Hepatic adenine nucleotides and DNA synthesis during the regenerative and atrophic process of the liver lobes after selective portal vein ligation

Physical prehabilitation improves the postoperative outcome of associating liver partition and portal vein ligation for staged hepatectomy in experimental model

Aiming to improve the postoperative outcome of associating liver partition and portal vein ligation for staged hepatectomy (ALPPS), the effect of physical prehabilitation (PP) was investigated in experimental model. Male Wistar rats (n = 106) divided to PP and sedentary (S) groups underwent ALPPS. Changes in liver weight, Ki67 index and liver volume by magnetic resonance imaging (MRI) were evaluated. Liver function was assessed by laboratory parameters and ^99mTc-mebrofenin single-photon emission computed tomography (SPECT) hepatobiliary scintigraphy (HBS). Utilizing endotoxemia model mortality and septic parameters were investigated. Liver mass (p < 0.001), Ki67 index (p < 0.001) and MRI liver volume (p < 0.05) increased in the PP group compared to the S group. Both standard laboratory parameters (p < 0.001) and HBS (p < 0.05) showed enhanced liver function in the PP group compared to the S group. The vulnerability of animals improved in the PP group, as mortality decreased (p < 0.001), while septic laboratory parameters improved (p < 0.05) compared to the S group in the endotoxemia model. Our study demonstrated for the first time the beneficial role of PP on not only volumetric but also functional liver regeneration and postoperative vulnerability after ALLPS.

Functional shift with maintained regenerative potential following portal vein ligation

Selective portal vein ligation (PVL) allows the two-stage surgical resection of primarily unresectable liver tumours by generating the atrophy and hypertrophy of portally ligated (LL) and non-ligated lobes (NLL), respectively. To evaluate critically important underlying functional alterations, present study characterised in vitro and vivo liver function in male Wistar rats (n = 106; 210-250 g) before, and 24/48/72/168/336 h after PVL. Lobe weights and volumes by magnetic resonance imaging confirmed the atrophy-hypertrophy complex. Proper expression and localization of key liver transporters (Ntcp, Bsep) and tight junction protein ZO-1 in isolated hepatocytes demonstrated constantly present viable and well-polarised cells in both lobes. In vitro taurocholate and bilirubin transport, as well as in vivo immunohistochemical Ntcp and Mrp2 expressions were bilaterally temporarily diminished, whereas LL and NLL structural acinar changes were divergent. In vivo bile and bilirubin-glucuronide excretion mirrored macroscopic changes, whereas serum bilirubin levels remained unaffected. In vivo functional imaging (indocyanine-green clearance test; ^99mTc-mebrofenin hepatobiliary scintigraphy; confocal laser endomicroscopy) indicated transitionally reduced global liver uptake and -excretion. While LL functional involution was permanent, NLL uptake and excretory functions recovered excessively. Following PVL, functioning cells remain even in LL. Despite extensive bilateral morpho-functional changes, NLL functional increment restores temporary declined transport functions, emphasising liver functional assessment.

Alterations in hepatic lobar function in regenerating rat liver

BACKGROUND

Ligation of a branch of the portal vein redirects portal blood to nonligated lobes resulting in lobar hypertrophy. Although the effect of portal vein ligation on liver volume is well documented, the parallel alterations in liver function are still the subject of controversy. Our aim was to assess the time-dependent reactions of regional hepatic function to portal vein ligation by selective biliary drainage.

METHODS

Male Wistar rats (n = 44) underwent 80% portal vein ligation. Before the operation as well as 1, 2, 3, 5, and 7 d after circulation, morphology and function (laboratory blood test; hepatic bile flow; plasma disappearance rate of indocyanine green; and biliary indocyanine green excretion) of the liver were examined.

RESULTS

Although portal vein ligation affected liver circulation and morphology to a great extent, serum albumin levels, bilirubin levels, and total hepatic bile flow did not change significantly after the operation. Nevertheless, plasma disappearance rate and biliary indocyanine green excretion indicated a temporary impairment of total liver function with the lowest value on the second day and normalization by the fifth day. Bile production and biliary indocyanine green excretion of ligated lobes decreased rapidly after the operation and remained persistently suppressed, whereas the secretory function of nonligated lobes--after a temporary decline--showed a greater increase than the weight of the lobes.

CONCLUSIONS

Portal vein ligation induced temporary impairment of total liver function, followed by rapid recovery mainly by reason of increase in the function of nonligated lobes. Functional increase in nonligated lobes was more pronounced than suggested by the degree of volume gain.

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.

Magnetic resonance imaging characteristics of hepatocyte apoptosis (induced by right portal vein ligation) and necrosis (induced by combined right portal vein and right hepatic artery ligation) in rats

Objective

Using magnetic resonance imaging (MRI), this study aimed to demonstrate the appearance of hepatocytes following ligation of the right portal vein or combined ligation of the right portal vein and right hepatic artery, in a rat model.

Methods

Ninety adult Sprague–Dawley rats (body weight 250–300 g) were divided into three groups ( n = 30 per group): ligation of the right portal vein (Group A); combined ligation of the right portal vein and right hepatic artery (Group B); no intervention to obstruct blood supply (control group). Rats were then randomly subdivided into five groups that underwent examination at 3 h and 1, 3, 7 and 14 days postprocedure ( n = 6 per group). Livers were examined by routine MRI, diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS). After examination, each group of rats was sacrificed. Right hepatic lobes were removed and examined by pathology in six rats per timepoint; transmission electron microscopy (TEM) was undertaken in up to three rats per timepoint.

Results

Hepatocyte apoptosis and necrosis, by right portal vein ligation and combined right portal vein and right hepatic artery ligation respectively, were confirmed by pathology and TEM. In Group A, there were slight increases in intensity of T1- and T2-weighted images and in the apparent diffusion coefficient (ADC). In addition there were larger areas under the lactic acid and lipid peaks on MRS. In Group B, there were increased T1 and T2 signals, a decrease in the ADC and an increase of the area under the lactic acid peaks on MRS.

Conclusions

Hepatocyte apoptosis and necrosis induced by ligation procedures exhibited specific changes that were evident on MRI, DWI and MRS, and could be detected in vivo by MRI, in a rat model.

Advantage of preoperative portal vein occlusion for hepatectomy that exceeds portal vein occluded lobes

BACKGROUND

The purpose of our study was to examine the effect of preoperative portal vein (PV) occlusion on hepatic reserve function after extended hepatectomy that is an excision of areas beyond the PV occluded lobes.

METHODS

Male Wistar rats were divided into three groups and underwent a two-stage operation: a PVL-hepatectomy group (ligation of the PV [PVL] of the left and median lobes followed by hepatectomy of the right lobes together with the PV occluded lobes), a sham-88% hepatectomy group (sham operation without PVL followed by hepatectomy corresponding to the lobes excised in the PVL-hepatectomy group), and a sham-67% hepatectomy group (sham operation followed by hepatectomy of the left and median lobes to approximate the volume excised in the PVL-hepatectomy group). In all subjects, hepatectomy was carried out 7 days after the PVL or sham operation. On days 0, 1, 2, and 3 after hepatectomy, liver weight, histologic elements, DNA synthesis rates, energy charge, adenine nucleotides, and lipoperoxide levels of the remaining liver were determined.

RESULTS

In the sham-88% hepatectomy group, the volume of resected liver was 88.2% +/- 0.5%. In the PVL-hepatectomy group it was 69.1% +/- 0.8%, although anatomically identical lobes were excised. At the time of hepatectomy, DNA synthesis, hepatic concentrations of adenine nucleotides and lipoperoxide, and serum liver function tests showed similar results in all three groups. The survival rate 3 days after hepatectomy was significantly low (53%) in the sham-88% hepatectomy group, whereas it was 100% in the PVL-hepatectomy and sham-67% hepatectomy groups. The gain in liver weight per day was significantly lower in the sham-88% hepatectomy group than in the other two groups. The decline in hepatic energy charge after hepatectomy was less, with less activated DNA synthesis, in the PVL-hepatectomy group compared with the sham-88% hepatectomy and sham-67% hepatectomy groups. Lipoperoxide concentration in the PVL-hepatectomy group was significantly lower than that in the sham-88% hepatectomy and sham-67% hepatectomy groups.

CONCLUSIONS

Preoperative PV occlusion not only increases the remaining liver volume but also is advantageous to hepatic reserve after hepatectomy that exceeds PV occluded lobes.

Serum hyaluronic acid level reflects volume and ATP levels of the liver after extended hepatectomy with and without preoperative portal vein occlusion

The purpose of this study was to examine the hypothesis that the serum hyaluronic acid (HA) level reflects the volume and adenosine triphosphate (ATP) levels of the liver after extended hepatectomy (ExHx) with and without preoperative portal vein occlusion (PVO). Rats were randomly divided into two groups, PVO-ExHx and sham-ExHx. At the first stage, they underwent PVO or sham surgery by an occlusion of the portal vein supplying the left lateral and median lobes or by similar manipulation but without PVO, respectively. Seven days after first-stage surgery, both groups received ExHx exceeding portal vein-occluded lobes, which was the excision of the left lateral, median, and right lateral lobes of the liver reported as a 90% hepatectomy model. On Days 0, 1, 2, and 3 after ExHx, the serum HA concentrations, liver weights, and hepatic ATP levels were determined. Liver volumes were restored to similar levels in both groups, but restoration was faster in the PVO-ExHx group because preoperative PVO allowed the excised liver less volume. Lower serum HA levels were significantly associated with significantly higher hepatic ATP levels and with a lower mortality rate in the PVO-ExHx group. The serum HA level correlated significantly (P < 0.001) with the liver weight and hepatic ATP level. The serum HA level serves as a proxy for clinically important parameters following major hepatic surgery.

Hepatic adenine nucleotides and microsomal cholesterol 7 alpha-hydroxylase activity in the obstructed and freely draining lobes of the liver after selective bile duct obstruction

BACKGROUND

The effect of selective bile duct obstruction (SBDO) on hepatic reserve function of the bile duct obstructed (BDO) and nonobstructed freely draining (FD) lobes of the liver is obscure.

METHODS

The bile duct branches draining from the left lateral and median lobes of the liver were ligated for 4 and 10 days in rats, and hepatic reserve functions in BDO and FD lobes were assessed by microsomal cholesterol 7 alpha-hydroxylase activities and by hepatic adenine nucleotides and energy charge levels. The values were compared with those in the sham-operated control liver. Cholesterol 7 alpha-hydroxylase activities were determined by gas-liquid chromatography--mass spectrometry, and hepatic adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) levels with high-pressure liquid chromatography.

RESULTS

The histological examination of the BDO lobes showed proliferation and formation of new bile ductules and fibrous connective tissues linking portal areas. Microsomal cholesterol 7 alpha-hydroxylase activities, hepatic energy charge and each adenine nucleotide level did not differ between FD and BDO lobes, and the values were similar to those in the sham-operated liver.

CONCLUSIONS

Selective bile duct obstruction shows no adverse effects on microsomal and mitochondrial functions in both the BDO and FD lobes of the liver.

Hepatic adenine nucleotides and microsomal cholesterol 7 alpha-hydroxylase activity in the obstructed and freely draining lobes of the liver after selective bile duct obstruction

BACKGROUND

The effect of selective bile duct obstruction (SBDO) on hepatic reserve function of the bile duct obstructed (BDO) and nonobstructed freely draining (FD) lobes of the liver is obscure.

METHODS

The bile duct branches draining from the left lateral and median lobes of the liver were ligated for 4 and 10 days in rats, and hepatic reserve functions in BDO and FD lobes were assessed by microsomal cholesterol 7 alpha-hydroxylase activities and by hepatic adenine nucleotide and energy charge levels. The values were compared with those in sham-operated control liver. Cholesterol 7 alpha-hydroxylase activities were determined by gas-liquid chromatography-mass spectrometry, and hepatic adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) levels with high-pressure liquid chromatography.

RESULTS

The histological examination of the BDO lobes showed proliferation and formation of new bile ductules and fibrous connective tissue linking portal areas. Microsomal cholesterol 7 alpha-hydroxylase activities, hepatic energy charge and adenine nucleotide levels did not differ between FD and BDO lobes, and the values were similar to those in the sham-operated liver.

CONCLUSIONS

Selective bile duct obstruction shows no adverse effects on microsomal and mitochondrial functions in either BDO or FD lobes of the liver.