Pim B. Olthof

Sterile inflammation in hepatic ischemia/reperfusion injury: Present concepts and potential therapeutics

Ischemia and reperfusion (I/R) injury is an often unavoidable consequence of major liver surgery and is characterized by a sterile inflammatory response that jeopardizes the viability of the organ. The inflammatory response results from acute oxidative and nitrosative stress and consequent hepatocellular death during the early reperfusion phase, which causes the release of endogenous self‐antigens known as damage‐associated molecular patterns (DAMPs). DAMPs, in turn, are indirectly responsible for a second wave of reactive oxygen and nitrogen species (ROS and RNS) production by driving the chemoattraction of various leukocyte subsets that exacerbate oxidative liver damage during the later stages of reperfusion. In this review, the molecular mechanisms underlying hepatic I/R injury are outlined, with emphasis on the interplay between ROS/RNS, DAMPs, and the cell types that either produce ROS/RNS and DAMPs or respond to them. This theoretical background is subsequently used to explain why current interventions for hepatic I/R injury have not been very successful. Moreover, novel therapeutic modalities are addressed, including MitoSNO and nilotinib, and metalloporphyrins on the basis of the updated paradigm of hepatic I/R injury.

The Mechanisms and Physiological Relevance of Glycocalyx Degradation in Hepatic Ischemia/Reperfusion Injury

SIGNIFICANCE Hepatic ischemia/reperfusion (I/R) injury is an inevitable side effect of major liver surgery that can culminate in liver failure. The bulk of I/R-induced liver injury results from an overproduction of reactive oxygen and nitrogen species (ROS/RNS), which inflict both parenchymal and microcirculatory damage. A structure that is particularly prone to oxidative attack and modification is the glycocalyx (GCX), a meshwork of proteoglycans and glycosaminoglycans (GAGs) that covers the lumenal endothelial surface and safeguards microvascular homeostasis. ROS/RNS-mediated degradation of the GCX may exacerbate I/R injury by, for example, inducing vasoconstriction, facilitating leukocyte adherence, and directly activating innate immune cells. RECENT ADVANCES Preliminary experiments revealed that hepatic sinusoids contain a functional GCX that is damaged during murine hepatic I/R and major liver surgery in patients. There are three ROS that mediate GCX degradation: hydroxyl radicals, carbonate radical anions, and hypochlorous acid (HOCl). HOCl converts GAGs in the GCX to GAG chloramides that become site-specific targets for oxidizing and reducing species and are more efficiently fragmented than the parent molecules. In addition to ROS/RNS, the GAG-degrading enzyme heparanase acts at the endothelial surface to shed the GCX. CRITICAL ISSUES The GCX seems to be degraded during major liver surgery, but the underlying cause remains ill-defined. FUTURE DIRECTIONS The relative contribution of the different ROS and RNS intermediates to GCX degradation in vivo, the immunogenic potential of the shed GCX fragments, and the role of heparanase in liver I/R injury all warrant further investigation.

Survival after associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) for advanced colorectal liver metastases: A case-matched comparison with palliative systemic therapy

Background. Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) allows the resection of colorectal liver metastases with curative intent which would otherwise be unresectable and only eligible for palliative systemic therapy. This study aimed to compare outcomes of ALPPS in patients with otherwise unresectable colorectal liver metastases with matched historic controls treated with palliative systemic treatment. Methods. All patients with colorectal liver metastases from the international ALPPS registry were identified and analyzed. Survival data were compared according to the extent of disease. Otherwise unresectable ALPPS patients were defined by at least 2 of the following criteria: ≥6 metastasis, ≥2 future remnant liver metastasis, ≥6 involved segments excluding segment 1. These patients were matched with patients included in 2, phase 3, metastatic, colorectal cancer trials (CAIRO and CAIRO2) using propensity scoring in order to compare survival. Results. Of 295 patients with colorectal liver metastases in the ALPPS registry, 70 patients had otherwise unresectable disease defined by the proposed criteria. Two‐year overall survival was 49% and 72% for patients with ≥2 and <2 criteria, respectively (P = .002). Median disease‐free survival was 6 months compared to 12 months (P < .001) in the ≥2 and <2 criteria groups, respectively. Median overall survival was comparable between ALPPS patients with ≥2 criteria and case‐matched patients who received palliative treatment (24.0 vs 17.6 months, P = .088). Conclusion. Early oncologic outcomes of patients with advanced liver metastases undergoing ALPPS were not superior to results of matched patients receiving systemic treatment with palliative intent. Careful patient selection is essential in order to improve outcomes.

External biliary drainage following major liver resection for perihilar cholangiocarcinoma: impact on development of liver failure and biliary leakage

BACKGROUND Preoperative biliary drainage is considered essential in perihilar cholangiocarcinoma (PHC) requiring major hepatectomy with biliary-enteric reconstruction. However, evidence for postoperative biliary drainage as to protect the anastomosis is currently lacking. This study investigated the impact of postoperative external biliary drainage on the development of post-hepatectomy biliary leakage and liver failure (PHLF). METHODS All patients who underwent major liver resection for suspected PHC between 2000 and 2015 were retrospectively analyzed. Biliary leakage and PHLF was defined as grade B or higher according to the International Study Group of Liver Surgery (ISGLS) criteria. RESULTS Eighty-nine out of 125 (71%) patients had postoperative external biliary drainage. PHLF was more prevalent in the drain group (29% versus 6%; P = 0.004). There was no difference in the incidence of biliary leakage (32% versus 36%). On multivariable analysis, postoperative external biliary drainage was identified as an independent risk factor for PHLF (Odds-ratio 10.3, 95% confidence interval 2.1-50.4; P = 0.004). CONCLUSIONS External biliary drainage following major hepatectomy for PHC was associated with an increased incidence of PHLF. It is therefore not recommended to routinely use postoperative external biliary drainage, especially as there is no evidence that this decreases the risk of biliary anastomotic leakage.

Assessment of Liver Function Using (99m)Tc-Mebrofenin Hepatobiliary Scintigraphy in ALPPS (Associating Liver Partition and Portal Vein Ligation for Staged Hepatectomy).

ALPPS (associating liver partition and portal vein ligation for staged hepatectomy) is a new surgical technique for patients in whom conventional treatment is not feasible due to insufficient future remnant liver (FRL). During the first stage of ALPPS, accelerated hypertrophy of the FRL is induced by ligation of the portal vein and in situ split of the liver. In the second stage, the deportalized liver is removed when the FRL volume has reached ≥25% of total liver volume. However, FRL volume does not necessarily reflect FRL function. 99mTc-mebrofenin hepatobiliary scintigraphy (HBS) with SPECT-CT is a quantitative test enabling regional assessment of parenchymal uptake function using a validated cut-off value for the prediction of postoperative liver failure (2.7%/min/m2). This paper describes the changes in FRL function and FRL volume in a 79-year-old patient diagnosed with metachronous colonic liver metastases who underwent ALPPS. We have observed a substantial difference between the increase in FRL volume and FRL function suggesting that HBS with SPECT-CT enables monitoring of the FRL function and could be a useful tool in the timing of resection in the second stage of the ALPPS procedure.

Hepatobiliary scintigraphy to evaluate liver function in associating liver partition and portal vein ligation for staged hepatectomy: Liver volume overestimates liver function

Background. Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) induces a rapid and extensive increase in liver volume. The functional quality of this hypertrophic response has been called into question because ALPPS is associated with a substantial incidence of liver failure and high perioperative mortality. This multicenter study aimed to evaluate functional liver regeneration in contrast to volumetric liver regeneration in ALPPS, using technetium‐99m hepatobiliary scintigraphy and computed tomography volumetry, respectively. Methods. Patients who underwent ALPPS and hepatobiliary scintigraphy in 6 centers were included. Hepatobiliary scintigraphy data were analyzed centrally at the Academic Medical Center in Amsterdam according to established protocols. Increase in liver function as measured by hepatobiliary scintigraphy after stage 1 of ALPPS was compared with the increase in liver volume. In addition, we analyzed the impact of liver function and volume on postoperative outcomes including liver failure, morbidity, and mortality. Results. In 60 patients, future liver remnant volume increased by a median 78% (interquartile range 48–110) during a median 8 (interquartile range 6–14) days after stage 1, while function as measured by hepatobiliary scintigraphy increased by a median 29% (interquartile range 1–55) throughout 7 days (interquartile range 6–10) in the 27 patients with paired measurements. After stage 2 of ALPPS, liver failure occurred in 5/60 (8%) patients, severe complications in 24/60 (40%), and mortality occurred in 4/60 (7%). Conclusion. In ALPPS, volumetry overestimates liver function as measured by hepatobiliary scintigraphy and may be responsible for the high rate of liver failure. Quantitative liver function tests are highly recommended to avoid post hepatectomy liver failure.

Postoperative Liver Failure Risk Score: Identifying Patients with Resectable Perihilar Cholangiocarcinoma Who Can Benefit from Portal Vein Embolization

BACKGROUND Major liver resection for perihilar cholangiocarcinoma (PHC) is associated with a 22% to 33% postoperative liver failure incidence. The aim of this study was analyze the predictive value of future liver remnant (FLR) volume for postoperative liver failure after resection for PHC and to develop a risk score to improve patient selection for portal vein embolization. STUDY DESIGN A consecutive series of 217 patients underwent major liver resection for PHC between 1997 and 2014 at 2 Western centers; FLR volumes were calculated with CT volumetry; other variables included jaundice at presentation, immediate preoperative bilirubin, and preoperative cholangitis. The FLR volume was categorized as <30%, 30% to 45%, or >45%. A risk score for postoperative liver failure (grade B/C according to the International Study Group of Liver Surgery criteria) was developed using multivariable logistic regression with 5 predefined variables. RESULTS Postoperative liver failure incidence was 24% and liver failure-related mortality was 12%. Risk factors for liver failure were FLR volume <30% (odds ratio 4.2; 95% CI 1.77 to 10.3) and FLR volume 30% to 45% (odds ratio 1.4; 95% CI 10.6 to 3.4). In addition, jaundice at presentation (odds ratio 3.1; 95% CI 1.1 to 9.0), immediate preoperative bilirubin >50 μmol/L (>2.9 mg/dL) (odds ratio 4.3; 95% CI 1.7 to 10.7), and preoperative cholangitis (odds ratio 3.4; 95% CI 1.6 to 7.4) were risk factors for liver failure. These variables were included in a risk score that showed good discrimination (area under the curve 0.79; 95% CI 0.72 to 0.86) and ranking patients in 3 risk sub-groups with predicted liver failure incidence of 4%, 14%, and 44%. CONCLUSIONS The selection of patients for portal vein embolization using only liver volume is insufficient, considering the other predictors of liver failure in PHC patients. The proposed risk score can be used for selection of patients for portal vein embolization, for adequate patient counseling, and identification of other modifiable risk factors besides liver volume.

Warm ischemia time-dependent variation in liver damage, inflammation, and function in hepatic ischemia/reperfusion injury

BACKGROUND Hepatic ischemia/reperfusion (I/R) injury is characterized by hepatocellular damage, sterile inflammation, and compromised postoperative liver function. Generally used mouse I/R models are too severe and poorly reflect the clinical injury profile. The aim was to establish a mouse I/R model with better translatability using hepatocellular injury, liver function, and innate immune parameters as endpoints. METHODS Mice (C57Bl/6J) were subjected to sham surgery, 30min, or 60min of partial hepatic ischemia. Liver function was measured after 24h using intravital microscopy and spectroscopy. Innate immune activity was assessed at 6 and 24h of reperfusion using mRNA and cytokine arrays. Liver inflammation and function were profiled in two patient cohorts subjected to I/R during liver resection to validate the preclinical results. RESULTS In mice, plasma ALT levels and the degree of hepatic necrosis were strongly correlated. Liver function was bound by a narrow damage threshold and was severely impaired following 60min of ischemia. Severe ischemia (60min) evoked a neutrophil-dominant immune response, whereas mild ischemia (30min) triggered a monocyte-driven response. Clinical liver I/R did not compromise liver function and displayed a cytokine profile similar to the mild I/R injury model. CONCLUSIONS Mouse models using ≤30min of ischemia best reflect the clinical liver I/R injury profile in terms of liver function dynamics and type of immune response. GENERAL SIGNIFICANCE This short duration of ischemia therefore has most translational value and should be used to increase the prospects of developing effective interventions for hepatic I/R.

Protective mechanisms of hypothermia in liver surgery and transplantation

Hepatic ischemia/reperfusion (I/R) injury is a side effect of major liver surgery that often cannot be avoided. Prolonged periods of ischemia put a metabolic strain on hepatocytes and limit the tolerable ischemia and preservation times during liver resection and transplantation, respectively. In both surgical settings, temporarily lowering the metabolic demand of the organ by reducing organ temperature effectively counteracts the negative consequences of an ischemic insult. Despite its routine use, the application of liver cooling is predicated on an incomplete understanding of the underlying protective mechanisms, which has limited a uniform and widespread implementation of liver-cooling techniques. This review therefore addresses how hypothermia-induced hypometabolism modulates hepatocyte metabolism during ischemia and thereby reduces hepatic I/R injury. The mechanisms underlying hypothermia-mediated reduction in energy expenditure during ischemia and the attenuation of mitochondrial production of reactive oxygen species during early reperfusion are described. It is further addressed how hypothermia suppresses the sterile hepatic I/R immune response and preserves the metabolic functionality of hepatocytes. Lastly, a summary of the clinical status quo of the use of liver cooling for liver resection and transplantation is provided.

The pathophysiology of human obstructive cholestasis is mimicked in cholestatic Gold Syrian hamsters

Obstructive cholestasis causes liver injury via accumulation of toxic bile acids (BAs). Therapeutic options for cholestatic liver disease are limited, partially because the available murine disease models lack translational value. Profiling of time-related changes following bile duct ligation (BDL) in Gold Syrian hamsters revealed a biochemical response similar to cholestatic patients in terms of BA pool composition, alterations in hepatocyte BA transport and signaling, suppression of BA production, and adapted BA metabolism. Hamsters tolerated cholestasis well for up to 28days and progressed relatively slowly to fibrotic liver injury. Hepatocellular necrosis was absent, which coincided with preserved intrahepatic energy levels and only mild oxidative stress. The histological response to cholestasis in hamsters was similar to the changes seen in 17 patients with prolonged obstructive cholestasis caused by cholangiocarcinoma. Hamsters moreover upregulated hepatic fibroblast growth factor 15 (Fgf15) expression in response to BDL, which is a cytoprotective adaptation to cholestasis that hitherto had only been documented in cholestatic human livers. Hamster models should therefore be added to the repertoire of animal models used to study the pathophysiology of cholestatic liver disease.