鼻疽诺卡菌感染小鼠足垫后组织病理变化以及细胞因子分泌情况的初步研究

Preliminary study of histopathologic changes and cytokine secretion in foot pad of mice infected with Nocardia farcinica

目的了解鼻疽诺卡菌感染动物模型小鼠足垫后不同时间的组织病理进展变化以及细胞因子分泌情况,为鼻疽诺卡菌致病机制研究提供依据。方法应用对数生长期的鼻疽诺卡菌注射于小鼠足垫,建立感染模型。将感染1、3、7、14 d后小鼠分别脱臼处死,用手术刀片切取感染小鼠的足垫,制备切片,应用HE染色观察组织不同时间的病理变化,通过免疫组化研究感染过程中IL-6、IL-12、IFN-γ、TNF表达分泌情况。结果通过HE染色观察到感染后第1天中性粒细胞浸润,炎症形成;感染后第3天中性粒细胞脓肿形成,进入急性感染时期;感染后第7天肌肉组织间大量肌纤维母细胞及血管内皮细胞增生,感染转入慢性感染时期;感染后第14天肌肉组织间大量肌纤维母细胞及血管内皮细胞增生,见局灶小脓肿,周围见片状增生的泡沫样巨噬细胞,进入感染修复期。组织免疫组化结果显示,在炎症形成时期,组织中的IL-6和TNF表达水平高于对照组,差异有统计学意义(P<0.05);在急性感染期,组织中仅可见TNF表达水平高于对照组,差异有统计学意义(P<0.05);在慢性感染期,组织中IL-6、IL-12、IFN-γ和TNF表达量均高于对照组,差异有统计学意义(P<0.05);在感染修复期,组织中的IL-6、IFN-γ和TNF表达水平高于对照组,差异有统计学意义(P<0.05)。结论鼻疽诺卡菌感染小鼠足垫后出现明显的病理变化周期,在感染第3天开始进入急性感染时期,感染后第7天转入慢性感染时期,感染后第14天进入组织修复期,并且IL-6、IFN-γ、TNF参与了炎症反应,尤其是IL-6表达量最高,主要促进Th0向Th1和Th17亚群分化,激活巨噬细胞、树突状细胞和NK细胞等,增强其吞噬和杀伤功能,以杀伤胞内鼻疽诺卡菌。

Objective To understand the histopathologic changes and cytokine secretion in the foot pads of mice infected with Nocardia farcinica at different times and the pathogenic mechanism of Nocardia farcinica. Methods The foot pads of mice were infected with Nocardia farcinica in logarithmic phase to establish an infection model. A mouse was killed and the foot pad was cut off with surgical blade at day 1, 3, 7 and 14 after infection. The foot pad tissues were collected and embedded in paraffin. Pathological changes were assessed by HE staining and the cytokines of IL-6, IL-12, IFN-γ and TNF were detected with immunohistochemistry assay. Results The results of HE staining showed that at day 1 after infection, neutrophil infiltrated and inflammation occurred; at day 3 after infection, neutrophils abscess was presented and it was the period of acute infection; at day 7 after infection, there were amount of myofibroblast and endothelial cells hyperplasia in the focus of infection and it was the period of chronic infection; and at day 14 after infection, besides the myofibroblast and endothelial cells hyperplasia, focal abscesses was formed and macrophage-derived foam cells was found. It was the period of recovery. The results of immunohistochemical detection indicated that in the inflammation phase, the expression levels of IL-6 and TNF were higher than those of control group （ P 〈 0. 05 ）, in acute phase, only TNF expression level was higher than control group （P 〈0. 05）, in chronic phase, the expression levels of IL-6,IL-12, IFN-γ and TNF were all higher than those in control group （ P 〈 0. 05 ） and in recovery phase, the expression levels of IL-6, IFN-γ and TNF were higher than those in control group （ P 〈 0. 05 ）. Conclusion The pathological change of mice foot pad infected with Ncardia farcinica was obvious. At 3,7 and 14 day after infection it was acute phase, chronic phase and recovery phase respectively. IL-6, IFN-γ and TNF involved in inflammation, especially the IL- 6.