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

背景：近年来，在成年啮齿动物的心室下区（SVZ）和海马齿状回中发现了神经干细胞。众所周知，低温在各种脑损伤后提供神经保护，在本研究中，我们检测了低温是否激活局灶性脑缺血时SVZ的神经干细胞。材料与方法：采用异氟醚和N_2O/O_2麻醉、插管、通气的方法对成年雄性Wistar大鼠进行麻醉。左侧脑室注射DiI（0.2%,10 μL）。制备后将动物分为3组：1组（低温32.5±0.5℃），2组（缺血/低温32.5±0.5℃），3组（缺血/常温37.5±0.5℃）。采用4-0尼龙缝合右脑中闭塞术诱导缺血（120min），激光多普勒血流仪证实局部脑血流减少。缺血开始后立即低温6小时。在体温升高或缺血后第7天，在牺牲前10小时和2小时分别腹腔注射溴脱氧尿苷（BrdU），取脑，用4%多聚甲醛PBS固定，用分级蔗糖溶液冷冻，冷冻切割，用于DiI荧光检测和荧光免疫组织化学。另外，用氯化三苯四唑染色评估脑梗死面积。结果：在第3组，dii阳性细胞在第7天和第14天从SVZ向纹状体迁移。第7天3组梗死面积明显大于2组。低温不能促进DiI阳性细胞从SVZ迁移。BrdU和双皮质素在各组SVZ和吻侧迁移流中表达，在2组和3组中表达到梗死区。在神经前体中表达的Nestih在整个缺血半球发育，而在对侧半球不发育。迁移的dii阳性细胞偶尔表达NeuN或GFAP。然而，低温不影响BrdU、双皮质素、巢蛋白、NeuN和GFAP的表达。结论：低温不能激活局灶性脑缺血损伤纹状体的脑室下神经干细胞增殖、迁移和分化为神经元或胶质细胞。少

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 … More 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. Less