title: Pronounced hypoxia in the subventricular zone following traumatic brain injury and the neural stem/progenitor cell response.
abstract: Traumatic brain injury (TBI) elicits identifiable changes within the adult subventricular zone (SVZ). Previously, we demonstrated that EphB3/ephrinB3 interaction inhibits neural stem/progenitor cell (NSPC) proliferation and downregulating this pathway following TBI plays a pivotal role in the expansion of the SVZ neurogenic compartment. It remains unclear, however, what early initiating factors may precede these changes. Using hypoxyprobe-1 (HPb) to identify regions of low oxygen tension or hypoxia (<1%), we found HPb uptake throughout the cortex (CTX), corpus callosum (CC) and SVZ within the first 24 h following controlled cortical impact (CCI) injury. At this early time point, HPb co-localized with EphB3 in the SVZ. NSPC specific markers also co-localized with HPb staining throughout the lateral wall of the ventricle. To determine the cell autonomous effects of hypoxia on EphB3/ephrinB3 signaling in NSPCs, we used an in vitro model of hypoxia to mimic 1% oxygen in the presence and absence of soluble aggregated ephrinB3 (eB3). As expected, hypoxia stimulated the uptake of 5-bromo-2'-deoxyuridine (BrdU) and reduced cell death. Coincident with these proliferative changes, both Hif1-α and phospho (p)-AKT were increased while EphB3 expression was decreased. Stimulation of EphB3 attenuated hypoxia-induced proliferation and prevented phosphorylation of AKT. Hif1-α accumulation, on the other hand, was not affected by EphB3/ephrinB3 signaling. These findings indicate that this pathway limits the NSPC response to hypoxic stimuli. These studies also suggest that early transient changes in oxygen tension following localized cortical injury may initiate a growth-promoting response in the SVZ.
authors.affiliation: The Miami Project to Cure Paralysis and Department of Neurological Surgery, University of Miami, Miami, FL 33136, USA; The Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24061, USA.
authors.forename: Gisela
authors.initials: G
authors.lastname: Baumann
authors.forename: Lissette
authors.initials: L
authors.lastname: Travieso
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Liebl
authors.forename: Michelle H
authors.initials: MH
authors.lastname: Theus
mesh_terms: D000818:Animals; D001930:Brain Injuries / Q000473:pathology* / Q000628:therapy*; D015687:Cell Hypoxia / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002552:Cerebral Ventricles / Q000473:pathology*; D036389:Ephrin-B3 / Q000378:metabolism / Q000494:pharmacology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008297:Male; D051379:Mice; D058953:Neural Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D009593:Nitroimidazoles / Q000378:metabolism; D036223:Receptor, EphB3 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D033581:Stem Cell Transplantation
chemical_list: D036389:Ephrin-B3; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009593:Nitroimidazoles; C033815:pimonidazole; D036223:Receptor, EphB3
keywords: AKT; Eph; Hif1-α; Hypoxia; ephrin; neural stem/progenitor cell; subventricular zone; traumatic brain injury