摘要目的:探讨黏附侵袭性大肠埃希菌( E. coli)LF82菌株对UC小鼠肠道屏障结构和功能的影响。 方法:将24只清洁级C57BL/6小鼠分为菌株UC组、UC组和健康对照组，每组8只。采用葡聚糖硫酸钠(DSS)诱导小鼠UC模型，造模前1周，给予菌株UC组小鼠1×10 9 CFU E． coli LF82菌株灌胃，使菌株定植。通过疾病活动指数(DAI)、结肠大体形态损伤评分、结肠黏膜损伤指数(CMDI)、结肠组织髓过氧化物酶(MPO)活性、组织病理学表现等比较 E. coli LF82对UC小鼠结肠炎症的作用。通过透射电子显微镜和直接免疫荧光染色法观察3组小鼠结肠组织超微结构和细胞骨架F-肌动蛋白的变化，采用过碘酸希夫反应(PAS)染色和天狼星红染色评估结肠黏液分泌能力和纤维化程度。采用 t检验、最小显著差异法、重复测量方差分析和单因素方差分析进行统计学分析。 结果:菌株UC组小鼠造模第4、5、6、7天DAI评分均高于UC组[分别为(2.53±0.38)分比(2.01±0.53)分、(3.02±0.62)分比(2.67±0.24)分、(3.13±0.61)分比(2.20±0.24)分、(3.27±0.28)分比(2.20±0.69)分]，差异均有统计学意义( t＝3.37、2.25、9.56、10.24， P均<0.05)。菌株UC组小鼠结肠的大体形态损伤评分高于UC组[(6.17±1.94)分比(2.83±0.98)分]，差异有统计学意义( t＝－3.75， P<0.05)。菌株UC组小鼠CMDI和结肠黏膜MPO活性均高于UC组[(16.80±2.79)分比(11.80±3.11)分、(729.3±77.5) U/mg比(594.4±31.9) U/mg]，差异均有统计学意义( t＝－2.83；均值差值为134.82，95% CI 72.12～197.51； P均<0.05)。透射电子显微镜下结果显示，菌株 E. coli LF82可侵入小鼠肠上皮下，引起结肠组织进一步损伤，使结肠骨架蛋白F-肌动蛋白分布状况发生改变。PAS染色结果显示，菌株UC组和UC组PAS阳性细胞百分比低于健康对照组[(32.40±8.02)%、(41.90±8.99)%比(57.70±11.52)%]，差异有统计学意义( F＝17.63， P<0.01)，菌株UC组PAS阳性细胞百分比低于UC组，差异有统计学意义(均值差值为－9.50，95% CI －18.33～－0.67， P<0.05)。天狼星红染色结果显示，菌株UC组结肠黏膜绒毛上皮部分被破坏，胶原纤维增生严重；菌株UC组和UC组胶原纤维面积比高于健康对照组[(51.83±5.78)%、(37.11±5.59)%比(15.41±2.25)%]，差异有统计学意义( F＝86.72， P<0.01)；菌株UC组胶原纤维面积比高于UC组，差异有统计学意义(均值差值为14.83，95% CI 8.91～20.76， P<0.05)。 结论:E． coli LF82可加重DSS诱导的UC小鼠结肠炎症，导致结肠超微结构和细胞骨架发生改变，还可降低小鼠结肠黏液分泌能力，增加结肠组织纤维化程度。

abstractsObjective:To investigate the effects of adherent-invasive Escherichia coli ( E. coli) LF82 on the structure and function of intestinal barrier in mice with ulcerative colitis (UC). Methods:Twenty-four specific pathogen free (SPF) C57BL/6 mice were divided into UC with E. coli LF82 group, UC group and healthy control group with eight mice in each group. The UC mice model was induced by dextran sulfate sodium (DSS). One week before modeling, the mice of UC with E. coli LF82 group were intragastric administrated with 1×10 9 colony-forming unit (CFU) E. coli LF82 to colonize the bacteria strain. The effects of E. coli LF82 on colitis of mice with UC were evaluated by disease activity index (DAI), gross morphological injury score, colonic mucosal injury index (CMDI), myeoloperoxidase (MPO) activity and pathological features. The ultrastructure and the changes of cytoskeleton F-actin of mice colonic tissues were detected by transmission electron microscope (TEM) and direct immunofluorescence. The ability of colonic mucin production and degree of fibrosis were estimated by periodic acid Schiff reaction (PAS) stain and sirius red stain. T test, least significant difference, repeated measurement analysis of variance and one-way analysis of variance were used for statistical analysis. Results:On the fourth, fifth, sixth and seventh day after the modeling, the DAI scores of UC with E. coli LF82 group were all higher than those of UC group ((2.53±0.38) points vs. (2.01±0.53) points, (3.02±0.62) points vs. (2.67±0.24) points, (3.13±0.61) points vs. (2.20±0.24) points, (3.27±0.28) points vs. (2.20±0.69) points, respectively), and the differences were statistically significant ( t=3.37, 2.25, 9.56 and 10.24, all P<0.05). The gross morphological injury score of mice colon of UC with E. coli LF82 group was higher than that of UC group ((6.17±1.94) points vs. (2.83±0.98) points), and the difference was statistically significant ( t=-3.75, P<0.05). The CMDI and MPO activity of UC with E. coli LF82 group were both higher than those of UC group ((16.80±2.79) points vs. (11.80±3.11) points, (729.3±77.5) U/mg vs. (594.4±31.9) U/mg), and the differences were statistically significant ( t=-2.83; mean difference=134.82, 95% confidence interval ( CI) 72.12 to 197.51; both P<0.05). The results of TEM showed that the E. coli LF82 could invade the submucosa of colon and caused further injury of colonic tissues in mice. The distribution of cytoskeleton F-actin of mice colonic tissues changed. The results of PAS staining showed that the percentages of PAS positive cells of UC with E. coli LF82 group and UC group were both lower than that of healthy control group ((32.40±8.02)% and (41.90±8.99)% vs. (57.70±11.52)%), and the difference was statistically significant ( F=17.63, P<0.01). The percentage of PAS positive cells of UC with E. coli LF82 group was lower than that of UC group, and the difference was statistically significant (mean difference=-9.50, 95% CI -18.33 to -0.67, P<0.05). The results of sirius red staining showed that the villous epithelium of colon mucosa of UC with E. coli LF82 group was partially injured and collagen fibers hyperplasia was serious. The area ratios of collagen fiber of UC with E. coli LF82 group and UC group were both higher than that of healthy control group ((51.83±5.78)% and (37.11±5.59)% vs. (15.41±2.25) %), and the difference was statistically significant ( F=86.72, P<0.01). The area ratio of collagen fiber of UC with E. coli LF82 group was higher than that of UC group, the difference was statistically significant (mean difference=14.83, 95% CI 8.91 to 20.76, P<0.05). Conclusions:E. coli LF82 can aggravate DSS-induced colitis in UC mice, leading to changes in colon ultrastructure and cytoskeleton, it can also reduce the ability of mucus secretion of colon of mice and increase the degree of colonic tissues fibrosis.