The effect of mechanically enhancing portal venous inflow on hepatic oxygenation, microcirculation, and function in a rabbit model with extensive hepatic fibrosis

Metabolic nuclear receptors coordinate energy metabolism to regulate Sox9+ hepatocyte fate

Recent research has indicated the adult liver Sox9⁺ cells located in the portal triads contribute to the physiological maintenance of liver mass and injury repair. However, the physiology and pathology regulation mechanisms of adult liver Sox9⁺ cells remain unknown. Here, PPARα and FXR bound to the shared site in Sox9 promoter with opposite transcriptional outputs. PPARα activation enhanced the fatty acid β-oxidation, oxidative phosphorylation (OXPHOS), and adenosine triphosphate (ATP) production, thus promoting proliferation and differentiation of Sox9⁺ hepatocytes along periportal (PP)-perivenous (PV) axis. However, FXR activation increased glycolysis but decreased OXPHOS and ATP production, therefore preventing proliferation of Sox9⁺ hepatocytes along PP-PV axis by promoting Sox9⁺ hepatocyte self-renewal. Our research indicates that metabolic nuclear receptors play critical roles in liver progenitor Sox9⁺ hepatocyte homeostasis to initiate or terminate liver injury-induced cell proliferation and differentiation, suggesting that PPARα and FXR are potential therapeutic targets for modulating liver regeneration.

•

PPARα promotes Sox9 expression and FXR inhibits Sox9 expression

•

PPARα promotes proliferation and differentiation of Sox9⁺ hepatocytes

•

FXR promotes Sox9⁺ hepatocyte self-renewal

•

PPARα and FXR coordinate energy metabolism to regulate Sox9⁺ hepatocyte fate

Increased susceptibility to liver damage from pneumoperitoneum in a murine model of biliary atresia

HYPOTHESIS

We hypothesized that livers with biliary atresia (BA) are more susceptible to the harmful effects of a high-pressure CO(2) pneumoperitoneum (PP) than healthy livers.

METHODS

A murine model of BA was used in this experiment. Mice were divided into 6 groups: (1) control Balb/c; (2) control Balb/c, CO(2)-PP; (3) control BA; (4) BA-sham; (5) BA, CO(2)-PP; and (6) BA, air-PP. Mice from groups 2, 5, and 6 underwent an 8-mm Hg-PP for 60 minutes. Liver samples were collected for histology, colorimetry, and flow cytometry analysis 18 to 24 hours after the procedure. Markers of apoptosis were investigated as indicators of acute cell damage.

RESULTS

We observed a statistically significant higher rate of apoptosis in livers with BA exposed to a prolonged CO(2)-PP or air-PP compared with control groups. There were no significant differences between groups 1 and 2, or between groups 5 and 6.

CONCLUSIONS

In this animal model, we have shown that livers with BA are more susceptible than healthy livers to injury by a prolonged PP. This injury was caused by both CO(2) and air-PP, implying that it is the direct result of pressure. These results may have implications for the success of minimally invasive Kasai procedures.

Long-term results of balloon-occluded retrograde transvenous obliteration for gastric variceal bleeding and risky gastric varices: a 10-year experience

BACKGROUND AND AIM

Balloon-occluded retrograde transvenous obliteration (B-RTO) is a new alternative treatment for gastric varices (GVx), but the long-term efficacy is not known. We investigated the long-term effects of B-RTO on rebleeding, prevention of first bleeding, mortality and occurrence of risky esophageal varices (EVx).

METHODS

B-RTO was performed in 68 cirrhotic patients with GVx. Twenty patients had recent bleeding, transiently treated by endoscopic Histoacryl injection or balloon tamponade. Forty-eight patients had varices likely to bleed, but no bleeding. After B-RTO, the recurrent bleeding, occurrence of EVx and mortality over the long-term were evaluated.

RESULTS

B-RTO was successfully performed in 63 of 68 patients (92.6%). Varices eradication was confirmed by endoscopy in 61 of 63 patients (96.6%). During follow up, GVx bleeding occurred in two patients (3.2%). The 8-year cumulative rebleeding rates of patients with bleeding and risky GVx were 14% and 0%, respectively. Risky EVx occurred in 10 patients (17%) and the cumulative occurrence rate was 22% in 8 years. The cumulative occurrence rate of risky EVx was higher in GVx with EVx (GOV2-GVx) compared to GVx without EVx (IGV1, P < 0.05). No ectopic variceal bleeding occurred. No patients died from variceal bleeding. Hepatocellular carcinoma was the only significant prognostic factor (P < 0.05).

CONCLUSION

B-RTO is beneficial over the long-term, despite worsening EVx in some patients, because of excellent treatment efficacy and improved mortality. We believe that B-RTO can become a first-choice radical treatment following hemostasis for gastric variceal bleeding and prophylactic treatment for risky GVx.

Accelerated orthotopic hepatocellular carcinomas growth is linked to increased expression of pro-angiogenic and prometastatic factors in murine liver fibrosis

BACKGROUND

Most experimental therapy studies are performed in mice that bear subcutaneous or orthotopic hepatoma but are otherwise healthy. We questioned whether a pre-existing fibrosis affects tumour development of implanted syngenic hepatoma cells. To further investigate a selected panel of factors involved in tumour growth, tumour organ samples were characterized for gene expression of vascular endothelial growth factor (VEGF)-A/-C, VEGF receptors Flt1, Flk-1, Flt-4 and for VEGF-A protein levels.

RESULTS

The presented data show that tumour sizes were 3.7-fold increased and fibrotic livers had numerous satellites. Increased tumour sizes were associated with elevated intratumoral VEGF-A protein amounts and intratumoral increased VEGF receptor gene expression levels in tumour tissue from fibrotic livers as compared with non-fibrotic livers. Additionally, intratumoral gene expression levels of matrix metalloproteinase-2 (MMP-2) and MMP-9 were elevated in fibrotic mice.

CONCLUSION

Our results indicate that liver fibrosis stimulates tumour development of implanted syngenic hepatoma cells. Accelerated tumour growth was going along with elevated intratumoral VEGF-A and VEGF-A receptor status, which most probably mediated pro-angiogenic and prometastatic effects in this model. Furthermore, advanced tumour spread was associated with increased MMP-2/-9 expression. These data suggest that the intratumoral VEGF-A proteins levels and VEGF receptor status contribute to accelerated hepatocellular carcinoma development in fibrotic mice and that elevated MMP-2, MMP-9 and VEGF-C levels could promote tumour metastasis in this model.

Arterialization of the portal vein improves hepatic microcirculation and tissue oxygenation in experimental cirrhosis

Background

Arterialization of the portal vein (APV) has shown beneficial effects on liver regeneration and function in selected patients undergoing liver resection and transplantation. Whether APV improves liver perfusion and function in cirrhosis is unclear. This study investigated the effect of APV on hepatic haemodynamics and liver function in a rat model of cirrhosis.

Methods

Male Sprague–Dawley rats (250–300 g) were divided into three groups: normal controls (n = 7), cirrhosis with sham laparotomy (sham; n = 7) and cirrhosis with APV (APV; n = 9). Portal venous blood flow, portal vein pressure and hepatic parenchymal microcirculation (HPM) were measured before and after APV. Hepatic parenchymal oxygenation was assessed by near-infrared spectroscopy and hepatocellular injury by standard liver function tests. Measurements were taken at baseline, after APV and 7 days after surgery.

Results

APV increased portal blood flow and pressure in cirrhotic rats without altering intrahepatic portal resistance. APV increased the HPM in cirrhotic rats by a mean(s.e.m.) of 28·5(0·1) per cent on day 0 and 54·6(0·1) per cent by day 7 (P = 0·001). Liver tissue oxygenation was increased by APV and the plasma γ-glutamyltranspeptidase level was reduced (mean(s.e.m.) 6·0(0·5) versus 3·8(0·3) units/l before and after APV respectively; P = 0·006) at day 7.

Conclusion

APV increases portal blood flow, tissue perfusion and oxygenation in cirrhosis.

Intravascular micropump for augmented liver perfusion: first in vivo experience

The aim of this study was to assess the in vivo performance of a new microaxial rotary blood pump developed for long-term intraportal implantation. The pump, measuring 7 mm in diameter, has a single stage impeller and is powered by a microelectric motor. The pump was implanted into the portal vein in 13 large white pigs under general anesthesia. All animals recovered after the portal pump implantation, and they were observed until the pump failed. The 2 longest running pumps performed for 40 and 36 h, respectively. Either thrombus formation or technical problems, especially in the bearings, were the main causes of pump failure during the experiment. No local or systemic adverse effects were observed during the portal pumping period. Full recovery of the animals following intraportal pump implantation was achieved. However, further technical improvements to the pump are required to maintain a longer performance in vivo.

In vivo evaluation of an implantable portal pump system for augmenting liver perfusion

BACKGROUND

Increasing portal inflow in cirrhosis using a mechanical pump reduces portal venous pressure and improves liver function. A pump has been developed for portal vein implantation in human cirrhosis. This study describes the initial in vivo evaluation in a porcine model.

METHODS

Five Large White pigs underwent laparotomy and exposure of the liver. Flow in the hepatic artery, portal vein and hepatic microcirculation was monitored continuously. Hepatic tissue oxygenation was measured by near-infrared spectroscopy. After baseline measurements the pump was inserted into the portal vein. Pump flow rate was then increased stepwise to 50 per cent over the baseline value for a period of 2 h. The pump was then stopped for 20 min and left in situ while continuing to collect systemic and hepatic haemodynamic data. The animal was killed and biopsies for histological examination were taken from the liver, small intestine and spleen.

RESULTS

The baseline total hepatic blood flow was 626(39) ml/min; the hepatic artery supplied 18.4(2.1) per cent and the portal vein 81.6(2.1) per cent. The pump was inserted successfully in all animals without surgical complications. During surgical insertion of the pump, the temporary portal vein occlusion resulted in a significant rise in hepatic artery blood flow (22(3) per cent; P < 0.01 versus baseline). Portal vein flow was augmented by pumping; there was a significant correlation between the pump motor speed and portal vein flow (P < 0.0001). This inflow correlated directly with flow in the hepatic microcirculation and hepatic tissue oxygenation (P < 0.001). The pump ran satisfactorily throughout the study. Histological examination revealed no evidence of structural damage to the liver or ischaemic changes in the small intestine or spleen.

CONCLUSION

It is technically possible and safe to insert an implantable pump in the portal vein. Portal venous blood flow can be increased up to 50 per cent with a resultant increase in flow in the hepatic microcirculation and hepatic oxygenation and without adverse effects on either hepatic or systemic haemodynamics.

Portal flow augmentation for liver cirrhosis

BACKGROUND

Portal hypertension due to chronic liver disease is a major cause of death worldwide. Orthotopic liver transplantation offers the best therapeutic option but is available to only a minority of patients. In the past few years mechanically pumping portal venous inflow has been reported to reduce portal hypertension and improve liver function.

METHODS

A review of the published data on augmented portal perfusion for the treatment of portal hypertension in cirrhosis was carried out by searching Medline and other online databases. From each published study portal pressure and blood flow data before and after augmented portal perfusion were used to calculate the change in mean intrahepatic portal vascular resistance (IHPR). The standardized data were then combined to allow meta-analysis.

RESULTS

Seven papers were identified on normal and cirrhotic animal and human livers with augmented flow (50% to fourfold over baseline) for 30-180 min. Meta-analysis revealed that the increased portal venous inflow was associated with a significant rise in portal venous pressure on the hepatic side (P < 0.001), a significant reduction on the mesenteric side (P < 0.001) and a significant reduction in IHPR (P = 0.013). Limited data were available to support improved liver function.

CONCLUSION

Detailed in vivo cirrhotic liver studies on augmented portal flow in experimental models assessing haemodynamic and functional changes are required before clinical evaluation.

Effect of liver blood flow and function on hepatic indocyanine green clearance measured directly in a cirrhotic animal model

BACKGROUND

Peripheral blood clearance of indocyanine green (ICG) has been used as a test of liver function but gives little information on biliary excretion. Hepatic ICG uptake and clearance can be measured directly by near-infrared spectroscopy (NIRS). Direct ICG measurement has not previously been correlated with liver blood flow and function in cirrhosis.

METHODS

Two groups of New Zealand white rabbits (n = 12) underwent laparotomy for liver exposure. Cirrhosis was induced by feeding animals (n = 6) with a high-cholesterol (2 per cent) diet for 16 weeks. Hepatic blood flow and microcirculation were measured. Hepatic ICG concentration was measured directly using NIRS probes on the liver surface. From the ICG concentration-time curve, hepatic ICG uptake and excretion rates were calculated by a non-linear least square curve fitting method.

RESULTS

There was a significant reduction in ICG uptake rate (mean(s.d.) 0.300(0.130) versus 2.040(0.420) min-1; P = 0.0001) and ICG excretion rate (0.007(0.009) versus 0.227(0.096) min-1; P = 0. 002) in cirrhotic animals. The hepatic ICG uptake rate correlated with hepatic blood flow and flow in the microcirculation (r = 0.81, P = 0.002; r = 0.92, P < 0.001, respectively). The hepatic ICG excretion rate was significantly associated with indicators of impaired liver function including bilirubin (r = - 0.86, P = 0.0004), aspartate aminotransferase (r = - 0.81, P = 0.001) and lactate dehydrogenase (r = - 0.83, P = 0.0008).

CONCLUSION

ICG uptake measured directly by NIRS reflects the reduced liver blood flow and perfusion in cirrhosis and its excretion correlates with the degree of liver parenchymal dysfunction. This technique may allow a more accurate method of liver function assessment than peripheral blood ICG clearance.