二甲基亚硝胺诱发大鼠肝纤维化模型肝脏超微结构形态学与血清透明质酸、层粘连蛋白、Ⅳ型胶原含量的变化

背景:肝纤维化的发展伴随诸多的形态学和机能学的改变,二甲基亚硝胺所致的大鼠肝纤维化模型病变类似于人类肝纤维化病变。目的:观察二甲基亚硝胺诱发大鼠肝纤维化发生过程中形态学与血清透明质酸、层粘连蛋白、Ⅳ型胶原含量的动态变化。设计:随机对照动物实验。单位:延边大学医学院病理教研室实验室。材料:选用80只3月龄Wistar雄性大鼠,清洁级,体质量175～200g,由延边大学医学院动物中心提供。试剂:二甲基亚硝胺美国Sigma公司产品,α-平滑肌肌动蛋白为Dako公司产品,天狼猩红(Siriusred)为Aldrichchem公司产品,血清透明质酸、层粘连蛋白和Ⅳ型胶检测试剂盒为华美生物工程公司产品,兔抗鼠的一抗为Dako,Denmak生物公司的产品。仪器:日本产JEM-1200EX透射电镜;日本产酶联免疫检测仪;北京航空航天大学研制开发的CMTAS多功能真彩色病理图象分析系统。方法:实验于2004-06/2005-12在延边大学医学院完成。摸球法随机将大鼠分成2组。模型组(n=40):给予腹腔注射10g/L二甲基亚硝胺(10μL/kg),1周连续注药3d(1次/d),持续4周;对照组(n=40):在同一时间段内注射同样剂量的生理盐水;分别在实验开始7,14,21,28d处死大鼠,处死前左心室取血,血清样品被冷冻在-70℃的低温冰箱中备实验用,处死后取其肝组织用于光镜和电镜的样品制备。①用ELISA法测定在肝纤维化形成过程中血清透明质酸、层粘连蛋白、Ⅳ型胶原含量的动态变化。②采用苏木精-伊红染色、组织化学的天狼猩红染色观察肝纤维化形成过程中组织形态学变化及对肝纤维化分级(肝纤维化程度分为0～4级,0级:没有肝纤维化;1级:汇管区有纤维化;2级:汇管区与汇管区之间形成纤维间隔;3级:肝小叶中出现纤维间隔,并且肝的正常结构出现病理改变;4级:形成肝硬化),同时计算胶原纤维的面密度。③采用透射电镜技术、免疫组织化学的α-平滑肌肌动蛋白染色观察肝星状细胞的转化情况及分布特点。④对肝纤维化形成过程中胶原纤维面密度的百分比与血清透明质酸、Ⅳ型胶原、层粘连蛋白含量的相关分析。主要观察指标:①肝纤维化形成过程中血清透明质酸、层粘连蛋白、Ⅳ型胶原含量的变化。②肝纤维化形成过程中形态学变化、肝纤维化的分级情况及胶原纤维的面密度。③肝星状细胞的转化情况及分布特点。④肝纤维化形成过程中胶原纤维面密度的百分比与血清透明质酸、Ⅳ型胶原、层粘连蛋白含量的相关分析结果。结果:纳入80只大鼠,实验组34只造模成功,与对照组40只全部进入结果分析。①模型组第7天至28天血清透明质酸、层粘连蛋白、Ⅳ型胶原含量明显高于对照组(P<0.05),其中第28天增加程度最大。②模型组汇管区在腹腔注射二甲基亚硝胺后第7天出现出血坏死,第14天仍可在汇管区观察到出血、坏死,并且还可见较薄的纤维间隔,第21和28天可见较厚的纤维间隔;模型组大鼠腹腔注射二甲基亚硝胺后第7,14,21,28天胶原纤维面密度的百分比明显高于对照组(P<0.05),其中第28天增加的幅度最大;对照组大鼠纤维化病理分级与模型组大鼠各时间点相比差异显著(P<0.01),模型组大鼠的第7天较第14,28天组有明显差异(P<0.01)。③a-平滑肌肌动蛋白染色有阳性细胞出现,并且在这一阶段在电镜下观察到正处在“转化的肝星状细胞”;模型组第21和28天,在电镜下观察到典型的成纤维细胞。④胶原纤维面密度的百分比与血清透明质酸、层粘连蛋白、Ⅳ型胶原含量呈正相关(r=0.707,0.675,0.662,P<0.01)。结论:二甲基亚硝胺诱发大鼠肝纤维化发生过程中,在不同时间段内形态学与血清标志物透明质酸、层粘连蛋白、Ⅳ型胶原呈动态变化,并且在不同的时间段内胶原纤维面密度的百分比与血清透明质酸、层粘连蛋白、Ⅳ型胶原含量呈正相关。

Dynamic changes in ultrastructural morphology and serum levels of hyaluronic acid, laminin and collagen in rats with dimethylnitrosamine-induced liver fibrosis

BACKGROUND: Development of liver fibrosis accompanies many morphological and functional changes. The pathological alterations of dimethylnitrosamine (DMN)-induced liver fibrosis in rats are similar to those of human liver fibrosis.OBJECTIVE: To observe the dynamic changes in morphology and serum hyaluronic acid (HA), laminin (LN), and type Ⅳ collagen in rats with liver fibrosis induced by DMN.DESIGN: Randomized controlled animal trial.SETTING: Laboratory of Teaching and Research Section of Pathology, College of Medicine, Yanbian University.MATERIALS: Eighty 3-month-old male rats of clean grade with 175-200 g body mass were selected, which were provided by the animal center of College of Medicine, Yanbian University. Agents: Dimethylnitrosamine provided by Sigma company, α smooth muscle actin by Dako company, Sirius red by Aldrich chem company, serum hyaluronic acid,laminin and type Ⅳ collagen kit by Sino-American Biotechnology Company, rabbit-anti-rat I g by Dako, Denmak company. Devices: JEM-1200EX transmission electron microscope made in Japan; enzyme linked immuno analyzer made in Japan; and CMTAS multifunction true color pathological image analysis system developed by Beijing University of Aeronautics and Astronautics.METHODS: The experiment was conducted in the College of Medicine, Yanbian University from June 2004 to December 2005. The rats were divided into 2 groups by lot: model group (n =40): The rats were intraperioneally injected with 10 g/L DMN (10 μL/kg) once daily, 3 days a week for 4 weeks; control group (n =40): The matching normal saline was injected at the same period; the blood from the left ventricle was collected and frozen in refrigerator at -70 ℃ before the rats were killed at days 7, 14, 21, and 28 and the liver tissue was removed for electron and light microscope observation. ①The dynamic changes in the content of serum HA, LN and type Ⅳ collagen were measured by enzyme-linked immunoabsorbent assay (ELISA). ②The morphological changes and liver fibrosis grading were examined by HE staining,immunohistochemical Sirius-red staining (liver fibrosis degree was classified into 5 grades: grade 0: no fibrosis; grade 1:fibrosis in portal area; grade 2: fibrotic septa between portal tracts; grade 3: fibrosis septa and structure disturbance of hepatic lobule; grade 4: cirrhosis), meanwhile, the area-density percentage of collagen fibrosis was calculated. ③The hepatic stellate cells were detected with transmission electron microscope and immunohistochemical alpha smooth muscle actin (SMA) staining. ④The correlation between area-density percentage of collagen fibrosis during liver fibrosis formation and the serum levels of HA, LN and type Ⅳ collagen was analyzed.MAIN OUTCOME MEASURES: ①The changes in the serum levels of HA, type Ⅳ collagen and LN during liver fibrosis formation; ②The morphological changes and liver fibrosis grading and area-density percentage of collagen fibrosis; ③Transformation and distribution characteristics of hepatic stellate cells; ④The correlation between area-density percentage of collagen fibrosis and the serum levels of HA, LN and type Ⅳ collagen.RESULTS: Among the 80 rats, 34 of the experimental group were modeled successfully, which were involved in the result analysis with the 40 rats in the control group. ①The levels of serum HA, type Ⅳ collagen and LN of the model group were significantly higher compared with the control group from day 7 to 28 (P ＜ 0.05), especially that on the 28th day. ②In the model group, the portal area of the rats showed hemorrhagic necrosis at day 7 after injection of DMN; at day 14,hemorrhage, necrosis and thin fibrotic septa joining central areas of liver were found; at days 21 and 28, thick septa was found; The area-density percentage of collagen fibrosis of the model group was significantly higher compared with the control group at days 7, 14, 21 and 28 (P ＜ 0.05), especially that on the 28th day. There were significant differences in the liver pathologic grading between the two groups at each time point (P ＜ 0.01); the pathologic grading of the model group at day 7 differed from those at days 14 and 28 (P ＜ 0.01). ③The α-SMA positive cells and a transitional hepatic stellate cell were found under the electron microscopy; typical myofibroblast was observed in the model group at day 21 and 28 under the electron microscopy. ④The area-density percentage of collagen fibrosis was positively correlated with the content of serum HA, LN and type Ⅳ collagen (r=0.707, 0.675, 0.662, P＜ 0.01).CONCLUSTON: There are significantly progressional changes in morphological and serum levels of HA, type Ⅳ collagen and LN in different stages of DMN-induced liver fibrosis in rats, moreover, the area-density percentage of collagen fibrosis is positively correlated with the serum levels of HA, LN and type Ⅳ collagen at different stages.