title: White matter protection with insulin-like growth factor 1 and hypothermia is not additive after severe reversible cerebral ischemia in term fetal sheep.
abstract: Moderate cerebral hypothermia significantly improves survival without disability from perinatal hypoxia-ischemia. However, protection is partial. Insulin-like growth factor 1 (IGF-1) plays a key role in oligodendrocyte survival and myelination. The purpose of this study was to test the hypothesis that the combination of IGF-1 plus hypothermia could reduce postischemic white matter damage compared with hypothermia alone. Unanesthetized near-term fetal sheep received 30 min of cerebral ischemia, followed by either an infusion of 3 μg of IGF-1 intracerebroventricularly from 4.5 to 5.5 h plus cooling from 5.5 to 72 h (IGF-1 + hypothermia; n = 8), vehicle infusion plus cooling from 5.5 to 72 h (vehicle + hypothermia; n = 12), sham cooling plus sham infusion (ischemia control; n = 12) or sham ischemia (n = 5). The fetal extradural temperature was reduced from 39.4 ± 0.1°C to between 30 and 33°C. White matter was assessed after 5 days. Ischemia was associated with severe loss of CNPase-positive oligodendrocytes in white matter compared with sham ischemia (380 ± 138 vs. 1,180 ± 152 cells/field; mean ± SD; p < 0.001). Delayed hypothermia reduced cell loss (847 ± 297 cells/field, p < 0.01, vs. ischemia control), but there was no significant difference between vehicle + hypothermia and IGF-1 + hypothermia (1,015 ± 211 cells/field; NS). Ischemia was associated with increased caspase 3 expression in white matter (216 ± 41 vs. 19 ± 18 cells/field; p < 0.001). Hypothermia reduced numbers of activated caspase 3-positive cells (116 ± 81 cells/field; p < 0.05), with no significant difference between vehicle + hypothermia and IGF-1 + hypothermia (91 ± 27 cells/field; NS). In conclusion, delayed cotreatment with IGF-1 plus hypothermia after ischemia was associated with an improvement in white matter damage similar to that achieved by hypothermia alone.
authors.affiliation: Department of Physiology, University of Auckland, Auckland, New Zealand.
authors.forename: S
authors.initials: S
authors.lastname: George
authors.forename: L
authors.initials: L
authors.lastname: Bennet
authors.forename: L
authors.initials: L
authors.lastname: Weaver-Mikaere
authors.forename: M
authors.initials: M
authors.lastname: Fraser
authors.forename: J
authors.initials: J
authors.lastname: Bouwmans
authors.forename: S
authors.initials: S
authors.lastname: Mathai
authors.forename: S J M
authors.initials: SJ
authors.lastname: Skinner
authors.forename: A J
authors.initials: AJ
authors.lastname: Gunn
mesh_terms: D000818:Animals; D001831:Body Temperature; D001921:Brain / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D002545:Brain Ischemia / Q000473:pathology* / Q000503:physiopathology*; D005333:Fetus / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007036:Hypothermia, Induced; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009413:Nerve Fibers, Myelinated / Q000187:drug effects* / Q000473:pathology; D012756:Sheep
chemical_list: D007334:Insulin-Like Growth Factor I