Preferential differentiation of the bile ducts along the portal vein in the development of mouse liver

Summary The development of bile ducts in the mouse liver was studied histochemically, with special reference to their preferential differentiation around the portal vein. Both portal vein and hepatic vein shared a common origin, the omphalomesenteric vein. In the early development of the liver, haematopoietic cells were predominant around both veins. With the progressive development of intrahepatic bile ducts, the following three steps were observed: cluster formation of type I hepatocytes around the portal vein, formation of primitive bile duct structures and basal lamina, then formation of ducts surrounded by connective tissue structures composed of type I and type III collagens and lectin-binding sites, which were predominant around the portal vein compared to the hepatic vein. These results suggest that the deposition of abundant connective tissue structures around the portal vein is a prerequisite for the cell differentiation and basal lamina formation in the bile duct precursors. A possible mechanism of the aggregation of type I hepatocytes around the portein vein is also discussed.     

Intrahepatic bile duct development in the rat: a cytokeratin-immunohistochemical study

The development of the intrahepatic bile ducts was studied in rats from day 12 of gestation until 10 days of age using three antibodies directed against cytokeratins in an immunohistochemical procedure on paraffin-embedded liver tissue. In adult rat liver, both hepatocytes and bile ducts were stained by the monoclonal anti-cytokeratin no. 8, whereas two polyclonal antibodies stained bile ducts only. Hepatocytes in developing rat liver were stained by monoclonal anti-cytokeratin no. 8 from day 12 of gestation on. On day 16, cells strongly immunoreactive for cytokeratin no. 8 were observed in a string of pearl-like arrangement around large vascular branches close to the liver hilum. Over the following days, similar structures appeared throughout the liver. Gradually, lumina were formed in these structures, again starting at the liver hilum and resulting in the formation of individual bile ducts. Immunoreactivity with the polyclonal antibodies was first detected in some of the string of pearl-like structures on day 19 and gradually increased until the intensity observed in adult rat liver was reached on day 1 after birth. Even on day 10, portal spaces still revealed more bile duct branches, rings of cells strongly positive for cytokeratin no. 8 and weakly positive with the polyclonal antibodies were present. It is concluded that the intrahepatic bile ducts develop from hepatocytes. The cells closest to large vascular spaces first become strongly positive for cytokeratin no. 8 and only later on acquire additional ("bile duct type") cytokeratins. This process starts at the liver hilum and spreads through the liver. Even at 10 days of age the bile duct system is still immature: around the smaller portal vein branches, rings of cells are still undergoing transformation into bile duct type cells. These data might be useful for reevaluation of pathologic phenomena.     

Embryology of Extra‐ and Intrahepatic Bile Ducts,the Ductal plate

In the human embryo, the first anlage of the bile ducts and the liver is the hepatic diverticulum or liver bud. For up to 8 weeks of gestation, the extrahepatic biliary tree develops through lengthening of the caudal part of the hepatic diverticulum. This structure is patent from the beginning and remains patent and in continuity with the developing liver at all stages. The hepatic duct (ductus hepaticus) develops from the cranial part (pars hepatica) of the hepatic diverticulum. The distal portions of the right and left hepatic ducts develop from the extrahepatic ducts and are clearly defined tubular structures by 12 weeks of gestation. The proximal portions of the main hilar ducts derive from the first intrahepatic ductal plates. The extrahepatic bile ducts and the developing intrahepatic biliary tree maintain luminal continuity from the very start of organogenesis throughout further development, contradicting a previous study in the mouse suggesting that the extrahepatic bile duct system develops independently from the intrahepatic biliary tree and that the systems are initially discontinuous but join up later. The normal development of intrahepatic bile ducts requires finely timed and precisely tuned epithelial–mesenchymal interactions, which proceed from the hilum of the liver toward its periphery along the branches of the developing portal vein. Lack of remodeling of the ductal plate results in the persistence of an excess of embryonic bile duct structures remaining in their primitive ductal plate configuration. This abnormality has been termed the ductal plate malformation. Anat Rec, 291:628–635, 2008. © 2008 Wiley‐Liss, Inc.     

肝内胆管的应用解剖与肝内胆管结石手术入路的研究

目的 探讨肝内叶、段胆管的解剖结构及肝内胆管结石的手术入路。方法 通过研究12例成人肝脏标本的肝内胆管与血管的位置、毗邻关系,设计出经肝的脏面显露左右肝管,经肝的膈面显露肝内叶、段胆管相对合的手术入路,并结合治疗56例复杂性肝内胆管结石患者。结果 左右肝管均位于肝脏脏面门静脉左右干的前上缘;左内叶、右前叶胆管位于相应门静脉的前内侧。右后叶胆管位于门静脉右前支或右前叶下段支脏面测侧者占66.7％(8/12);位于门静脉右后支脏面深侧或后上缘者占83.3％(10/12)。左外叶胆管位于门静脉矢状部脏面深侧者占91.7％(11/12)。选择经肝的脏面显露左右肝管,经肝的膈面显露肝内叶、段胆管相结合的手术入路,治疗复杂性肝内胆管结石患者56例,临床疗效满意。结论 选择经肝的脏面与膈面相结合的手术方式,较易取出结石。     

Morphogenesis of intrahepatic bile ducts of the human fetus

Summary The development of the intrahepatic bile ducts of the human fetus was investigated by light and electron microscopy. Bile canaliculi with microvilli and junctional complexes are already found in the embryo of 7 mm. Some of them are of the intracellular type. At six to seven weeks, large bile canaliculi bounded by four to seven liver cells appear. Subsequently, bile canaliculi are formed predominantly between three to four adjoining liver cells and this arrangement persists throughout later fetal life.The early intrahepatic bile ducts develop around the portal vein as epithelial cell plates derived from the hepatic duct and the branches sprout from the epithelial cell plates in several different places. The epithelial cell plates are separated from each other by primitive connective tissue and they change into a complex network of bile ducts. Formation of the intrahepatic bile ducts is completed by three months.Biliary duct cells at the end of the developing bile ducts are thought to transform into liver cells. Therefore, at the ducts of Hering various transitional cells appear between biliary duct cells and liver cells.The fine structure of the developing liver cells and biliaryduct cells is also described.     

Distortion in TGFβ1 peptide immunolocalization in biliary atresia: Comparison with the normal pattern in the developing human intrahepatic bile duct system

Biliary atresia is an important cause of neonatal obstructive jaundice in which there is inflammation, sclerosis and eventual obliteration of the bile duct system. Its onset may be antenatal, affecting the normal development of the biliary system. The intrahepatic biliary system is derived from the ductal plate, a sheath of cuboidal epithelium that appears at the hepatocyte-mesenchymal junction around the portal vein branches at 6 weeks gestation. This epithelial structure is moulded into a network of tubular bile ducts by the proliferating mesenchyme. Certain portions of the ductal plate are selected to become definitive bile ducts, while redundant biliary epithelium is deleted. The molecular dynamics controlling the intra-uterine development of the biliary system in humans are not yet clearly understood. Transforming growth factor-β1 is a cytokine that stimulates mes-enchymal proliferation and inhibits epithelial growth, and has been shown to be important in organogenesis. In the present study, the pattern of TGFβ1 peptide immunolocalization was investigated with the aid of computerized image analysis, in normal human bile duct development and in biliary atresia. TGFβ1 peptide was detected within hepata-cytes and ductal plate epithelium from 7 weeks gestation; increased TGFβ1 immunoreactivity was present within the epithelium of developing bile ducts at 13 weeks gestation, and apical polarization of the cytokine was observed from 16 weeks gestation. In biliary atresia, the TGFβ1 immunoreactivity pattern within the bile duct structures at the porta hepatis and within intrahepatic portal tracts resembled that of the primitive ductal plate, and there was no significant apical polarization. This may indicate a developmental arrest in the normal ductal plate remodelling process in biliary atresia, and suggests an underlying epithelial-mesenchymal interactive disorder.     

左外叶活体肝移植的解剖学研究

目的：模拟左外叶活体肝移植门静脉、肝动脉和胆管的切取方法。方法：解剖正常人肝脏标本30具，观察肝脏铸型标本30具，测量门静脉、肝动脉及胆管长度、管径及属支或分支分布情况。结果：左外叶门静脉的血供来自门静脉左支，主要为左外叶上段门静脉支、左外叶下段门静脉支；动脉主要来源于肝固有动脉、肝左动脉、肝中动脉，偶有迷走动脉支；胆道引流属支有左外叶上段胆管支、左外叶下段胆管支。结论：左外叶解剖变异较多，活体取肝前应仔细研究其结构特点，设计合理的切取模式；对门静脉、肝动脉和胆管支需行必要的整形，以便与受体相应的管道进行吻合。     

Quantification of the intrahepatic biliary tree during human fetal development

Development and differentiation of bile ducts have been studied for the understanding of pathogenesis of biliary atresia and other diseases of the intrahepatic biliary tree. The aim of this study is to correlate the type of biliary structure with the size of the portal tract and the gestational age. Twenty-four human livers were studied. Fetuses were assigned to four gestational age groups: group I, up to 20 postfecundation weeks (PFW); group II, from 21–26 PFW; group III, from 27–32 PFW; and group IV, from 33–38 PFW. In each specimen, 30 portal tracts were classified as small, medium, or large according to the diameter of the portal vein. In order to identify the bile duct cells, the sections were immunolabeled with anti-cytokeratin antibody, and the biliary structure was classified as absent (bile ducts (BD) = 0), presence of bile duct cells without lumen (BD = 1), or presence of bile duct with lumen (BD = 2). In the small portal tracts, either there were no biliary structures or just a few. There was a substantial increase in the number of medium portal tracts that included a bile duct as a function of gestational age. The majority of large portal tracts exhibited a bile duct. In human fetus up to 20 PFW, it is possible to find 70% of portal tracts without bile ducts, and at 38 PFW it is expected that more than 50% of the portal tract has a BD > 0. We suggest the use of the diameter of the portal vein and the gestational age for the quantification of biliary structures and the evaluation of maturity of intrahepatic biliary tree. Anat. Rec. 251:297–302, 1998. © 1998 Wiley-Liss, Inc.     

Phylogenetic analyses of the hepatic architecture in vertebrates

The mammalian liver has a structural and functional unit called the liver lobule, in the periphery of which the portal triad consisting of the portal vein, bile duct and hepatic artery is developed. This type of hepatic architecture is detectable in many other vertebrates, including amphibians and birds, whereas intrahepatic bile ducts run independently of portal vein distribution in actinopterygians such as the salmon and tilapia. It remains to be clarified how the hepatic architectures are phylogenetically developed among vertebrates. The present study morphologically and immunohistochemically analyzed the hepatic structures of various vertebrates, including as many classes and subclasses as possible, with reference to intrahepatic bile duct distribution. The livers of vertebrates belonging to the Agnatha, Chondrichthyes, Amphibia, Aves, Mammalia, and Actinopterygii before Elopomorpha, had the portal triad‐type architecture. The Anguilliformes livers developed both periportal bile ducts and non‐periportal bile ducts. The Otocephala and Euteleostei livers had independent configuration of bile ducts and portal veins. Pancreatic tissues penetrated the liver parenchyma along portal veins in the Euteleostei. The liver of the lungfish, which shares the same origin with amphibians, did not have the portal triad‐type architecture. Teleostei and lungfish livers had ductular development in the liver parenchyma similar to oval cell proliferation in injured mammalian livers. Euteleostei livers had penetration of significant numbers of independent portal veins from their intestines, suggesting that each liver lobe might receive a different blood supply. The hepatic architectures of the portal triad‐type changed to non‐portal triad‐type architecture along the evolution of the Actinopterygii. The hepatic architecture of the lungfish resembles that of the Actinopterygii after Elopomorpha in intrahepatic biliary configuration, which may be an example of convergent evolution.     

活体造影法肝内胆管的解剖学研究及临床意义

目的　通过经皮胆道直接造影,研究肝内胆管的解剖与变异的类型与分布。 方法　经皮胆道造影50例, 用20 ml注射器接体外引流管进行造影,胆管充分显影的状态下,旋转拍摄胆管,观察胆管解剖与变异。 结果　50例成像中胆管变异42.0％（21例）。12.0% (6例)显示右前叶肝管、右后叶肝管及肝左管呈三分叉状汇合形成肝总管。8.0% (4例) 肝左管先和右前叶肝管汇合,在肝门处与右后叶肝管汇合。20.0% (10例) 肝左管先和右后叶肝管汇合,在肝门处与右前叶肝管汇合。2.0% (1例)多个肝管在肝门处汇合。 结论　胆管解剖与变异的分析对术前手术方式的确定有一定的临床意义。     

Three-dimensional computer-assisted reconstruction of ductal plate in the rat embryo (Carnegie stages 19–23)

In bile duct morphogenesis it has been established that the extrahepatic bile ducts in human originate from hepatic diverticulum while intrahepatic bile ducts arise from the ductal plate (DP), a network of primitive biliary epithelium that develops in the periportal connective tissue. The aim of this work was to reconstruct in rat embryos, stages 19–23, the three-dimensional (3D) distribution of the DP by means of a computer-assisted method. Six specimens, stages 19–23, fixed, dehydrated and paraffin-embedded, were submitted to serial histological sections and stained by hematoxylin-eosin and Heidenhain techniques. The images were directly digitalized with a CCD camera. The serial views were aligned anatomically by software and the data were analyzed following segmentation and thresholding. At stage 19, the DP was not yet organized. The periportal mesoderm (M) was gaining ground with some cords of cubic cells evoking primitive ductal cells. At stage 20, a row of ductal cubic cells went around the transverse portal sinus at the junction between M and liver cells. At stage 21, the DP developed at the periphery of periportal connective tissue and appeared in direct continuity with the hepatic duct (HDu). Four evaginations emerged from the DP and were growing up in the hepatic parenchyma. At stage 23, the DP appeared as a large network in continuity with the HDu located at the periphery of periportal M and presenting several evaginations radiating in the liver parenchyma. This work in the rat embryo permits the clear visualization of the development of the junctional zone in the hepatic hilum. Three phenomena are observed: (1) proximal left and right hepatic ducts and their segmental branches are derived from DP and not from the HDu; (2) the extrahepatic biliary system is in contact with the developing hilar ducts; (3) ductal maturation begins at the hilum and proceeds centrifugally. These observations are of great relevance in explaining pathological changes appearing at the hepatic hilum of neonates: hepatic polycystic disease, intrahepatic bile duct agenesis or atresia, and cyst of the extrahepatic bile duct.     

Intrahepatic distribution of nerves in the rat

The intrahepatic distribution of nerves in the rat was studied using neurohistochemical and electron microscopic methods. Innervation was restricted primarily to vessels in the portal space and hilus. Both adrenergic and cholinergic fibers were observed in the adventitia of hepatic arteries, and to a lesser extent adjacent to portal veins. Some of the cholinergic fibers, however, were not contiguous with the vasculature. Near the hilus many of these fibers were associated with ganglia while peripherally some coursed into the immediately adjacent parenchyma where end bulbs abutted on hepatocytes. Ultrastructurally, scattered small nerves, devoid of neurolemma, were found contiguous with the portal lamina of hepatocytes. Nerve fibers deeper within the lobule were not seen but numerous gap junctions were observed between contiguous hepatocytes. Central and sublobular hepatic veins lacked innervation but adrenergic nerves were demonstrated in the walls of larger hepatic veins. Innervation of the biliary system was sparse. While nerves were interposed between vessels and bile ducts, such nerves tended to be associated more closely with the vasculature.     

Development of Dolichos biflorus agglutinin (DBA) binding sites in the bile duct of the embryonic mouse liver

Summary The distribution of binding sites for Dolichos biflorus agglutinin (DBA) was studied by histochemical staining in the embryonic mouse liver. The liver primordium consists of cranial and caudal diverticula. DBA bound to the pseudostratified endodermal cells of the caudal hepatic diverticulum, and also to some endodermal cells of the cranial one. Most extrahepatic bile duct cells and all epithelial cells of the gall bladder were consistently DBA-positive. In intrahepatic bile ducts and their precursors, the DBA binding sites showed a patchy distributon. Most hepatocytes were DBA-negative, though some young hepatocytes were DBA-positive. The results suggest that DBA binding sites are useful markers of epithelial cells of the gall bladder and the bile ducts, especially the extrahepatic bile duct. Differentiation of bile duct cells was also discussed with special reference to the developmental change of the distribution of the DBA binding sites.     

Anatomy and function of sensory hepatic nerves

Vagal and spinal afferent innervation of the portal hepatic area has not been studied as thoroughly as the innervation of other important organs. It is generally agreed that unlike noradrenergic sympathetic efferent nerve fibers, sensory nerve fibers of either vagal or dorsal root/spinal origin do not directly innervate hepatocytes, but are restricted to the stroma surrounding triades of hepatic vasculature and bile ducts, and to extrahepatic portions of the portal vein and bile ducts. For vagal afferent innervation, retrograde and anterograde tracing studies in the rat have clearly shown that only a minor portion of the common hepatic branch innervates the liver area, while the major portion descends in the gastroduodenal branch toward duodenum, pancreas, and pylorus. Hepatic paraganglia, bile ducts, and portal vein receive the densest vagal afferent innervation. Calretinin may be a relatively specific marker for vagal afferent innervation of the portal-hepatic space. Calcitonin gene-related peptide (CGRP) is a specific marker for dorsal root afferents, and CGRP-immunoreactive fibers are mainly present near the intrahepatic vascular bundles and bile ducts, and in the same extrahepatic compartments that contain vagal afferents. Because of the specific anatomical organization of hepatic nerves, selective hepatic denervation, whether selective for the vagal or sympathetic division, or for efferents and afferents, is nearly impossible. Great caution is therefore necessary when interpreting functional outcomes of so-called specific hepatic denervation studies.     

Aberrant bile ducts, 'remnant surface bile ducts,' and peribiliary glands: descriptive anatomy, historical nomenclature, and surgical implications

The term "aberrant bile ducts" has been used to designate three heterogeneous groups of biliary structures: (1) bile ducts degenerating or disappearing (unknown etiology, diverse locations); (2) curious biliary structures in the transverse fissure; and (3) aberrant right bile ducts draining directly into the common hepatic duct. We report our observations on these three groups. Twenty-nine fresh human livers of stillborns and adults were injected differentially with colored latex and dissected. Adult livers showed portal venous and hepatic arterial branches, and bile ducts not associated with parenchyma, subjacent to and firmly adherent with the liver capsule: elements of ramifications of normal sheaths were present on the liver's surface. These ramifications, having lost parenchyma associated with them, then sequentially lost their portal branches, bile ducts and arterial branches. This process affected the ramifications of the sheaths in the left triangular ligament, adjacent to the inferior vena cava, in the gallbladder bed and anywhere else on the liver's surface and resulted in the presence of bile ducts accompanied by portal venous and/or hepatic arterial branches and not associated with parenchyma for a period of time. This first group represented normal bile ducts that do not meet the criteria of aberration and could be appropriately designated "remnant surface bile ducts." Such changes were not found in the transverse fissures and review of the literature revealed that the curious biliary structures are the microscopic peribiliary glands. The third group met the criteria of aberration and the anatomy of a representative duct is described.     

Intraductal oncocytic papillary neoplasm of the liver

A very rare case of intraductal oncocytic papillary carcinoma of the liver is reported. A 63-year-old Japanese man was admitted to our clinic because of abdominal pain and jaundice. Imaging techniques revealed a unilocular cystic neoplasm of 14 cm diameter in the medial segment of the left hepatic lobe. Combined percutaneous and endoscopic retrograde cholangiographies revealed the unilocular cystic neoplasm contained a lot of mucus and communicated with the left segmental intrahepatic bile duct, and that mucus filled the left segmental and hepatic ducts. Left lobectomy was performed. The postoperative course was good, and the patient is free of disease 30 months after operation. Pathological examination revealed that the cavity of the neoplasm was continuous with the left segmental intrahepatic bile duct, and that a lot of mucus was present in the neoplasm, as well as in the left segmental and hepatic ducts. The neoplasm consisted of papillary growth of atypical epithelial cells with oncocytic changes. Atypical goblet cells were also recognized. No invasion into the surrounding liver was noted. Non-tumorous intrahepatic bile ducts near the lesion occasionally showed epithelial dysplasia and contained a lot of mucus. Immunohistochemically, the tumor cells were rich in mitochondria and were immunoreactive for cytokeratins 7, 18 and 19, carbohydrate antigen 19-9, and hepatocyte-specific antigen. Some tumor cells were immunoreactive for pancreatic alpha-amylase and lipase. Ultrastructurally, the tumor cells showed numerous mitochondria and mucus droplets. Intraductal neoplasm communicating with the intrahepatic bile ducts has rarely been reported. The present case suggests that intraductal oncocytic papillary neoplasm, as described in the pancreas, may also occur in the intrahepatic bile ducts, and that such hepatic intraductal neoplasm may express hepatocellular and pancreatic acinar phenotypes.     

Hepatic parenchyma, biliary ducts and gall bladder forming potency in the hepatic primordium in the quail embryo

Summary Differentiation potency of the hepatic primordium isolated from 21-to 35-somite stage quail embryos was examined by the transplantation in the coelomic cavity of the chick embryo. The hepatic primordium differentiates into hepatic parenchyma, intra- and extrahepatic bile ducts, and gall bladder. The hepatic parenchyma and two types of biliary ducts can differentiate from any fragment of the hepatic primordium divided at craniocaudal or proximodistal levels, while the gall bladder develops mainly from the proximal area of the primordium. These results indicate that the presumptive areas of hepatic parenchyma and biliary ducts are not arranged in a mosaic way in the young primordium, whereas the presumptive area of the gall bladder is restricted.Isolated hepatic primordial endoderm was found to differentiate to the epithelia of the hepatic parenchyma, bile ducts, and gall bladder under the influence of heterologous mesenchyme.     

Portal tract fibrogenesis in the liver

The portal area is the 'main entrance' and one of the two main exits of the liver lobule. Through the main entrance portal and arterial blood reach the liver sinusoids. Through the exit the bile flows towards the duodenum. The three main structures, portal vein and artery with their own wall (and vascular smooth muscle cells) and bile duct with its basal membrane, are surrounded by loose myofibroblasts and by the first layer of hepatocytes and non-parenchymal cells. Chronic diseases of the liver can lead to development of liver cirrhosis, characterized by formation of fibrotic septa which can be portal-portal in the case of the chronic biliary damage or portal-central in the case of the chronic viral hepatitis. Central-central septa can also be observed under other pathological conditions. When damaging noxae are introduced to the liver, inflammatory cells are first recruited to the portal field, the first layer of hepatocytes may be destroyed (enlargement of the portal field) and portal (myo)fibroblasts become activated. A similar reaction may take place when the target of inflammation is the bile duct with consecutive reduction of the bile flow, activation of the portal (myo)fibroblasts, proliferation of bile ducts and destruction of the hepatocytes around the portal field. Increased matrix deposition may be the consequence. During the past years several publications dealt with the pathomechanisms of portal fibrogenesis as well as with its resolution. One of the most intriguing observations was that it is not hepatic stellate cells of the hepatic sinusoid, but portal (myo)fibroblasts which rapidly acquire the phenotype of 'activated' (myo)fibroblasts in the early stages of cholestatic fibrosis. These may also become the main mesenchymal cells of the porto-portal or porto-central fibrotic septa. This article reviews the similarities as well as differences between the mesenchymal cells of the portal tract and of the fibrotic septa vs 'activated' stellate cells of the hepatic sinusoids, and discusses the debate over their relative contributions to liver fibrogenesis.     

Multiple cysts in the hepatic hilum and their pathogenesis

Summary Multiple serous cysts involving only the hepatic hilum and larger portal tracts were found incidentally in 8 autopsy cases with several underlying liver diseases. The cysts were mostly small in size, and did not communicate with the lumena of the biliary tree. The lining of the cysts consisted of a single layer of columnar or cuboidal epithelium and the surrounding fibrous tissue was scanty. These were not associated with polycystic disease of the kidneys or cystic dilatation of the biliary tree. Cysts were absent in the liver parenchyma and an association with von Meyenburg complexes was rare. In the vicinity of the cysts there were many lobules of the glands which are physiologically present in the periductal connective tissue of the large intrahepatic bile ducts. It was noted that some of these glandular elements around the cysts disclosed varying degrees of cystic luminal dilatations. Almost all patients with such cysts had severe portal hypertension and over a half had occluding thromboemboli in the portal veins. These results lead us to propose the hypothesis that multiple cysts involving the hepatic hilum and the larger portal tracts are derived from the periductal glands in close association with an intrahepatic circulatory disturbance of the portal venous system.