Lymph Circulation in the Liver

The liver produces a large amount of lymph, which is estimated to be 25 to 50 % of lymph flowing through the thoracic duct. The hepatic lymphatic system falls into three categories depending on their locations: portal, sublobular, and superficial lymphatic vessels. It is suggested that 80 % or more of hepatic lymph drains into portal lymphatic vessels, while the remainder drains through sublobular and capsular lymphatic vessels. The hepatic lymph primarily comes from the hepatic sinusoids. Our tracer studies, together with electron microscopy, show many channels with collagen fibers traversing through the limiting plate and connecting the space of Disse with the interstitial space either in the portal tracts, or around the sublobular veins. Fluid filtered out of the sinusoids into the space of Disse flows through the channels traversing the limiting plate either independently of blood vessels or along blood vessels and enters the interstitial space of either portal tract or sublobular veins. Fluid in the space of Disse also flows through similar channels traversing the hepatocytes intervening between the space of Disse and the hepatic capsule and drains into the interstitial space of the capsule. Fluid and migrating cells in the interstitial space pass through prelymphatic vessels to finally enter the lymphatic vessels. The area of the portal lymphatic vessels increases in liver fibrosis and cirrhosis and in idiopathic portal hypertension. Lymphatic vessels are abundant in the immediate vicinity of the hepatocellular carcinoma (HCC) and liver metastasis. HCCs expressing vascular endothelial growth factor‐C are more liable to metastasize, indicating that lymphangiogenesis is associated with their enhanced metastasis. Anat Rec, 291:643–652, 2008. © 2008 Wiley‐Liss, Inc.     

Pathways for movement of fluid and cells from hepatic sinusoids to the portal lymphatic vessels and subcapsular region in rat livers

It has long been a mystery how fluid and migrating cells in the hepatic sinusoids reach lymphatic vessels in the portal tract. Here we describe previously-unknown channels that connect the space of Disse with the portal tract in the rat liver. Transmission electron microscopy was performed on livers injected with either horseradish peroxidase (HRP) or lipopolysaccharide, and scanning electron microscopy was carried out on livers macerated with KOH. Transmission electron microscopy revealed the presence of channels with collagen fibers traversing the limiting plate. A tracer study showed that HRP was in the channels as well as along inlet venules. Dendritic cells in the hepatic sinusoids or between hepatocytes of the limiting plate were also observed extending their pseudopodia through the channels in the limiting plate to the interstitial space of the portal tract. Scanning electron microscopy further showed that many channels (1-3microm in diameter) penetrated through the limiting plate independently of blood vessels and connected the space of Disse with the interstitial space of the portal tract. In addition, the portal tract possessed prelymphatic vessels that were lined with fibroblast-like cells and frequently contained dendritic cells. The initial segment of the portal lymphatic vessels opened to the interstitial tissue space. These results indicate that fluid and dendritic cells in the hepatic sinusoids probably pass through both the space of Disse and the channels traversing the limiting plate, enter the interstitial space of the portal tracts, and finally move from the prelymphatic vessels to the portal lymphatic vessels.     

Pathways of interstitial fluid and lymph flow in the liver acinus of the sheep and mouse

In the acinus of the sheep and mouse liver, lymphatic vessels are restricted to the portal tracts. Vessels less than about 25 μm across form a network around portal venules, and are closely associated with the limiting plate of hepatocytes. The perisinusoidal space of Disse is continuous with the interstitial space of the portal tracts at the origin of the sinusoids. It seems likely that excess interstitial fluid derived from the sinusoids flows along the perisinusoidal space of Disse to enter the portal tracts near the portal venules, and then enters the small lymphatics which lie adjacent to those venules. It then enters the larger vessels, which are adjacent to hepatic arterioles and bile ductules.     

The lymphatics of the liver

An overview of our current knowledge of the hepatic lymph vessels is given, and the different lymph node stations that are related to the liver are described. The lymphatics of the liver itself can be divided into a superficial and a deep system. The superficial vessels are mainly situated in the liver capsule, the deep ones follow the triads of Glisson or the efferent hepatic veins. There are no direct communications between spaces in the liver parenchyma and the first lymphatic capillaries, which end blindly in the surrounding connective tissue. Nevertheless, the perisinusoidal space of Disse, the space of Mall, directly adjacent to the outer limiting plate of the parenchyma, and the space of Comparini, surrounding the sublobular hepatic veins can be regarded as prelymphatic spaces from which the hepatic lymph could originate. The extracellular matrix in the space of Disse is apparently continuous with the extraparenchymal areas of the connective tissue. Collagens and proteoglycans offer a morphological pathway for the transport of fluid, the physiological prerequisites of which are discussed.     

The lymphatics of the liver

An overview of our current knowledge of the hepatic lymph vessels is given, and the different lymph node stations that are related to the liver are described. The lymphatics of the liver itself can be divided into a superficial and a deep system. The superficial vessels are mainly situated in the liver capsule, the deep ones follow the triads of Glisson or the efferent hepatic veins. There are no direct communications between spaces in the liver parenchyma and the first lymphatic capillaries, which end blindly in the surrounding connective tissue. Nevertheless, the perisinusoidal space of Disse, the space of Mall, directly adjacent to the outer limiting plate of the parenchyma, and the space of Comparini, surrounding the sublobular hepatic veins can be regarded as prelymphatic spaces from which the hepatic lymph could originate. The extracellular matrix in the space of Disse is apparently continuous with the extraparenchymal areas of the connective tissue. Collagens and proteoglycans offer a morphological pathway for the transport of fluid, the physiological prerequisites of which are discussed.     

Three-dimensional organization of the collagen fibrillar framework of the human and rat livers

The collagen fibrillar framework in the human and rat liver was demonstrated by a cell-maceration/scanning electron microscope (SEM) method. Maceration of fixed tissues with alkali plus water successfully removed the cellular elements, exposing collagen fibrils which measured about 60 nm in diameter and were identified as such by transmission electron microscopy (TEM). The normal human liver contained 12.4 mg of collagen fibrils/g of wet tissue, while rat livers contained 1.3 mg of collagen fibrils/g of wet tissue. In the Glisson's sheaths were condensations of collagen fibrils which extended to the hepatic lobules. In the spaces of Disse collagen fibrils ran either solitarily or in bundles and formed sheaths for housing the sinusoids. The central veins and the sublobular veins were also surrounded by the collagen fibrillar sheaths which were continuous with those in the spaces of Disse. Between adjacent sheaths of sinusoids frequently stretched collagen fibrillar bundles which were confirmed by TEM to occur in inter-hepatocellular spaces continuous with the spaces of Disse. The collagen fibrillar layer of the human liver capsule was much thicker (70-100 microns in thickness) than that of the rat liver (less than 5 microns in thickness). The collagen fibrils of the capsule were also continuous with those in the spaces of Disse. The collagen fibrillar framework of the liver is presumed not only to mechanically support the tissue, but also to form a microenvironment for hepatocytes and cells in the Disse's space.     

Pattern and distribution of intrahepatic lymph vessels in the rat

The pattern and distribution of intrahepatic lymph vessels were examined by light and electron microscopy in rat livers fixed by perfusion through the portal vein. Lymph vessels were found in the connective tissue of the larger portal canals, where they coursed in close association with branches of the hepatic artery. The smallest portal canals contained no lymphatics. Of the portal canals that lacked a lymphatic, over 50% also lacked an arterial component. Direct connections between the lymphatic lumen and the spaces of Disse or Mall were not observed but lymphatics were found close to Mall's space, separated by only a sparse connective tissue space containing a few collagen fibrils. Lymphatics were neither seen within the parenchyma, nor associated with intercalated (sublobular) veins. Cross-sectional area (223.2 +/- 48.7 micron2 SEM), maximum diameter (20.5 +/- 2.0 microns), volume density (0.00098 +/- 0.00046 micron3/micron3) and profile density (1.8 +/- 0.3 lymphatics per 1 mm2) of hepatic lymph vessels were determined by stereological measurement by a computer-based image analyzer. These data were used to estimate the rate of lymph formation in the liver. It was concluded that 1) initial lymphatics probably originate in the portal canals; 2) the concept that fluid in the space of Disse can be regarded as the principal source of fluid-forming hepatic lymph is questioned, since initial lymphatics appear to be separated from the space of Disse by hepatocytes and the space of Mall; and 3) the rate of lymph formation in the liver of the rat is approximately 0.06-0.08 microliter/min/cm2 of lymphatic endothelium.     

结扎大鼠胸导管诱发胰组织结构的形态学变化

目的 观察胰淋巴淤滞动物模型胰组织结构变化和胰淀肽沉积情况,探讨淋巴淤滞对胰组织细微和超微结构的影响. 方法 10月龄大鼠20只,采用腹部结扎大鼠胸导管,建立胰淋巴淤滞动物模型,造模后6个月取材,部分胰组织经石蜡包埋切片,行HE和刚果红染色;部分经冷冻切片,行免疫组织化学染色和光镜观察;部分标本进行透射电镜样品制备和观察. 结果 HE和刚果红染色切片光镜观察显示,胰腺小叶间隙增宽,呈明显的结缔组织增生、脂肪堆积;胰岛淡染或着朱红色,组织间隙明显增宽.免疫组织化学染色切片光镜观察显示,在胰岛及其周围,呈现胰淀肽强阳性棕褐色着色反应.超薄切片透射电镜观察显示,胰腺小叶间隙增宽,可见血管和扩大的淋巴管;胰岛细胞间隙增宽,细胞间隙内可见大量脂滴样物质和胶原原纤维样结构.结论 胸导管结扎可导致胰淋巴引流障碍,引起胰淋巴管扩张,结缔组织间隙增宽,脂肪堆积,胰岛细胞间隙扩大,胰淀肽沉积等,这些结构变化可能影响胰岛的功能.     

胸导管结扎对大鼠脂质代谢和胰组织结构的影响

目的:探讨胸导管结扎对脂质代谢的影响,揭示淋巴回流障碍诱发胰组织的显微和超微结构变化.方法:SD大鼠随机分为假手术对照组和结扎胸导管模型组.术后6个月取静脉血标本进行血脂检测;部分胰组织标本,H-E和刚果红染色光镜观察;部分胰组织进行透射电镜观察.结果:(1)模型组大鼠游离脂肪酸和甘油三酯浓度明显下降,胆固醇浓度无显著变化.(2)光镜观察显示模型组大鼠的胰腺小叶间隙增宽,脂肪堆积和淋巴管扩张.(3)透射电镜观察显示模型组大鼠的胰岛细胞间隙增宽,细胞间隙及细胞内可见大量脂滴样物质、红细胞和胶原原纤维样结构.结论:胸导管结扎可引起胰腺结构变化和影响胰腺的内、外分泌功能.     

Modifications of the sinusoidal barrier in a model of postsinusoidal hypertension in the rat. An ultrastructural study of endothelial cells

Sinusoids and sinusoidal cells were examined by light and electron microscopy, using a rat model of postsinusoidal hypertension. One month after partial ligation of the vena cava (PLVC) above the hepatic veins, subcapsular hemorrhagic areas were visible with proliferation of hepatic veins; in non hemorrhagic areas, sinusoidal congestion was found. Postsinusoidal hypertension led to a significant increase in sinusoidal volume and to major abnormalities of the endothelium such as endothelial processes and pouches with numerous diaphragmed fenestrae; some red blood cells could be seen in these pouches. Endothelial cells sent out processes in between hepatocytes. Complete and incomplete pseudo-neolumens were found near sinusoids. Numerous Kupffer cells were located either in the sinusoidal barrier or infiltrating the Disse space close to extravasated red blood cells and perisinusoidal cell processes. 18 months after PLVC, lesions were much the same except for the presence of red blood cells in the Disse space.     

Correction of Lymph Circulation during Immediate Hypersensitivity Reaction

We measured lymph flow rate in the thoracic lymphatic duct of dogs with anaphylactic shock receiving mono- or combination therapy with norepinephrine and hydrocortisone. Intensification of lymph circulation improved resorption and transport of metabolic products from the interstitial space through lymphatic vessels and stimulated exchange processes in the blood and tissues during allergic alterations.     

Lymphatic vessels of the human dental pulp in different conditions.

The characteristics of the lymphatic vessel endothelial wall have been investigated in human normal and inflamed dental pulps. In normal pulps the endothelial wall is characterized by the presence of micropinocytotic vesicles and intraparietal channels. In the inflamed pulpal tissue, where an increase in interstitial fluid pressure occurs, the distended endothelial wall presents open junctions between endothelial cells and the openings of the intraparietal channels. Moreover the micropinocytotic vesicles disappear. The cytoplasm of the endothelial cells is characterized by the presence of numerous Weibel-Palade bodies, which increase in number in the dilated vessels. In the fibrillar apparatus surrounding the lymphatic vessel wall collagen fibrils are the prevalent component, while elastic fibers are not present. The different morphological properties of the lymphatic vessels are compared and discussed with regard to the variation of the functional conditions of the tissue.     

Lymphatic capillaries of the pig lung: TEM and SEM observations

Pulmonary lymphatic vessels extend within the connective tissue sheets surrounding airways and blood vessels. Frequently in this location they also border the lobular parenchyma, but no lymphatic vessels have been found within intralobular compartments between blood capillaries and alveoli. The presence and distribution of lymphatic vessels in pulmonary tissue are consistent with an important role for the lymphatic system in the clearance of interstitial fluids in the lung. Pulmonary lymphatic channels have structural characteristics of initial lymphatics; their walls are formed only by an endothelial layer, and no muscular cells are present. A network of anchoring filaments and collagen and elastic fibers surrounds the vessel walls. Because the lung is a mobile organ the tissue undergoes compression and distension during respiratory phase. These modifications could have a role in the mechanisms for lymph formation and flow. © 1994 Wiley-Liss, Inc.     

Lymphatic vessels of the human dental pulp in different conditions

The characteristics of the lymphatic vessel endothelial wall have been investigated in human normal and inflamed dental pulps. In normal pulps the endothelial wall is characterized by the presence of micropinocytotic vesicles and intraparietal channels. In the inflamed pulpal tissue, where an increase in interstitial fluid pressure occurs, the distended endothelial wall presents open junctions between endothelial cells and the openings of the intraparietal channels. Moreover the micropinocytotic vesicles disappear. The cytoplasm of the endothelial cells is characterized by the presence of numerous Weibel-Palade bodies, which increase in number in the dilated vessels. In the fibrillar apparatus surrounding the lymphatic vessel wall collagen fibrils are the prevalent component, while elastic fibers are not present. The different morphological properties of the lymphatic vessels are compared and discussed with regard to the variation of the functional conditions of the tissue. © 1992 Wiley-Liss, Inc.     

Liver Fibrosis in Elderly Cadavers: Localization of Collagen Types I,III, and IV, α‐Smooth Muscle Actin,and Elastic Fibers

We have shown a high prevalence of liver fibrosis in elderly cadavers with diverse causes of death by Sirius red stain; however, the various collagen types in these samples have yet to be evaluated. To further characterize the histopathology of the fibrotic lesions in the livers of these elderly cadavers, this study used immunohistochemistry and histochemistry to identify the principal collagens produced in liver fibrosis, fibrogenic cells and elastic fibers. Collagen I and III immunoreactions were found to colocalize in collagen fibers of fibrotic central veins, perisinusoidal fibrotic foci, portal tract stroma, and fibrous septa. α‐Smooth muscle actin‐expressing perisinusoidal hepatic stellate cells (HSCs), as well as perivenular, portal, and septal myofibroblasts, were closely associated with collagen fibers, reflecting their fibrogenic functions. HSCs and myofibroblasts were also noted to express collagen IV, which may contribute to production of basal lamina‐like structures. In fibrotic livers, the sinusoidal lining showed variable immunostaining for collagen IV. Collagen IV immunostaining revealed vascular proliferation and atypical ductular reaction at the portal–septal parenchymal borders, as well as capillary‐like vessels in the lobular parenchyma. While elastic fibers were absent in the space of Disse, they were found to codistribute with collagens in portal tracts, fibrous septa and central veins. Our combined assessment of collagen types, HSCs, myofibroblasts, and elastic fibers is significant in understanding the histopathology of fibrosis in the aging liver. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.     

Ultrastructure of Sinusoidal Cells in a Benign Liver Cell Adenoma

A typical benign liver cell adenoma was removed from a 25-year-old female taking an oral contraceptive. The biopsy was perfusion-fixed, allowing good visualization of sinusoids and sinusoidal cells. Kupffer cells were seldom seen. Endothelial cells were of irregular thickness; most of them had few fenestrae and were attached to each other by well visible junctions. Normal perisinusoidal cells (PSC) were not seen but were replaced by myofibroblast-like cells with thick subendothelial processes. A basement membrane often underlaid endothelial cells and the processes of PSC. The enlarged Disse space with a flattened sinusoidal hepatocyte membrane contained occasional red blood cells and an abundant extracellular matrix but few collagen fibers. These sinusoidal abnormalities leading to the capillarization of sinusoids, either the cause or the consequence of the disease, indicated a loss of normal hepatocyte homeostasis.     

The normal human thymic vasculature: an ultrastructural study.

Electron microscopy of the normal human thymus demonstrates a characteristic vascular-parenchymal relationship. The vascular lumen is always separated from the thymic parenchyma by: the endothelial cell cytoplasm, a muscular coat in arterioles and veins, the vascular basal lamina, a perivascular space containing collagen fibers and cells, the epithelial-reticular cell basal lamina and the epithelial-reticular cell cytoplasm. The width of this perivascular space is proportional to the size of the vessel it surrounds; it is wide around the vessels in the septa and at the cortical-medullary junction, but narrow around capillaries. While many cells are present in this space around larger vessels, only collagen is observed around the capillaries. Lymphocytes are the predominant cell type in the space; however, plasma cells, eosinophils, histiocytes, polymorphonuclear leukocytes, mast cells and unidentified granulated cells are also seen. The vascular complex described above may function as a blood-thymus barrier, as the initial site of exposure of the lymphocytes to circulating antigen and as the route of lymphocytes from the thymus.     

DISTRIBUTION OF COLLAGEN TYPES I, III, AND V IN FIBROTIC AND NEOPLASTIC HUMAN LIVER

The distribution of collagen types I, III, and V in normal and fibrotic human livers and hepatocellular carcinoma was studied by indirect immunofluorescence procedure using type specific antibodies. Type I collagen as well as type III collagen was present in normal liver within the portal tracts and along the perisinusoidal spaces. Basement membrane collagen, type V collagen, was demonstrated only around the bile ducts and vessels of the portal tracts and central veins. In fibrotic liver, both type I and III collagens were found in increased amounts in fibrotic areas. In fibrous septa of active cirrhosis, however, type I collagen as well as type III collagen was abundant, whereas in inactive cirrhosis type I fibers were predominant. Type V collagen was observed in the walls of proliferative bile ductules and vessels in the fibrotic liver, and also along the sinusoids in the periportal areas. In hepatocellular carcinoma, each type of collagen was distributed regularly along the sinusoid-like vascular channels within the tumor.     

Structural characterization and rapid manual isolation of a reptilian testicular tunic rich in Leydig cells.

During the annual breeding season, the testes of the lizard Cnemidophorus gularis are yellow-orange, oviod organs measuring almost 1 cm in greatest diameter. The pigment is confined to the testicular tunic, which contains a zone of Leydig cells and vascular channels more than 50 mu thick. Leydig cells constitute approximately 60% of the zone, with remaining space occupied by capillaries, sinusoids, and lymphatic vessels. Lymphatics are concentrated at the interface between tunic and seminiferous tubules. Interstitial space is poorly developed among the tubules, accounting for less than 3% of tissue volume. Capillaries, lymphatics, and few widely scattering Leydig cells occur in the sparse interstitial space. Leydig cells in the tunic and elsewhere in the testis show ultrastructural features commonly found in mammalian Leydig cells. Separation of the tunic from the seminiferous tubules is achieved in a few seconds by manual decapsulation of the testis and yields an enriched preparation of Leydig cells that is essentially uncontaminated by tubular elements.     

Ultrastructure of rat liver cells after exhausting physical training

In rats, running of the maximum intensity caused death of some hepatocytes, an increase in the number of phagosomes in Kuppfer cells, and the emergence of connective tissue fibers in the space of Disse. Ultrastructural investigation of hepatocytes showed delayed release of bile products into bile capillaries, decrease in glycogen content, increase in the number of mitochondria (many of them were divided by the cristae), and irregular distribution of ribosomes in the rough endoplasmic reticulum. Accumulation of erythrocytes in the sinusoids, fragments of dead hepatocytes, Kuppfer cells with numerous phagosomes, and connective tissue fibers in the space of Disse were observed in rat liver after exhausting swimming. Study of hepatocyte ultrastructure revealed intense protein synthesis (as evidenced by increased number of ribosomes and unchanged mitochondria and cisternae of the rough endoplasmic reticulum), separation of cytoplasmic fragments with ribosomes into sinusoids, absence of glycogen, and lipid accumulation. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 7, pp. 101–104, July, 1998