title: 56Fe Particle Exposure Results in a Long-Lasting Increase in a Cellular Index of Genomic Instability and Transiently Suppresses Adult Hippocampal Neurogenesisin Vivo.
abstract: The high-LET HZE particles from galactic cosmic radiation pose tremendous health risks to astronauts, as they may incur sub-threshold brain injury or maladaptations that may lead to cognitive impairment. The health effects of HZE particles are difficult to predict and unfeasible to prevent. This underscores the importance of estimating radiation risks to the central nervous system as a whole as well as to specific brain regions like the hippocampus, which is central to learning and memory. Given that neurogenesis in the hippocampus has been linked to learning and memory, we investigated the response and recovery of neurogenesis and neural stem cells in the adult mouse hippocampal dentate gyrus after HZE particle exposure using two nestin transgenic reporter mouse lines to label and track radial glia stem cells (Nestin-GFP and Nestin-CreERT2/R26R:YFP mice, respectively). Mice were subjected to56Fe particle exposure (0 or 1 Gy, at either 300 or 1000 MeV/n) and brains were harvested at early (24h), intermediate (7d), and/or long time points (2-3mo) post-irradiation.56Fe particle exposure resulted in a robust increase in 53BP1+ foci at both the intermediate and long time points post-irradiation, suggesting long-term genomic instability in the brain. However,56Fe particle exposure only produced a transient decrease in immature neuron number at the intermediate time point, with no significant decrease at the long time point post-irradiation.56Fe particle exposure similarly produced a transient decrease in dividing progenitors, with fewer progenitors labeled at the early time point but equal number labeled at the intermediate time point, suggesting a recovery of neurogenesis. Notably,56Fe particle exposure did not change the total number of nestin-expressing neural stem cells. These results highlight that despite the persistence of an index of genomic instability,56Fe particle-induced deficits in adult hippocampal neurogenesis may be transient. These data support the regenerative capacity of the adult SGZ after HZE particle exposure and encourage additional inquiry into the relationship between radial glia stem cells and cognitive function after HZE particle exposure.
authors.affiliation: Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: DeCarolis
authors.affiliation: Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Rivera
authors.affiliation: Dept Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Francisca
authors.initials: F
authors.lastname: Ahn
authors.affiliation: Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Wellington Z
authors.initials: WZ
authors.lastname: Amaral
authors.affiliation: Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Junie A
authors.initials: JA
authors.lastname: LeBlanc
authors.affiliation: Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Shveta
authors.initials: S
authors.lastname: Malhotra
authors.affiliation: Dept Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Hung-Ying
authors.initials: HY
authors.lastname: Shih
authors.affiliation: Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: David
authors.initials: D
authors.lastname: Petrik
authors.affiliation: Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Neal
authors.initials: N
authors.lastname: Melvin
authors.affiliation: Dept Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Benjamin P C
authors.initials: BP
authors.lastname: Chen
authors.affiliation: Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Amelia J
authors.initials: AJ
authors.lastname: Eisch
keywords: BrdU; adult neurogenesis; galactic cosmic radiation; recovery; subgranular zone; transgenic mice