions, stress significantly inhibited AHN independently of microglial activation, suggesting a novel mechanism mediating stress-impaired AHN. Since stress modulates peripheral immune cells, we examined the distribution of immune cells infiltrating the brain. We found a significant decrease of infiltrated Ly6C