活动性结核病铁过载小鼠模型建立及相关指标分析

目的 建立一种外源性铁过载结核病小鼠模型。方法 采用完全随机法将20只C57BL/6N小鼠分为阴性对照、低剂量、中剂量和高剂量组,每组5只,分别经腹腔注射右旋糖酐铁溶液(0、3.75、7.50、15.00 mg/次,3 次/周,共4周)。建模结束后对铁过载小鼠的器官组织形态及体质量进行评估,ELISA法检测血清铁、铁蛋白、转铁蛋白及可溶性转铁蛋白受体含量。心脏、肝脏、脾脏、肺、肾脏和小肠等器官进行组织铁含量和铁沉积病理分析。经尾静脉注射结核分枝杆菌(Mtb)标准株H37Rv感染中等剂量铁过载小鼠建立活动性结核病铁过载小鼠模型,采用HE染色和Mtb培养分析肺、脾脏和肝脏等组织结核性病变和荷菌量。结果 铁过载小鼠肝脏颜色加深,呈暗褐色,其他脏器组织无明显颜色和形态改变。阴性对照组,低、中、高剂量组小鼠的体质量增长百分比分别为25.47%、25.22%、24.74%、21.36%,其中,高剂量组的体质量增长明显低于阴性对照组(F=17.235,P=0.027)和低(F=15.206,P=0.031)、中剂量组(F=11.061,P=0.036)。肝脏组织铁含量最高,其他依次为脾脏、肾脏和小肠,低剂量组小鼠心脏和肺组织铁含量与阴性对照组相比差异无统计学意义(F=19.023,P=0.715;F=23.193,P=0.902)。铁过载小鼠外周血血清铁和铁蛋白水平随铁剂注射量增加而升高,转铁蛋白和可溶性转铁蛋白受体无明显变化。各脏器组织HE染色与普鲁士蓝染色结果发现,铁过载动物各脏器均出现不同程度铁沉积,且高剂量铁剂引发小鼠肝肾损伤。铁过载Mtb感染组小鼠的肺(F=23.227,P=0.017)、脾脏(F=19.023,P=0.021)和肝脏(F=17.392,P=0.009)细菌培养报阳时间明显低于Mtb感染对照组,肺(F=21.012,P=0.007)、脾脏(F=20.173,P=0.002)和肝脏(F=19.091,P=0.005)荷菌量明显高于Mtb感染对照组。结论 腹腔注射中等剂量(7.50 mg/次,3 次/周,共4周)右旋糖酐铁溶液成功构建与临床铁过载疾病患者症状类似的外源性铁过载小鼠模型,通过尾静脉注射Mtb可构建活动性结核病铁过载小鼠模型。

Establishment of an Iron-overloaded Mouse Model with Tuberculosis and Analysis of the Iron Metabolism Index

Objective To establish a mouse model of exogenous iron overload combined with tuberculosis(TB). Methods C57BL/6N mice were divided into negative control, low-, medium-, and high-dose iron groups and received intraperitoneal injection of iron dextran at 0, 3.75, 7.50, and 15.00 mg/dose(3 times/week for 4 weeks), respectively.After 4 weeks, the organ morphology and body weight of the mice were evaluated.The content of serum iron, ferritin, transferrin, and transferrin receptor was determined by ELISA.Heart, liver, spleen, lung, kidney, and small intestine were analyzed for tissue iron content and iron deposition pathology.Mycobacterium tuberculosis(Mtb)standard strain H37Rv was injected via tail vein to infect the mice receiving moderate-dose iron to establish an iron-overloaded mouse model of active TB.HE staining and Mtb culture were employed to analyze tuberculous lesions and bacterial loads of lung, spleen and liver tissues. Results The weight gain percentages of mice in the negative control, low-, medium-, and high-dose iron groups were 25.47%, 25.22%, 24.74%, and 21.36%, respectively, which was significantly lower in the high-dose group than in the negative control(F=17.235, P=0.027), low-dose(F=15.206, P=0.031), and medium-dose(F=11.061, P=0.036)groups.Liver had the highest iron content, followed by spleen, kidney, and small intestine.The iron content in heart and lung tissues of the low-dose group had no significant difference compared with those of the negative control group(F=19.023, P=0.715;F=23.193, P=0.902).Serum iron and ferritin in the iron-overloaded mice increased in a dose-dependent manner, while transferrin and transferrin receptor had no significant changes.HE and Prussian blue staining showed that the iron-overloaded mice had different degrees of iron deposition in tissues and high-dose iron caused liver and kidney damage.The lung(F=23.227, P=0.017), spleen(F=19.023, P=0.021), and liver(F=17.392, P=0.009)of the iron-overloaded mice with TB had a significantly shorter time of bacterial culture than those of the TB-infected mice without iron overload.The lung(F=21.012, P=0.007), spleen(F=20.173, P=0.002), and liver(F=19.091, P=0.005)of the iron-overloaded mice with TB had significantly higher bacterial loads than those of the TB-infected mice without iron overload. Conclusions The exogenous iron-overloaded mouse model with similar symptoms to patients with clinical iron overload can be established by intraperitoneal injection of medium-dose(7.50 mg/dose, 3 times/week for 4 weeks)iron dextran.Mtb injection through the tail vein can help construct a mouse model of iron overload combined with active TB.