Portal branch ligation induces a hepatic arterial buffer response, microvascular remodeling, normoxygenation, and cell proliferation in portal blood-deprived liver tissue

Acute portal hypertension using portal vein ligation abrogates TRAIL expression of liver-resident NK cells

The effects of acute portal hypertension (PHT), which is reported as poor prognostic factors in patients with hepatocellular carcinoma, are not well known on the liver immune system, including natural killer (NK) cells. The aim of this study, therefore, was to investigate how acute PHT influences the functions and characteristics of liver‐resident NK (lr‐NK) cells using an acute PHT mouse model. Acute PHT decreased the number of tumor necrosis factor–related apoptosis‐inducing ligand (TRAIL⁺) lr‐NK cells by about 20% and attenuated cytotoxic activity against the Hepa1‐6 cell line by about 40%. Among various cytokine, only interleukin‐33 (IL‐33), which inhibits NK activity, significantly increased after portal vein ligation (PVL). Because lr‐NK cells highly expressed ST2/IL‐33R, IL‐33 co‐culture significantly suppressed TRAIL expression on lr‐NK cells by about 50%, and IL‐33 administration markedly decreased TRAIL expression and cytotoxic activity of lr‐NK cells. Furthermore, the TRAIL⁺ NK cells population was maintained by anti‐IL33 antibody or following portosystemic shunt procedure even after PVL. Finally, we demonstrated that IL‐33 decreased TRAIL expression in lr‐NK cells via AKT–forkhead box O (FoxO) and mitogen‐activated protein kinase (MAPK) signaling. Conclusion: This work demonstrates that PHT suppresses the TRAIL⁺ lr‐NK cell population and antitumor activities in the liver. Additionally, Akt‐FoxO and MAPK signaling pathways attenuate the TRAIL expression in lt‐NK cells via IL‐33 receptor in mice.

Increased Hepatic Microvascular Density, Oxygenation, and VEGF in the Hypertrophic Lobe following Portal Vein Embolization in Rabbits

INTRODUCTION

The microvascular events following portal vein embolization (PVE) are poorly understood despite the pivotal role of the microcirculation in liver regeneration and tumor progression. We aimed to assess the changes in hepatic microvascular perfusion and neo-angiogenesis after experimental PVE.

METHODS

PVE of the cranial liver lobes was performed in 12 New Zealand White rabbits divided into 2 groups of permanent (P-PVE) and reversible PVE (R-PVE), respectively. Hepatobiliary scintigraphy and CT were used to evaluate hepatic function and volume. Hepatic microcirculation was assessed using a handheld vital microscope (Cytocam) to measure microvascular density (total vessel density; TVD) before PVE, right after PVE, and 20 min after PVE, as well as at 14 days (D14 post-PVE) and 35 days (D35 post-PVE). Additionally, on D35, microvascular PO2 and liver parenchymal VEGF were assessed.

RESULTS

Eleven rabbits were included after PVE (R-PVE, n = 5; P-PVE, n = 6). TVD in the nonembo-lized (hypertrophic) lobes was higher than in the embolized (atrophic) lobes of the P-PVE group at D35 post-PVE (36.7 ± 7.2 vs. 23.4 ± 4.9 mm/mm2; p < 0.05). In the R-PVE group, TVD in the nonembolized lobes was not increased at D35. Function and volume were increased in the nonembolized lobes of the P-PVE group compared to the embolized lobes, but not in the R-PVE group. Likewise, the mmicrovascular PO2 and VEGF staining rate were higher in the nonembolized lobes of the P-PVE group at D35 post-PVE.

DISCUSSION/CONCLUSION

Successful volumetric and functional hypertrophy of the nonembolized lobe was accompanied by microvascular alterations featuring increased neo-angiogenesis, microvascular density, and microvascular oxygen pressure following P-PVE.

Assessment of hepatic microvascular flow and density in patients undergoing preoperative portal vein embolization

BACKGROUND

The microvascular effects occurring after unilateral preoperative portal vein embolization (PVE) are poorly understood. The aim of this study was to assess the microvascular changes in the embolized and the non-embolized lobes after right PVE.

METHODS

Videos of the hepatic microcirculation in patients undergoing right hemihepatectomy following PVE were recorded using a handheld vital microscope (Cytocam) based on incident dark field imaging. Hepatic microcirculation was measured in the embolized and the non-embolized lobes at laparotomy, 3-6 weeks after PVE. The following microcirculatory parameters were assessed: total vessel density (TVD), microcirculatory flow index (MFI), proportion of perfused vessel (PPV), perfused vessel density (PVD), sinusoidal diameter (SinD) and the absolute red blood cell velocity (RBCv).

RESULTS

16 patients after major liver resection were included, 8 with and 8 without preoperative PVE. Microvascular density parameters were higher in the non-embolized lobes when compared to the embolized lobes (TVD: 40.3 ± 8.9 vs. 26.8 ± 4.6 mm/mm² (p < 0.003), PVD: 40.3 ± 8.8 vs. 26.7 ± 4.7 mm/mm² (p < 0.002), SinD: 9.2 ± 1.7 vs. 6.3 ± 0.8 μm (p < 0.040)). RBCv, PPV and the MFI were not significantly different.

CONCLUSION

The non-embolized lobe has a significantly higher microvascular density, however without differences in microvascular flow. These findings indicate increased angiogenesis in the hypertrophic lobe.

In situ splitting after selective partial portal vein ligation or simultaneous hepatic artery ligation promotes liver regeneration

This study seeks to compare the impact of selective partial portal vein ligation (PPVL) or the combination of simultaneous hepatic artery ligation (PPVAL) with in situ splitting (ISS) on liver regeneration and injury. Rats were randomized into three groups; namely: selective PVL, PPVL + ISS and PPVAL + ISS. The changes in hepatic hemodynamics, liver regeneration and hepatocytic injury were examined. Blood flow to the left portal branch and the microcirculation of the left median lobe after PPVL or PPVAL was significantly reduced. Liver regeneration of PPVAL + ISS group was more pronounced than that in the PPVL + ISS and PVL groups at 48 and 72 hours as well as 7 d postoperatively. The serum biochemical markers and histopathological examination demonstrated reduced levels of liver injury in the PPVL + ISS group. Injury to hepatocytes was more pronounced with PPVAL + ISS than PVL. HGF, TNF-α and IL-6 expression in the regenerated lobes in both PPVAL + ISS and PPVL + ISS groups increased significantly when compared to the PVL group. We demonstrated that both PPVL + ISS and PPVAL + ISS were effective and feasible means of inducing remnant liver hypertrophy and could serve as a rapid clinical application for qualified patients.

Laparoscopic associating liver tourniquet and portal ligation combined rescue transhepatic arterial embolization for staged hepatectomy: A case report

RATIONALE

Staged hepatectomy is an important surgical method for large hepatocellular carcinoma (HCC). However, the insufficient future liver remnant (FLR) is still the major barrier in stage II hepatectomy. We herein reported a case of laparoscopic associating liver tourniquet and portal ligation combined rescue transhepatic arterial embolization (TAE) for staged hepatectomy.

PATIENT CONCERNS

Laparoscopic associating liver tourniquet and portal ligation for staged hepatectomy (ALTPS) was performed for cirrhotic HCC in stage I. To stimulate the growth of FLR, a "rescue" TAE was initiated before stage II.

DIAGNOSE

HCC with hepatitis B cirrhosis.

OUTCOMES

Two weeks later after TAE, the FLR achieved sufficient hypertrophy and stage II surgery was successfully performed. The patient was discharged 7 days after the second stage without serious complication. During the follow-up at postoperative 6 months, the patient underwent radiofrequency ablation, because contrast-enhanced ultrasonography showed 1 cm tumor recurrence in the remnant liver.

LESSONS

Rescue TAE plays an important role to stimulate the increasing of FLR after ALTPS.

Next generation sequencing of progressive colorectal liver metastases after portal vein embolization

Portal vein embolization (PVE) can be required to stimulate liver regeneration before hepatectomy for colorectal liver metastasis (CRCLM), however PVE may also trigger CRCLM progression in patients initially exhibiting chemotherapy response. Using RNA-seq, we aimed to determine the molecular networks involved in metastatic progression in this context. A prospective study including all CRCLM patients undergoing PVE prior to hepatectomy was conducted. Paired biopsies of metastatic lesions were obtained prior to and after PVE and total RNA was isolated and used to prepare Illumina rRNA-depleted TruSeq stranded cDNA libraries for HiSeq 100 bp paired-end sequencing. Patients were classified with progression of disease (PD_PVE) or stable disease (SD_PVE) post-PVE using 3D-CT tumor volumetric analysis.

RESULTS

Twenty patients were included, 13 (65.0%) in the PD_PVE group (median 58.0% (18.6-234.3) increase in tumor volume) and 7 (35.0%) in the SD_PVE group exhibiting continuous chemotherapy response (median -14.3% (-40.8 to -2.8) decrease in tumor volume) (p < 0.0001). Our results showed that progressive CRCLM after PVE undergo gene expression changes that indicate activation of core cancer pathways (IL-17 (p = 5.94 × 10^-03), PI3K (p = 8.71 × 10^-03), IL6 and IGF-1 signaling pathways), consistent with changes driven by cytokines and growth factors. Differential expression analysis in a paired model of progression (EdgeR, DeSeq) identified significantly dysregulated genes in the PD_PVE group (FOS, FOSB, RAB20, IRS2).

CONCLUSION

Differentially expressed genes and pathways with known links to cancer and metastasis were identified post-PVE in patients with disease progression. Highlighting these molecular changes is a crucial first step towards development of targeted therapeutic strategies that may mitigate the effects of PVE on tumor growth.

Portal branch ligation does not counteract the inhibiting effect of temsirolimus on extrahepatic colorectal metastatic growth

The mTor-inhibitor temsirolimus (TEM) has potent anti-tumor activities on extrahepatic colorectal metastases. Treatment of patients with advanced disease may require portal branch ligation (PBL). While PBL can induce intrahepatic tumor growth, the effect of PBL on extrahepatic metastases under TEM treatment is unknown. Therefore, we analyzed the effects of TEM treatment on extrahepatic metastases during PBL-associated liver regeneration. GFP-transfected CT26.WT colorectal cancer cells were implanted into the dorsal skinfold chamber of BALB/c-mice. Mice were randomized to four groups (n = 8). One was treated daily with TEM (1.5 mg/kg), PBS-treated animals served as controls. Another group underwent PBL of the left liver lobe and received daily TEM treatment. Animals with PBL and PBS treatment served as controls. Tumor vascularization and growth as well as tumor cell migration, proliferation and apoptosis were studied over 14 days. In non-PBL animals TEM treatment inhibited tumor cell proliferation as well as vascularization and growth of the extrahepatic metastases. PBL did not influence tumor cell engraftment, vascularization and metastatic growth. Of interest, TEM treatment significantly reduced tumor cell engraftment, neovascularization and metastatic groth also after PBL. PBL does not counteract the inhibiting effect of TEM on extrahepatic colorectal metastatic growth.

Systematic review of the influence of chemotherapy-associated liver injury on outcome after partial hepatectomy for colorectal liver metastases

BACKGROUND

The impact of chemotherapy-associated liver injury (CALI) on postoperative outcome in patients undergoing partial hepatectomy for colorectal liver metastases (CRLM) remains controversial. The objective of this study was to clarify the effect of CALI (sinusoidal dilatation (SD), steatosis and steatohepatitis) on postoperative morbidity and mortality by investigating a large data set from multiple international centres.

METHODS

PubMed and Embase were searched for studies published between 1 January 2004 and 31 December 2013 with keywords 'chemotherapy', 'liver resection', 'outcome' and 'colorectal metastases' to identify potential collaborating centres. Univariable and multivariable analyses were performed using binary logistic regression models, with results presented as odds ratios (ORs) with 95 per cent confidence intervals.

RESULTS

A consolidated database comprising 788 patients who underwent hepatectomy for CRLM in eight centres was obtained. In multivariable analyses, severe SD was associated with increased major morbidity (Dindo-Clavien grade III-V; OR 1·73, 95 per cent c.i. 1·02 to 2·95; P = 0·043). Severe steatosis was associated with decreased liver surgery-specific complications (OR 0·52, 95 per cent c.i. 0·27 to 1·00; P = 0·049), whereas steatohepatitis was linked to an increase in these complications (OR 2·08, 1·18 to 3·66; P = 0·012). Subgroup analysis showed that lobular inflammation was the sole component associated with increased overall morbidity (OR 2·22, 1·48 to 3·34; P = 0·001) and liver surgery-specific complications (OR 3·35, 2·11 to 5·32; P < 0·001). Finally, oxaliplatin treatment was linked to severe SD (OR 2·74, 1·67 to 4·49; P < 0·001).

CONCLUSION

An increase in postoperative major morbidity and liver surgery-specific complications was observed after partial hepatectomy in patients with severe SD and steatohepatitis. Postoperative liver failure occurred more often in patients with severe SD.

Limits of and Complications after Embolization of the Hepatic Artery and Portal Vein to Induce Segmental Hypertrophy of the Liver: A Large Mini-Pig Study

Background: The aim of this study was to compare arterial embolization (AE) with portal vein embolization (PVE) for the induction of segmental hypertrophy regarding procedural efficacy, safety and outcome. Methods: A total of 29 mini pigs were subjected to PVE, AE or assigned to the sham (SO) group. Correspondingly, 75% of the hepatic artery or portal vein branches were embolized. Growth and atrophy of the liver lobes, calculating the liver-to-body weight index (LBWI), laboratory data, arteriography, portography, Doppler ultrasound (US) and histopathology were analyzed. Results: After PVE, 2 animals had to be excluded due to technical problems. After AE, 4 animals had to be excluded because of technical problems and early sacrifice. Postprocedural US demonstrated effective AE and PVE of the respective lobes. Four weeks after PVE, portography showed a slow refilling of the embolized lobe by collateral portal venous vessels. Four weeks after AE, arteriography revealed a slight revascularization of the embolized lobes by arterial neovascularization. Segmental AE led to extensive necrotic and inflammatory alterations in the liver and bile duct parenchyma. Significant hypertrophy of the non-embolized lobe was only noted in the PVE group (LBWI: 0.91 ± 0.28%; p = 0.001). There was no increase in the non-embolized lobe in the AE (LBWI: 0.45 ± 0.087%) and SO group (LBWI: 0.45 ± 0.13%). Conclusion: PVE is safe and effective to induce segmental hypertrophy. Portal reperfusion by collateral vessels may limit hypertrophy. AE did not increase the segmental hepatic volume but carries the risk of extensive necrotic inflammatory damage.

Increased Hepatic Arterial Blood Flow Measured by Hepatic Perfusion Index in Hepatosplenic Schistosomiasis: New Concepts for an Old Disease

BACKGROUND

Portal vein obstructive lesions associated with hypertrophy of the hepatic artery territory are observed in Schistosoma mansoni schistosomiasis. Liver perfusion scintigraphy is a method used for evaluation of hepatic perfusion changes in liver diseases. It has been suggested that, like in cirrhosis, where compensatory increase in perfusion through the hepatic artery is documented, perfusion changes occur in hepatosplenic schistosomiasis (HSS).

AIMS

This study aims to determine changes in liver hemodynamics using hepatic perfusion scintigraphy and correlate them with clinical and laboratory variables and ultrasound findings in HSS.

METHODS

Nineteen patients with schistosomiasis underwent ultrasound evaluation of degree of liver fibrosis, splenic length, and splenic and portal vein diameter, digestive endoscopy, and quantification of platelets. Subsequently, perfusion scintigraphy with measurement of hepatic perfusion index (HPI) was performed.

RESULTS

It was observed that patients with hepatosplenic schistosomiasis had significantly higher HPI compared with normal individuals (p = 0.0029) and that this increase correlated with splenic length (p = 0.038) and diameter of esophageal varices (p = 0.0060). Angioscintigraphy showed high accuracy for predicting presence of large esophageal varices.

CONCLUSIONS

Angioscintigraphy could show that patients with HSS had increased HPI, featuring greater liver "arterialization," as previously described for cirrhotic patients. Correlations were also observed between HPI and longitudinal splenic length, caliber of esophageal varices, caliber of portal vein, and blood platelet count. Angioscintigraphy is a promising technique for evaluation of hepatosplenic schistosomiasis.

[Contralateral hepatic hypertrophy following unilateral yttrium-90 radioembolization : Implications for liver surgery]

BACKGROUND

Preservation of an adequate future liver remnant (FLR) is the principal limitation to liver surgery in patients with primary or secondary liver malignancies. Hence, methods to increase the volume of the FLR in preparation for liver resection are gaining in importance.

OBJECTIVE

In addition to the traditional methods for induction of FLR hypertrophy, such as portal vein embolization (PVE) or portal vein ligation (PVL) with or without parenchymal dissection (ALPPS, in situ split), radioembolization (RE) using yttrium-90 microspheres also leads to a volume increase of non-embolized liver parenchyma. This review outlines its potential role as an alternative procedure for induction of liver hypertrophy.

MATERIAL AND METHODS

Synopsis and critical discussion of the available literature on the mechanisms of induction of liver hypertrophy, the advantages and drawbacks of the traditional methods, and current research on volume changes associated with RE as well as their implications for possible clinical use in preparation for liver surgery.

RESULTS

Both PVE and PVL can achieve a substantial contralateral volume gain of up to 70 %. The development of contralateral hypertrophy can be accelerated by dissecting the liver parenchyma along the intended plane of resection in addition to PVL (in situ split). Compared to these methods, RE achieves less contralateral liver hypertrophy; however, this effect should not be disregarded as RE provides effective treatment of ipsilateral liver tumors along with induction of hypertrophy and may be associated with a reduced risk of tumor progression compared to PVE and PVL.

CONCLUSION

The available data suggest that RE can complement the armamentarium of methods for induction of FLR hypertrophy in specific situations. Further studies are needed to establish its definitive role for this indication and are in preparation.

The significance of nonobstructive sinusoidal dilatation of the liver: Impaired portal perfusion or inflammatory reaction syndrome

Sinusoidal dilatation found in the absence of an impaired sinusoidal blood outflow has been so far of unclear significance. Sinusoidal dilatation may actually be a nonspecific feature of impaired portal venous blood inflow, whatever the cause, or a feature of severe systemic inflammatory reaction syndrome, whatever the cause. Sinusoidal dilatation is mainly located in the centrilobular area even in the absence of an outflow block. A predominantly periportal location is specifically found in oral contraceptive users, associated with an inflammatory condition. There is strong evidence for the association of sinusoidal dilatation and oxaliplatin-based chemotherapy but not for estroprogestative steroids or thiopurine derivatives. Exposure to anabolic androgen steroids appears to cause sinusoidal changes different from a mere sinusoidal dilatation.

CONCLUSION

There is evidence of activation of the interleukin-6 and vascular endothelial growth factor pathways in sinusoidal dilatation, but the mechanisms linking the activation of these pathways with the microvascular changes must be identified.

Liver regeneration model in growing rats with hepatic artery ligation: histologic and molecular studies

BACKGROUND

Liver transplantation is an effective treatment for irreversible liver diseases. The incidence of hepatic artery thrombosis remains high. Our objective was to analyze the effect of ligature of the hepatic artery on liver regeneration in a growing animal model.

METHODS

Seventy-five male Wistar rats were divided into the following 3 groups: group 1 (sham, G1): incision without intervention; group 2 (G2): 70% hepatectomy; group 3 (G3): 70% hepatectomy and ligation of the hepatic artery. Preceding the 70% hepatectomy, a hepatic artery ligature was performed with resection of a segment of the artery. The liver specimens were stained with hematoxylin-eosin, and immunohistochemical staining for Ki-67 was performed. The expression of the interleukin (IL) 6 gene was studied by means of reverse-transcription polymerase chain reaction.

RESULTS

G2 and G3 demonstrated similar tendencies toward an increase in the gain weight ratio over time. The mitotic activity was significantly lower at 72 hours in G3 than in G2. There was no difference between Ki-67 staining between G2 and G3. The expression of the IL-6 gene was present in all of the groups, lower in G1, with no difference between G2 and G3.

CONCLUSIONS

The experimental model was feasible and adequate for these investigations. Hepatectomy stimulated hepatocyte proliferation, and the obstruction of the arterial flow did not affect liver regeneration.

Hepatic proliferation and angiogenesis markers are increased after portal deprivation in rats: a study of molecular, histological and radiological changes

Background & Aims

To determine the pathogenesis of liver nodules, and lesions similar to obliterative portal venopathy, observed after portosystemic shunts or portal vein thrombosis in humans.

Methods

We conducted an experimental study comparing portacaval shunt (PCS), total portal vein ligation (PVL), and sham (S) operated rats. Each group were either sacrificed at 6 weeks (early) or 6 months (late). Arterial liver perfusion was studied in vivo using CT, and histopathological changes were noted. Liver mRNA levels were quantified by RT-QPCR for markers of inflammation (Il10, Tnfa), proliferation (Il6st, Mki67, Hgf, Hnf4a), angiogenesis: (Vegfa, Vegfr 1, 2 and 3; Pgf), oxidative stress (Nos2, and 3, Hif1a), and fibrosis (Tgfb). PCS and PVL were compared to the S group.

Results

Periportal fibrosis and arterial proliferation was observed in late PCS and PVL groups. CT imaging demonstrated increased arterial liver perfusion in the PCS group. RT-QPCR showed increased inflammatory markers in PCS and PVL early groups. Tnfa and Il10 were increased in PCS and PVL late groups respectively. All proliferative markers increased in the PCS, and Hnf4a in the PVL early groups. Mki67 and Hnf4a were increased in the PCS late group. Nos3 was increased in the early and late PCS groups, and Hif1a was decreased in the PVL groups. Markers of angiogenesis were all increased in the early PCS group, and Vegfr3 and Pgf in the late PCS group. Only Vegfr3 was increased in the PVL groups. Tgf was increased in the PCS groups.

Conclusions

Portal deprivation in rats induces a sustained increase in intrahepatic markers of inflammation, angiogenesis, proliferation, and fibrosis.

Tumour growth of colorectal rat liver metastases is inhibited by hepatic arterial infusion of the mTOR-inhibitor temsirolimus after portal branch ligation

Portal branch ligation (PBL) can be performed before major hepatic resection of colorectal liver metastases (mCRC) to increase the remnant liver mass. However, PBL may also stimulate mCRC growth through hepatic arterial hyperperfusion and growth factor release. Herein, we studied whether hepatic arterial infusion (HAI) of the mTOR-inhibitor temsirolimus (Tem) is capable of inhibiting the growth of colorectal liver metastases after PBL. WAG/Rij rats were randomized to four groups (n=6 each) and underwent subcapsular implantation of 5×10(5) CC531 cells into the left liver lobe. The animals of two groups underwent simultaneous PBL of the tumour bearing liver lobe. Ten days later animals underwent a HAI either of temsirolimus (Tem and PBL Tem) or saline solution (Sham and PBL Sham). Tumour size was analyzed at days 10 and 13 using three-dimensional ultrasound. In Sham controls tumour volume increased by 43%. After PBL Sham tumour volume increased by 52%. In contrast, in animals undergoing HAI of temsirolimus the tumour growth was not only completely inhibited, but tumour volume was found decreased, irrespective of PBL. After HAI of temsirolimus immunohistochemistry revealed an increased cleaved caspase-3 activity, indicating stimulation of apoptotic cell death. In parallel temsirolimus treatment was associated with a significant reduction of PECAM-1 positive cells within the tumour tissue, implying a reduced tumour vascularisation. HAI of temsirolimus is capable of inhibiting the growth of CC531 colorectal rat liver metastases also after PBL.

Triggered liver regeneration: from experimental model to clinical implications

BACKGROUND

Major liver resection is the only therapeutic option for patients with malignant liver tumors. However, extended hepatectomy often leads to postoperative liver failure, mainly due to insufficient amounts of the remnant liver. Recently, selective portal vein occlusion (PVO) has been introduced to increase the remnant liver volume. This novel surgical technique initiated a progressive development in liver surgery, resulting in a significant increment in potential candidates for curative liver resection.

SUMMARY

The theoretical basis for this great advancement is formed by an understanding of the mechanisms of PVO-induced liver regeneration, mainly obtained from animal studies. The aim of this review is to give a comprehensive overview of the relevant animal models of PVO and to discuss the main characteristics of triggered liver regeneration, including the induced hemodynamic, morphological and functional alterations as well as the underlying molecular mechanisms, which might be of interest in both the laboratory and the clinic. Key Messages: Although basic research revealed the main characteristics of PVO-triggered liver regeneration within the last decades, several important issues regarding the regenerative process remain uncertain. To answer these open questions, additional well-designed animal experiments are needed in the future, which allow further refinement of this surgical technique.

Safety and efficacy of sequential transcatheter arterial chemoembolization and portal vein embolization prior to major hepatectomy for patients with HCC

OBJECTIVE

To evaluate the safety and efficacy of sequential transcatheter arterial chemoembolization (TACE )and portal vein embolization (PVE) before major hepatectomy for patients with hepatocellur carcinoma (HCC).

METHODS

In this retrospective case-control study, data were collected from patients who underwent sequential TACE and PVE prior to major hemihepactectomy. Liver volumes were measured by computed tomography volumetry before TACE, and preoperation to assess degree of future remnant liver (FRL) hypertrophy and to check whether intro- or extrohepatic metastasis existed. Liver function was monitored by biochemistry after TACE, prior to and after major hepatectomy.

RESULTS

Mean average FRL volume increased 32.3-71.4% (mean 55.4%) compared with preoperative FRL volume. After TACE, liver enzymes were elevated, but returned to normal in four weeks. During PVE and resection, no patient had intro- or extrohepatic metastasis.

CONCLUSION

Sequential TACE and PVE is an effective method to improve resection opportunity, expand the scope of surgical resection, and greatly reduce postoperative intra- and extrahepatic metastasis.

Effects of tacrolimus and insulin in a liver regeneration model in growing animals with portal vein stenosis: immunohistochemical and molecular studies

The aim of the present investigation was to describe a new model of liver regeneration in growing rats with reduced portal flow. In addition, it was studied whether tacrolimus and insulin could have any pro-regenerative effect under such conditions. Ninety-five rats were divided into five groups: Group 1 (sham), abdominal incision without intervention; Group 2, 70% hepatectomy; Group 3, 70% hepatectomy + PV stenosis; Group 4, 70% hepatectomy + portal vein stenosis + insulin; and Group 5, 70% hepatectomy + portal vein stenosis + tacrolimus. The remnant liver lobes were harvested for analyses. The liver weight decreased in the PV stenosis group and it increased with the use of insulin and tacrolimus. The mitotic activity was higher in the hepatectomy, insulin and tacrolimus groups and this parameter was reduced by portal stenosis. Levels of interleukin 6 (IL-6) were higher in the hepatectomy group compared to the sham and PV stenosis groups. The expression of IL-6 and Ki67 was significantly increased in the insulin and tacrolimus groups compared to the portal stenosis group. A highly reproducible model was standardized to study liver regeneration with portal blood inflow reduction in weaning rats. It was demonstrated that insulin or tacrolimus administration may partially reverse the harmful effects of PV stenosis.

Pathogenesis of Portal Cavernoma Cholangiopathy: Is it Compression by Collaterals or Ischemic Injury to Bile Ducts During Portal Vein Thrombosis?

The pathogenesis of portal cavernoma cholangiopathy (PCC) is important as it can impact the choice of treatment modalities. PCC consists of a reversible component, which resolves by decompression of collaterals as well as a fixed component, which persists despite the decompression of collaterals. The reversible component is due to compression by large collaterals located adjacent to the bile duct as well as possibly intracholedochal varices. The fixed component is likely to be due to ischemia at the time of portal vein thrombosis, local ischemia by compression as well as encasement by a solid tumor-like cavernoma comprising of fibrous hilar mass containing multiple tiny collateral veins rather than markedly enlarged portal collaterals. Although cholangiographic abnormalities in portal hypertension are common, the prevalence of symptomatic PCC is low. This is likely to be related to the cause of portal hypertension, the duration of portal hypertension and possibly the pattern of occlusion of the splenoportal axis. There may possibly be higher prevalence of symptomatic PCC in extension of the thrombosis to the splenomesentric veins.

Portal cavernoma cholangiopathy: consensus statement of a working party of the Indian national association for study of the liver

Portal cavernoma cholangiopathy (PCC) is defined as abnormalities in the extrahepatic biliary system including the cystic duct and gallbladder with or without abnormalities in the 1st and 2nd generation biliary ducts in a patient with portal cavernoma. Presence of a portal cavernoma, typical cholangiographic changes on endoscopic or magnetic resonance cholangiography and the absence of other causes of these biliary changes like bile duct injury, primary sclerosing cholangitis, cholangiocarcinoma etc are mandatory to arrive a diagnosis. Compression by porto-portal collateral veins involving the paracholedochal and epicholedochal venous plexuses and cholecystic veins and ischemic insult due to deficient portal blood supply or prolonged compression by collaterals bring about biliary changes. While the former are reversible after porto-systemic shunt surgery, the latter are not. Majority of the patients with PCC are asymptomatic and approximately 21% are symptomatic. Symptoms in PCC could be in the form of long standing jaundice due to chronic cholestasis, or biliary pain with or without cholangitis due to biliary stones. Endoscopic retrograde cholangiography has no diagnostic role because it is invasive and is associated with risk of complications, hence it is reserved for therapeutic procedures. Magnetic resonance cholangiography and portovenography is a noninvasive and comprehensive imaging technique, and is the modality of choice for mapping of the biliary and vascular abnormalities in these patients. PCC is a progressive condition and symptoms develop late in the course of portal hypertension only in patients with severe or advanced changes of cholangiopathy. Asymptomatic patients with PCC do not require any treatment. Treatment of symptomatic PCC can be approached in a phased manner, coping first with biliary clearance by nasobiliary or biliary stent placement for acute cholangitis and endoscopic biliary sphincterotomy for biliary stone removal; second, with portal decompression by creating portosystemic shunt; and third, with persistent biliary obstruction by performing second-stage biliary drainage surgery such as hepaticojejunostomy or choledochoduodenostomy. Patients with symptomatic PCC have good prognosis after successful endoscopic biliary drainage and after successful shunt surgery.

Tumour progression and liver regeneration--insights from animal models

Surgery remains the only curative treatment for colorectal liver metastases. For patients with multiple bilobar spread, extended hepatectomy might be required to achieve complete margin-free resection. In such cases, portal vein occlusion has been developed to induce preoperative hypertrophy of the future remnant liver and increase the resectability rate. Evidence now suggests that liver regeneration after hepatectomy and portal vein occlusion has a protumorigenic role, either through an upregulation of growth factors and cytokines or by haemodynamic changes in the blood supply to the liver. Experimental studies have reported a stimulatory effect of liver regeneration on the tumoral volume of liver metastases and on the metastatic potential of cells engrafted in the liver; this effect seems to depend on the timing of hepatectomy and portal vein occlusion. However, the variability of animal tumour models that are used for research in experimental colorectal liver metastases might account for some of the inconsistent and conflicting results. This Review presents clinical and experimental data pertaining to whether liver regeneration causes proliferation of tumour cells. We also analyse the different animal models of colorectal liver metastases in use and discuss current controversies in the field.

Portal vein embolization: rationale, technique, and current application

Portal vein embolization (PVE) is a technique used before hepatic resection to increase the size of liver segments that will remain after surgery. This therapy redirects portal blood to segments of the future liver remnant (FLR), resulting in hypertrophy. PVE is indicated when the FLR is either too small to support essential function or marginal in size and associated with a complicated postoperative course. When appropriately applied, PVE has been shown to reduce postoperative morbidity and increase the number of patients eligible for curative intent resection. PVE is also being combined with other therapies in novel ways to improve surgical outcomes. This article reviews the rationale, technical considerations, and current use of preoperative PVE.

Massive hepatic necrosis with toxic liver syndrome following portal vein ligation

Right portal vein ligation (PVL) is a safe and widespread procedure to induce controlateral liver hypertrophy for the treatment of bilobar colorectal liver metastases. We report a case of a 60-year-old man treated by both right PVL and ligation of the glissonian branches of segment 4 for colorectal liver metastases surrounding the right and median hepatic veins. After surgery, the patient developed massive hepatic necrosis with secondary pulmonary and renal insufficiency requiring transfer to the intensive care unit. This so-called toxic liver syndrome finally regressed after hemofiltration and positive oxygen therapy. Diagnosis of acute congestion of the ligated lobe was suspected. The mechanism suspected was an increase in arterial inflow secondary to portal vein ligation concomitant with a decrease in venous outflow due to liver metastases encircling the right and median hepatic vein. This is the first documented case of toxic liver syndrome in a non-cirrhotic patient with favorable issue, and a rare complication of PVL.

Laser speckle contrast imaging for assessment of liver microcirculation

OBJECTIVE

Laser speckle contrast imaging (LSCI) is a novel technique for microcirculation imaging not previously used in the liver. The aim of the present experimental study was to evaluate the use of LSCI for assessing liver microcirculation.

MATERIALS AND METHODS

In six male Wistar rats, the median liver lobe was exposed through a midline laparotomy. Liver blood perfusion was measured simultaneously with LSCI and sidestream dark-field (SDF) imaging at baseline and during sequential temporary occlusions of the portal vein, hepatic artery, and total blood inflow occlusion. Both the inter-individual variability associated with perfusion sampling area and comparisons in perfusion measurements between both imaging techniques were investigated and validated for the application of LSCI in the liver.

RESULTS

Occlusion of the hepatic artery, portal vein, and total inflow occlusion resulted in a significant decrease in LSCI signal to 74.7±6.4%, 15.0±2.3%, and 10.4±0.5% respectively (p<0.005 vs. baseline). The LSCI perfusion units correlated with sinusoidal blood flow velocity as measured with SDF imaging (Pearson's r=0.94, p<0.001). In a 10 mm diameter region of interest, as measured with LSCI, baseline inter-individual variability measured by the coefficient of variability was 13%.

CONCLUSION

Alterations in LSCI signal during sequential inflow occlusions were in accordance with previously published results on hepatic hemodynamics in the rat and correlated well with our SDF imaging-derived sinusoidal blood flow velocity measurements. We found that LSCI was able to produce reproducible real-time blood perfusion measurements of hepatic microcirculation. Compared to established techniques for liver blood perfusion measurements LSCI holds the advantages of non-contact measurements over large surfaces with a high speed of data acquisition.

Gastric estrogen increases pituitary estrogen receptor α and prolactin mRNAs during the different pathological conditions of the liver

Mammalian liver is an estrogen-responsive tissue mediated by hepatic estrogen receptors. Although Ueyama et al. (Endocrinology 143:3162-3170, 2002) have reported the presence of aromatase and active production of gastric 17β-estradiol in parietal cells, there are a few studies on gastric 17β-estradiol exploring the relationship between gastro-hepato function and the gastro-pituitary-gonadal axis. The alteration of gastric 17β-estradiol flow into the systemic circulation by portal vein ligation (PVL) or partial hepatectomy (PH), and the effect of gastric 17β-estradiol on the pituitary function was investigated. In the PVL rats, arterial 17β-estradiol increased 9.5 times that of controls on day 3, and gradually decreased near to control levels in the portal vein by 4 weeks, which was still 5 times higher than those in the arteries of the control rats. In the PH rats, arterial 17β-estradiol increased 2 times that of controls on day 3, and gradually decreased to the control levels. Regeneration and growth of the liver remnants were observed about 2 weeks after PH. In the PVL and PH animals, pituitary ERα and prolactin mRNAs levels increased, positively correlating with an increase of arterial 17β-estradiol levels. Both reduced LHβ mRNA. It is apparent that hepatic dysfunction causes changes in gastric 17β-estradiol levels in the systemic circulation; and that elevated gastric 17β-estradiol affects pituitary function(s). This data suggest that gastric 17β-estradiol has a pivotal role in the regulation of the gastro-hepato-pituitary axis.

Role of portal vein embolization in hepatocellular carcinoma management and its effect on recurrence: a case-control study

BACKGROUND

Liver regeneration that occurs after portal vein embolization (PVE) may have adverse effects on the microscopic tumor foci in the residual liver mass in patients with hepatocellular carcinoma (HCC).

METHODS

Fifty-four HCC patients with inadequate functional residual liver volume were offered PVE during a seven-year period. Among them, 34 (63%) patients underwent curative resection. They were compared with a matched control group (n = 102) who underwent surgery without PVE. Postoperative complications, pattern of recurrence, and survival were compared between groups.

RESULTS

In the PVE group, a pre-embolization functional residual liver volume of 23% (12-33.5%) improved to 34% (20-54%) (p = 0.005) at the time of surgery. When the two groups were compared, minor (PVE, 24%; control, 29%; p = 0.651) and major (PVE, 18%; control, 15%; p = 0.784) complications were similar. After a follow-up period of 35 months (standard deviation 25 months), extrahepatic recurrences were detected in 10 PVE patients (29%) and 41 control patients (40%) (p = 0.310). Intrahepatic recurrences were seen in 10 (29%) and 47 (46%) cases (p = 0.109) in the PVE and control groups, respectively. In the PVE group, 41% (n = 14) of the recurrences were detected before one year, compared with 42% (n = 43) in the control group (p = 1). Disease-free survival rates at 1, 3, and 5 years were 57, 29, and 26% in the control group and 60, 42, and 42% in the PVE group (log-rank, p = 0.335). On multivariate analysis, PVE was not a factor affecting survival (p = 0.821).

CONCLUSIONS

Portal vein embolization increases the resectability of initially unresectable HCC due to inadequate functional residual liver volume, and it has no deleterious oncological effect after major resection of HCC.

Hepatic arterial infusion with tumor necrosis factor-α induces early hepatic hyperperfusion

BACKGROUND

Hepatic arterial infusion (HAI) has been developed for high-dose regional chemotherapy of unresectable liver metastases or primary liver malignancies. While it is well known that high concentrations of tumor necrosis factor (TNF)-α damage tumor blood perfusion, there is no information on whether autochthonous liver perfusion is affected by HAI with TNF-α. Therefore, we investigated the effects of HAI with TNF-α on hepatic macro- and microvascular perfusion.

METHODS

Swabian Hall pigs were randomized into three groups. HAI was performed with either 20 or 40 µg/kg body weight TNF-α (n = 6 each group). Saline-treated animals served as controls (n = 6). Analyses during a 2-hour post-HAI observation period included systemic hemodynamics, portal venous and hepatic arterial blood flow, portal venous pressure, and the blood flow in the hepatic microcirculation.

RESULTS

HAI with TNF-α caused a slight decrease of mean arterial blood pressure (p < 0.001), which was compensated by a moderate increase of heart rate (p < 0.001). No further systemic side effects of TNF-α were observed. HAI with TNF-α further caused a slight but not significant decrease of portal venous blood flow (p = 0.737) in both experimental groups, paralleled by an increase of hepatic arterial blood flow (p = 0.023, 20 µg/kg; p = 0.034, 40 µg/kg) resulting in an overall hepatic hyperperfusion. The hepatic hyperperfusion after HAI with 20 µg/kg TNF-α was more pronounced and associated with a 40% decrease of the blood flow in the hepatic microcirculation (p = 0.009). HAI with 40 µg/kg TNF-α was only associated with a temporary and moderate total hepatic hyperperfusion and did not affect the blood flow in the hepatic microcirculation.

CONCLUSION

HAI with TNF-α causes a decrease of portal venous flow; however, this is overcompensated by an increased hepatic arterial blood flow, resulting in a total hepatic hyperperfusion. Moderate total hepatic hyperperfusion does not affect the blood flow in the hepatic microcirculation, while a persistent and more pronounced hyperperfusion may cause hepatic microcirculatory disturbances.

Impact of biomarkers expression before and after portal vein embolization on recurrence after two-stage hepatectomy for colorectal liver metastases

BACKGROUND

The adverse oncological effect of portal vein embolization (PVE) in patients with colorectal liver metastases (CLM) remains controversial. This study was designed to evaluate the effect of PVE on change of tumor characteristics using tumor specimens obtained from sequential hepatectomy before and after PVE.

METHODS

Between December 1996 and April 2009, among 55 patients who achieved two-stage hepatectomy (TSH) combined with PVE, 39 had available cancer tissue blocks from both the first- and second-stage hepatectomy and constituted the study population. The immunohistochemistry of Ki67 and Bcl-2 before and after PVE was performed. Biomarker expressions and clinicopathological variables were assessed and their impact on recurrence was analyzed.

RESULTS

Whereas tumor volume and carcinoembryonic serum level significantly increased after PVE, the expression of Ki67 and Bcl-2 remained similar before and after PVE. The Bcl-2 ratio (expressed as Bcl-2 after PVE over Bcl-2 before PVE) was an independent prognostic factor for recurrence-free survival (P=0.030). Patients with Bcl-2 ratio ≤ 1 had a significantly longer median recurrence-free survival compared with those with Bcl-2 ratio >1 receiving or not receiving adjuvant chemotherapy (24.8 months versus 8.9 or 5.8 months, respectively).

CONCLUSION

Bcl-2 ratio may predict early recurrence and identify patients who do not require postoperative chemotherapy in patients undergoing TSH with PVE for CLM.

Darbepoetin-α promotes neovascularization and cell proliferation in established colorectal liver metastases

BACKGROUND

The erythropoietin-analogue darbepoetin-α (DPO) improves liver function and regeneration after hepatectomy (Phx), however, also enhances Phx-induced tumor cell engraftment and neovascularization. Because it is unknown whether DPO also enhances the growth of established tumors, we herein studied the effect of DPO on established colorectal liver metastases after Phx.

METHODS

CT26.WT cells were implanted into the liver of BALB/c mice. Five days after tumor establishment, animals underwent 50% Phx and received 10 μg/kgBW DPO or saline. Non-Phx animals with DPO or saline-treatment served as controls. Seven days after Phx tumors were analyzed regarding blood vessel formation, leukocyte adhesion, cell proliferation, apoptotic cell death, and growth using intravital fluorescence microscopy, histology, and immunohistochemistry.

RESULTS

The growth of established colorectal liver metastases was slightly stimulated after DPO-treatment in hepatectomized and non-hepatectomized animals. However, tumor vessel formation and tumor cell proliferation were significantly enhanced after DPO-treatment in hepatectomized and non-hepatectomized mice compared with controls. Apoptotic cell death and leukocyte-endothelial cell interaction were significantly reduced after DPO-treatment.

CONCLUSION

Our study indicates that DPO-treatment promotes neovascularization and cell proliferation in established colorectal liver metastases of hepatectomized and non-hepatectomized mice. DPO-application in patients with colorectal liver metastases might promote tumor progression and should therefore be avoided.

Impact of portal branch ligation on tissue regeneration, microcirculatory response and microarchitecture in portal blood-deprived and undeprived liver tissue

Partial ligation of portal branches leads to atrophy of the deprived lobes and hypertrophy of the intact lobes. In this study we investigated the microcirculatory response and their consequences on tissue regeneration after left-sided portal branch ligation (PBL) in Sprague-Dawley rats. At day 1 and 3 after PBL the hepatic microcirculation was assessed by intravital microscopy (IVM). In addition histological, immunohistochemical and biochemical techniques were used to determine alterations of hepatic microarchitecture. IVM analysis of the microcirculation of the ligated hepatic lobes revealed significant alterations with a reduction in sinusoidal perfusion rate, a decrease of red blood cell velocity, an increase of sinusoidal diameter and a marked reduction in shear stress at days 1 and 3 after PBL. On the contrary, the non-ligated lobes presented with higher blood flow velocities, marked sinusoidal vasoconstriction and thus, shear stress elevation. In consequence, ligated liver lobes exhibited marked cell apoptosis and necrosis, being accompanied by massive intrahepatic leukocyte accumulation and a ~30% weight loss. The non-ligated liver tissue showed marked PCNA expression and thereby completely compensated weight loss. Beside full restoration of liver mass, sinusoidal blood flow was comparable in ligated and non-ligated lobes as well as in sham-treated controls. This study shows that the liver aims at constant tissue mass and blood flow, most probably for maintenance of adequate clearance function. In addition, it supports the hypothesis that shear stress plays a pivotal role in triggering liver hypertrophy in the non-ligated lobes.

Portal blood flow via the peribiliary vascular plexus demonstrated by contrast-enhanced ultrasonography with Sonazoid

PURPOSE

We report two cases in which portal blood flow via the peribiliary vascular plexus (PBP) was clearly demonstrated using contrast-enhanced intra-operative ultrasonography (CE-IOUS).

METHODS

Two patients who underwent hemihepatectomies were investigated using CE-IOUS. Before injection of the contrast medium, both the hepatic arterial and portal venous flows of the hemiliver to be resected were interrupted by ligating those corresponding vessels at the hepatic hilum. Subsequently, the perfluorobutane microbubbles were injected intravenously.

RESULTS

In the early vascular phase, a remarkable intermittent flow was visualized in the lumen of the portal branches whose inflows were interrupted. The flow of the portal vein then disappeared as a result of ligating the hepatic duct concomitantly with the surrounding connective tissue. We considered that the portal venous flow appearing under the condition of total disruption of original inflow was supplied from the hepatic artery through the PBP.

CONCLUSIONS

This is the first report of blood flow via the PBP in human liver visualized by dynamic image study.

High-dose vitamin C: does it exacerbate the effect of psychosocial stress on liver? Biochemical and histological study

AIM

Chronic stress has been implicated as a contributing factor in liver injury. However, other factors that can contribute to the severity of stress effect in liver injury have not been well characterized. In this study, the combined effect of chronic psychosocial stress and variable dosing levels of vitamin C on liver injury, have been studied.

METHODS

Stress was chronically induced using intruder method. Vitamin C was administered by oral gavage. Both biochemical and histopathological measures were undertaken.

RESULTS

The results showed that low (50mg/kg/day) and moderate (150 mg/kg/day) doses of vitamin C alone or in combination with chronic stress had no effect on liver. However, combination of high dose of vitamin C (500 mg/kg/day) and chronic stress induced various histopathological liver lesions in most of animals in the group that was stressed and supplemented with high dose vitamin C.

CONCLUSION

Results of this study show a dose-dependent effect for vitamin C in exacerbating stress contribution to liver injury.

Tumour growth following portal branch ligation in an experimental model of liver metastases

BACKGROUND

Portal branch ligation (PBL) is being used increasingly before hepatectomy for colorectal metastases. This study evaluated the effect of PBL on angiogenesis, growth factor expression and tumour growth in a mouse model of hepatic colorectal metastases.

METHODS

CT26.WT cells were implanted into the left liver lobe of BALB/c mice. Animals underwent PBL of the left liver lobe or sham treatment. Angiogenesis, microcirculation, growth factor expression, cell proliferation and tumour growth were studied over 14 and 21 days by intravital multifluorescence microscopy, laser Doppler flowmetry, immunohistochemistry and western blotting.

RESULTS

Left hilar blood flow and tumour microcirculation were significantly diminished during the first 7 days after PBL. This resulted in tumour volume being 20 per cent less than in sham controls by day 14. Subsequently, PBL-treated animals demonstrated recovery of left hilar blood flow and increased expression of hepatocyte growth factor and transforming growth factor alpha, associated with increased cell proliferation and acceleration of growth by day 21.

CONCLUSION

PBL initially reduced vascular perfusion and tumour growth, but this was followed by increased growth factor expression and cell proliferation. This resulted in delayed acceleration of tumour growth, which might explain the stimulated tumour growth observed occasionally after PBL.

A canine portal hypertension model induced by intra-portal administration of Sephadex microsphere

BACKGROUND AND AIM

Big animal models of portal hypertension are important for the research into this disease. The aim of this study was to establish a canine portal hypertension model by intra-portal administration of microspheres.

METHODS

Sixteen mongrel dogs were assigned to control group and experimental group randomly. The catheterization of portal vein was performed by laparotomy and the outer end of the catheter was fixed subcutaneously in the abdominal wall. The dogs of the experimental group were given intra-portal injections of microspheres at a five-day interval, six times in total. Portal hemodynamics, blood cell counting, liver and renal function test, portography, gastroscopy, liver, spleen and lung histological examination were taken to evaluate the model.

RESULTS

1, 2, 3 and 4 months after initial injection of microspheres, portal venous pressure rose from baseline 8.7 +/- 0.7 mmHg to 24.3 +/- 1.6, 20.6 +/- 2.1, 19.0 +/- 1.8 and 17.7 +/- 2.0 mmHg, respectively (P < 0.01). The diameter of portal vein increased from 7.6 +/- 0.3 to 8.6 +/- 0.3 mm, calculated portal resistance increased from 0.46 +/- 0.06 to 1.06 +/- 0.20 (mmHg/mL/min/kg body weight); velocity of portal blood flow decreased from 35.1 +/- 1.7 to 26.1 +/- 2.4 cm/s (P < 0.01, respectively). The animals of experimental group developed marked splenomegaly and profuse portosystemic collateral circulations with normal liver and renal function.

CONCLUSION

Repeated intra-portal administration of microspheres can induce stable and reproducible chronic portal hypertension in dogs with normal liver and renal functions. This model can meet multiple demands of both basic and clinical research of portal hypertension.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Phosphodiesterase-5 inhibitors have distinct effects on the hemodynamics of the liver

Background

The NO - cGMP system plays a key role in the regulation of sinusoidal tonus and liver blood flow with phosphodiesterase-5 (PDE-5) terminating the dilatory action of cGMP. We, therefore, investigated the effects of PDE-5 inhibitors on hepatic and systemic hemodynamics in rats.

Methods

Hemodynamic parameters were monitored for 60 min. after intravenous injection of sildenafil and vardenafil [1, 10 and 100 μg/kg (sil1, sil10, sil100, var1, var10, var100)] in anesthetized rats.

Results

Cardiac output and heart rate remained constant. After a short dip, mean arterial blood pressure again increased. Systemic vascular resistance transiently decreased slightly. Changes in hepatic hemodynamic parameters started after few minutes and continued for at least 60 min. Portal (var10 -31%, sil10 -34%) and hepatic arterial resistance (var10 -30%, sil10 -32%) decreased significantly (p < 0.05). At the same time portal venous (var10 +29%, sil10 +24%), hepatic arterial (var10 +34%, sil10 +48%), and hepatic parenchymal blood flow (var10 +15%, sil10 +15%) increased significantly (p < 0.05). The fractional liver blood flow (total liver flow/cardiac output) increased significantly (var10 26%, sil10 23%). Portal pressure remained constant or tended to decrease. 10 μg/kg was the most effective dose for both PDE-5 inhibitors.

Conclusion

Low doses of phosphodiesterase-5 inhibitors have distinct effects on hepatic hemodynamic parameters. Their therapeutic use in portal hypertension should therefore be evaluated.

Rapamycin inhibits hepatectomy-induced stimulation of metastatic tumor growth by reduction of angiogenesis, microvascular blood perfusion, and tumor cell proliferation

BACKGROUND

Liver regeneration after hepatectomy stimulates metastatic tumor growth through the release of potent growth factors. In the signaling cascades of several growth factors, mTOR is a downstream mediator, triggering cell survival and cell cycle progression. The mTOR inhibitor rapamycin (RAPA) has been shown to exhibit potent antitumor activities. However, it is unknown whether RAPA is capable of exerting these effects under the conditions of hepatectomy-associated liver regeneration. We therefore analyzed the effect of RAPA and cyclosporine A (CyA) on tumor growth characteristics after major hepatectomy using a mouse model of colorectal metastasis.

METHODS

Tumor growth was studied by using GFP-transfected CT26.WT colorectal cancer cells, which were implanted into the dorsal skinfold chambers of BALB/c-mice after 70% hepatectomy. The animals were treated daily with RAPA (1.5 mg/kg) or CyA (10 mg/kg). Tumors were analyzed for angiogenesis, microvascular blood perfusion, cell proliferation, apoptotic cell death, and tumor growth.

RESULTS

RAPA significantly inhibited tumor growth compared with CyA and sham treatment. This was associated with a decreased microvascular density within the tumors and a markedly reduced microvascular blood perfusion. CyA only slightly reduced angiogenesis and tumor growth. The effects of RAPA were associated with a significant reduction of tumor cell proliferation, whereas manifestation of apoptotic cell death was not affected by the immunosuppressive treatment regimen.

CONCLUSIONS

RAPA is capable of inhibiting angiogenesis, microvascular blood perfusion, and tumor growth of colorectal metastasis during hepatectomy-associated liver regeneration. Thus, targeting mTOR might represent an interesting strategy to prevent tumor recurrence after hepatectomy for colorectal metastasis.

Induction of tumor growth after preoperative portal vein embolization: is it a real problem?

Although preoperative portal vein embolization (PVE) is an effective means to increase future remnant liver (FRL) volume, little has been published on possible adverse effects. This review discusses the clinical and experimental evidence regarding the effect of PVE on tumor growth in both embolized and nonembolized liver lobes, as well as potential strategies to control tumor progression after PVE. A literature review was performed using MEDLINE with keywords related to experimental and clinical studies concerning PVE, portal vein ligation (PVL), and tumor growth. Cross-references and references from reviews were also checked. Clinical and experimental data suggest that tumor progression can occur after preoperative PVE in embolized and nonembolized liver segments. Clinical evidence indicating possible tumor progression in patients with colorectal metastases or with primary liver tumors is based on studies with small sample size. Although multiple studies demonstrated tumor progression, evidence concerning a direct increase in tumor growth rate as a result of PVE is circumstantial. Three possible mechanisms influencing tumor growth after PVE can be recognized, namely changes in cytokines or growth factors, alteration in hepatic blood supply and an enhanced cellular host response promoting local tumor growth after PVE. Post-PVE chemotherapy and sequential transcatheter arterial chemoembolization (TACE) before PVE have been proposed to reduce tumor mass after PVE. We conclude that tumor progression can occur after PVE in patients with colorectal metastases as well as in patients with primary liver tumors. However, further research is needed in order to rate this risk of tumor progression after PVE.

Major hepatectomy for colorectal metastases: is preoperative portal occlusion an oncological risk factor?

BACKGROUND

This study investigates oncological risks and benefits of portal occlusion (PO) in major resection for colorectal liver metastases (CLM).

METHODS

Between 1995 and 2004, 107 patients were scheduled for major hepatectomy for CLM. Of these, 53 patients were selected for PO due to insufficient future liver remnant (FLR), and 54 patients had straightforward hepatectomy. Associations of clinicopathologic factors with resectability, and outcome after PO were analyzed.

RESULTS

21 of 53 patients (39.6%) after PO were unresectable. These patients had a significant smaller volume of the FLR than the 32 resected patients after PO (P = .029). In total, 17 patients (80.9%) did not undergo resection due to cancer progression. Among these, 11 patients (52.4%) exhibited either a progression of known metastases located in the occluded lobes, or new metastases in the nonoccluded portion of the liver. In another 4 individuals (19%), the decision against resection resulted from insufficient hypertrophy of the FLR. Following major hepatectomy, the 5-year survival was 43.66%. Although there was a significantly higher rate of extended hepatectomies versus formal hepatectomies (P < .001), more bilobar distributed metastases versus unilobar manifestations (P = .015), and a smaller resection margin (P = .01) in patients who had PO, no adverse effect on mortality, morbidity, recurrence and survival was observed.

CONCLUSION

Unresectability after PO is a major problem that warrants multidisciplinary improvements, and randomization to resection with or without PO remains ethically problematic. However, following adequate patient selection, PO may provide a significant survival benefit for patients with prior unresectable CLM.