title: Mouse intermittent hypoxia mimicking apnoea of prematurity: effects on myelinogenesis and axonal maturation.
abstract: Premature babies are at high risk for both infantile apnoea and long-term neurobehavioural deficits. Recent studies suggest that diffuse structural changes in brain white matter are a positive predictor of poor cognitive outcomes. Since oligodendrocyte maturation, myelination, axon development, and synapse formation mainly occur in the third trimester of gestation and first postnatal year, infantile apnoea could lead to and/or exaggerate white matter impairments in preterm neonates. Therefore, we investigated oligodendroglia and axon development in a neonatal mouse model of intermittent hypoxia between postnatal days 2 and 10. During critical phases of central nervous system development, intermittent hypoxia induced hypomyelination in the corpus callosum, striatum, fornix, and cerebellum, but not in the pons or spinal cord. Intermittent hypoxia-elicited alterations in myelin-forming processes were reflected by decreased expression of myelin proteins, including MBP, PLP, MAG, and CNPase, possibly due to arrested maturation of oligodendrocytes. Ultrastructural abnormalities were apparent in the myelin sheath and axon. Immature oligodendrocytes were more vulnerable to neonatal intermittent hypoxia exposures than developing axons, suggesting that hypomyelination may contribute, at least partially, to axonal deficits. Insufficient neurofilament synthesis with anomalous components of neurofilament subunits, β-tubulin, and MAP2 isoforms indicated immaturity of axons in intermittent hypoxia-exposed mouse brains. In addition, down-regulation of synapsin I, synaptophysin, and Gap-43 phosphorylation suggested a potential stunt in axonogenesis and synaptogenesis. The region-selective and complex impairment in brain white matter induced by intermittent hypoxia was further associated with electrophysiological changes that may underlie long-term neurobehavioural sequelae.
authors.affiliation: Kosair Children's Hospital Research Institute, Department of Pediatrics, University of Louisville School of Medicine, Louisville, KY 40202, USA. j0cai002@louisville.edu
authors.forename: Jun
authors.initials: J
authors.lastname: Cai
authors.forename: Chi Minh
authors.initials: CM
authors.lastname: Tuong
authors.forename: Yiping
authors.initials: Y
authors.lastname: Zhang
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Shields
authors.forename: Gang
authors.initials: G
authors.lastname: Guo
authors.forename: Hui
authors.initials: H
authors.lastname: Fu
authors.forename: David
authors.initials: D
authors.lastname: Gozal
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001049:Apnea / Q000503:physiopathology*; D001369:Axons / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D016923:Cell Death; D002454:Cell Differentiation; D000860:Hypoxia / Q000503:physiopathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009185:Myelin Proteins / Q000378:metabolism; D009186:Myelin Sheath / Q000502:physiology*; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009836:Oligodendroglia / Q000502:physiology*; D014404:Tubulin / Q000378:metabolism
chemical_list: D008869:Microtubule-Associated Proteins; D009185:Myelin Proteins; D009419:Nerve Tissue Proteins; D014404:Tubulin