Changes In Hepatic Microcirculation Research Articles

Endothelial dysfunction in pathological processes of chronic liver disease during aging.

Aging is associated with gradual changes in liver structure and physiological/pathological functions in hepatic cells including hepatocytes, cholangiocytes, Kupffer cells, hepatic stellate cells (HSCs), and liver sinusoidal endothelial cells (LSECs). LSECs are specialized hepatic endothelial cells that regulate liver homeostasis. These cells actively impact the hepatic microenvironment as they have fenestrations and a thin morphology to allow substance exchange between circulating blood and the liver tissue. As aging occurs, LSECs have a reduction in both the number and size of fenestrations, which is referred to as pseudocapillarization. This along with the aging of the liver leads to increased oxidative stress, decreased availability of nitric oxide, decreased hepatic blood flow, and increased inflammatory cytokines in LSECs. Vascular aging can also lead to hepatic hypoxia, HSC activation, and liver fibrosis. In this review, we described the basic structure of LSECs, and the effect of LSECs on hepatic inflammation and fibrosis during aging process. We briefly summarized the changes of hepatic microcirculation during liver inflammation, the effect of aging on the clearance function of LSECs, the interactions between LSECs and immunity, hepatocytes or other hepatic nonparenchymal cells, and the therapeutic intervention of liver diseases by targeting LSECs and vascular system. Since LSECs play an important role in the development of liver fibrosis and the changes of LSEC phenotype occur in the early stage of liver fibrosis, the study of LSECs in the fibrotic liver is valuable for the detection of early liver fibrosis and the early intervention of fibrotic response.

Quantitative assessment of liver function using hepatobiliary scintigraphy: the effect of microcirculatory alterations after portal vein embolization.

Hepatobiliary scintigraphy using technetium-99m mebrofenin has been validated as a quantitative liver function test. Preoperative portal vein embolization (PVE) is performed in patients to increase future remnant liver function and volume. Changes in hepatic microcirculation after PVE remain largely unknown and may influence the uptake of mebrofenin. The aim was to evaluate microcirculatory changes after PVE to examine differences in perfusion that might influence the uptake of mebrofenin, and consequently, assessment of function. Patients undergoing liver resection with or without preoperative PVE were included. Future remnant liver volume and function were measured before and after PVE. Hepatic microcirculation was measured in the embolized and the nonembolized lobes during resection. Microcirculatory flow index, perfused vessel density, sinusoidal diameter and red blood cell velocity were assessed. A total of 16 patients, eight with preoperative PVE and eight control patients without PVE, were included. After PVE, both function and volume of the nonembolized lobe were significantly increased, and the functional increase exceeded the increase in volume. Perfused vessel density and sinusoidal diameter were significantly higher in the nonembolized liver lobe (P<0.002 and <0.04). No significant differences between both lobes were found concerning microcirculatory flow index or red blood cell velocity. After PVE, the nonembolized lobe had a significantly higher (functional) microvascular density compared with the embolized lobe, without differences in microvascular flow. These findings indicate that the measured functional increase using hepatobiliary scintigraphy, which exceeded the volumetric increase, was not the consequence of an increase in hepatic perfusion, therefore, providing adequate representation of the liver function.

Microcirculatory disturbances and cellular changes during progression of hepatic steatosis to liver tumors.

Non-alcoholic fatty liver disease is closely associated with metabolic syndrome and comprises a pathological spectrum of liver disease ranging from steatosis to steatohepatitis and can progress to fibrosis/cirrhosis and hepatocellular carcinoma. In 2013, a mouse model was described that mimics non-alcoholic fatty liver disease progression from steatohepatitis to tumors in a short time span and with high incidence. As microcirculatory disturbances play a crucial role in liver disease, the suitability of the steatosis-inflammation-tumor model for microcirculatory studies was assessed. Herein, we present a comprehensive view on morphological, microvascular, cellular, and functional aspects of non-alcoholic fatty liver disease progression in the steatosis-inflammation-tumor model using intravital microscopy, biochemical, and histological techniques. Mice develop steatohepatitis, mild fibrosis, and liver tumors at ages of 6, 12, and 20 weeks, respectively. Non-alcoholic fatty liver disease progression was accompanied by several general aspects of disease severity like increasing liver/body weight index, non-alcoholic fatty liver disease activity score, and hepatocellular apoptosis. Intravital microscopic analysis revealed significant changes in hepatic microcirculation with increasing structural alterations, elevated leukocyte adherence, and impaired nutritive perfusion. Non-alcoholic fatty liver disease was further characterized by a lower sinusoidal density with a striking rise at 20 weeks. The characteristic microcirculatory changes make the model a convenient tool for analysis of microcirculation during progression from steatosis to liver tumor. Impact statement Significant alterations of microcirculation contribute to progression of NAFLD, a chronic liver disease with increasing medical and socio-economic impact. Characterization of microcirculation in a NAFLD model reflecting all relevant stages of disease progression was still missing. Thus, we evaluated microcirculatory and cellular changes in a steatosis-inflammation-tumor model using in vivo microscopy. Analyses revealed increasing structural alterations, elevated leukocyte-endothelial interaction, and impaired nutritive perfusion. Thus, this model is suitable for further studies investigating therapeutic approaches targeting these progressive microcirculatory disturbances.

Evaluation of liver function and electroacupuncture efficacy of animals with alcoholic liver injury by the novel imaging methods.

Imaging methods to evaluate hepatic microcirculation (HM) and liver function (LF) by directly monitoring overall liver tissue remain lacking. This study establish imaging methods for LF that combines Laser speckle perfusion imaging (LSPI) and in vivo optical imaging (IVOI) technologies to investigate changes of hepatic microcirculation and reserve function in the animals gavaged with 50% ethanol (15 ml/kg·bw) for a model of acute alcoholic liver injury (ALI), and for evaluation of electroacupuncture (EA) effect. The liver blood perfusion and indocyanine green (ICG) distribution were observe by LSPI and IVOI separately. After EA, the livers were collected to measure the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), thromboxane A (TXA2), prostacyclin (PGI2) and endothelin (ET). The acquisitions of newly established LSPI of liver and ICG in vivo fluorescence imaging (ICG-IVFI), combining the results of other indexes showed: hepatic microcirculation perfusion (HMP) significantly reduced, ICG metabolism reduced, and ALT/AST increased in animal model with acute ALI. EA can reverse these changes. The use of LSPI of liver and ICG-IVFI, which was novel imaging methods for LF established in this study, could display the LF characteristics of ALI and the EA efficacy.

Application of intravital fluorescence microscopy in the observation of the changes of hepatic microcirculation in rat with hepatic cirrhosis and portal hypertension

Objective To investigate the value of intravital fluorescence microscopy in the observation of the changes of hepatic microcirculation in the rat model with hepatic cirrhosis and portal hypertension.Methods Seventy male SD rats were selected.According to the random number table,40 SD rats were randomly divided into the sham operation group,bile duct ligation (BDL) 2 weeks group,4 weeks group and 6 weeks group,there were 10 rats in each group,and the hepatic microcirculation of the rats was observed with intravital fluorescence microscope; the remaing 30 SD rats were randomly divided into the normal saline (NS) group,endothelin-1 (ET-1) group and the S-nitrosoglutathion (GSNO) group at 4 weeks later after the establishment of BDL model.The changes of hepatic microcirculation of the 3 groups were observed.All data were analyzed using the one-way analysis of variance (ANOVA) or paired samples t test.Results Nine rats died in the BDL model groups,and the survival rate was 85.0％ (51/60).All rats in the sham operation group were survived.The hepatic sinusoid diameters were decreased as time passed by.The hepatic sinusoid diameters of the BDL 2 weeks group,4 weeks group and 6 weeks group were (13.6 ± 1.0) μm,(8.8 ± 0.7) μm and (8.0 ± 0.5) μm,respectively,which were significantly shorter than (17.4 ± 1.0) μm of the sham operation group (t =5.86,18.24,15.57,P ＜ 0.05).The hepatic sinusoid densities of the BDL 2 weeks group,4 weeks group and 6 weeks group were (6.8 ±0.8)/ 200 μm,(4.3 ± 1.8)/200 μm and (4.0 ± 1.2)/200 μm,which were significandy lesser than (8.8 ± 0.5)/200 μm (t =3.25,2.77,2.12,P ＜ 0.05).At 15 minutes after injection of NS,the hepatic sinusoid diameter of the NS group was (7.2 ± 1.2) μm,which was significantly different from (6.9 ± 0.5) μm before injection of NS (t =0.89,P ＞ 0.05) ; the hepatic sinusoid density of the NS group before and after injection of NS were (6.6 ± 0.4) / 200 μm and (6.8 ± 1.4)/200 μm,with no significant difference(t =1.12,P ＞0.05).At 15 minutes after injection of ET-1,the hepatic sinusoid diameter of the ET-1 group was (5.4 ±0.5) μm,which was significantly different from (7.9 ± 0.6) μm before injection of ET-1 (t =7.39,P ＜ 0.05) ; the hepatic sinusoid density of the ET-1 group before and after ET-1 injection were (5.8 ± 1.2)/200 μm and (5.4 ± 1.8)/200 μm,with no significant difference(t =0.84,P ＞0.05).At 15 minutes after injection of the GSNO,the hepatic sinusoid diameter of the GSNO group was (11.4 ± 1.3) μm,which was significantly different from (7.5 ± 1.7) μm before injection of GSNO (t =5.95,P ＜ 0.05) ; the hepatic sinusoid density of the GSNO group before and after GSNO injection were(5.6 ± 0.8)/200 μm and (6.4 ± 1.6)/200 μm,with no significant difference (t =0.54,P ＞ 0.05).Conclusions The changes of hepatic microcirculation observed under intravital fluorescence microscope could reflect the progress of hepatic cirrhosis,and the changes of hepatic sinusoid diameters caused by drugs could be dynamically monitored under the intravital fluorescence microscope. Key words: Liver cirrhosis ; Portal hypertension; Hepatic microcirculation ; Intravital fluorescence microscope

Altered activation of a different type of nitric oxide synthase over the course of repeated hepatic ischemia/reperfusion in rats

ObjectiveThe aim of this study was to determine the intrahepatic kinetics of nitric oxide synthase during ischemia/reperfusion (I/R).MethodsIntrahepatic nitric oxide (NO) levels were measured using a selective NO sensor. Changes in hepatic microcirculation were investigated using intravital microscopy. Hepatic expression of endothelial nitric oxide synthase (eNOS), phospho‐eNOS, and inducible NOS (iNOS) were evaluated by western blot, reverse transcription polymerase chain reaction (RT‐PCR), and immunohistochemical analysis.ResultsIntrahepatic NO levels gradually increased and then reached a plateau approximately 15 min after starting ischemia. The sinusoids after reperfusion were dilated compared with the sinusoids before ischemia. The expression of phospho‐eNOS during I/R markedly increased during the first ischemia, and then the levels attenuated during the subsequent repeating I/R cycles; however, the expression of iNOS gradually increased, as observed by western blot, RT‐PCR, and immunohistochemical analysis.ConclusionOur results indicate that eNOS, through activation of the phospho‐eNOS system, promptly responds to ischemic stress in the super‐acute phase of ischemia. Subsequently, repeating I/R stress induces iNOS gene expression, although it may take at least an hour to upregulate the iNOS protein.

Endothelial nitric oxide synthase plays a main role in producing nitric oxide in the superacute phase of hepatic ischemia prior to the upregulation of inducible nitric oxide synthase

BackgroundThe aim of this study was to determine the intrahepatic kinetics of different types of nitric oxide (NO) synthase, such as endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS), during repeated ischemia/reperfusion (I/R). MethodsThree different protocols of hepatic I/R in rats were designed as follows: 60 min of ischemia and 30 min of reperfusion (I/R 60/30); 5 min of ischemia and 5 min of reperfusion (I/R 5/5); and repeating 15 min of ischemia and 5 min of reperfusion for four cycles (I/R 15/5 × 4). Intrahepatic NO levels were measured using a selective NO sensor. Changes in hepatic microcirculation during I/R 5/5 were investigated using intravital microscopy. Hepatic expression of eNOS, phospho-eNOS, and iNOS were evaluated during repeated I/R by Western blot, reverse transcription polymerase chain reaction, and immunohistochemistry. ResultsDuring I/R 60/30, intrahepatic NO levels gradually increased and then reached a plateau approximately 15 min after starting ischemia. During I/R 5/5, the sinusoids after 5 min reperfusion were dilated compared with the sinusoids before ischemia. The expression of phospho-eNOS during I/R 15/5 × 4 markedly increased during the first ischemia, and then the levels attenuated during the subsequent repeating I/R cycles; however, the expression of iNOS gradually increased, as observed by Western blot, reverse transcription polymerase chain reaction, and immunohistochemical analysis. An impact of NO production by phospho-eNOS activation during the superacute phase of I/R was also confirmed using pharmacologic NOS inhibitors. ConclusionOur results firstly demonstrated an altered activation of the phospho-eNOS system and iNOS over the course of repeated hepatic I/R.

Directly acting drugs prostacyclin or nitroglycerine and endothelin receptor blocker bosentan improve cell engraftment in rodent liver

To optimize strategies for liver-directed cell therapy, prevention of initial transplanted cell losses is particularly important for subsequent liver repopulation. After cell transplantation in hepatic sinusoids, perturbations in hepatic microcirculation along with changes in various liver cell types are among the earliest changes. Therefore, for advancing further concepts in cell engraftment we studied vascular and related events in the liver after transplanting syngeneic hepatocytes into dipeptidyl peptidase IV-deficient rats. We treated rats with vascular drugs to define whether deleterious cell transplantation-induced events could be controlled followed by improvements in transplanted cell engraftment and proliferation. We found cell transplantation altered liver gene expression related to vessel tone, inflammation, cell adhesion, thrombosis, or tissue damage/remodeling. This was due to hepatic ischemia, endothelial injury, and activation of neutrophils, Kupffer cells, and hepatic stellate cells. Treatment of rats before cell transplantation with the angiotensin converting enzyme blocker, lisinopril, or angiotensin II receptor blocker, losartan, did not improve cell engraftment. By contrast, direct-acting nitroglycerine or prostacyclin improved cell engraftment and also kinetics of liver repopulation. These drugs lowered hepatic ischemia and inflammation, whereas pretreatment of rats with the dual endothelin-1 receptor blocker, bosentan, improved cell engraftment independently of hepatic ischemia or inflammation, without improving liver repopulation. However, incubation of hepatocytes with bosentan protected cells from cytokine toxicity in vitro and produced superior cell engraftment and proliferation in vivo. Cell transplantation-induced changes in hepatic microcirculation contributed to transplanted cell clearances from liver. Vascular drugs, such as nitroglycerine, prostacyclin, and bosentan, offer opportunities for improving cell therapy results through superior cell engraftment and liver repopulation. Ongoing clinical use of these drugs will permit rapid translation of the findings in people.

Effect of thalidomide on the expression of vascular endothelial growth factor in a rat model of liver regeneration

Liver regeneration is an angiogenesis-associated phenomenon. The present study investigated the influence of thalidomide, an antiangiogenic agent, on vascular endothelial growth factor (VEGF) expression and liver regeneration after 70% partial hepatectomy (PH) in rats. PH was performed on 50 rats dosed with either thalidomide (100 mg/kg) or a vehicle (controls) by intragastric administration. Serial changes in hepatic microcirculation were evaluated by laser Doppler flowmetry. The VEGF expression in liver tissue was assessed by immunohistochemical study and western blot analysis. Following hepatectomy, the liver regeneration rate increased markedly and reached a peak at 96 h in the two groups. Thalidomide did not affect the overall restoration of liver mass, although a delay in cell proliferation was observed. Prior to PH, the liver microcirculation in rats treated with thalidomide for 2 days was comparatively less than that in their corresponding controls; however, no significant difference between the groups was detected at any time-point following PH. Western blotting showed that the expression of VEGF was upregulated by hepatectomy and the expression levels in the two groups were equal at all studied time-points. The immunohistochemical staining revealed a waved pattern of VEGF expression which advanced from the periportal to pericentral area in both groups, but a slower advancement was detected in thalidomide-treated rats. In conclusion, thalidomide exerted no significant effects on the expression of VEGF and did not impair the overall restoration of liver mass in a rat model of PH-induced liver regeneration, providing supportive evidence for its use as an adjunct treatment modality for liver cancers.

Activated Protein C Restores Hepatic Microcirculation During Sepsis by Modulating Vasoregulator Expression

Activated protein C (aPC) promotes fibrinolysis while inhibiting coagulation and inflammation. In septic patients, aPC levels are depleted, and aPC treatment has emerged as a therapeutic option. To better understand the mechanism(s) by which aPC improves survival in sepsis, we sought to determine the effect of aPC treatment on hepatic vasoactive gene and protein expression, leading to changes in hepatic vascular responsiveness in a septic animal model. Under anesthesia, rats underwent sham or cecal ligation and puncture followed by aPC treatment (1 mg/kg, twice daily, i.v.). Treatment with aPC significantly decreased hepatic endothelin 1 (ET-1)/ET A receptor mRNA and protein expression. To determine the effect of aPC on hepatic microvasculature, ET-1-induced changes in liver microcirculation were assessed by intravital microscopy. This approach demonstrated aPC significantly improved hepatic perfusion index in the animals that underwent cecal ligation and puncture in the absence of significant changes in portal venous pressure. Furthermore, although aPC did not affect ET-1-dependent sinusoidal vasoconstriction, aPC induced hepatoprotective effects via enhanced red blood cell velocity. Collectively, these data demonstrate aPC ameliorates ET-1-dependent changes in hepatic microcirculation and improves hepatic function in the setting of sepsis.

In vivo assessment of the hepatic microcirculation after mesenterico-portal bypass (REX-shunt) using orthogonal polarization spectral imaging

Extrahepatic portal vein thrombosis, not associated with cirrhosis or tumours, is the second most frequent cause of portal hypertension worldwide. Especially in children, anatomic mesenterico-portal interposition (REX-shunt) has become an established treatment. The changes in hepatic microcirculation after reperfusion of the shunt have not been investigated so far. This study investigates the hepatic microcirculation before and after REX-shunt interposition using orthogonal polarization spectral imaging (OPS). Since 2004, three consecutive patients with extrahepatic portal vein thrombosis underwent REX-shunt interposition. We measured the hepatic microcirculation by OPS before and directly after REX-shunt reperfusion and analysed the capillary vessel diameter, red blood cell velocity, functional capillary density and volumetric blood flow. Furthermore, we compared our values with the physiological values of the hepatic microcirculation defined previously by other investigators. All shunts showed an excellent function in the follow-up investigations. The intra-individual microcirculatory analysis revealed a reduction in the red blood cell velocity after shunt reperfusion in particular. Our results provide preliminary evidence for the reversal of the hepatic arterial buffer response following the restoration of the portal venous blood flow. This may be a short-term effect because of the restored portal venous blood flow.

Perfusion CT findings in liver of patients with tumor during chemotherapy

To investigate the microcirculation changes in liver of patients with tumor during chemotherapy by perfusion computed tomography (CT). Sixty patients with tumor and 20 controls were enrolled in this study. Perfusion CT parameters of patients and controls were compared, including hepatic perfusion index (HPI), mean transit time (MTT), and permeability-surface area product (PS). Correlation between perfusion CT parameters, treatment cycle and alanine aminotransferase (ALT) level was studied. No difference was found in HPI (25.68% +/- 7.38% vs 26.82% +/- 5.13%), MTT (19.67 +/- 5.68 s vs 21.70 +/- 5.43 s) and PS (17.00 +/- 4.56 mL/100 mL per min vs 19.92 +/- 6.35 mL/100 mL per min) between patients and controls. The HPI and MTT were significantly higher in patients undergoing 2 cycles of chemotherapy than in controls and those undergoing 1 cycle of chemotherapy (29.76% +/- 5.87% vs 25.68% +/- 7.38% and 25.35% +/- 4.05%, and 25.61 +/- 5.01 s vs 19.67 +/- 5.68 s and 19.74 +/- 4.54 s, respectively, P < 0.05). The HPI was higher in patients with hepatic steatosis than in controls and those without hepatic steatosis (30.85% +/- 6.17% vs 25.68% +/- 7.38% and 25.70% +/- 4.24%, P < 0.05). Treatment cycle was well correlated with HPI and MTT (r = 0.40, r = 0.50, P < 0.01). ALT level was not correlated with perfusion CT parameters. HPI and MTT are significantly increased in patients with tumor during chemotherapy and well correlated with treatment cycle. Chemotherapy affects hepatic microcirculation in patients with tumor. Changes in hepatic microcirculation can be quantitatively assessed by perfusion CT.

Effect of Ischemic Preconditioning on Rat Liver Microcirculation Monitored with Laser Doppler Flowmetry

Ischemic preconditioning (IP) may protect the liver from ischemia-reperfusion (I-R) injury during liver resection. This study investigated the effect of IP on hepatic microcirculation (HM) and analyzed the objective parameters of the HM using laser Doppler flowmetry (LDF). We used male Wistar rats (250-280 g) that underwent normothermic, segmental liver ischemia. The animals were divided into eight groups: 30, 45, 60, and 90 min of ischemia with, or without, IP. Five minutes ischemia and 10 min reperfusion, in two cycles, were used to elicit IP. Changes of the hepatic microcirculation were studied by LDF with on-line computer monitoring and processing. Histological alterations, liver enzymes, bilirubin, and TNF-alpha level were all measured simultaneously. Reperfusion was assessed by post-ischemia flux plateau maximum (PM) and by the area under the reperfusion-curve (RA). Both PM and RA are inversely correlated with the duration of ischemia. The groups with IP had significantly (P < 0.05) higher flow values than groups without preconditioning. IP before liver ischemia resulted in significantly (P < 0.05) lower TNF-alpha levels at the end of the 30-min reperfusion. Lower serum ALT, LDH, and bilirubin levels could only be observed at 45 and 60 min I-R during the first post-operative day. On the seventh post-operative day there were no significant differences between the I-R and IP + IR groups in any of these parameters. The benefit of ischemic preconditioning on hepatic microcirculation was well demonstrated with this method, which has never been described before, in this context. Changes in hepatic microcirculation can be precisely investigated by laser Doppler flowmetry using the standardization and transformation described in this paper.

Effects of acetaminophen on hepatic microcirculation in mice

Acetaminophen (APAP) intoxication from overdosing can result in severe hepatic damage, which is characterized by hemorrhagic centrilobular necrosis and by towering the levels of transaminase. The APAP-induced hepatic necrosis is preceded by centrilobular microvascular congestion thought to be due to collapse of the sinusoidal wall and the infiltration of blood elements into the space of Disse [1]. These findings suggest that, in addition to direct hepatocellular damage, sinusoidal endothelial cells (SECs) participate in liver injury elicited by APAP overdose. As a result, the present study was conducted to examine changes in hepatic microcirculation after APAP administration using in vivo microscopic methods.

Impairment of hepatic microcirculation as an early manifestation of acute rejection after clinical liver transplantation

DURING REJECTION episodes after liver transplantation, T cell activation is partly the result of intracellular adhesion molecule–I (ICAM-I) expression on hepatocytes. As an adhesion molecule, ICAM-I generally induces leucocyte-endothelium interaction in the liver predominantly along postsinusoidal venules. An increase of endothelial leucocyte adherence is considered to be a mechanism of hepatic microcirculatory impairment after ischemia and reperfusion. However, clinical data on potential changes of hepatic microcirculation during rejection are missing. After experimental validation, thermodiffusion represents a tool to allow continuous monitoring of liver microcirculation during the first week postoperatively. It was the goal of this study to quantify hepatic microperfusion in patients with early rejection.

Effect of lipopolysaccharides on erythrocyte flow velocity in rat liver.

Although endotoxin exacerbates hepatic microcirculatory disturbance, little is known of the way in which it acts on the hepatic microcirculation. We measured endotoxin-induced changes in hepatic microcirculation and investigated the effect of endotoxin on hepatic microcirculation in rats. After male Wistar rats were anesthetized, a lobe of the liver was observed with an inverted intravital microscope. Erythrocytes (RBC) were labeled with fluorescein isothiocyanate (FITC) and injected. The flow velocity (FV) of FITC-RBC in sinusoids was measured with an off-line velocimeter. Portal pressure (PP) and mean arterial pressure (MAP) were measured with a catheter cannulated in the portal vein and the left carotid artery, respectively. After a small dose (1 mg/kg) of endotoxin had been administered intravenously, FV decreased and PP increased gradually after 30 min. MAP showed no significant change, except for an initial decrease. However, when 5 mg/kg of endotoxin was administered, FV and PP increased, with a peak at 10 min, which was not observed with the small dose. In the late phase, FV decreased and PP increased, as was seen with the small dose. Endotoxin increased serum aspartate aminotransferase and lactate dehydrogenase activities. These results suggest that endotoxin induces hepatic microcirculatory disturbance, which may cause liver injury.

Transcatheter liver lobar ablation: an experimental trial in an animal model.

Complete embolization of tumor tissue together with surrounding liver sufficiently prevents collateral blood supply to the tumor, offering curative treatment for hepatic malignancies. The present experiment was designed to test the feasibility of hepatic lobar ablation by means of the transcatheter chemoembolization technique. Five groups of rats (n = 6) were treated with a mixture of iodized oil/ethanol in ratios of 5:1, 4:1, 3:1, 1:1, and 1:0, which was injected selectively into the right-lobe artery until saturation during open surgery. Another group (n = 6) was studied using in vivo microscopy to observe the distribution of the mixture in the liver and changes in hepatic microcirculation. Ethiodol/ethanol mixture entered the portal vein after injection into the hepatic artery creating dual, complete arterial and portal venous embolization. Lobar ablation effects were achieved in 2 weeks in the 5:1, 4:1, and 3:1 ratio groups, indicated by the lobe/liver weight measurements (p < 0.001 vs normal liver). Hepatic arterial administration of the Ethiodol/ethanol mixture creates dual hepatic arterial and portal venous embolization, achieving a lobar ablation effect.

Liver resection: prolonged inflow occlusion in human cirrhotic livers.

To evaluate the tolerance of the cirrhotic liver to extended warm ischaemia, 47 patients with cirrhosis who underwent liver,resection over a 4-year period were studied retrospectively. Three groups of patients were identified. In group 1 (14 patients) liver resection was performed under conditions of portal triad occlusion ranging from 50 to 75 (mean 57.1) min. Group 2 (12 patients) was treated with portal occlusion for a period ranging from 30 to 42 (mean 33.1) min. Group 3 comprised 21 patients who underwent hepatectomy using conventional techniques. Mean blood loss was significantly reduced by portal triad occlusion (819 ml in group 1,523 ml in group 2) compared with the conventional techniques (1652 ml in group 3) (P<0.05, group 1 versus group 3; P<0.01, group 2 versus group 3). Hospital death occurred in three of the 21 patients in group 3 but in no patient who underwent portal triad occlusion. The morbidity rate was lower in the two occlusion groups (four of 26 patients) than in group 3 (six of 21). Bilirubin metabolism was substantially better after surgery in the occlusion groups (P<0.05, groups 1 and 2 versus group 3 at day 14). Although the serum levels of transaminases were significantly raised until day 3 in patients undergoing long term occlusion, the cirrhotic liver withstood the ischaemia-reperfusion insult, as assessed by changes in hepatic microcirculation, lipid peroxidation and the morphology of hepatic sinusoids. It is concluded that prolonged ischaemia during liver resection can be sustained in patients with cirrhosis and without high-risk factors.

Tumor necrosis factor-alpha produces hepatocellular dysfunction despite normal cardiac output and hepatic microcirculation

Although plasma levels of tumor necrosis factor (TNF) are elevated and hepatocellular dysfunction occurs even in the early hyperdynamic stage of sepsis, the precise mechanism responsible for this dysfunction remains unknown. Although TNF at high doses produces circulatory failure, it is not known whether the dose of TNF that does not adversely affect hemodynamics alters hepatocellular function. To study this, recombinant murine TNF-alpha was infused intravenously (0.05 or 0.25 mg/kg) over 30 min in normal rats. At 1 and 4 h after infusion of TNF-alpha or an equivalent volume of saline, hepatocellular function [i.e., maximum velocity (Vmax) and Michaelis constant (Km)] was assessed using in vivo indocyanine green clearance without blood sampling. Additional parameters measured were as follows: cardiac output by dye dilution, hepatic microcirculation by laser Doppler flowmetry and colloidal carbon infusion, plasma TNF and interleukin-6 (IL-6) by cytokine-dependent cellular assays, and plasma glucose enzymatically. The results indicate that although infusion of 0.05 mg/kg TNF-alpha did not affect Vmax and Km, its infusion at 0.25 mg/kg produced a significant depression of hepatocellular function and markedly increased the synthesis and/or release of IL-6. TNF-alpha-induced hepatocellular dysfunction was not associated with any significant changes in hepatic microcirculation, plasma glucose, cardiac output, and other measured hemodynamic parameters. Thus hepatocellular dysfunction observed after TNF infusion may be due to the direct effect of this cytokine alone or in combination with IL-6.

Morphological changes of hepatic microcirculation in experimental rat cirrhosis: A scanning electron microscopic study

Morphological changes of hepatic microcirculation, especially peribiliary plexus, in experimental rat cirrhosis that resulted from the repeated intraperitoneal injections of N-diethylnitrosamine, 100 mg/kg body weight/one shot/week, were examined by scanning electron microscope. Control rats were treated with saline. Whole blood vessels of the rats were perfused by saline and stuffed with methylmethacrylated resin. Multiple nodular changes were seen in the livers after the five injections (5 wk) of N-diethylnitrosamine, and diffuse nodular transformations mimicking human cirrhosis after six injections (6 wk) were also seen. Overall changes in experimental rats were numerous vascular channels mainly composed of venous branches around the parenchymal nodules, increased arterioportal anastomoses and flattening of veins, especially hepatic vein branches. Peribiliary plexuses of the experimental rats were much richer in the vessels than those of the controls, and many dilated veins, ramified from portal vein branches, were present in the former. Direct connections between peribiliary plexuses and sinusoids or between peribiliary plexuses and portal veins increased in the experimental rats. Studies concerning microcirculatory changes of peribiliary plexuses in experimental rat cirrhosis are rare. It was concluded that the abnormal peribiliary plexuses in this experimental series might participate in a collateral circulation under a state of portal hypertension. (HEPATOLOGY 1991;13:952–956).