The lymphatics of the liver

Blood defense system - Proposal for a new concept of an immune system against blood borne pathogens comprising the liver, spleen and bone marrow

Blood-borne pathogen (BBP) infections can rapidly progress to life-threatening sepsis and must therefore be promptly eliminated by the host's immune system. Intravascular macrophages of the liver sinusoid, splenic marginal zone and red pulp and perisinusoidal macrophage protrusions in the bone marrow (BM) directly phagocytose BBPs in the blood as an innate immune response. The liver, spleen and BM thereby work together as the blood defence system (BDS) in response to BBPs by exerting their different immunological roles. The liver removes the vast majority of these invading organisms via innate immunity, but their complete elimination is not possible without the actions of antibodies. Splenic marginal zone B cells promptly produce IgM and IgG antibodies against BBPs. The splenic marginal zone transports antigenic information from the innate to the adaptive immune systems. The white pulp of the spleen functions as adaptive immune tissue and produces specific and high-affinity antibodies with an immune memory against BBPs. The BM works to maintain immune memory by supporting the survival of memory B cells, memory T cells and long-lived plasma cells (LLPCs), all of which have dedicated niches. Furthermore, BM perisinusoidal naïve follicular B cells promptly produce IgM antibodies against BBPs in the BM sinusoid and the IgG memory B cells residing in the BM rapidly transform to plasma cells which produce high-affinity IgG antibodies upon reinfection. This review describes the complete immune defence characteristics of the BDS against BBPs through the collaboration of the liver, spleen and BM with combined different immunological roles.

Microanatomical organization of hepatic venous lymphatic system in humans

Lymphatic fluid drains from the liver via the periportal lymphatic, hepatic venous lymphatic, and superficial lymphatic systems. We performed a postmortem study to clarify the three-dimensional structure and flow dynamics of the human hepatic venous lymphatic system, as it still remains unclear. Livers were excised whole from three human cadavers, injected with India ink, and sliced into 1-cm sections from which veins were harvested. The distribution of lymphatic vessels was observed in 5 μm sections immunostained for lymphatic and vascular markers (podoplanin and CD31, respectively) using light microscopy. Continuity and density of lymphatic vessel distribution were assessed in en-face whole-mount preparations of veins using stereomicroscopy. The structure of the external hepatic vein wall was assessed with scanning electron microscopy (SEM). The lymphatic dynamics study suggested that lymphatic fluid flows through an extravascular pathway around the central and sublobular veins. A lymphatic vessel network originates in the wall of sublobular veins, with a diameter greater than 110 μm, and the peripheral portions of hepatic veins and continues to the inferior vena cava. The density distribution of lymphatic vessels is smallest in the peripheral portion of the hepatic vein (0.03%) and increases to the proximal portion (0.22%, p = 0.012) and the main trunk (1.01%, p < 0.001), correlating positively with increasing hepatic vein diameter (Rs = 0.67, p < 0.001). We revealed the three-dimensional structure of the human hepatic venous lymphatic system. The results could improve the understanding of lymphatic physiology and liver pathology.

The influence of the extent of lymph node metastasis on the prognosis for patients with intrahepatic cholangiocarcinoma

Purpose

Reports showed that some of intrahepatic cholangiocarcinoma (ICC) patients with lymph node metastasis (LNM) may also gain survival benefit undergone resection. However, the effect of the extent of LNM on prognosis and surgical indication is barely discussed.

Methods

From September 1994 to November 2018, primary ICC patients undergone initial curable surgery were enrolled. Based on the extent of LNM, we divided these patients into 4 groups, including patients with no LNM (group N0), LNM to hepatoduodenal ligament or common hepatic artery (region A, group A), LNM to gastrohepatic lymph nodes for left liver ICC and periduodenal and peripancreatic lymph node for right liver ICC (region B, group B), or LNM beyond these regions (region C, group C). Multivariable Cox regression analysis was performed to identify the prognostic factors for recurrence-free survival (RFS) and overall survival (OS) in all groups.

Results

A total of 133 patients were enrolled. There were 56, 21, 17, and 39 patients in groups N0, A, B, and C, respectively. There was significant difference between groups N0 and C in RFS (P < 0.001) and OS (P = 0.002). When we compared group N0 + A + B with group C, we also found that RFS (P < 0.001) and OS (P = 0.007) were significantly different. In multivariable analysis, the extent of LNM was an independent risk factor for RFS (P < 0.050).

Conclusion

ICC patients with the LNM to regions A and B could still achieve good prognosis with resection. Surgery should be carefully considered when LNM to region C.

Prognostic Role of the Intrahepatic Lymphatic System in Liver Cancer

Although several prognosticators, such as lymph node metastasis (LNM), were reported for hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC), the prognostic impact of intrahepatic lymphatic vessel invasion (LVI) in liver cancer has rarely been reported. We sought to clarify the prognostic impact of intrahepatic lymphatic system involvement in liver cancer. We systematically reviewed retrospective studies that described LVI and clinical outcomes of liver cancer and also included studies that investigated tumor-associated lymphangiogenesis. We conducted a meta-analysis using RevMan software (version 5.4.1; Cochrane Collaboration, Oxford, UK). The prognostic impact of intrahepatic LVI in HCC was not reported previously. However, tumor-associated lymphangiogenesis reportedly correlates with prognosis after HCC resection. The prognostic impact of intrahepatic LVI was reported severally for ICC and a meta-analysis showed that overall survival was poorer in patients with positive LVI than with negative LVI after resection of ICC. Lymphangiogenesis was also reported to predict unfavorable prognosis in ICC. Regarding colorectal liver metastases, LVI was identified as a poor prognosticator in a meta-analysis. A few reports showed correlations between LVI/lymphangiogenesis and LNM in liver cancer. LVI and lymphangiogenesis showed worse prognostic impacts for liver cancer than their absence, but further study is needed.

Volumetric imaging reveals VEGF-C-dependent formation of hepatic lymph vessels in mice

The liver is a major biosynthetic and detoxifying organ in vertebrates, but also generates 25%–50% of the lymph passing through the thoracic duct and is thereby the organ with the highest contribution to lymph flow. In contrast to its metabolic function, the role of the liver for lymph generation and composition is presently severely understudied. We took a rigorous, volume imaging-based approach to describe the microarchitecture and spatial composition of the hepatic lymphatic vasculature with cellular resolution in whole mount immune stained specimen ranging from thick sections up to entire mouse liver lobes. Here, we describe that in healthy adult livers, lymphatic vessels were exclusively located within the portal tracts, where they formed a unique, highly ramified tree. Ragged, spiky initials enmeshed the portal veins along their entire length and communicated with long lymphatic vessels that followed the path of the portal vein in close association with bile ducts. Together these lymphatic vessels formed a uniquely shaped vascular bed with a delicate architecture highly adapted to the histological structure of the liver. Unexpectedly, with the exception of short collector stretches at the porta hepatis, which we identified as exit point of the liver lymph vessels, the entire hepatic lymph vessel system was comprised of capillary lymphatic endothelial cells only. Functional experiments confirmed the space of Disse as the origin of the hepatic lymph and flow via the space of Mall to the portal lymph capillaries. After entry into the lymphatic initials, the lymph drained retrograde to the portal blood flow towards the exit at the liver hilum. Perinatally, the liver undergoes complex changes transforming from the main hematopoietic to the largest metabolic organ. We investigated the time course of lymphatic vessel development and identified the hepatic lymphatics to emerge postnatally in a process that relies on input from the VEGF-C/VERGFR-3 growth factor—receptor pair for formation of the fully articulate hepatic lymph vessel bed.

Extent of Lymph Node Dissection for Accurate Staging in Intrahepatic Cholangiocarcinoma

BACKGROUND

Although lymph node metastasis is a known factor predictive of a poor prognosis after radical surgery for intrahepatic cholangiocarcinoma (ICC), few studies have investigated lymph node dissection (LND) areas for accurate staging. The aim of this study was to identify the optimal LND level for ICC considering lymphatic flow.

METHODS

Clinical characteristics and pathologic nodal status (presence of metastasis) for 163 patients were reviewed according to tumor location. In the node-positive (N1) group, the distribution of metastatic nodes was described. The coverage of metastatic nodes according to dissection level was assessed, and the minimum dissection level for accurate ICC staging was estimated accordingly. For validation, the node-negative (N0) group was divided into two subgroups according to the estimated dissection level, and survival outcomes were compared.

RESULTS

In the N1 group, expanding dissection to stations no. 12 and 8 covered 82.0% (n = 50) of metastatic cases regardless of tumor location. In survival analysis of N0 group, patients who underwent LND covering stations no. 8+12 showed better disease-free survival (DFS) and overall survival (OS), although the differences were not statistically significant (DFS: covering no. 12+8 vs. not covering no. 12+8, 109.0 months [24.2-193.8] vs. 33.0 months [10.3-55.7], p = 0.078; OS: covering no. 12+8 vs. not covering no. 12+8, 180.0 months [21.6-338.4] vs. 73.0 months [42.8-103.2], p = 0.080).

CONCLUSION

LND including at least stations no. 12 (hepatoduodenal ligament) and 8 (common hepatic artery), regardless of tumor location, is recommended for accurate staging in ICC patients.

Targeting Lymphangiogenesis and Lymph Node Metastasis in Liver Cancer

Increased lymphangiogenesis and lymph node metastasis, the important prognostic indicators of aggressive hepatobiliary malignancies such as hepatocellular cancer and cholangiocarcinoma, are associated with poor patient outcome. The liver produces 25% to 50% of total lymphatic fluid in the body and has a dense network of lymphatic vessels. The lymphatic system plays critical roles in fluid homeostasis and inflammation and immune response. Yet, lymphatic vessel alterations and function are grossly understudied in the context of liver pathology. Expansion of the lymphatic network has been documented in clinical samples of liver cancer; and although largely overlooked in the liver, tumor-induced lymphangiogenesis is an important player, increasing tumor metastasis in several cancers. This review aims to provide a detailed perspective on the current knowledge of alterations in the hepatic lymphatic system during liver malignancies, as well as various molecular signaling mechanisms and growth factors that may provide future targets for therapeutic intervention. In addition, the review also addresses current mechanisms and bottlenecks for effective therapeutic targeting of tumor-associated lymphangiogenesis.

The Impact of Postoperative Ascites on Survival After Surgery for Hepatocellular Carcinoma: a National Study

BACKGROUND

Postoperative ascites (POA) is the most common complication after liver surgery for hepatocarcinoma (HCC), but its impact on survival is not reported. The aim of the study is to investigate its impact on overall survival (OS) and disease-free survival (DFS), and secondarily to identify the factors that may predict the occurrence.

METHOD

Data were collected from 23 centers participating in the Italian Surgical HCC Register (HE.RC.O.LE.S. Group) between 2008 and 2018. POA was defined as ≥500 ml of ascites in the drainage after surgery. Survival analysis was conducted by the Kaplan Meier method. Risk adjustment analysis was conducted by Cox regression to investigate the risk factors for mortality and recurrence.

RESULTS

Among 2144 patients resected for HCC, 1871(88.5%) patients did not experience POA while 243(11.5%) had the complication. Median OS for NO-POA group was not reached, while it was 50 months (95%CI = 41-71) for those with POA (p < 0.001). POA independently increased the risk of mortality (HR = 1.696, 95%CI = 1.352-2.129, p < 0.001). Relapse risk after surgery was not predicted by the occurrence of POA. Presence of varices (OR = 2.562, 95%CI = 0.921-1.822, p < 0.001) and bilobar disease (OR = 1.940, 95%CI = 0.921-1.822, p: 0.004) were predictors of POA, while laparoscopic surgery was protective (OR = 0.445, 95%CI = 0.295-0.668, p < 0.001). Ninety-day mortality was higher in the POA group (9.1% vs 1.9% in NO-POA group, p < 0.001).

CONCLUSION

The occurrence of POA after surgery for HCC strongly increases the risk of long-term mortality and its occurrence is relatively frequent. More efforts in surgical planning should be made to limit its occurrence.

Liver lymphatic anatomy and role in systemic lymphatic disease

Objectives

To characterize hepatic to systemic lymphatic connections in patients with systemic lymphatic disease using intra-hepatic lymphangiography and to compare outcomes after lymphatic intervention.

Methods

In this retrospective study, patients with intra-hepatic lymphangiography from May 2014 – April 2019 at our institution were included. Imaging review was performed and hepatic lymphatic connections and flow patterns were characterized. Clinical data were reviewed and comparisons between patients undergoing lymphatic intervention with or without abnormal hepatic lymphatics were performed.

Results

During the study period, 105 patients underwent intra-hepatic lymphangiography. Primary clinical presentation included ascites (19/105), chylothorax (27/105), plastic bronchitis (PB) (17/105), and protein losing enteropathy (PLE) (42/105). Five categories of hepatic lymphatic connections and flow patterns were identified (%): normal (25%, 26/105), hepatoperitoneal (12%, 13/105), hepatopulmonary (10.5%, 11/105), hepatomesenteric (7.5%, 8/105), and hepatoduodenal (41%, 43/105) with four patients having more than one abnormal pattern. A comparison between clinical presentation and imaging category revealed an increased likelihood of having ascites with hepatoperitoneal (p < .0001), chylothorax/PB with hepatopulmonary (p = .01), and PLE with hepatoduodenal (p < .001) connections. Seventy-six patients had a lymphatic intervention, 24% with normal, and 76% with abnormal liver lymphatics. There was no difference in length of hospital stay or mortality between the two groups, but there was a prolonged time to symptom resolution (p = .006) and persistent symptoms after 6 months (5% vs 44%, p = .002) in the group with abnormal liver lymphatics.

Conclusion

We identified five liver lymphatic imaging categories with a substantial correlation to presenting lymphatic disease. Abnormal imaging patterns correlated with increased morbidity. Evaluation of liver lymphatics should be considered in patients with a systemic lymphatic disease if central lymphatic imaging is normal.

Key Points

• We identified five liver lymphatic imaging patterns: normal, hepatoperitoneal, hepatomesenteric, hepatopulmonary, and hepatoduodenal.

• Imaging patterns were correlated with disease presentation (normal – chylothorax/PB, hepatoperitoneal – ascites/chylothorax, hepatopulmonary – chylothorax/PB, hepatoduodenal – PLE).

• Abnormal imaging patterns correlated with increased morbidity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00330-021-08098-z.

Lymphatic dysfunction in advanced cirrhosis: Contextual perspective and clinical implications

The lymphatic system plays a very important role in body fluid homeostasis, adaptive immunity, and the transportation of lipid and waste products. In patients with liver cirrhosis, capillary filtration markedly increases, primarily due to a rise in hydrostatic pressure, leading to enhanced production of lymph. Initially, lymphatic vasculature expansion helps to prevent fluid from accumulating by returning it back to the systemic circulation. However, the lymphatic functions become compromised with the progression of cirrhosis and, consequently, the lymphatic compensatory mechanism gets overwhelmed, contributing to the development and eventual worsening of ascites and edema. Neurohormonal changes, low-grade chronic inflammation, and compounding effects of predisposing factors such as old age, obesity, and metabolic syndrome appear to play a significant role in the lymphatic dysfunction of cirrhosis. Sustained portal hypertension can contribute to the development of intestinal lymphangiectasia, which may rupture into the intestinal lumen, resulting in the loss of protein, chylomicrons, and lymphocyte, with many clinical consequences. Rarely, due to high pressure, the rupture of the subserosal lymphatics into the abdomen results in the formation of chylous ascites. Despite being highly significant, lymphatic dysfunctions in cirrhosis have largely been ignored; its mechanistic pathogenesis and clinical implications have not been studied in depth. No recommendation exists for the diagnostic evaluation and therapeutic strategies, with respect to lymphatic dysfunction in patients with cirrhosis. This article discusses the perspectives and clinical implications, and provides insights into the management strategies for lymphatic dysfunction in patients with cirrhosis.

Excretion of Necrotic Hepatocellular Carcinoma Tissues into Hepatic Lymphatic Vessels after Conventional Transarterial Chemoembolization

We report a case of necrotic hepatocellular carcinoma tissue excretion into the hepatic lymphatic system after conventional transarterial chemoembolization (cTACE) in an 80-year-old man with liver cirrhosis. A tumor measuring 19 mm in diameter in segment 5 was successfully treated with superselective cTACE. Hepatic lymphatic vessels were not opacified with iodized oil during the procedure. Computed tomography (CT) performed 1 week after cTACE showed dense accumulation of iodized oil in the tumor and in the surrounding liver without opacification of the hepatic lymphatics. Excretion of necrotic tumor tissues containing iodized oil into the lymphatic system was initially observed on CT 9 months after cTACE and the amount of excreted tumor tissues had increased 2 years and 2 months after cTACE without tumor recurrence or any clinical symptoms.

Liver lymphatic drainage patterns follow segmental anatomy in a murine model

The liver’s cellular functions are sustained by a hierarchical, segmentally-organized vascular system. Additionally, liver lymphatic vessels are thought to drain to perihepatic lymph nodes. Surprisingly, while recent findings highlight the importance of organ-specific lymphatics, the functional anatomy of liver lymphatics has not been mapped out. In literature, no segmental or preferential lymphatic drainage patterns are known to exist. We employ a novel murine model of liver lymphangiography and in vivo microscopy to delineate the lymphatic drainage patterns of individual liver lobes. Our data from blue dye liver lymphangiography show preferential lymphatic drainage patterns: Right lobe mainly to hepatoduodenal ligament lymph node 1 (LN1); left lobe to hepatoduodenal ligament LN1 + LN2 concurrently; median lobe showed a more variable LN1/LN2 drainage pattern with increased (sometimes exclusive) mediastinal thoracic lymph node involvement, indicating that part of the liver can drain directly to the mediastinum. Upon ferritin lymphangiography, we observed no functional communication between the lobar lymphatics. Altogether, these results show the existence of preferential lymphatic drainage patterns in the murine liver. Moreover, this drainage can occur directly to mediastinal lymph nodes and there is no interlobar lymphatic flow. Collectively, these data provide the first direct evidence that liver lymphatic drainage patterns follow segmental anatomy.

Case report: hepatobronchial lymphatic communications in single ventricle patients as a pathophysiological mechanism of plastic bronchitis: diagnosis and treatment

Background 

Plastic bronchitis is a rare but devastating complication in single ventricle patients after Fontan completion. Recent advances in dynamic contrast-enhanced magnetic resonance lymphangiogram demonstrate the typical pathophysiological mechanism of the thoracic duct leaking lymphatic fluid towards the bronchi resulting in intraluminal casts. This has been termed abnormal pulmonary lymphatic perfusion and has been successfully treated in 94% of patients with thoracic duct occlusion. However, in some cases, this aberrant flow is not identified and therefore no intervention is available. This case report identifies a newly discovered origin of abnormal lymphatic flow from the liver to the bronchi and the treatment of these patients.

Case summary 

We report two cases of plastic bronchitis in single ventricle patients with no identified abnormal lymphatic pulmonary perfusion from the thoracic duct. Both patients underwent liver lymphangiogram and demonstrated aberrant flow from the hepatic lymphatic ducts to the bronchi. These were successfully occluded, and plastic bronchitis symptoms resolved in both cases.

Discussion 

The recent discovery of the abnormal pulmonary lymphatic perfusion from the thoracic duct to the bronchi has allowed successful treatment of 94% of single ventricle patients with plastic bronchitis. The discovery of hepatobronchial lymphatic perfusion reveals an occult aetiology of plastic bronchitis and a second target for embolization and successful treatment.

Liver Lymphatic Imaging and Interventions: Resurrection of the Forgotten Knowledge

Lymphatic imaging and interventions are gaining wider acceptance as the treatment of various lymphatic diseases. Meanwhile, the liver lymphatic system remains relatively unknown despite its physiological importance. Liver lymph has been at the center of the lymphatic research since the 19th century; however, the acquired knowledge has not been used in clinical research and treatment due to the lack of robust imaging methods. Recently introduced liver lymphangiography and interstitial embolization allow for the diagnosis and treatment of several diseases associated with the lymphatic system of the congested liver, providing additional treatment options for conditions that were considered incurable until now.

Emerging Roles for Lymphatics in Chronic Liver Disease

Chronic liver disease (CLD) is a global health epidemic causing ∼2 million deaths annually worldwide. As the incidence of CLD is expected to rise over the next decade, understanding the cellular and molecular mediators of CLD is critical for developing novel therapeutics. Common characteristics of CLD include steatosis, inflammation, and cholesterol accumulation in the liver. While the lymphatic system in the liver has largely been overlooked, the liver lymphatics, as in other organs, are thought to play a critical role in maintaining normal hepatic function by assisting in the removal of protein, cholesterol, and immune infiltrate. Lymphatic growth, permeability, and/or hyperplasia in non-liver organs has been demonstrated to be caused by obesity or hypercholesterolemia in humans and animal models. While it is still unclear if changes in permeability occur in liver lymphatics, the lymphatics do expand in number and size in all disease etiologies tested. This is consistent with the lymphatic endothelial cells (LEC) upregulating proliferation specific genes, however, other transcriptional changes occur in liver LECs that are dependent on the inflammatory mediators that are specific to the disease etiology. Whether these changes induce lymphatic dysfunction or if they impact liver function has yet to be directly addressed. Here, we will review what is known about liver lymphatics in health and disease, what can be learned from recent work on the influence of obesity and hypercholesterolemia on the lymphatics in other organs, changes that occur in LECs in the liver during disease and outstanding questions in the field.

Lymphatics in the liver

The liver is the largest lymph producing organ. A significant increase in the number of hepatic lymphatic vessels, or lymphangiogenesis, has been reported in various liver diseases, including, but not limited to, cirrhosis, viral hepatitis and hepatocellular carcinoma. Despite its apparent relevance in healthy and diseased livers as these and other observations indicate, the hepatic lymphatic system has been poorly studied. With knowledge of the lymphatic system in other organs and tissues incorporated, this review article addresses the current knowledge of the hepatic lymphatic system and the potential role of lymphatic endothelial cells in the health and the disease of the liver and concludes with a brief description on future directions of the study of the hepatic lymphatic system.

Periportal lymphatic system on post-hepatobiliary phase Gd-EOB-DTPA-enhanced MR imaging in normal subjects and patients with chronic hepatitis C

PURPOSE

We sought to evaluate visualization of periportal lymphatics and lymph nodes (lymphatic system) on Gd-EOB-DTPA-enhanced magnetic resonance (MR) images using a fat-suppressed T2-weighted sequence with 3-dimensional (3D) volume isotropic turbo spin echo acquisition (VISTA) at 3.0 T in normal subjects and patients with chronic hepatitis C.

METHODS

MR imaging was performed in 254 subjects between June 2013 and May 2016. After applying inclusion and exclusion criteria, the final population was 31 normal subjects and 34 patients with chronic hepatitis C. Images were acquired after the hepatobiliary phase following intravenous administration of Gd-EOB-DTPA, which causes signal loss in the bile ducts, to facilitate the visualization of the periportal lymphatic system. Two radiologists assessed the visualization of the periportal lymphatic system in 31 normal subjects. The axial dimensions of the main periportal lymphatic system in normal subjects were measured and compared with those of 34 patients with chronic hepatitis C using the Mann-Whitney U-test, and their correlation with a hepatic fibrosis marker, the Fibrosis-4 (FIB-4), was assessed using Spearman's rank correlation test.

RESULTS

The periportal lymphatic system was detected as high signal intensity areas surrounding the portal vein up to the third branches by each reader in all normal subjects. The axial dimensions of the main periportal lymphatic system in patients with chronic hepatitis C were significantly larger than those in normal subjects (p < 0.0001), and showed a significantly positive correlation with the FIB-4 score (ρ = 0.73, p < 0.001).

CONCLUSIONS

Fat-suppressed T2-weighted MR imaging with 3D-VISTA acquired after the hepatobiliary phase on Gd-EOB-DTPA-enhanced imaging may be a useful noninvasive method for evaluating the periportal lymphatic system and the degree of hepatic fibrosis.

Importance Rat Liver Morphology and Vasculature in Surgical Research

BACKGROUND The laboratory rat is one of the most popular experimental models for the experimental surgery of the liver. The objective of this study was to investigate the morphometric parameters, physiological data, differences in configuration of liver lobes, biliary system, and vasculature (arteries, veins, and lymphatic vessels) of the liver in laboratory rats. In addition, this study supports the anatomic literature and identified similarities and differences with human and other mammals. MATERIAL AND METHODS Forty laboratory rats were dissected to prepare corrosion casts of vascular system specimens (n=20), determine the lymph vessels and lymph nodes (n=10), and for macroscopic anatomical dissection (n=10) of the rat liver. The results are listed in percentages. The anatomical nomenclature of the liver morphology, its arteries, veins, lymph nodes, and lymphatic vessels are in accordance with Nomina Anatomica Veterinaria. RESULTS We found many variations in origin, direction, and division of the arterial, venous, and lymphatic systems in rat livers, and found differences in morphometric parameters compared to results reported by other authors. The portal vein was formed by 4 tributaries in 23%, by 3 branches in 64%, and by 2 tributaries in 13%. The liver lymph was drained to the 2 different lymph nodes. The nomenclature and morphological characteristics of the rat liver vary among authors. CONCLUSIONS Our results may be useful for the planing of experimental surgery and for cooperation with other investigation methods to help fight liver diseases in human populations.

Proposal of Perihilar Surrounding Area in Relation to Regional Lymphadenectomy in Selected Patients With Intrahepatic Cholangiocarcinoma

Lymph node (LN) metastasis is well recognized as a poor prognostic factor in intrahepatic cholangiocarcinoma (ICC); however, the efficacy of LN dissection for ICC remains unclear. We clarify a targeted papulation of ICC to evaluate it in this study. A retrospective study of patients who underwent liver resection without the extrahepatic bile duct for ICC was conducted. The pattern of LN recurrence and the location of the primary tumor were evaluated. Between January 2003 and July 2014, 52 patients with ICC underwent surgery. Fourteen patients had LN recurrence, 6 of whom had LN recurrence only. Excluding patients with LN dissection at surgery, the primary tumor was limited to the perihilar surrounding area in patients with LN recurrence only. Recurrence rate in LNs was 50% in patients with primary tumors originating in the perihilar surrounding area, which was significantly higher than the rate of 13% in patients with primary tumors originating in other areas. Primary tumors in the perihilar surrounding area have a high risk of LN recurrence. Regional lymphadenectomy combined with hepatectomy should be carried out in patients with ICC located in this area. The incidence of LN metastasis and the possibility of preventing LN recurrence could be effectively revealed by regional lymphadenectomy in selected patients.

The Hepatic Lymphatic Vascular System: Structure, Function, Markers, and Lymphangiogenesis

The lymphatic vascular system has been minimally explored in the liver despite its essential functions including maintenance of tissue fluid homeostasis. The discovery of specific markers for lymphatic endothelial cells has advanced the study of lymphatics by methods including imaging, cell isolation, and transgenic animal models and has resulted in rapid progress in lymphatic vascular research during the last decade. These studies have yielded concrete evidence that lymphatic vessel dysfunction plays an important role in the pathogenesis of many diseases. This article reviews the current knowledge of the structure, function, and markers of the hepatic lymphatic vascular system as well as factors associated with hepatic lymphangiogenesis and compares liver lymphatics with those in other tissues.

Correlation between the serum levels of type IV collagen 7s domain and the risk of intractable ascites following liver resection for hepatocellular carcinoma: A propensity score-matched analysis

BACKGROUND

The severity of liver fibrosis has been reported to be correlated with the risk of intractable ascites after hepatectomy for hepatocellular carcinoma. Since 2009, we have measured routinely the serum concentrations of type IV collagen 7s domain (7s collagen), a biochemical marker of liver fibrosis and applied limited resection to patients with elevation of the serum 7s collagen concentrations above the upper limit of normal (6.0 ng/mL). The aim of this study was to assess the potential benefits of our treatment strategy on the postoperative outcomes of patients with hepatocellular carcinoma.

METHODS

A propensity score-matched analysis was performed to compare the outcomes between patients who underwent initial hepatectomy for hepatocellular carcinoma before or after 2009 (2009 to April 2015; period 2) and those who underwent the operation prior to 2009 (1990-2008; period 1; n = 129 in each period).

RESULTS

The incidence of intractable ascites was significantly lower in period 2 than in period 1 (2.3 vs 14.7%; P < .001), although the other short-term and long-term outcomes were comparable between the 2 groups. A multivariate analysis identified elevation of the serum 7s collagen concentrations to ≥7.4 ng/mL as an independent predictor of IA (odds ratio 14.1, 95% confidence interval 2.8 to 106.7; P = .001), with the area under the receiver-operating characteristic curve of 0.820 (0.648-0.919, P = .005).

CONCLUSION

Modification of the surgical procedure according to the serum 7s collagen concentration is beneficial for reducing the risk of development of intractable ascites after hepatectomy for hepatocellular carcinoma.

Functional Immune Anatomy of the Liver-As an Allograft

The liver is an immunoregulatory organ in which a tolerogenic microenvironment mitigates the relative "strength" of local immune responses. Paradoxically, necro-inflammatory diseases create the need for most liver transplants. Treatment of hepatitis B virus, hepatitis C virus, and acute T cell-mediated rejection have redirected focus on long-term allograft structural integrity. Understanding of insults should enable decades of morbidity-free survival after liver replacement because of these tolerogenic properties. Studies of long-term survivors show low-grade chronic inflammatory, fibrotic, and microvascular lesions, likely related to some combination of environment insults (i.e. abnormal physiology), donor-specific antibodies, and T cell-mediated immunity. The resultant conundrum is familiar in transplantation: adequate immunosuppression produces chronic toxicities, while lightened immunosuppression leads to sensitization, immunological injury, and structural deterioration. The "balance" is more favorable for liver than other solid organ allografts. This occurs because of unique hepatic immune physiology and provides unintended benefits for allografts by modulating various afferent and efferent limbs of allogenic immune responses. This review is intended to provide a better understanding of liver immune microanatomy and physiology and thereby (a) the potential structural consequences of low-level, including allo-antibody-mediated injury; and (b) how liver allografts modulate immune reactions. Special attention is given to the microvasculature and hepatic mononuclear phagocytic system.

Hepatic lymphatics: anatomy and related diseases

The liver normally produces a large amount of lymph. It is estimated that between 25% and 50% of the lymph received by the thoracic duct comes from the liver. In normal conditions, hepatic lymphatics are not depicted on cross-sectional imaging. They are divided in lymphatics of deep system (lymphatics following the hepatic veins and the portal tract) and those of superficial system (convex surface and inferior surface). A variety of diseases may affect hepatic lymphatics and in general they manifest as lymphedema, lymphatic mass, or cystic lesions. Abnormal distended lymphatics are especially seen in periportal spaces as linear hypoattenuations on CT or strong linear hyperintensities on heavily T2-weighted MR imaging. Lymphatic tumor spread as in lymphoma and lymphangitic carcinomatosis manifests as periportal masses and regional lymph node enlargement. Lymphatic disruption after trauma or surgery is depicted as perihepatic fluid collections of lymph (lymphocele). Lymphatic malformation such as lymphangioma is seen on imaging as cystic spaces of variable size.

The value of systematic lymph node dissection for intrahepatic cholangiocarcinoma from the viewpoint of liver lymphatics

Lymph node (LN) metastasis from intrahepatic cholangiocarcinoma (IHCC) might be one of the most important indicators of aggressive surgical resection, yet the value of LN dissection is still controversial. To address this clinical problem, we need to better understand the multidirectional lymphatic outflow from the liver. Although most hepatic lymph flows into the hilar LNs along portal triads, there are also several lymphatic outflows directly communicating with distant areas or the general lymphatic system. Moreover, it has been revealed that LN metastasis spreads to more distal LNs through the hepatoduodenal ligament or other multidirectional lymphatic pathways connected to the general lymphatic system. Therefore, systematic LN dissection might merely be LN sampling in IHCC with LN metastasis. A multidisciplinary strategy focusing on adjuvant treatment after surgery is immediately necessary in these cases. In IHCC without LN metastasis, the accuracy of preoperative imaging assessment of LN metastasis is unsatisfactory and useless for detecting metastatic LNs in clinical settings. Therefore, prophylactic systematic LN dissection for IHCC without preoperative LN swelling is recommended for accurate LN status assessment and reduction of local recurrences. However, this procedure might not offer any clinical benefit according to the results of retrospective comparative studies. In this review, we summarize previous reports regarding lymphatic outflow of the liver and discuss LN dissection for IHCC.

Twisting Tourniquet(©) Technique: introducing Schnogh, a novel device and its effectiveness in treating primary and secondary lymphedema of extremities

Twisting Tourniquet^© or in Thai “Schnogh” is a new invention for compression therapy of lymphedema. Twisting Tourniquet^© Technique (TTT) is totally noninvasive for lymphedema management. After the amazing successful evidence in the first series of 28 patients, we have conducted preliminary studies in lymphedema clinics. It was found that the combination of gradually increasing constriction force by Schnogh until desired pressure was reached and maintained for 15 min, followed by a 5-min release, doing repeatedly this compression-decompression for at least 10 sessions a day, can generate acceptable results. The aim of the study was to evaluate the scientific effectiveness and establish a treatment protocol of TTT proposed as a therapeutic approach for clinical management of lymphedema. During 2006–2013, from over 3500 patients, 647 with primary/secondary lymphedema passed inclusion criteria, 307 for upper, and 340 for lower extremity. In the 5-day course of TTT, each day patients underwent 10 sessions of a 15-min compression followed by a 5-min decompression. Vegan diet was encouraged as an adjuvant therapy. Among lymphedema patients whose spectrum of edema severity ranged from mild to gigantic, TTT yielded an average volume reduction rate (VR) at 50.2% and 55.6%, making the average edema reduction volume attained at 463 and 1856 mL for upper and lower limb, respectively. The uniformed practice by Schnogh which supports a continual compression–decompression maneuver over 3.5 h daily for five consecutive days could induce an average VR at above half of the swelling in extremities of 647 patients. Schnogh is therefore effective in clinical management of lymphedema under TTT treatment of fibroblastic interstitium.

Plasmodium cellular effector mechanisms and the hepatic microenvironment

Plasmodium falciparum malaria remains one of the most serious health problems globally. Immunization with attenuated parasites elicits multiple cellular effector mechanisms capable of eliminating Plasmodium liver stages. However, malaria liver stage (LS) immunity is complex and the mechanisms effector T cells use to locate the few infected hepatocytes in the large liver in order to kill the intracellular LS parasites remain a mystery to date. Here, we review our current knowledge on the behavior of CD8 effector T cells in the hepatic microvasculature, in malaria and other hepatic infections. Taking into account the unique immunological and lymphogenic properties of the liver, we discuss whether classical granule-mediated cytotoxicity might eliminate infected hepatocytes via direct cell contact or whether cytokines might operate without cell–cell contact and kill Plasmodium LSs at a distance. A thorough understanding of the cellular effector mechanisms that lead to parasite death hence sterile protection is a prerequisite for the development of a successful malaria vaccine to protect the 40% of the world’s population currently at risk of Plasmodium infection.

Serosal invasion strongly associated with recurrence after curative hepatic resection of hepatocellular carcinoma: a retrospective study of 214 consecutive cases

The purpose of this study was to clarify the individual prognostic factors after curative and primary resection of hepatocellular carcinoma (HCC).Reliable prognostic factors and tumor staging for HCC have been required to predict an appropriate prognosis. However, in HCC, no staging system has received universal acceptance, and several tumor factors seem to relate to HCC prognosis, but they are not definitive. At present, few studies have mentioned the importance of serosal invasion as a prognostic factor.A retrospective search of our database identified 214 consecutive patients who underwent primary and curative hepatectomy for HCC at our department between January 1998 and December 2011. Risk factors for recurrence-free survival (RFS) and overall survival (OS) were analyzed with Cox proportional hazard model, Kaplan-Meier method, and log-rank tests.Multivariate analyses showed that serosal invasion (hazard ratio [HR], 2.75; P = 0.0005) and vascular invasion (HR, 1.71; P = 0.0331) were independently correlated with RFS. Serosal invasion was significantly correlated with HCC recurrence (P = 0.0230). The Kaplan-Meier method and log-rank tests revealed that the patients with serosal invasion showed significantly worse prognosis both in RFS (P < 0.0001) and OS (P = 0.0016).Serosal invasion should be regarded as a strong independent predictor for recurrence in curatively resected HCC cases.

Immunobiology of Plasmodium in liver and brain

Malaria remains one of the most serious health problems globally, but our understanding of the biology of the parasite and the pathogenesis of severe disease is still limited. Multiple cellular effector mechanisms that mediate parasite elimination from the liver have been described, but how effector cells use classical granule-mediated cytotoxicity to attack infected hepatocytes and how cytokines and chemokines spread via the unique fluid pathways of the liver to reach the parasites over considerable distances remains unknown. Similarly, a wealth of information on cerebral malaria (CM), one of the most severe manifestations of the disease, was gained from post-mortem analyses of human brain and murine disease models, but the cellular processes that ultimately cause disease are not fully understood. Here, we discuss how imaging of the local dynamics of parasite infection and host response as well as consideration of anatomical and physiological features of liver and brain can provide a better understanding of the initial asymptomatic hepatic phase of the infection and the cascade of events leading to CM. Given the increasing drug resistance of both parasite and vector and the unavailability of a protective vaccine, the urgency to reduce the tremendous morbidity and mortality associated with severe malaria is obvious.

In vivo CD8+ T cell dynamics in the liver of Plasmodium yoelii immunized and infected mice

Plasmodium falciparum malaria remains one of the most serious health problems globally and a protective malaria vaccine is desperately needed. Vaccination with attenuated parasites elicits multiple cellular effector mechanisms that lead to Plasmodium liver stage elimination. While granule-mediated cytotoxicity requires contact between CD8+ effector T cells and infected hepatocytes, cytokine secretion should allow parasite killing over longer distances. To better understand the mechanism of parasite elimination in vivo, we monitored the dynamics of CD8+ T cells in the livers of naïve, immunized and sporozoite-infected mice by intravital microscopy. We found that immunization of BALB/c mice with attenuated P. yoelii 17XNL sporozoites significantly increases the velocity of CD8+ T cells patrolling the hepatic microvasculature from 2.69±0.34 μm/min in naïve mice to 5.74±0.66 μm/min, 9.26±0.92 μm/min, and 7.11±0.73 μm/min in mice immunized with irradiated, early genetically attenuated (Pyuis4-deficient), and late genetically attenuated (Pyfabb/f-deficient) parasites, respectively. Sporozoite infection of immunized mice revealed a 97% and 63% reduction in liver stage density and volume, respectively, compared to naïve controls. To examine cellular mechanisms of immunity in situ, naïve mice were passively immunized with hepatic or splenic CD8+ T cells. Unexpectedly, adoptive transfer rendered the motile CD8+ T cells from immunized mice immotile in the liver of P. yoelii infected mice. Similarly, when mice were simultaneously inoculated with viable sporozoites and CD8+ T cells, velocities 18 h later were also significantly reduced to 0.68±0.10 μm/min, 1.53±0.22 μm/min, and 1.06±0.26 μm/min for CD8+ T cells from mice immunized with irradiated wild type sporozoites, Pyfabb/f-deficient parasites, and P. yoelii CS_280–288 peptide, respectively. Because immobilized CD8+ T cells are unable to make contact with infected hepatocytes, soluble mediators could potentially play a key role in parasite elimination under these experimental conditions.

Characterization of the liver-draining lymph nodes in mice and their role in mounting regional immunity to HBV

The lymphatic system is important in mounting an immune response to foreign antigens and tumors in humans and animal models. The liver produces a large amount of lymph, and its lymphatic system is divided into three major components: the portal, sublobular and superficial lymphatic vessels. Despite the fact that mice are the most commonly used laboratory animals, detailed descriptions of the anatomical location and function of the lymph nodes (LNs) that drain the liver are surprisingly absent. In this study, we found that the portal and celiac LNs adjacent to mouse liver were stained with Evans blue within 5-8 min. Enhanced green fluorescence protein (EGFP)-positive cells from the liver also drained into the two aforementioned LNs. These data indicate that the portal and celiac LNs drain the mouse liver. Lymphadenectomy of the identified liver-draining LNs resulted in hepatitis B virus (HBV) persistence in immunocompetent mice compared with the sham group. In addition, the frequencies of CD8(+) T cells and dendritic cells (DCs) increased significantly in the liver-draining LNs after hydrodynamic injection of HBV plasmid. Liver-draining LN cells in HBV plasmid-injected mice also showed significant antigen-specific proliferation in response to stimulation with recombinant hepatitis B core antigen in vitro. Adoptive transfer of these cells into Rag1(-/-) mice induced a reduction in the serum concentration of hepatitis B surface antigen (HBsAg) compared to liver-draining LN cells in uninjected mice. Altogether our data characterize the liver-draining LNs and provide evidence that the liver-draining LNs induce an anti-HBV-specific immune response responsible for HBV clearance.

Impact of hepatic lymph node metastasis on survival of patients with synchronous resectable or unresectable liver metastases of colorectal cancer

BACKGROUND

The goals of this retrospective study were to comprehensively evaluate the impact of hepatic lymph node (HLN) involvement on survival in patients with synchronous resectable or unresectable liver metastases from colorectal cancer and to highlight how to deal with such cases in the light of recent advances in chemotherapy.

METHODS

The impact of HLN involvement on survival, along with various clinical, pathological, and therapeutic factors, was retrospectively evaluated in 61 patients with synchronous liver metastases from colorectal cancer (resectable, 26; unresectable, 35), undergoing resection of the primary tumor and histopathological evaluation between July 2000 and April 2008.

RESULTS

The proportion with HLN metastasis was 11.5 % in resectable cases and 28.6 % in unresectable cases. On multivariate analysis using the Cox proportional hazards model, HLN metastasis (P < 0.001), along with non-resection of hepatic lesions (P < 0.001), larger metastatic tumor volume (P < 0.001), non-use of oxaliplatin-based chemotherapy (P < 0.001), involvement of 4 or more regional lymph nodes (P < 0.001), and excessive lymphatic invasion (P = 0.02), was identified as an independent risk factor for shorter survival.

CONCLUSIONS

To establish a new therapeutic strategy for synchronous liver metastasis of colorectal cancer, the HLNs should be examined histologically in patients undergoing resection of their primary colon and rectal cancer.

Significance of Hepatic Lymph Node Metastasis in Patients With Unresectable Synchronous Liver Metastasis of Colorectal Cancer

The frequency and significance of hepatic lymph node (HLN) metastasis were retrospectively evaluated in 43 patients with unresectable synchronous liver metastasis of colorectal cancer who underwent resection of the primary tumor and histopathologic evaluation of HLNs between March 1997 and August 2007. HLN metastasis was detected in 12 patients (27.9%). No significant correlations were observed between the presence of HLN metastasis and any of the 12 clinicopathologic factors examined. On multivariate analysis using the Cox proportional hazards model, the presence of HLN metastasis (P  =  0.002), along with a large number (≥4) of regional lymph node metastases (P  =  0.003), and nonuse of oxaliplatin-based chemotherapy (P  =  0.005) were identified as independent risk factors for shorter survival. To establish a new therapeutic strategy for initially unresectable liver metastasis of colorectal cancer, HLNs should be examined histologically in patients undergoing resection of hepatic lesions when they are rendered resectable by effective chemotherapy.

Mechanisms regulating colorectal cancer cell metastasis into liver (Review)

The metastatic spread of tumor cells is one of the most common causes of mortality in cancer patients. The elucidation of the molecular mechanisms that underlie the formation of metastatic colonies has been one of the major objectives of cancer research. Organ-specific colonization of cancer cells is a significant and noteworthy feature of metastasis. Colorectal cancer (CRC) is one of the most common causes of cancer-related mortality. The liver is commonly the sole site of metastasis for CRC and represents a major cause of mortality in CRC patients. However, what regulates CRC cell metastasis into liver and the reasons for the liver-specific metastasis of CRC have yet to be adequately elucidated. Recent progress provides indications and a conceptual framework with which to investigate this issue. This review evaluated experimental and clinical evidence to support a mechanistic role for circulation patterns and microvessels in liver, metastasis-related genes, chemokines and their receptors, and cellular adhesion molecules in the process of CRC liver metastasis.

Hepatectomy for colorectal metastases in the presence of extrahepatic disease

This article focuses on hepatectomy for colorectal liver metastases (CLM) in the presence of intra-abdominal extrahepatic disease. The results reported in the literature are reviewed, and the indications and contraindications for hepatectomy in patients who have CLM with extrahepatic disease are discussed in light of the available evidence.

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.

Visualization of hepatic lymphatic vessels during transcatheter arterial chemoembolization for hepatocellular carcinoma

PURPOSE

To analyze visualization of hepatic lymphatic vessels during transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Retrospective review was conducted of 255 tumors in 161 patients treated by TACE with catheterization of the most distal portion of the tumor-feeding branches. All TACE procedures were performed with use of a mixture of iodized oil and anticancer drugs followed by gelatin sponge particles. Arteriograms and spot radiographs obtained during TACE were reviewed to determine whether hepatic lymphatic vessels appeared. Serial computed tomography (CT) images after TACE were evaluated along with clinical symptoms in cases that exhibited lymphatic vessel visualization.

RESULTS

Hepatic lymphatic vessels were demonstrated in eight tumors (3.1%) in eight patients during TACE. The mean tumor diameter was 1.7 cm +/- 0.7 (range, 1.0-3.3 cm), and mean volume of injected iodized oil was 1.7 mL +/- 1.0 (range, 1-4 mL). Lymphatic vessels were demonstrated followed by marked portal vein visualization (n = 5) or extravasation of a small amount of contrast material (n = 2). In the remaining patient, these were depicted during the early stage of the TACE procedure. On CT after 1 week, iodized oil in the lymphatic systems in the hepatoduodenal ligament was seen in six patients, and it was shown to have been retained in four of these patients on follow-up CT performed 2, 7, 11, and 21 months later, respectively. None of these patients presented any clinical symptom other than postembolization syndrome.

CONCLUSIONS

Hepatic lymphatic vessels were demonstrated in 3.1% of tumors treated by ultraselective TACE. Iodized oil in the lymphatic vessels may be retained for a relatively long time without specific symptoms.

Molecular Profile and Proliferative Responses of Rat Lymphatic Endothelial Cells in Culture

BACKGROUND

Lymphangiogenesis plays an important role in metastasis of many solid tumors. To study lymphangiogenesis under controlled conditions, an in vitro model is needed. The goal of this work was to establish such an in vitro model by determining a molecular profile of rat mesenteric lymphatic endothelial cells (RMLEC) and characterizing their proliferative responses to angiogenic and lymphangiogenic factors, such as vascular endothelial growth factor A and C (VEGF-A and VEGF-C).

METHODS AND RESULTS

RMLEC strongly expressed most lymphatic-specific markers, including Prox-1, LYVE-1, and VEGFR-3. Proliferation of RMLEC was serum and heparin dependent. In the presence of low (2%) serum concentration, exogenously added VEGF-A and VEGFC stimulated RMLEC in a linear and dose-dependent manner. This effect was abrogated by anti-VEGF-A and VEGF-C antibodies, as well as by soluble Tie-2 and Flt-4 fusion proteins. Abrogation was reversed by VEGF-A, suggesting that this factor as an important regulator of lymphangiogenesis.

CONCLUSIONS

Cultured RMLEC preserved a molecular profile consistent with the phenotype of lymphatic endothelium in vivo and respond to either VEGF-A or VEGF-C factors. VEGFA was able to rescue RMLEC proliferation inhibited by a neutralizing VEGF-C antibody or soluble Tie-2 fusion protein. These results support the existence of cross-talk among angiogenic and lymphangiogenic factors. This work established experimental conditions that allow in vitro modeling of lymphatic endothelial responses to lymphangiogenic regulators. Preliminary results using this model suggest that VEGF-A, VEGF-C, and angiopoietins work in concert to promote lymphangiogenesis in vivo.

Transgenic expression of Angiopoietin 1 in the liver leads to changes in lymphatic and blood vessel architecture

To investigate the possible role of the Angiopoietins in vessel remodelling, we overexpressed one of the angiopoietins, Angiopoietin-1 (Ang1), in the hepatocytes of mice by means of the conditional binary transgenic system. Animals were examined by Doppler ultrasound, and dissected livers were analyzed by immunohistochemical staining. Double transgenic mice presented with enlarged spleens and kidneys, enlarged, disorganized blood vessels located near the surface of the liver, sprouting, dilation, and disorganization of liver lymphatics, and turbulent flow in about 1/4 of the blood vessels sampled. Most of these characteristics completely resolved within 12 weeks of turning off the expression of the Ang1 transgene, illustrating a dependence on the continual presence of Ang1 for maintenance of the vascular phenotype. Conditional Angiopoietin-1 overexpression in the liver of mice leads to a phenotype highly reminiscent of portal hypertension illustrating that Ang1 can drive both vascular and lymphatic vessel remodelling and may play a role in portal hypertension.

Alphavbeta5-integrins mediate early steps of metastasis formation

Tumour cell adhesion within the microvasculature of host organs, its stabilisation and cell invasion into the host organs, appear to be important steps in the formation of distant metastases. Intravital fluorescence-video microscopy was used to investigate the early steps in metastasis formation of colon carcinoma cells within the liver, which is the main target organ of colorectal carcinomas. The involvement of alphav-integrins was analysed in vivo using HT-29 cells after treatment with different function-blocking antibodies [pan-alphav (n=9 animals), specific alphavbeta3 (n=8 animals) and alphavbeta5 (n=8 animals)] or linear Arg-Gly-Asp (RGD)-containing peptides (RGD-peptides) (n=6 animals). Treatment with anti-alphav and anti-alphavbeta5 antibodies resulted in significantly (P<0.001) decreased tumour cell adhesion in vivo within the hepatic microvasculature. Cells treated with anti-alphavbeta3 antibodies or unspecific immunoglobulin-G (IgG) did not show significant changes in their adhesive properties. Furthermore, inhibition of cell adhesion was achieved by linear RGD-peptides in a dose-dependent manner. Relative numbers of migrated cells were not affected by any of the treatments. These results suggest that alphav-integrins, especially alphavbeta5, can influence the ability of circulating tumour cells to adhere within the hepatic microvessels. In contrast, migration of adherent cells into the liver parenchyma was not affected by alphav-integrin inhibition. Our findings support the hypothesis that specific interactions between circulating tumour cells and host organs are required for organ-specific tumour cell arrest.

The significance of hepatic pedicle lymph nodes metastases in surgical management of colorectal liver metastases and of other liver malignancies

BACKGROUND

Surgical resection of colorectal liver metastases (CLM) is the only hope for cure, with a 5-year survival rate ranging from 20% to 54%. However, the resectability rate of CLM is reported to be <20%. This limitation is mainly due to insufficient remnant liver and to extrahepatic disease. Among extrahepatic locations, lymph node metastases are often considered indications of a very poor prognosis and a contra-indication to resection.

METHODS

and

RESULTS

Our studies showed that the prevalence of hepatic pedicle lymph node metastases ranges from 10% to 20%. When located near the hilum and along the hepatic pedicle (area 1) they should not be considered an absolute contra-indication to resection of CLM, and an extended lymphadenectomy should be performed. However, when they reach the celiac trunk (area 2), there is no survival benefit after resection of CLM. For other cases of liver malignancies, lymph node dissection seems justified only in cases of fibrolamellar hepatocellular carcinoma and in case of hilar cholangiocarcinoma. However, few data are available, and they are controversial.

CONCLUSIONS

There is a need for more evaluation of lymph node involvement, at least in patients with high risk of such an extension, i.e., patients with more than three metastases, located in segment 4 or 5. There is also a need for prospective trials in order to evaluate the survival benefit of liver resection in such circumstances and the impact of extensive lymphadenectomy.

Naive and Memory T Lymphocytes Migrate in Comparable Numbers Through Normal Rat Liver: Activated T Cells Accumulate in the Periportal Field

Although the liver is known to contain a significant number of lymphocytes, migration of these through the compartments of the liver, parenchyma and periportal field, has not been studied. The periportal field, in particular, is affected in several immunological disorders of the liver. Populations of labeled naive, activated, and memory T cells were injected into congenic rats. The recipient livers and draining lymph nodes were removed at various time points, and cryostat sections were analyzed for the presence of donor cells using quantitative immunohistology. Donor cell proliferation and apoptosis were examined in vivo by BrdU (5 μM 5-bromo-2-deoxyuridine) incorporation and the TUNEL technique, respectively. Early after injection (0.5–1 h), naive, activated, and memory T cells were localized to the parenchyma and periportal field in comparable numbers. With time, all T cell subsets left the parenchyma but remained or, in the case of activated T cells, significantly accumulated in the periportal field. Furthermore, 12% of activated donor T cells proliferated in vivo within the periportal field, and 0.5% showed evidence of apoptosis. Taken together, not only activated and memory, but also naive T cells continuously migrate through the liver, showing a preference for the periportal field, and activated T cells mainly proliferate there. This may explain why many immunological liver diseases predominantly affect the periportal field.

Hepatic lymph node involvement in resected cases of liver metastases from colorectal cancer

PURPOSE

Lymph node metastasis in the hepatoduodenal ligament is known as one of the most significant prognostic factors after liver resection for colorectal metastasis. However, there have been very few articles on the clinical features of node-positive patients and on detailed distribution of positive nodes. Further, there has been no established strategy on how to handle hepatic lymph nodes during liver resection. To address these subjects, a retrospective study was conducted.

METHODS

During the period of 1980 through April 1998, 182 hepatic resections were performed for metastatic colorectal carcinoma. Of these, 78 cases had hepatic lymph node sampling during the operation. Distribution of positive nodes, location of liver metastasis, stage of the primary lesion, and outcome after liver resection were analyzed.

RESULTS

Nine cases (12 percent) had secondary lymph node metastases in the hepatoduodenal ligament. The incidence was slightly higher (13.5 percent) in the most recent 44 consecutive cases. There was a tendency for liver metastases in the right lobe to metastasize to No. 12b (or node of the foramen of Winslow, lymph nodes along the common bile duct) and liver metastases in the left lobe to metastasize to No. 8a (anterosuperior group of the lymph nodes along the common hepatic artery). Outcome of node-positive patients (n = 9) was extremely poor (P < 0.001) compared with that of node-negative patients (n = 66), and the most common site of recurrence in the node-positive patients was remnant liver and hepatic lymph nodes. Preoperatively, there were no significant predicting factors for positive hepatic lymph nodes.

CONCLUSIONS

No. 8a and No. 12b nodes are principal nodes that should be palpated and sampled during liver resection to check the secondary lymphatic spread from liver metastases. Hepatic nodal involvement indicates the progression of disease beyond simple liver metastases and may not be the indication for simple surgical removal. Further study, including hepatoduodenal dissection and systemic adjuvant chemotherapy, may elucidate the survival benefit, if any, of liver resection in node-positive patients.