Effects of Neonatal Hypoxic-Ischemic Injury and Hypothermic Neuroprotection on Neural Progenitor Cells in the Mouse Hippocampus

Abstract

Neonatal hypoxic-ischemic injury (HI) results in widespread cerebral encephalopathy and affects structures that are essential for neurocognitive function, such as the hippocampus. The dentate gyrus contains a reservoir of neural stem and progenitor cells (NSPCs) that are critical for postnatal development and normal adult function of the hippocampus, and may also facilitate the recovery of function after injury. Using a neonatal mouse model of mild-to-moderate HI and immunohistochemical analysis of NSPC development markers, we asked whether these cells are vulnerable to HI and how they respond to both injury and hypothermic therapy. We found that cleaved caspase-3 labeling in the subgranular zone, where NSPCs are located, is increased by more than 30-fold after HI. The population of cells positive for both proliferating cell nuclear antigen and nestin (PCNA+Nes+), which represent primarily actively proliferating NSPCs, are acutely decreased by 68% after HI. The NSPC population expressing NeuroD1, a marker for NSPCs transitioning to become fate-committed neural progenitors, was decreased by 47%. One week after HI, there was a decrease in neuroblasts and immature neurons in the dentate gyrus, as measured by doublecortin (DCX) immunolabeling, and at the same time PCNA+Nes+ cell density was increased by 71%. NSPCs expressing Tbr2, which identifies a highly proliferative intermediate neural progenitor population, increased by 107%. Hypothermia treatment after HI partially rescues both the acute decrease in PCNA+Nes+ cell density at 1 day after injury and the chronic loss of DCX immunoreactivity and reduction in NeuroD1 cell density measured at 1 week after injury. Thus, we conclude that HI causes an acute loss of dentate gyrus NSPCs, and that hypothermia partially protects NSPCs from HI.

RNA binding motif protein 3: a potential biomarker in cancer and therapeutic target in neuroprotection

“…Clinically relevant moderate (33.5°C) hypothermia treatment leads to significant RBM3 mRNA and protein up-regulation in murine organo-typic hippocampal slice culture (a suitable tissue culture system to investigate various aspect of neuronal-protection and function in vitro ) [63]. Hypothermia is also associated with protecting neuron stem cells in the dentate gyrus (DG) region [65]. RBM3 was dramatically up-regulated in the DG region in cultured hippocampal slices [66].…”

Neurogenesis and developmental anesthetic neurotoxicity

“…With ongoing primate studies, it should easily be possible to do a comprehensive immunohistochemical screening using a panel of stem cell markers to assess for changes in stem cell populations caused by anesthetic exposure e.g. (Kwak et al, 2015). At this point it is likely that a point of diminishing returns has been reached with further cell culture or rodent in vivo studies that simply ask whether neural stem cells are vulnerable to anesthetics.…”

Focal Brain Injury Associated with a Model of Severe Hypoxic-Ischemic Encephalopathy in Nonhuman Primates

“…In a recent study by Pagida et al, involving 15 human neonates (14 delivered at or near term, 1 preterm) mainly delivered by emergency cesarean section (11/15), subjects with neuropathological lesions consistent with abrupt/severe perinatal hypoxic/ischemic injury demonstrated intense immunohistochemical tyrosine hydroxylase expression in the majority of locus coeruleus neurons, a finding which the author’s suggest may lead to monoaminergic neurotransmission dysregulation and predispose survivors to long-term psychiatric disorders with or without neurological problems [49]. Future UCO studies in nonhuman primates may benefit from a broader repertoire of immunohistochemical staining (e.g., tyrosine hydroxylase expression or neural stem and progenitor cells)[49,50] in order to better correlate abnormalities present in human neonates with HIE. Despite the small sample size, this pilot study was a necessary step for model refinement and provided useful information relevant to human newborns with HIE.…”