肝窦毛细血管化的形成机制研究

目的　探讨二甲基亚硝胺 (DMN)致大鼠肝纤维化过程中肝窦壁病理变化及其与门脉压力的关系。方法　雄性Wistar大鼠 4 0只用 0 .5 %DMN每周连续 3d共 4周 12次腹腔注射制作大鼠肝纤维化模型 ,分别于造模后 1d、2d、3d、1周、2周、4周、6周、8周作为动态观察时相点 ;分别取 5只模型大鼠和 3只正常大鼠肠系膜前静脉分支插管法测门脉压力 (Ppv) ;免疫组化染色观察肝组织Ⅳ型胶原(ColⅣ )、层粘连蛋白 (LM)和Ⅰ型胶原 (ColⅠ )表达 ;透射电镜观察肝组织超微结构。结果　正常大鼠肝窦壁ColⅣ阳性表达 ;模型组肝窦壁除ColⅣ阳性染色呈现为先弱后强外 ,LM和ColⅠ的沉积均随造模时间的延长而进行性增加 ,4周时表达最为明显 ,电镜下可见肝窦内皮失窗孔和内皮下完整基底膜形成 ;模型组Ppv与肝窦壁LM的表达量呈显著正相关 (P <0 .0 5 )。结论　DMN大鼠肝窦内皮下基底膜是在功能性基底膜破坏的基础上 ,随着LM与新合成ColⅣ沉积以及两者结合的增加、加之ColⅠ的沉积而形成     

肝窦毛细血管化在二甲基亚硝胺大鼠肝纤维化门静脉高压形成中的作用

目的 研究肝窦毛细血管化在二甲基亚硝胺(DMN)大鼠肝纤维化门静脉高压形成中的作用。方法经4周12次腹腔注射DMN制备火鼠肝纤维化模型,应用电镜技术、免疫组织化学方法结合大鼠门静脉压力测定,24周动态分析肝纤维化形成过程中肝窦毛细血管化与门静脉压力变化的相关性。结果 大鼠门静脉压力随着造模的进行不断升高,造模4周时达(1.10 ±0.18)kPa,明显高于对照组(0.52±0.04)kPa(t=6.41.P<0.0 1)。造模停止后,大鼠门静脉压力逐渐恢复正常。其动态变化与电镜下肝窦毛细血管化的变化规律一致;与反映肝窦内皮表型改变的第Ⅷ因子相关抗原的动态变化成正相关(r=0.833,P<0.01);与反映肝窦内皮下基底膜形成的层黏连蛋白的动态变化成正相关(r=0.953,P<0.01);与反映肝窦壁星状细胞活化收缩的α-平滑肌肌动蛋白的动态变化成正相关(r=0.919,P<0.01)。结论 肝窦毛细血管化是DMN肝纤维化模型门静脉高压产生的主要原因。     

肝窦毛细血管化的研究进展

肝窦是不连续毛细血管 ,为通透性最大的血窦之一 ,其内皮细胞扁而薄 ,上有发达的窗孔 ,且窗孔无隔膜 ,整个细胞呈筛型状态。透射电镜在正常肝窦内皮外看不到有基底膜存在 ,如用特殊方法可显示少量网状纤维或 型胶原 ( - C)。肝纤维化过程中肝窦内皮窗孔逐渐减少或消失 ,内皮下基底膜形成 ,类似于连续性毛细血管 ,此过程称为肝窦毛细血管化 ( sinusoid capillarizatin) ,是肝纤维化的重要病理过程 ,对肝细胞功能影响很大 ,不仅发生较早 ,与肝星状细胞 ( HSC)的活化及窦内皮细胞的表型转化直接相关 ,还参与促进形成门脉高压症。病理刺激持…     

肝窦内皮细胞与肝窦毛细血管化研究进展

肝窦内皮细胞具有开放的、没有横膈膜的窗孔,内皮下没有基底膜。这种结构有利于调控肝细胞与肝窦血液的物质交换。肝窦内皮细胞能分泌内皮素-1和一氧化氮,并通过窗孔的变化,对肝脏微循环进行调节,同时可分泌大量的形成基底膜的成分,在肝窦毛细血管化的过程中起主导作用。肝窦内皮细胞表型标志发生变化,Ⅷ因子相关抗原、CD44等表达增强,也是肝窦毛细血管化的重要标志。笔者对肝窦内皮细胞的结构及其在肝窦毛细血管化中的功能和表型变化进行综述。     

肝窦毛细血管化的研究进展

肝窦毛细血管化是肝纤维化的重要特征,对肝纤维化的发生和发展有重要影响。本综述了近年来有关肝窦毛细血管化的发生机制、后果、时间进程、可逆性和判定等同研究进展。     

四氯化碳诱导的肝纤维化大鼠肝窦毛细血管化的形成

目的：观察四氯化碳（CCl4）诱导的大鼠肝纤维化过程中肝窦毛细血管化的形成过程,探讨其与肝纤维化的关系。方法32只清洁级雄性SD大鼠,随机分为正常对照组,肝纤维化模型组,正常对照组大鼠腹腔注射0．9％氯化钠溶液2 mL/kg ,模型组大鼠腹腔注射50％ CCl4-蓖麻油混合液2 mL/kg ,每周2次,共8周;分别于造模第2、4、6、8周处死大鼠,观察肝组织炎症及纤维化程度,放射免疫法检测血清中透明质酸（HA）的含量,透射电镜观察肝窦窦壁结构,S-P 免疫组织化学检测各组大鼠肝组织CD31、层黏连蛋白（LN）、IV型胶原（Col-IV）的表达。结果肝脏组织学证实CCl4诱导的大鼠肝纤维化模型构建成功,6周可见纤维间隔形成;透射电镜显示,CCl4诱导2周时,部分肝窦内皮细胞（liver sinusoidal endothelial cells ,LSEC）窗孔减少,内皮下未见基底膜（Basement membrane,BM）,随着造模的进程,LSEC 窗孔进一步减少,部分甚至消失,第6、8周时局部肝窦内皮下形成连续的BM。同时,随着肝纤维化的进程,HA浓度逐渐升高,肝窦内皮细胞表面标志物CD31及基底膜主要成分Col-IV、LN表达逐渐增强。结论在CCl4诱导大鼠肝纤维化过程中,肝窦毛细血管化是逐渐形成的,LSEC失窗孔早于纤维间隔的形成,而肝窦内皮下基底膜出现在纤维间隔形成以后。     

肝窦毛细血管化的研究进展

肝窦毛细血管化是肝纤维化的重要特征,对肝纤维化的发生和发展有重要影响。本文综述了近年来有关肝窦毛细血管化的发生机制、后果、时间进程、可逆性和判定等方面的研究进展。     

肝星状细胞与肝窦毛细血管化

肝星状细胞(Hepatic stellate cells,HSC)位于肝细胞与肝窦之间的Disse间隙,有丰富的伪足包绕肝窦,是来源于间质的一种肝脏非实质细胞。1876年Kuffer通过氯化银(AgCl)组织化学染色,首先发现该细胞,并根据其星形形态将其命名为HSC,认为是肝脏的一种吞噬细胞,与Kuffer细胞相似。直到1951年,Ito应用电子显微镜发现HSC与Kuffcr细胞是两类不同的组织细胞并将其区分开。1971年Wake[1]重复Kuffer的AgCl化学染色实验,证实HSC的存在。HSC的命名很混杂,有20余种,如贮脂细胞、储脂细胞、肝窦星形细胞、lto细胞、窦周细胞和星型细胞等。在正…     

肝纤维化过程中一个重要的病理改变—肝窦毛细血管化

肝窦属不连毛细胞血管,窦壁主要由一层内皮细胞组成,其窦腔面可见少量微绒毛,扁薄的部分有发达的窗孔,细胞呈筛状形态,内皮窗孔无隔膜,肝窦内皮外无基底膜,仅见少量网状纤维,肝窦是通透性最大的血窦之一,是保证血淮和肝细胞间正常物质交换的组织学基础,1963年Schaffner发现随着肝硬化的发生,肝窦内皮窗孔数逐渐减少或消失,内皮下基阍膜程为肝窦毛细胞血管化（sinusoid capil-larization),研究肝窦毛细胞血管化的形成机理以及和肝纤维化,肝硬化的发生关系已成为世界肝病研究领域的一个热点。     

慢性肝炎肝窦毛细血管化的临床病理研究

目的观察慢性肝炎患者的肝窦毛细血管化与其病理改变、血清学指标相关性,以进一步探索肝窦毛细血管化在疾病诊疗中的意义。方法符合入选条件的68例慢性肝炎患者,行肝穿刺活组织病理检查,用免疫组化方法进行CD34染色,显示肝窦毛细血管化的程度。并于当日晨采血检测肝功能、肝纤维化四项,进行相关性分析。结果肝窦毛细血管化程度与血清肝功能指标中GGT明显相关（r=0.385,P〈0.01）;与血清肝纤维化指标中的HA显著相关（r=0.502,P〈0.001）;与肝组织炎症分级、纤维化分期呈正相关,与分期相关性更强（分别为r=0.426,P〈0.01;r=0.569,P〈0.001）。结论血清学肝功能指标中单独GGT异常预示存在着不断进展的肝损伤;HA是判断肝窦毛细血管化与肝纤维化的一个灵敏的无创性指标;肝窦毛细血管化可能在某种意义上加剧了肝组织炎症的进展。     

层黏连蛋白及其整合素受体在肝窦毛细血管化时的协调表达

目的：探讨层黏连蛋白（LN）及其整合素受体在肝窦毛血管化时的协调表达。方法：皮下注射四氯化碳制备大鼠肝纤维化模型,取肝组织用扫描电镜、特殊染色等进行病理组织形态学观察;层黏连蛋白及其整合素受体α6斑点免疫印迹研究。结果：动态观察了肝纤维化的特征病理变化;肝窦毛细血管化,即窗孔消失,基底膜形成及表型改变。LN在肝纤维化各期窦周阳性着色面积分别为0、1．902％、6．02％、9．68％、14．14％,其差异有显著性（P＜0．001）;正常时α6在肝窦内皮细胞（SEC）上无表达,肝窦毛细血管化时SEC出现α6表达与LN在窦周沉积一致,α6在纤维化时组织中含量明显高于正常（P＜0．05）。结论：LN于肝纤维经时在肝组织中不断沉积,并沿肝窦壁形成基底膜,使肝窦毛细血管化,且SEC出现LN整合素受体的诱导表达。提示LN及其整合素受体的协调表达在肝窦毛细血管化及肝纤维化的发病机制中有着重要的作用。     

The role of capillarization in hepatic failure: studies in carbon tetrachloride-induced cirrhosis.

During the cirrhotic process, the hepatic microvascular phenotype is transformed from sinusoids (discontinuous capillaries) into continuous capillaries. This transformation has been termed capillarization. Many hepatic functions depend on the rapid, bidirectional exchange of macromolecules between plasma and hepatocytes. To determine whether capillarization contributes to hepatic failure in cirrhosis, we decided to study the plasma clearance (125I) and hepatocyte uptake (electron microscopy) of three tracers in normal and cirrhotic rats. The tracers chosen were a hemeundecapeptide with peroxidatic activity (fluid-phase pinocytosis), asialofetuin (receptor-mediated endocytosis of a medium size protein) and ferritin (receptor-mediated endocytosis of a large size protein). The results demonstrate a decreased hepatocyte uptake of hemeundecapeptide; a significant delay in plasma clearance of asialofetuin; and a minor delay in plasma clearance of ferritin, but a striking trapping of ferritin in the cirrhotic capillary basement membrane. The delayed plasma clearance in cirrhosis cannot be ascribed to a decreased number of surface receptors because, in isolated hepatocytes, the number of molecules bound per cell was equivalent in normal and cirrhotic livers. These findings support the concept of capillarization, with the formation of continuous diffusion and filtration barriers between plasma and hepatocytes, representing a significant hindrance to the bidirectional macromolecular exchange normally taking place between these two compartments. Furthermore, at least in the case of ferritin, the capillary basement membrane of cirrhotic livers seems to be the major filtration barrier. This hindrance to hepatocyte uptake, and presumably also to secretion, may be the cause (or at least a major determinant) of the hepatic failure characteristic of cirrhosis.     

Myofibroblasts in the cirrhotic rat liver reflect hepatic remodeling and correlate with fibrosis and sinusoidal capillarization

BACKGROUND/AIMS: Myofibroblasts are essential in fibrogenesis during development of cirrhosis. In the present study we stereologically quantitated MFB's and correlated them with fibrosis and sinusoidal capillarization. METHODS: Male SD rats were rendered cirrhotic by chronic exposure to phenobarbital/CCl4, (CIR; n = 16); untreated littermates served as controls (CTR; n = 10). Sinusoidal capillarization was assessed by a multiple indicator dilution technique as previously described. The volume fractions of myofibroblasts and other liver components were estimated by morphometry. RESULTS: Myofibroblasts averaged 15.7 +/- SD 0.7% in CIR as compared to 6.7% +/- SD 0.4% in CTR (p < 0.01). An extra-littoral compartment of myofibroblasts was found in portal tracts and within fibrous septa. In CIR, hepatocytes showed a bimodal distribution of volume fractions, and hepatocyte volume distribution disclosed a mirror image of that of myofibroblasts. Connective tissue was markedly increased in CIR, averaging 13.2 +/- 1.2% in CIR vs. 1.2 +/- 0.3% in CTR (p < 0.0001). Extravascular albumin space--a measure of sinusoidal capillarization--was reduced by 44% in CIR (0.028 +/- 0.017 vs. 0.050 +/- 0.010 ml/g; p < 0.001). The volume fraction of myofibroblasts correlated best with extravascular albumin space (r = -0.84, p < 0.001). Multiple regression analysis selected only extravascular albumin space and connective tissue to be determined by the volume fraction of myofibroblasts (r = 0.923; p < 0.001). CONCLUSION: We conclude that increased myofibroblasts reflect the degree of hepatic remodeling rather than cirrhosis inasmuch as myofibroblast volume fraction inversely reflects that of hepatocyte bimodality. Myofibroblasts form an extra-littoral compartment in this model of CIR and correlate with hepatic fibrosis and sinusoidal capillarization.     

布-加综合征、肝血窦阻塞综合征与肝硬化的鉴别

布-加综合征是由肝静脉或其开口以上的下腔静脉阻塞性病变引起的以下腔静脉阻塞、门静脉高压为特点的综合征,诊断依靠影像学检查,治疗的关键是解除梗阻。肝血窦阻塞综合征是指肝窦内皮完整性破坏和肝窦内充血阻塞而产生的肝内窦后性门静脉高压症,临床表现类似布-加综合征,诊断依靠肝组织活检。这两种疾病的治疗和预后均与肝实质病变导致的肝硬化不同,所以临床上需要注意这三种疾病的鉴别。     

Arsenic stimulates sinusoidal endothelial cell capillarization and vessel remodeling in mouse liver

Trivalent arsenic [As(III)] is a well-known environmental toxicant that causes a wide range of organ-specific diseases and cancers. In the human liver, As(III) promotes vascular remodeling, portal fibrosis, and hypertension, but the pathogenesis of these As(III)-induced vascular changes is unknown. To investigate the hypothesis that As(III) targets the hepatic endothelium to initiate pathogenic change, mice were exposed to 0 or 250 parts per billion (ppb) of As(III) in their drinking water for 5 weeks. Arsenic(III) exposure did not affect the overall health of the animals, the general structure of the liver, or hepatocyte morphology. There was no change in the total tissue arsenic levels, indicating that arsenic does not accumulate in the liver at this level of exposure. However, there was significant vascular remodeling with increased sinusoidal endothelial cell (SEC) capillarization, vascularization of the peribiliary vascular plexus (PBVP), and constriction of hepatic arterioles in As(III)-exposed mice. In addition to ultrastructural demonstration of SEC defenestration and capillarization, quantitative immunofluorescence analysis revealed increased sinusoidal PECAM-1 and laminin-1 protein expression, suggesting gain of adherens junctions and a basement membrane. Conversion of SECs to a capillarized, dedifferentiated endothelium was confirmed at the cellular level with demonstration of increased caveolin-1 expression and SEC caveolae, as well as increased membrane-bound Rac1-GTPase. CONCLUSION: These data demonstrate that exposure to As(III) causes functional changes in SEC signaling for sinusoidal capillarization that may be initial events in pathogenic changes in the liver.     

Pathogenesis of cirrhosis

Abstract   Cirrhosis develops by the accumulation of many focal lesions of parenchymal extinction. Parenchymal extinction is accompanied and presumably caused by obliteration of small portal and hepatic veins. Fibrosis occurs during the acute phase of injury but is rapidly removed leaving collapsed preformed stroma and obliterated small veins. Portal vein supply is replaced by arterial flow. Dominant arterial flow may prevent healing of extinction lesions and restoration of obliterated portal veins.