A novel rat model of liver regeneration: possible role of cytokine induced neutrophil chemoattractant-1 in augmented liver regeneration

Circulating proliferative factors versus portal inflow redistribution: mechanistic insights of ALPPS-derived rapid liver regeneration

BACKGROUND

Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) can induce accelerated regeneration of future liver remnant (FLR) and effectively reduce the occurrence of liver failure due to insufficient FLR after hepatectomy, thereby increasing the probability of radical resection for previously inoperable patients with liver cancer. However, the exact mechanism by which ALPPS accelerates liver regeneration remains elusive.

METHODS

A review of the literature was performed utilizing MEDLINE/PubMed and Web of Science databases in March of 2024. The key words "liver regeneration/hypertrophy", "portal vein ligation/embolization", "two-stage hepatectomy", "liver partition/split" and "future liver remnant" in combination with "mechanisms", "hemodynamics", "cytokines", "growth factors" or "collaterals" were searched in the title and/or abstract. The references of relevant articles were reviewed to identify additional eligible publications.

RESULTS

Previously, a widely accepted view is that the primary role of liver splitting in ALPPS stage 1 is to accelerate liver regeneration by promoting proliferative factor release, but increasing evidence in recent years reveal that not the circulating factors, but the portal hemodynamic alternations caused by liver parenchyma transection play a pivotal role in ALPPS-associated rapid liver hypertrophy.

CONCLUSION

Parenchyma transection-induced portal hemodynamic alternations are the main triggers or driving forces of accelerated liver regeneration following ALPPS. The release of circulating proliferative factors seems to be a secondary response to liver splitting and plays an auxiliary role in this process.

Impact of endothelial nitric oxide synthase activation on accelerated liver regeneration in a rat ALPPS model

BACKGROUND

Although the associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) induces more rapid liver regeneration than portal vein embolization, the mechanism remains unclear.

AIM

To assess the influence of inflammatory cytokines and endothelial nitric oxide synthase (eNOS) activation on liver regeneration in ALPPS.

METHODS

The future liver remnant/body weight (FLR/BW) ratio, hepatocyte proliferation, inflammatory cytokine expression, and activation of the Akt-eNOS pathway were evaluated in rat ALPPS and portal vein ligation (PVL) models. Hepatocyte proliferation was assessed based on Ki-67 expression, which was confirmed using immunohistochemistry. The serum concentrations of inflammatory cytokines were measured using enzyme linked immune-solvent assays. The Akt-eNOS pathway was assessed using western blotting. To explore the role of inflammatory cytokines and NO, Kupffer cell inhibitor gadolinium chloride (GdCl₃), NOS inhibitor N-nitro-arginine methyl ester (L-NAME), and NO enhancer molsidomine were administered intraperitoneally.

RESULTS

The ALPPS group showed significant FLR regeneration (FLR/BW: 1.60% ± 0.08%, P < 0.05) compared with that observed in the PVL group (1.33% ± 0.11%) 48 h after surgery. In the ALPPS group, serum interleukin-6 expression was suppressed using GdCl₃ to the same extent as that in the PVL group. However, the FLR/BW ratio and Ki-67 labeling index were significantly higher in the ALPPS group administered GdCl₃ (1.72% ± 0.19%, P < 0.05; 22.25% ± 1.30%, P < 0.05) than in the PVL group (1.33% ± 0.11% and 12.78% ± 1.55%, respectively). Phospho-Akt Ser⁴⁷³ and phospho-eNOS Ser¹¹⁷⁷ levels were enhanced in the ALPPS group compared with those in the PVL group. There was no difference between the ALPPS group treated with L-NAME and the PVL group in the FLR/BW ratio and Ki-67 labeling index. In the PVL group treated with molsidomine, the FLR/BW ratio and Ki-67 labeling index increased to the same level as in the ALPPS group.

CONCLUSION

Early induction of inflammatory cytokines may not be pivotal for accelerated FLR regeneration after ALPPS, whereas Akt-eNOS pathway activation may contribute to accelerated regeneration of the FLR.

Impact of laparoscopic liver resection on liver regeneration

BACKGROUND

Liver regeneration after liver resection plays an important role in preventing posthepatectomy liver failure. In this study, we aimed to evaluate and compare the impact of laparoscopic liver resection (LLR) and open liver resection (OLR) on liver regeneration.

METHODS

Patients who underwent curative anatomical liver resection for hepatocellular carcinoma, cholangiocellular carcinoma, and colorectal liver metastases at our institution between January 2010 and December 2018 were included in this study. The patients were divided into the OLR and LLR groups. Preoperative liver volume (PLV), future remnant liver volume, resected liver volume (RLV), liver volume at 1 month after the surgery, and liver volume at 6 months after the surgery were calculated. The liver regeneration rate was defined as the increase in the rate of RLV, and the liver recovery rate was defined as the rate of return to the PLV.

RESULTS

The study included 72 patients. Among them, 43 were included in the OLR group and 29 were included in the LLR group. No differences were observed in the baseline characteristics and surgical procedures between the two groups. Moreover, no significant difference was observed in the liver regeneration rate at 1 month after the surgery (OLR vs. LLR: 68.9% vs. 69.0%, p = 0.875) and at 6 months after the surgery (91.8% vs. 93.2%, p = 0.995). Furthermore, the liver recovery rates were not significantly different between the two groups at 1 month after the surgery (90.3% vs. 90.6%, p = 0.893) and at 6 months after the surgery (96.9% vs. 98.8%, p = 0.986).

CONCLUSION

Liver regeneration after liver resection is not affected by the type of surgical procedure and both laparoscopic and open procedures yield similar regeneration and recovery rates.

Associating liver partition and portal vein ligation for staged hepatectomy in the treatment of colorectal cancer liver metastases

Colorectal cancer (CRC) is a common malignancy of the digestive system. Colorectal liver cancer metastasis (CRLM) occurs in approximately 50% of the patients and is the main cause of CRC mortality. Surgical resection is currently the most effective treatment for CRLM. However, given that the remnant liver volume after resection should be adequate, only a few patients are suitable for radical resection. Since Dr. Hans Schlitt first performed the associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) for CRLM in 2012, ALPPS has received considerable attention and has continually evolved in recent years. This review explains the technical origin of the ALPPS procedure for CRLM and evaluates its efficacy, pointing to its favorable postoperative outcomes. We also discuss the patient screening strategies and optimization of ALPPS to ensure long-term survival of patients with CRLM in whom surgery cannot be performed. Finally, further directions in both basic and clinical research regarding ALPPS have been proposed. Although ALPPS surgery is a difficult and high-risk technique, it is still worth exploration by experienced surgeons.

RNA-Seq transcriptome profiling in three liver regeneration models in rats: comparative analysis of partial hepatectomy, ALLPS, and PVL

The liver is a unique organ that has a phenomenal capacity to regenerate after injury. Different surgical procedures, including partial hepatectomy (PH), intraoperative portal vein ligation (PVL), and associated liver partition and portal vein ligation for staged hepatectomy (ALPPS) show clinically distinct recovery patterns and regeneration. The observable clinical differences likely mirror some underlying variations in the patterns of gene activation and regeneration pathways. In this study, we provided a comprehensive comparative transcriptomic analysis of gene regulation in regenerating rat livers temporally spaced at 24 h and 96 h after PH, PVL, and ALPPS. The time-dependent factors appear to be the most important determinant of post-injury alterations of gene expression in liver regeneration. Gene expression profile after ALPPS showed more similar expression pattern to the PH than the PVL at the early phase of the regeneration. Early transcriptomic changes and predicted upstream regulators that were found in all three procedures included cell cycle associated genes (E2F1, CCND1, FOXM1, TP53, and RB1), transcription factors (Myc, E2F1, TBX2, FOXM1), DNA replication regulators (CDKN1A, EZH2, RRM2), G1/S-transition regulators (CCNB1, CCND1, RABL6), cytokines and growth factors (CSF2, IL-6, TNF, HGF, VEGF, and EGF), ATM and p53 signaling pathways. The functional pathway, upstream, and network analyses revealed both unique and overlapping molecular mechanisms and pathways for each surgical procedure. Identification of molecular signatures and regenerative signaling pathways for each surgical procedure further our understanding of key regulators of liver regeneration as well as patient populations that are likely to benefit from each procedure.

ALPPS for hepatocarcinoma under cirrhosis: a feasible alternative to portal vein embolization

Hepatocellular carcinoma (HCC) is one of the most common and malignant tumors. Preoperative portal vein embolization (PVE) is currently the most accepted treatment before major hepatic resection for HCC in patients with liver fibrosis or cirrhosis and associated insufficient future liver remnant (FLR). In the last decade, associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) technique has been described to obtain an increase of volume regarding PVE and a decrease of drop out. The initial excessive morbidity and mortality of this technique have decreased drastically due to a better selection of patients, the learning curve and the use of less aggressive variations of the original technique in the first stage. For both techniques a complete preoperative assessment of the FLR is the most important issue and only patients with and adequate FLR should be resected. ALPPS could be a feasible technique in very selected patients with HCC and cirrhosis. As long as it is performed in an experienced center could be used as a first choice technique versus PVE or could be used as a rescue technique in case of PVE failure.

Hypoxia protects the liver from Small For Size Syndrome: A lesson learned from the associated liver partition and portal vein ligation for staged hepatectomy (ALPPS) procedure in rats

Portal hyperperfusion and "dearterialization" of the liver remnant are the main pathogenic mechanisms for Small For Size syndrome (SFSS). Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) induces rapid remnant hypertrophy. We hypothesized a similar increase in portal pressure/flow into the future liver remnant in ALPPS and SFSS-setting hepatectomies. In a rodent model, ALPPS was compared to SFSS-setting hepatectomy. We assessed mortality, remnant hypertrophy, hepatocyte proliferation, portal and hepatic artery flow, hypoxia-induced response, and liver sinusoidal morphology. SFSS-hepatectomy rats were subjected to local (hepatic artery ligation) or systemic (Dimethyloxalylglycine) hypoxia. ALLPS prevented mortality in SFSS-setting hepatectomies. Portal hyperperfusion per liver mass was similar in ALLPS and SFSS. Compared to SFSS, efficient arterial perfusion of the remnant was significantly lower in ALPPS causing pronounced hypoxia confirmed by pimonidazole immunostaining, activation of hypoxia sensors and upregulation of neo-angiogenic genes. Liver sinusoids, larger in ALPPS, collapsed in SFSS. Induction of hypoxia in SFSS reduced mortality. Hypoxia had no impact on hepatocyte proliferation but contributed to the integrity of sinusoidal morphology. ALPPS hemodynamically differ from SFSS by a much lower arterial flow in ALPPS's FLR. We show that the ensuing hypoxic response is essential for the function of the regenerating liver by preserving sinusoidal morphology.

[Preconditioning of the liver]

Posthepatectomy liver failure (PHLF) still represents a severe complication after major liver resection associated with a high mortality. In addition to an insufficient residual liver volume various factors play an important role in the pathophysiology of PHLF. These include the quality of the parenchyma, liver function, perfusion, i.e. maintenance of adequate inflow and outflow, as well as the condition of the patient and comorbidities. While the liver volume is relatively easy to evaluate using modern imaging techniques, the evaluation of liver function and liver quality require a differentiated approach. Both factors can be influenced by the constitutional status of the patient, medical history and previous treatment and must be given sufficient consideration in the risk evaluation. An adequate perfusion, e.g. portal and arterial circulation and adequate outflow by at least one hepatic vein as well an adequate biliary drainage should be always guaranteed in order to allow regeneration of the residual liver tissue. Only the understanding of all these aspects will support the surgeon in a correct and safe evaluation of the resectability. Additionally, the liver surgeon should be aware of all available perioperative and postoperative options to treat and to prevent PHLF. In this review article the most important questions regarding the risk factors related to PHLF are presented and the potential therapeutic and prophylactic management is described. The main goal is to ensure functional operability of the patient if oncological resectability is possible. In other words: in the case of correct oncological indication, the liver surgeon should be able to resect what is resectable or, alternatively, make resectable what primarily was not resectable.

Associating liver partition and portal vein ligation for staged hepatectomy: establishment of an animal model with insufficient liver remnant

Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) allows extended hepatectomy in patients with an extremely small future liver remnant (FLR). Current rodent models of ALPPS do not include resection resulting in insufficient-for-survival FLR, or they do incorporate liver mass reduction prior to ALPPS. Differences in FLR volume and surgical procedures could bias our understanding of physiological and hemodynamic mechanisms. We aimed to establish a rat ALPPS model with minimal FLR without prior parenchymal resection. In rodents, the left median lobe (LML) represents 10% of total liver. Partial hepatectomy (PHx) sparing LML and pericaval parenchyma represents our reference 87% resection. The first step in the procedure is either portal vein ligation (PVL) corresponding to ligation of all but the LML portal branches, or PVL with transection between the left and right median lobe segments (PVLT), and is defined as ALPPS stage-1. Second, ligated lobes were removed: PVL-PHx represents a conventional 2-stage hepatectomy, while PVLT followed by PHx is a strict reproduction of human ALPPS. In Group A, liver hypertrophy was analyzed after PVL (n = 38), PVLT (n = 47), T (n = 10), and sham (n = 10); In group B, mortality and FLR hypertrophy was assessed after PHx (n = 42), Sham-PHx (n = 6), PVL-PHx (n = 37), and PVLT-PHx (n = 45). In group A, PVLT induced rapid FLR hypertrophy compared to PVL (p < 0,05). Hepatocyte proliferation was higher in PVLT remnants (p < 0,05). In group B, PHx had a 5-day mortality rate of 84%. Sham operation prior to PHx did not improve survival (p = 0.23). In both groups, major fatalities occurred within 48 h after resection. PVL or PVLT prior to PHx reduced mortality to 33.3% (p = 0,007) or 25% (p = 0.0002) respectively, with no difference between the 2 two-stage procedures (p = 0.6). 7-day FLR hypertrophy was higher after the PVLT-PHx compared to PVL-PHx and PHx (p = 0.024). Our model reproduces human ALPPS with FLR that is insufficient for survival without liver resection prior to the stage-1 procedure. It offers an appropriate model for analyzing the mechanisms driving survival rescue and increased hypertrophy.

NAFLD Induction Delays Postoperative Liver Regeneration of ALPPS in Rats

BACKGROUND

Associating liver partition and portal vein ligation (ALPPS) is a promising two-step hepatectomy that is beneficial for accumulative regeneration of the future liver remnant (FLR) and avoids postoperative liver failure.

AIMS

Our study aimed to evaluate whether nonalcoholic fatty liver disease affected the liver regeneration induced by ALPPS.

METHODS

Sprague-Dawley rats fed a high-fat diet were used to construct the NAFLD model. ALPPS were performed, and blood and future liver remnant samples were collected at postoperative days 1 (POD1), POD3, and POD7.

RESULTS

The hepatic regeneration rate (HRR) of ALPPS was higher than that of portal vein ligation (PVL) at POD3 and POD7 (p < 0.05), and the number of Ki-67-positive hepatocytes (POD3) and CD68-positive Kupffer cells (POD7) per visual field was higher in the ALPPS group than in the PVL group (p < 0.05). The serum TNF-α, hepatocyte growth factor protein, and the serum IL-6 level were higher in the ALPPS group than in the PVL group at POD3 and POD7. Compared with those of the standard laboratory diet (SLD)-fed rats, the rats with NAFLD exhibited a decrease in the HRR, Ki-67-positive hepatocytes, and CD68-positive Kupffer cells in the FLR. The number of CD68-positive Kupffer cells was lower in rats with NAFLD than that in SLD-fed rats; noteworthily, the serum level of IL-6 and TNF-α changed dramatically after surgeries.

CONCLUSIONS

NAFLD induction delayed liver regeneration induced by the ALPPS procedure, which might be associated with hepatocyte proliferation and the number of Kupffer cells.

Hepatic regeneration by associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) is feasible but attenuated in rat liver with thioacetamide-induced fibrosis

BACKGROUND

The associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) procedure promotes the proliferation of the future liver remnant, but evidence to support the feasibility of ALPPS in livers with fibrosis is needed. Therefore the aim of this study was to establish a fibrotic ALPPS model in the rat to compare the capacity of regeneration in the remnant liver with or without fibrosis.

METHODS

In our study we first established a thioacetamide-induced fibrotic ALPPS model in rats. Then the ALPPS-induced regenerative capacities of normal and fibrotic liver were compared in this animal model. In addition, markers of regeneration, including the proliferative index and cyclin D1 and proliferating cell nuclear antigen levels, as well as various indicators of liver function were determined to evaluate the quality of the hepatic regeneration.

RESULTS

Compared with that of the sham group (opening of the peritoneal cavity with no further operative manipulation), the proliferation of the future liver remnant in fibrotic rat liver after the ALPPS procedure was increased on postoperative days 1, 2, and 5 (P < .039 each). In addition, the proliferative response was greater in the ALPPS group than in the ligation group subjected only to portal vein ligation of the left lateral, left middle, right, and caudate lobes (P = .099, P = .006, and P = .020 on postoperative days 1, 2, and 5, respectively). In contrast, the ALPPS-induced regenerative capacity in the fibrotic rat livers was attenuated compared with that in the normal liver on postoperative days 1, 2, and 5 (P < .031 for each) after stage I and on postoperative day 5 after stage II of the ALPPS procedure (P < .005). This attenuated the recovery of liver function, and the greater mortality rate indicated that functional proliferation was either delayed or not as extensive in the fibrotic rat livers.

CONCLUSION

Through establishing a rat model of thioacetamide-induced liver fibrosis, we found that ALPPS-derived liver regeneration was present and feasible in fibrotic livers, but this effect was attenuated compared with that in normal liver.

Assessment of liver regeneration after associating liver partition and portal vein ligation for staged hepatectomy: a comparative study with portal vein ligation

BACKGROUND

To investigate the diagnostic value of diffusion kurtosis imaging (DKI) and diffusion-weighted imaging (DWI) in assessing liver regeneration after associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) compared with portal vein ligation (PVL).

METHODS

Thirty rats were divided into the ALPPS, PVL, and control groups. DKI and DWI were performed before and 7 days after surgery. Corrected apparent diffusion (D), kurtosis (K) and apparent diffusion coefficient (ADC) were calculated and compared, radiologic-pathologic correlations were evaluated.

RESULTS

The volume of the right median lobe increased significantly after ALPPS. There were larger cellular diameters after ALPPS and PVL (P = 0.0003). The proliferative indexes of Ki-67 and hepatocyte growth factor were higher after ALPPS (P = 0.0024/0.0433). D, K and ADC values differed between the groups (P = 0.021/0.0015/0.0008). A significant correlation existed between D and the hepatocyte size (r = -0.523), no correlations existed in ADC and K (P = 0.159/0.111). The proliferative indexes showed moderate negative correlations with ADC (r = -0.484/-0.537) and no correlations with D and K (P = 0.100-0.877).

DISCUSSION

Liver regeneration after ALPPS was effective and superior to PVL. DKI, especially the D map, may provide added value in evaluating the microstructure of liver regeneration after ALPPS, but this model alone may perform no better than the standard monoexponential model of DWI.

Rapid Liver Hypertrophy After Portal Vein Occlusion Correlates with the Degree of Collateralization Between Lobes-a Study in Pigs

BACKGROUND

Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) induces more rapid liver growth than portal vein ligation (PVL). Transection of parenchyma in ALPPS may prevent the formation of collaterals between lobes. The aim of this study was to determine if abrogating the formation of collaterals through parenchymal transection impacted growth rate.

METHODS

Twelve Yorkshire Landrace pigs were randomized to undergo ALPPS, PVL, or "partial ALPPS" by varying degrees of parenchymal transection. Hepatic volume was measured after 7 days. Portal blood flow and pressure were measured. Portal vein collaterals were examined from epoxy casts.

RESULTS

PVL, ALPPS, and partial ALPPS led to volume increases of the RLL by 15.5% (range 3-22), 64% (range 45-76), and 32% (range 18-77), respectively, with significant differences between PVL and ALPPS/partial ALPPS (p < 0.05). In PVL and partial ALPPS, substantial new portal vein collaterals were found. The number of collaterals correlated inversely with the growth rate (p = 0.039). Portal vein pressure was elevated in all models after ligation suggesting hyperflow to the portal vein-supplied lobe (p < 0.05).

CONCLUSIONS

These data suggest that liver hypertrophy following PVL is inversely proportional to the development of collaterals. Hypertrophy after ALPPS is likely more rapid due to reduction of collaterals through transection.

[Robotic approach to hepatobiliary surgery. German version]

Robot-assisted hepatobiliary surgery has been steadily growing in recent years. It represents an alternative to the open and laparoscopic approaches in selected patients. Endowristed instruments and enhanced visualization provide important advantages in terms of selective bleeding control, microsuturing, and dissection. Cholecystectomies and minor hepatectomies are being performed with comparable results to open and laparoscopic surgery. Even complex procedures, such as major and extended hepatectomies, can have excellent outcomes, in expert hands. The addition of indocyanine green fluorescence provides an additional advantage for recognition of the vascular and biliary anatomy. Future innovations will allow for expanding its use and indications. Robotic surgery has become a very important component of modern minimally invasive surgery and the development of new robotic technology will facilitate a broader adoption of this technique.

Portal vein ligation alters coding and noncoding gene expression in rat livers

Portal vein occlusion increases the resectability of initially unresectable liver cancer by inducing hypertrophy in non-occluded liver lobes. However, the mechanisms of how portal vein occlusion induces hepatic hypertrophy remain unclear. A cDNA microarray was used to identify the gene expression signatures of ligated (LLLs) and nonligated liver lobes (NLLLs) at different time points after portal vein ligation (PVL). The results of a bioinformatics analysis revealed that LLLs and NLLLs displayed different gene expression profiles. Moreover, the expression levels of both coding and noncoding RNA were different between LLLs and NLLLs at different time points after PVL. A series test of cluster analysis revealed that the No. 22 and No. 5 expression patterns, which showed altered expression at 24 h and maintained this altered expression over the following 14 days, had the lowest P values and the highest number of differentially expressed genes in both the LLLs and NLLLs. The results of a GO analysis showed the activation of hypoxia pathways in LLLs and the activation of cell proliferation and cell-cycle pathways in NLLLs, suggesting the involvement of these pathways in PVL-induced hepatic hypertrophy and regeneration. These results provide insight into the molecular mechanisms underlying hepatic hypertrophy and regeneration induced by portal vein occlusion, and they identify potential targeting pathways that can promote the clinical application of PVL in liver cancer therapy.

Rat Model of the Associating Liver Partition and Portal Vein Ligation for Staged Hepatectomy (ALPPS) Procedure

Recent clinical data support an aggressive surgical approach to both primary and metastatic liver tumors. For some indications, like colorectal liver metastases, the amount of liver tissue left behind after liver resection has become the main limiting factor of resectability of large or multiple liver tumors. A minimal amount of functional tissue is required to avoid the severe complication of post-hepatectomy liver failure, which has high morbidity and mortality. Inducing liver growth of the prospective remnant prior to resection has become more established in liver surgery, either in the form of portal vein embolization by interventional radiologists or in the form of portal vein ligation several weeks prior to resection. Recently, it was shown that liver regeneration is more extensive and rapid, when the parenchymal transection is added to portal vein ligation in a first stage and then, after only one week of waiting, resection performed in a second stage (Associating Liver Partition and Portal vein ligation for Staged hepatectomy = ALPPS). ALPPS has rapidly become popular across the world, but has been criticized for its high perioperative mortality. The mechanism of accelerated and extensive growth induced by this procedure has not been well understood. Animal models have been developed to explore both the physiological and molecular mechanisms of accelerated liver regeneration in ALPPS. This protocol presents a rat model that allows mechanistic exploration of accelerated regeneration.

Animal Models for Associating Liver Partition and Portal Vein Ligation for Staged Hepatectomy (ALPPS): Achievements and Future Perspectives

Background: Since 2012, Associated Liver Partition and Portal vein ligation for Staged hepatectomy (ALPPS) has been standing in the limelight of modern liver surgery and numerous questions have been raised regarding this novel approach. On the one hand, ALPPS has proved to be a valuable method in the treatment of hepatic tumors, while on the other hand, there are many controversies, such as high mortality and morbidity rates. Further surgical research is essential for a better understanding of underlying mechanisms and for enhancing patient safety. Summary: Until recently, only 8 animal models have been created with the purpose to mimic ALPPS-induced liver regeneration. From these 7 are rodent (6 rat and 1 mouse) models, while only 1 is a large animal model, which uses pigs. In case of rodent models, portal flow deprivation of 75-90% is achieved via portal vein ligation leaving only the right (20-25%) or left median (10-15%) lobes portally perfused, while liver splitting in general is carried out positioned according to the falciform ligament. As for the swine model, the left lateral and medial lobes (70-75% of total liver volume) are portally ligated, and the right lateral lobe (accounting for 20-24% of the parenchyma) is partially resected in order to reach critical liver volume. Each model is capable of reproducing the accelerated liver regeneration seen in human cases. However, all species have significantly different liver anatomy compared with the human anatomic situation, making clinical translation somewhat difficult. Key Messages: Unfortunately, there are no perfect animal models available for ALPPS research. Small animal models are inexpensive and well suited for basic research, but may only provide limited translational potential to humans. Clinically large animal models may provide more relevant data, but currently no suitable one exists.

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.

The Future Liver Remnant in Patients Undergoing the Associating Liver Partition with Portal Vein Ligation for Staged Hepatectomy (ALPPS) Maintains the Immunological Components of a Healthy Organ

Background and Aims

A short-interval, two-stage approach termed associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) increases the number of patients with extensive malignant disease of the liver and a small future liver remnant (FLR) that can undergo liver resection. While this approach results in accelerated liver hypertrophy of the FLR, it remains unknown whether this phenomenon is restricted to liver parenchymal cells. In the current study, we evaluated whether ALPPS alters the immunological composition of the deportalized lobe (DL) and the FLR.

Methods

In this prospective, single-center study, liver tissue from the DL and the FLR were collected intra-operatively from adult patients undergoing ALPPS for their liver metastases. The extent of hypertrophy of the FLR was determined by volumetric helical computed tomography. Flow cytometry and histological analyses were conducted on liver tissues to compare the frequency of several immune cell subsets, and the architecture of the liver parenchyma between both stages of ALPPS.

Results

A total of 12 patients completed the study. Histologically, we observed a patchy peri-portal infiltration of lymphocytes within the DL, and a significant widening of the liver cords within the FLR. Within the DL, there was a significantly higher proportion of B cells and CD4⁺ T cells as well innate-like lymphocytes, namely mucosa-associated invariant T (MAIT) cells and natural killer T (NKT) cells following ALPPS. In contrast, the frequency of all evaluated immune cell types remained relatively constant in the FLR.

Conclusion

Our results provide the first description of the immunological composition of the human liver following ALPPS. We show that following the ALPPS procedure, while the immune composition of the FLR remains relatively unchanged, there is a moderate increase in several immune cell populations in DL. Overall, our results support the continued utilization of the ALPPS procedure.

Establishment of a rat model: Associating liver partition with portal vein ligation for staged hepatectomy

BACKGROUND

We adapted the anatomically oriented parenchyma-preserving resection technique for associating liver partition with portal vein ligation (PVL) for staged hepatectomy (ALPPS) in rats and examined the role of revascularization in intrahepatic size regulation.

METHODS

We performed the procedures based on anatomic study. The ALPPS procedure consisted of a 70% PVL (occluding the left median, left lateral, and right lobes), parenchymal transection (median lobe) and partial (10%) hepatectomy (PHx; caudate lobe). The transection effect was evaluated by measuring the extent of hepatic atrophy or regeneration of individual liver lobes in the ALPPS and control groups (70% PVL and 10% PHx without transection). The survival rates after stage II resection and collateral formation within the portal vein system was examined.

RESULTS

Anatomic study revealed a close spatial relationship between the demarcation line and the middle median hepatic vein. This enabled placing the transection plane without injuring the hepatic vein. Transection was achieved via stepwise clamping, followed by 2-3 parenchyma-preserving piercing sutures on both sides of the clamp. Ligated liver lobes atrophy was significantly enhanced after ALPPS compared with the control group. In contrast, both a significantly greater relative weight of the regenerated lobe and proliferation index on the first postoperative day were observed. All animals tolerated stage II-resection without complications. Portoportal collaterals were only observed in the control group.

CONCLUSION

We developed an anatomically precise technique for parenchymal transection. The lack of a dense vascular network between the portalized and deportalized lobes may play an important role in accelerating regeneration and atrophy augmentation.