Increased sinusoidal flow is not the primary stimulus to liver regeneration

Mechanical homeostasis of liver sinusoid is involved in the initiation and termination of liver regeneration

Organogenesis and regeneration are fundamental for developmental progress and are associated with morphogenesis, size control and functional properties for whole-body homeostasis. The liver plays an essential role in maintaining homeostasis of the entire body through various functions, including metabolic functions, detoxification, and production of bile, via the three-dimensional spatial arrangement of hepatic lobules and has high regenerative capacity. The regeneration occurs as hypertrophy, which strictly controls the size and lobule structure. In this study, we established a three-dimensional sinusoidal network analysis method and determined valuable parameters after partial hepatectomy by comparison to the static phase of the liver. We found that mechanical homeostasis, which is crucial for organ morphogenesis and functions in various phenomena, plays essential roles in liver regeneration for both initiation and termination of liver regeneration, which is regulated by cytokine networks. Mechanical homeostasis plays critical roles in the initiation and termination of organogenesis, tissue repair and organ regeneration in coordination with cytokine networks.

Markers of liver regeneration-the role of growth factors and cytokines: a systematic review

Background

Post-hepatectomy liver failure contributes significantly to postoperative mortality after liver resection. The prediction of the individual risk for liver failure is challenging. This review aimed to provide an overview of cytokine and growth factor triggered signaling pathways involved in liver regeneration after resection.

Methods

MEDLINE and Cochrane databases were searched without language restrictions for articles from the time of inception of the databases till March 2019. All studies with comparative data on the effect of cytokines and growth factors on liver regeneration in animals and humans were included.

Results

Overall 3.353 articles comprising 40 studies involving 1.498 patients and 101 animal studies were identified and met the inclusion criteria. All included trials on humans were retrospective cohort/observational studies. There was substantial heterogeneity across all included studies with respect to the analyzed cytokines and growth factors and the described endpoints.

Conclusion

High-level evidence on serial measurements of growth factors and cytokines in blood samples used to predict liver regeneration after resection is still lacking. To address the heterogeneity of patients and potential markers, high throughput serial analyses may offer a method to predict an individual’s regenerative potential in the future.

The effects of terlipressin and direct portacaval shunting on liver hemodynamics following 80% hepatectomy in the pig

Liver failure is the major cause of death following liver resection. Post-resection portal venous pressure (PVP) predicts liver failure, is implicated in its pathogenesis, and when PVP is reduced, rates of liver dysfunction decrease. The aim of the present study was to characterize the hemodynamic, biochemical, and histological changes induced by 80% hepatectomy in non-cirrhotic pigs and determine if terlipressin or direct portacaval shunting can modulate these effects. Pigs were randomized (n=8/group) to undergo 80% hepatectomy alone (control); terlipressin (2 mg bolus + 0.5-1 mg/h) + 80% hepatectomy; or portacaval shunt (PCS) + 80% hepatectomy, and were maintained under terminal anesthesia for 8 h. The primary outcome was changed in PVP. Secondary outcomes included portal venous flow (PVF), hepatic arterial flow (HAF), and biochemical and histological markers of liver injury. Hepatectomy increased PVP (9.3 ± 0.4 mmHg pre-hepatectomy compared with 13.0 ± 0.8 mmHg post-hepatectomy, P<0.0001) and PVF/g liver (1.2 ± 0.2 compared with 6.0 ± 0.6 ml/min/g, P<0.0001) and decreased HAF (70.8 ± 5.0 compared with 41.8 ± 5.7 ml/min, P=0.002). Terlipressin and PCS reduced PVP (terlipressin = 10.4 ± 0.8 mmHg, P=0.046 and PCS = 8.3 ± 1.2 mmHg, P=0.025) and PVF (control = 869.0 ± 36.1 ml/min compared with terlipressin = 565.6 ± 25.7 ml/min, P<0.0001 and PCS = 488.4 ± 106.4 ml/min, P=0.002) compared with control. Treatment with terlipressin increased HAF (73.2 ± 11.3 ml/min) compared with control (40.3 ± 6.3 ml/min, P=0.026). The results of the present study suggest that terlipressin and PCS may have a role in the prevention and treatment of post-resection liver failure.

Post hepatectomy liver failure - A comprehensive review of current concepts and controversies

Post hepatectomy liver failure (PHLF) comprises of a conundrum of symptoms and signs following major hepatic resections. The pathophysiology essentially revolves around disruption of the normal hepatocyte regeneration and disturbed liver homeostasis. Prompt identification of the pre-operative predictors of PHLF in the form of biochemical parameters and imaging features are of paramount importance for any hepatic surgeon and forms the cornerstone of its management. Treatment revolves around a goal-directed resuscitation of the systemic organ failure. Auxiliary support systems such as liver dialysis devices and stem cell therapy are still under investigational trials for treatment of the same. Orthotopic liver transplantation (OLT) is the last resort in most cases not responding to other measures.

Porcine model characterizing various parameters assessing the outcome after acetaminophen intoxication induced acute liver failure

AIM

To investigate the changes of hemodynamic and laboratory parameters during the course of acute liver failure following acetaminophen overdose.

METHODS

Eight pigs underwent a midline laparotomy following jejunal catheter placement for further acetaminophen intoxication and positioning of a portal vein Doppler flow-probe. Acute liver failure was realized by intrajejunal acetaminophen administration in six animals, two animals were sham operated. All animals were invasively monitored and received standardized intensive care support throughout the study. Portal blood flow, hemodynamic and ventilation parameters were continuously recorded. Laboratory parameters were analysed every eight hours. Liver biopsies were sampled every 24 h following intoxication and upon autopsy.

RESULTS

Acute liver failure (ALF) occurred after 28 ± 5 h resulted in multiple organ failure and death despite maximal support after further 21 ± 1 h (study end). Portal blood flow (baseline 1100 ± 156 mL/min) increased to a maximum flow of 1873 ± 175 mL/min at manifestation of ALF, which was significantly elevated (P < 0.01). Immediately after peaking, portal flow declined rapidly to 283 ± 135 mL/min at study end. Thrombocyte values (baseline 307 × 10³/µL ± 34 × 10³/µL) of intoxicated animals declined slowly to values of 145 × 10³/µL ± 46 × 10³/µL when liver failure occurred. Subsequent appearance of severe thrombocytopenia in liver failure resulted in values of 11 × 10³/µL ± 3 × 10³/µL preceding fatality within few hours which was significant (P > 0.01).

CONCLUSION

Declining portal blood flow and subsequent severe thrombocytopenia after acetaminophen intoxication precede fatality in a porcine acute liver failure model.

Mechanistic insights of rapid liver regeneration after associating liver partition and portal vein ligation for stage hepatectomy

AIM

To highlight the potential mechanisms of regeneration in the Associating Liver Partition and Portal vein ligation for Stage hepatectomy models (clinical and experimental) that could unlock the myth behind the extraordinary capability of the liver for regeneration, which would help in designing new therapeutic options for the regenerative drive in difficult setup, such as chronic liver diseases. Associating Liver Partition and Portal vein ligation for Stage hepatectomy has been recently advocated to induce rapid future liver remnant hypertrophy that significantly shortens the time for the second stage hepatectomy. The introduction of Associating Liver Partition and Portal vein ligation for Stage hepatectomy in the surgical armamentarium of therapeutic tools for liver surgeons represented a real breakthrough in the history of liver surgery.

METHODS

A comprehensive literature review of Associating Liver Partition and Portal vein ligation for Stage hepatectomy and its utility in liver regeneration is performed.

RESULTS

Liver regeneration after Associating Liver Partition and Portal vein ligation for Stage hepatectomy is a combination of portal flow changes and parenchymal transection that generate a systematic response inducing hepatocyte proliferation and remodeling.

CONCLUSION

Associating Liver Partition and Portal vein ligation for Stage hepatectomy represents a real breakthrough in the history of liver surgery because it offers rapid liver regeneration potential that facilitate resection of liver tumors that were previously though unresectable. The jury is still out though in terms of safety, efficacy and oncological outcomes. As far as Associating Liver Partition and Portal vein ligation for Stage hepatectomy -induced liver regeneration is concerned, further research on the field should focus on the role of non-parenchymal cells in liver regeneration as well as on the effect of Associating Liver Partition and Portal vein ligation for Stage hepatectomy in liver regeneration in the setup of parenchymal liver disease.

Liver regeneration after partial hepatectomy

Liver regeneration after partial hepatectomy is an extremely complicated pathophysiologic process, which involves the up-regulation of many proliferation associated proteins and genes. The molecular mechanisms responsible for initiating, maintaining, and terminating this process are still under active investigation and remain one of the research focuses in the field of regenerative medicine. Studies of the mechanism of liver regeneration can provide a theoretical foundation for regeneration promotion and hepatic failure prevention, which is extremely important in clinical practice. This review aims to elucidate the molecular mechanism responsible for the initiation, proliferation and termination of liver regeneration.

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.

ALPPS: challenging the concept of unresectability--a systematic review

INTRODUCTION

Hepatic resection for malignancy is limited by the amount of liver parenchyma left behind. As a result, two-staged hepatectomy and portal vein occlusion (PVO) have become part of the treatment algorithm. Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) has been recently described as a method to stimulate rapid and profound hypertrophy.

MATERIALS AND METHODS

A systematic review of the literature pertaining to ALPPS was undertaken. Peer-reviewed articles relating to portal vein ligation (PVL) and in situ split (ISS) of the parenchyma were included.

RESULTS

To date, ALPPS has been employed for a variety of primary and metastatic liver tumors. In early case series, the perioperative morbidity and mortality was unacceptably high. However with careful patient selection and improved technique, many centers have reported a 0% 90-day mortality. The benefits of ALPPS include hypertrophy of 61-93% over a median 9-14 days, 95-100% completion of the second stage, and high likelihood of R0 resection (86-100%).

DISCUSSION

ALPPS is only indicated when a two-stage hepatectomy is necessary and the future liver remnant (FLR) is deemed inadequate (<30%). Use in patients with poor functional status, or advanced age (>70 years) is cautioned. Discretion should be used when considering this in patients with pathology other than colorectal liver metastases (CRLM), especially hilar tumors requiring biliary reconstruction. Biliary ligation during the first stage and routine lymphadenectomy of the hepatoduodenal ligament should be avoided.

CONCLUSIONS

A consensus on the indications and contraindications for ALPPS and a standardized operative protocol are needed.

New paradigms in post-hepatectomy liver failure

INTRODUCTION

Liver failure after hepatectomy remains the most feared postoperative complication. Many risk factors are already known, related to patient's comorbidities, underlying liver disease, received treatments and type of resection. Preoperative assessment of functional liver reserve must be a priority for the surgeon.

METHODS

Physiopathology of post-hepatectomy liver failure is not comparable to fulminant liver failure. Liver regeneration is an early phenomenon whose cellular mechanisms are beginning to be elucidated and allowing most of the time to quickly recover a functional organ. In some cases, microscopic and macroscopic disorganization appears. The hepatocyte hyperproliferation and the asynchronism between hepatocytes and non-hepatocyte cells mitosis probably play a major role in this pathogenesis.

RESULTS

Many peri- or intra-operative techniques try to prevent the occurrence of this potentially lethal complication, but a better understanding of involved mechanisms might help to completely avoid it, or even to extend the possibilities of resection.

CONCLUSION

Future prevention and management may include pharmacological slowing of proliferation, drug or physical modulation of portal flow to reduce shear-stress, stem cells or immortalized hepatocytes injection, and liver bioreactors. Everything must be done to avoid the need for transplantation, which remains today the most efficient treatment of liver failure.

A critical appraisal of the hemodynamic signal driving liver regeneration

BACKGROUND

Many aspects of the signaling mechanisms involved in the initiation of hepatic regeneration are under current investigation. Nevertheless, the actual mechanisms switching liver regeneration on and off are still unknown. Hemodynamic changes in the liver following partial hepatectomy have been suggested to be a primary stimulus in triggering liver regeneration. Most of the new knowledge about the impact of hemodynamic changes on liver regeneration is both conceptually important and directly relevant to clinical problems.

PURPOSE

The purpose of this review is therefore to exclusively address the hemodynamic signal driving the liver regeneration process.