中文摘要：

目的 探讨micro RNA Let-7a在小鼠变应性鼻炎中的作用。方法 选取32只8周龄成熟雌性C57BL/6小鼠随机分成4组：Let-7a组、Let-7a对照组、OVA组和PBS组,每组8只。Let-7a组、Let-7a对照组及OVA组采用卵清蛋白（OVA）致敏激发,建立小鼠变应性鼻炎模型。Let-7a组于第1、2、3次激发前半小时给予Let-7a和脂质体2000混合物,而Let-7a对照组给予Let-7a对照和脂质体2000混合物。PBS组以PBS代替OVA。造模成功后计数小鼠搔鼻次数、鼻腔灌洗液中炎性细胞情况,取小鼠鼻腔黏膜固定后染色评估鼻黏膜杯状细胞增生病理学变化,检测小鼠鼻腔灌洗液中IL-4、IL-13及IFN-γ水平。结果 与Let-7a对照组小鼠相比,Let-7a组小鼠搔鼻次数明显增加,鼻腔黏膜嗜酸性粒细胞浸润及杯状细胞增生显著,具有明显统计学差异（P〈0.05）,鼻黏膜中IL-4及IL-13显著增高（P〈0.05）,而IFN-γ无明显差异（P〉0.05）。结论 Let-7a促进变应性鼻炎的发生及发展。

英文摘要：

To investigate the role of Let-7a in mouse allergic rhinitis, a total of 24 8-week old mature female C57BL/6 mice were randomly divided into four groups： Let-7a group, Let-7a control group, OVA group and PBS group, with 8 mice in each group. Mice in Let-Ta group, Let-Ta control group and OVA group were sensitized with ovalbumin （OVA） to construct allergic rhinitis model. Mice in Let-Ta group were administrated with Let-7a and liposome2000 mixture half an hour before the first, second and third challenge, and mice in Let-7a control group received Let-Ta control and liposome2000. PBS group was given PBS instead of OVA. Nasal rubs, eosinophilic cell infiltration and goblet cell hyperplasia was estimated and local IL-4, IL-13 and IFN-γ cytokines in the local mucosa were measured. We found that compared with Let-Ta control group, Let-Ta group had more nasal rubs, eosinophilic infiltration and goblet cell hyperplasia, and increased levels of IL-4 and IL-13 in nasal mucosa （P〈 0.05）, while no significant difference was observed for IFN-γ. So we concluded that Let-Ta promotes the occurrence and development of allergic rhinitis.