Institute of Pediatrics, Children's Hospital, Fudan University, 399 Wanyuan Road, Shanghai 201102, China.
Neurosci Lett. 2012 Aug 8;523(1):87-92. doi: 10.1016/j.neulet.2012.06.054. Epub 2012 Jun 27.
Hypothermia is a potential therapy for cerebral hypoxic ischaemic injury in adults and neonates. The mechanism of the neuroprotective effects of hypothermia after hypoxia-ischaemia (HI) in the developing rat brain remains unclear. In this research, 7-day-old rats underwent left carotid artery ligation followed by the administration of 8% oxygen for 2 h. These rats were divided into hypothermic (rectal temperature, 32-33 °C for 24 h) and normothermic (36-37 °C for 24 h) groups immediately after HI. All rats were given 50 mg/kg/day 5-bromodeoxyuridine (BrdU) intraperitoneally at 4-6 days and sacrificed at 1 or 2 weeks after HI. We found a significant decrease in infarct volume and the neuron loss were also detected in the subgranular zone (SGZ) in the hypothermic group at 7 and 14 days after HI compared with the normothermic group. BrdU immunopositive cells were reduced greatly in the hypothermic group compared with the normothermic group. Hypothermia did not change the number of nestin-labelled cells in the ipsilateral SGZ at 1 and 2 weeks after HI. The differentiation of newly generated cells was assessed by double immunolabelling of BrdU with glial fibrillary acidic protein (GFAP), O4 or Neuronal Nuclei (NeuN). The ratio of BrdU(+)-GFAP(+) or BrdU(+)-O4(+) to total BrdU(+) staining decreased dramatically, but the ratio of BrdU(+)-NeuN(+) to total BrdU(+) staining increased significantly in the hypothermic group compared to the normothermic group at 2 and 6 weeks after HI. These results suggest that the reduction in neuron loss observed after mild hypothermia may be associated with enhanced neuronal differentiation and decreased glial differentiation in the SGZ after HI. These observations are noteworthy for clinical hypothermia therapy following cerebral HI injury during the perinatal period.
低温是治疗成人和新生儿脑缺氧缺血损伤的一种潜在疗法。在发育中的大鼠脑缺氧缺血后，低温的神经保护作用机制尚不清楚。在这项研究中，7 日龄大鼠行左侧颈总动脉结扎，然后给予 8%氧气 2 小时。这些大鼠在缺氧缺血后立即分为低温组（直肠温度 32-33°C 持续 24 小时）和常温组（36-37°C 持续 24 小时）。所有大鼠在缺氧缺血后 4-6 天给予 50mg/kg/天 5-溴脱氧尿苷（BrdU）腹腔内注射，并在缺氧缺血后 1 或 2 周处死。我们发现，与常温组相比，低温组在缺氧缺血后 7 和 14 天，梗死体积明显减小，颗粒下区（SGZ）神经元丢失也减少。与常温组相比，低温组 BrdU 免疫阳性细胞明显减少。低温组在缺氧缺血后 1 和 2 周，同侧 SGZ 中巢蛋白标记细胞的数量没有改变。通过 BrdU 与胶质纤维酸性蛋白（GFAP）、O4 或神经元核（NeuN）的双重免疫标记评估新生成细胞的分化。BrdU(+)-GFAP(+)或 BrdU(+)-O4(+)与总 BrdU(+)染色的比值显著降低，但 BrdU(+)-NeuN(+)与总 BrdU(+)染色的比值在低温组显著增加，与常温组相比，在缺氧缺血后 2 和 6 周时。这些结果表明，轻度低温后观察到的神经元丢失减少可能与 SGZ 中神经元分化增强和神经胶质分化减少有关。这些观察结果对于围产期脑 HI 损伤后临床低温治疗具有重要意义。
