Effects of Hypothermia on Subventricular Neural Stem Cells Following Focal Cerebral Ischemia in Adult Rats

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 15591641
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Anesthesiology/Resuscitation studies
• Research Institution: Kumamoto University
• Principal Investigator: YANO Toshiyuki Kumamoto University, Hospital, Assistant Professor, 医学部附属病院, 講師 (50253729)
• Project Period (FY): 2003 – 2004
• Keywords: hypothermia / neural stem cells / subventricular zone / focal cerebral ischemia / immunohistochemistry / DiI / rat

Research Abstract

Background : Recently, neural stem cells have been identified in the subventricular zone(SVZ) and the hippocampal dentate gyrus of adult rodents. Hypothermia is well known to provide neuroprotection following various brain insults, In this study, we examined if hypothermia activated neural stem cell of the SVZ exposed to focal cerebral ischemia.
Materials and Methods : Adult male Wistar rats were anesthetized, intubated and ventilated with isoflurane and N_2O/O_2. DiI(0.2%,10 μL) was injected into the left lateral ventricle. After preparation the animals were assigned to the following groups : group 1(hypothermia 32.5±0.5℃), group 2(ischemia/hypothermia 32.5±0.5℃), and group 3(ischemia/normothermia 37.5±0.5℃. Ischemia(120 min) was induced by right middle cerebral occlusion with a 4-0 nylon suture and confirmed by the decreased regional cerebral blood flow using laser Doppler flowmetry. Hypothermia for 6 hours was applied immediately after the initiation of ischemia. Seven days after hyp othermia or ischemia, bromodeoxyuridine(BrdU) was administered intraperitoneally 10 and 2 hours before sacrifice and the brains were removed, fixed with 4% paraformadlehyde in PBS, cryoprotected with graded sucrose solutions, frozen and cut for DiI fluolescence detection and fluolescent immunohistochemistry. Separately, the brains were stained with triphenyltetrazolium chloride for assessment of infarct area.
Results : In the group 3,DiI-positive cells migrated from the SVZ toward the striatum on days 7 and 14. Infarct area on day 7 was much larger in the group 3 than in the group 2. Hypothermia did not facilitate the migration of DiI positive cells from the SVZ. BrdU and doublecortin were expressed in the SVZ and the rostral migratory stream in all groups and into the infarct region in the groups 2 and 3. Nestih that is expressed in neural precursors was developed in the whole ischemic hemisphere but not in the contralateral hemisphere. Migrating DiI-positive cells occasionally expressed NeuN or GFAP. Howerver, hypothermia did not influence the expression of BrdU, doublecortin, nestin, NeuN, and GFAP.
Conclusion : Hypothermia did not activate the subventricular neural stem cells to prolirerate, migrate, and difierentiate into neurons or glia in the injured striatum following focal cerebral ischemia.