背景:治疗性低温显著改善中重度缺氧缺血性脑病(HIE)后的预后,但它是部分有效的。虽然体温过低与小胶质细胞增生减少有关,目前尚不清楚它是否能使小胶质细胞形态和表型正常化.
方法:将近期胎羊(n=24)随机分为假对照,缺血-正常体温,或缺血-低温。对大脑切片进行免疫组织化学标记以评估神经元,小胶质细胞和它们与神经元的相互作用,星形胶质细胞,髓鞘形成,脑缺血后7天和gitter细胞(具有细胞质脂质颗粒的小胶质细胞)。损伤定义为细胞完全丧失的区域。RNAscope®用于评估小胶质细胞表型标记CD86和CD206。
结果:缺血-正常体温与神经元和髓磷脂的严重丧失有关(p<0.05),有广泛的病变,星形胶质细胞增生和小胶质细胞增生比例较高(p<0.05)。在两个缺血组中都存在神经元的小胶质细胞包裹。低温改善了神经元的存活,抑制病变,gitter细胞和神经胶质增生(p<0.05),并减弱髓鞘面积分数的减少。缺血后,“M1”标记CD86和“M2”标记CD206上调。低温仅部分抑制皮质中的CD86(p<0.05),但不影响CD206。
结论:低温可以预防脑缺血后的病变,但仅部分抑制小胶质细胞包裹和M1标记表达。这些数据支持以下假设:低温后,有害小胶质细胞活性的持续上调可能有助于部分神经保护。复温后的免疫调节可能是一个重要的治疗靶点。
BACKGROUND: Therapeutic hypothermia significantly improves outcomes after moderate-severe hypoxic-ischemic encephalopathy (HIE), but it is partially effective. Although hypothermia is consistently associated with reduced microgliosis, it is still unclear whether it normalizes microglial morphology and phenotype.
METHODS: Near-term fetal sheep (n = 24) were randomized to sham control, ischemia-normothermia, or ischemia-hypothermia. Brain sections were immunohistochemically labeled to assess neurons, microglia and their interactions with neurons, astrocytes, myelination, and gitter cells (microglia with cytoplasmic lipid granules) 7 days after cerebral ischemia. Lesions were defined as areas with complete loss of cells. RNAscope® was used to assess microglial phenotype markers CD86 and CD206.
RESULTS: Ischemia-normothermia was associated with severe loss of neurons and myelin (p < 0.05), with extensive lesions, astrogliosis and microgliosis with a high proportion of gitter cells (p < 0.05). Microglial wrapping of neurons was present in both the ischemia groups. Hypothermia improved neuronal survival, suppressed lesions, gitter cells and gliosis (p < 0.05), and attenuated the reduction of myelin area fraction. The \"M1\" marker CD86 and \"M2\" marker CD206 were upregulated after ischemia. Hypothermia partially suppressed CD86 in the cortex only (p < 0.05), but did not affect CD206.
CONCLUSIONS: Hypothermia prevented lesions after cerebral ischemia, but only partially suppressed microglial wrapping and M1 marker expression. These data support the hypothesis that persistent upregulation of injurious microglial activity may contribute to partial neuroprotection after hypothermia, and that immunomodulation after rewarming may be an important therapeutic target.