Progressive histological damage in liver allografts following pediatric liver transplantation

Two-Dimensional Shear Wave Ultrasound Elastography for Monitoring Pediatric Liver Transplantation: A Review of Recent Advances

Pediatric liver transplantation (PLT) is a life-saving procedure for children with end-stage liver disease. However, post-transplant monitoring, particularly the diagnosis and prognosis of complications such as allograft fibrosis, remains challenging. Traditionally, liver biopsy has been the gold standard for assessing allograft fibrosis, despite its invasive nature and inherent procedural risks. Recently, shear wave ultrasound elastography (SWE) has seen increasing use as a noninvasive method to provide real-time, quantitative measurements of liver stiffness as a proxy for fibrosis. In this review, the latest developments in the use of SWE as a method to assess allograft fibrosis post-PLT are presented, including the current technical challenges associated with its clinical implementation.

Less is more: The use of single biodegradable stenting to treat biliary anastomotic strictures in pediatric liver transplantation

This study reports our experience of using biodegradable biliary stents (BBSs) for anastomotic biliary strictures (ABSs) in pediatric patients undergoing liver transplants. It involves the analysis of a retrospective data collection from January 2014 to January 2023, including all pediatric recipients of liver transplants in our center treated for ABSs with BBSs. In phase 1 (2014-2019), there was an initial percutaneous transhepatic cholangiography with anastomotic dilatation followed 2 weeks after a second percutaneous transhepatic cholangiography with BBS insertion. In phase 2 (2019-2023), the BBS was placed shortly after ABS dilatation, requiring only 1 percutaneous transhepatic cholangiography. All patients were followed up with routine tests and ultrasound. Forty-six ABSs were diagnosed in 43 pediatric recipients of liver transplants with a median of 6.7 months after liver transplantation (0.1-246.8 mo). Eight out of 46 ABSs (17.4%) treated with BBSs relapsed (median recurrence time: 6.5 mo; 1.6-17.0 mo). Four resolved with further BBS placement; only 4 needed surgical revision (8.7%) after a median follow-up time of 43.9 months (0.3-106.3). There were no differences in ABS recurrence rate, time between stent placement and recurrence, or the presence of cholangitis based on whether the BBS was deployed in 1 or 2 steps. Patients with end-to-end anastomosis had a higher ABS recurrence (OR 10.8; 1.4-81.3, p = 0.008) than those with bilioenteric anastomosis. The use of biodegradable stents could be a good option for treating ABSs in pediatric patients undergoing liver transplants, with our series showing a success rate of over 90% and an average follow-up of 43.9 months.

Transient Elastography for Noninvasive Evaluation of Posttransplant Liver Graft Fibrosis in Turkish Children, Ege University Children Hospital Experience

OBJECTIVES

The influence of advancing fibrosis on graft survival in the context of pediatric liver transplantation accentuates the critical role of protocol-driven liver biopsies, a practice adopted by numerous medical centers. Consequently, the exigency for noninvasive methodologies to assess graft fibrosis assumes heightened importance when conventional clinical and laboratory parameters fail to reveal signs of liver damage.

METHODS

This study aimed to assess the reliability of transient elastography (TE) in pediatric liver transplant recipients to detect graft fibrosis and compare the results of TE in patients who underwent biopsy.

RESULTS

This prospective cohort study included liver transplanted children who underwent biopsy at Ege University Children's Hospital between October 1, 2021, and October 31, 2022, and a healthy control group. According to TE, fibrosis was detected in 40 patients, and no fibrosis was detected in 50. The median time to develop fibrosis was 100 months (95% CI [83.1-116.8]). A statistically significant positive correlation existed between LSM and METAVIR fibrosis score (r = 0.562, p = 0.001). There was a statistically significant difference in LSM between patients with F2 fibrosis (7.8-8.8 kPa ± 3.2) compared to patients with F0 fibrosis (5.2 kPa ± 0.7) (p = 0.005) and F1 fibrosis (6.1 kPa ± 1.5) (p = 0.041), on ANOVA.

CONCLUSION

Liver allograft fibrosis is common in long-term follow-up in children who have undergone liver transplantation. Abnormal TE may guide physicians to consider liver biopsy to detect late allograft fibrosis in these children.

Elastography-The New Standard in the Assessment of Fibrosis After Pediatric Liver Transplantation?

BACKGROUND

The development of graft fibrosis after pediatric liver transplantation (PLT) remains a major concern as it can lead to graft failure and ultimately graft loss. Elastography is a non-invasive method to assess liver fibrosis, but its role in the posttransplant setting is unclear. The aim of our study was to evaluate shear wave elastography (SWE) in the assessment of liver fibrosis after PLT, including split-liver recipients.

METHODS

We retrospectively analyzed data from PLT recipients who underwent surveillance liver biopsy and concurrent 2D-SWE during the study period from April 2018 to July 2021. Spearman's correlation was used to compare histologic fibrosis stages with liver stiffness measurements (LSM) by 2D-SWE. AUROC analysis was performed to evaluate the performance. One sample t-test was used to compare results with reference values of healthy children.

RESULTS

62 cases were included. 29% showed histologic fibrosis. LSM by 2D-SWE were feasible in all children regardless of age or graft type. There was a significant correlation between LSM and fibrosis stage for all three scoring systems used (Ishak, p = 0.003; METAVIR, p = 0.005; LAF Score, p = 0.003). Patients with a history of biliary complications had increased liver stiffness (p = 0.015). The AUROC of 2D-SWE for predicting significant liver graft fibrosis was 0.81. Liver stiffness after PLT without graft fibrosis was higher than in healthy subjects, but comparable to that in children with chronic liver disease without fibrosis.

CONCLUSION

2D-SWE can reliably detect children with significant liver graft fibrosis, even in split-liver recipients. This study demonstrates the value of a non-invasive tool for fibrosis staging after PLT. 2D-SWE has the potential to improve long-term outcomes after PLT and to reduce the number of surveillance liver biopsies. But elastography is not a substitute for liver biopsy.

Banff 2022 Liver Group Meeting report: Monitoring long-term allograft health

The Banff Working Group on Liver Allograft Pathology met in September 2022. Participants included hepatologists, surgeons, pathologists, immunologists, and histocompatibility specialists. Presentations and discussions focused on the evaluation of long-term allograft health, including noninvasive and tissue monitoring, immunosuppression optimization, and long-term structural changes. Potential revision of the rejection classification scheme to better accommodate and communicate late T cell-mediated rejection patterns and related structural changes, such as nodular regenerative hyperplasia, were discussed. Improved stratification of long-term maintenance immunosuppression to match the heterogeneity of patient settings will be central to improving long-term patient survival. Such personalized therapeutics are in turn contingent on a better understanding and monitoring of allograft status within a rational decision-making approach, likely to be facilitated in implementation with emerging decision-support tools. Proposed revisions to rejection classification emerging from the meeting include the incorporation of interface hepatitis and fibrosis staging. These will be opened to online testing, modified accordingly, and subject to consensus discussion leading up to the next Banff conference.

Plasma Cell Infiltrate in Liver Allograft Biopsy: Clinical and Histological Implications

Introduction:

The relevance of plasma cells in the allograft liver is of utmost importance and objective assessment of these infiltrates and correlation with other ancillary findings needs to be evaluated.

Materials and Methods:

Three hundred and sixty-eight graft liver biopsies received in the department from 2012 to 2022 and 115 allograft liver biopsies with histopathological diagnosis of rejection were selected. Based on plasma cells percentage in the portal tracts, the biopsies were divided into three groups: Group 1 showing not more than an occasional plasma cell, Group 2 showing <10% plasma cells, and Group 3 showing >10% plasma cells. Rejection activity index (RAI), portal/lobular inflammation, interface activity, subendothelial inflammation (portal and central vein), duct damage/loss, presence of cholestasis, apoptosis, perivenulitis, necrosis, rosette along with serial liver function tests (LFTs), and patient status at 1 year of follow-up were recorded and compared between the groups.

Results:

Plasma cell infiltrates were observed in 52.6% of the specimens, with the mean percentage of plasma cells in the infiltrates being 4.9. Increased plasma cell infiltrates were associated with higher RAI scores, marked duct damage, marked portal and central vein endotheliitis, marked portal inflammation, and presence of interface activity. Higher levels of transaminitis were recorded at the time of biopsy, but no significant association was observed in the fall of serial LFTs over a 2-week period with the presence of plasma cells.

Conclusion:

Identifying plasma cell infiltrates in liver allografts can serve as a clue toward increased severity of rejection in liver allograft biopsies. Further studies with emphasis on correlation with the clinical outcome and response to treatment are needed to validate its utility as an objective tool.

Immunosuppression-Free Life after Pediatric Liver Transplant: A Case-Control Study from the Society of Pediatric Liver Transplant (SPLIT) Registry

OBJECTIVE

To compare long-term outcomes of pediatric liver transplant (LT) recipients off immunosuppression (IS) with matched controls on IS using data from the Society of Pediatric Liver Transplant (SPLIT) registry.

STUDY DESIGN

This was a retrospective case-control study. SPLIT participants <18 years of age, ≥4 years after isolated LT, and off IS for ≥1 year (cases) were age- and sex-matched 1:2 to patients with the same primary diagnosis and post-LT follow-up duration (controls). Primary outcomes included retransplantation, allograft rejection, IS comorbidities, and prevalence of SPLIT-derived composite ideal outcome (c-IO) achieved at the end of the follow-up period. Differences were compared using multiple linear regression for continuous outcomes and logistic regression for dichotomous data.

RESULTS

The study cohort was composed of 33 cases (42.4% male, 60.6% biliary atresia, median age at LT of 0.7 [P25, P75, 0.5, 1.6] years, median IS withdrawal time of 9 [P25, P75, 6, 12] years after LT) and 66 age- and sex-matched controls. No cases required retransplantation. Cases and controls had similar growth parameters, laboratory values, calculated glomerular filtration rates, rates of post-transplant lymphoproliferative disease, graft rejection, and attainment of c-IO.

CONCLUSIONS

No differences in allograft rejection rates, IS complications, or c-IO prevalence were seen between SPLIT patients off IS and age- and sex-matched controls remaining on IS. Discontinuation of IS most commonly occurred in the context of rigorously designed IS withdrawal trials. The available sample size was small, affecting generalizability to the broader pediatric LT population.

Balancing immunosuppression in pediatric liver transplantation: Playing the long game

The overarching goal in the care of pediatric liver transplant recipients is to optimize allograft and patient health. Balancing immunosuppression to maintain allograft health while avoiding medication side effects is essential for long-term survival and optimal quality of life in pediatric liver transplant recipients. Utilizing precision medicine to personalize immunosuppression, which includes minimization and withdrawal, is core to this effort. The unique anatomy and physiology of the liver make it more tolerant to immune-mediated injury and a more favorable organ for immunosuppression minimization and withdrawal. However, several challenges exist. Standard biochemical values and histologic features may not reliably predict allograft health after a reduction in immunosuppression. Additionally, biochemical values alone do not reliably identify which patients can successfully develop operational tolerance, as there may be occult allograft injury despite normal liver enzymes. Finally, the durability of tolerance after successful reduction in immunosuppression remains uncertain over time. Innovative tools show promise in circumventing these challenges, but more research is needed to determine actual clinical utility. While immunosuppression-free transplant may not be a current reality for most pediatric liver transplant recipients, strategies to safely minimize immunosuppression without compromising allograft health are within reach. Each liver allograft and recipient pair requires a different degree of immune modulation, and through a structured process of minimization and withdrawal, immunosuppression can indeed be tailored in a precise, personalized way to optimize outcomes. This review focuses on the progress that has been made to individualize immunosuppression in pediatric liver transplantation to ensure optimal allograft and recipient health.

Long-term Outcome of Asymptomatic Patients With Graft Fibrosis in Protocol Biopsies After Pediatric Liver Transplantation

BACKGROUND

The histological prevalence of allograft fibrosis in asymptomatic children after liver transplantation (LT) is well documented. However, long-term graft and patient survival remain unclear. This retrospective multicenter study aims to determine the prevalence of allograft fibrosis and analyze the long-term outcome for patients transplanted in childhood.

METHODS

We reviewed clinical data of children who had undergone 10-y protocol liver biopsies. We excluded patients with autoimmune hepatitis, primary sclerosing cholangitis, hepatitis B or C, and retransplantation. In total, 494 patients transplanted in childhood across 12 international transplant centers were included. We evaluated the development of fibrosis by comparing the results with biopsies obtained 5 and 15 y post-LT. Histological findings were correlated with graft and patient survival up to 20 y post-LT.

RESULTS

In the 10-y biopsies, periportal or pericentral fibrosis was observed in 253 patients (51%), 87 (18%) had bridging fibrosis, 30 (6%) had cirrhosis, and 124 (25%) had no fibrosis. The prevalence and stage of graft fibrosis significantly progressed from 5 to 10 y. At 10 y, the severity of fibrosis correlated significantly with inflammation. Patients with graft cirrhosis in the 10-y biopsy were more likely to die or require retransplantation subsequently ( P = 0.027).

CONCLUSIONS

At 10 y post-LT, most patients transplanted in childhood developed fibrosis, based on the protocol liver biopsies. Although mild-to-moderate graft fibrosis did not largely affect patient or graft survival up to 20 y post-LT, this progressive fibrosis finding has substantial implications for developing cirrhosis and portal hypertension in adult care.

Shear wave elastography and shear wave dispersion correlated to biopsy at the scheduled follow-up of pediatric liver grafts

BACKGROUND

It is unknown how shear wave dispersion (SWD) is displayed in pediatric liver transplant recipients and not fully elucidated how ultrasound shear wave elastography (2D-SWE) display within this cohort, which is important to determine to improve noninvasive surveillance of these patients. The study aimed to compare SWE and SWD values with histopathology in pediatric liver recipients.

METHODS

Forty-eight pediatric liver recipients were examined with SWE in conjunction with an elective liver biopsy (clinically without complication). Additionally, SWD values were measured in 21 children. SWE and SWD values were compared to histologically determined fibrosis graded as none-to-mild (F0-1) and moderate-to-severe (F2-4), and inflammation graded as low (grade 0-1) and high (grade 2-4).

RESULTS

Two children were excluded due to SWE IQR/median > 30% kPa. The mean age across 46 included patients was 10.9 years (range 1.4-18). The number of patients and median (range) SWE value (kPa) for each stage of fibrosis were: F0-1 [n = 23; 5.8 (3.2-16.1)], F2 [n = 22; 6.0 (4.5-25.9)], F3 [n = 1; 33.3], and F4 [n = 0]. Significantly higher SWE values and greater variability were registered in F2-4 vs. F0-1 (p = .05). Grade of fibrosis correlated weakly to SWE values (r = .3; p = .05), but not to SWD values (r = .2; p = .27). In patients with low-grade inflammation, median SWD was 13.7 m/s KHz (10.7-17.6). Only one patient had high-grade inflammation.

CONCLUSIONS

Uncomplicated transplanted liver grafts in a small pediatric cohort revealed slightly increased SWE and SWD values compared to previously reported values in healthy children. This likely reflect both the fibrotic and inflammatory elements in the grafts; however, other confounders impacting the liver's viscoelastic properties are also probable factors.

Fibrosis and steatosis of the liver graft: Are non-invasive tests useful? A short review

As life expectancy of liver transplanted patients improves, new questions are arising to avoid progressive graft loss. The spectrum of chronic inflammation and fibrosis are known to be important triggers in the alteration of graft function. Liver biopsy remains the gold standard to better understand progressive, normal, and abnormal histological modifications of the graft. In parallel, the interest for metabolic steatosis development in post-transplantation is also growing. Long-term survival of these patients involves the management of comorbidities including metabolic syndrome and cardiovascular diseases. Early detection of altered graft parenchyma, and monitoring of its evolution are undoubtedly essential. Non-invasive methods including transient elastography and fibrosis biomarkers are attractive tools to avoid drawbacks and complications of liver biopsy. Accuracy of these methods are well-known in a pre-transplantation setting, but evidence is lacking in post-transplantation setting. We review current knowledge of progressive liver fibrosis and steatosis development after transplantation and non-invasive methods of their assessment.

Mapping children by ALT 4-5 years after liver transplant: Potential individual and population applications

INTRODUCTION

Although clinicians repeatedly measure ALT to assess allograft health in children with liver transplants, they generally make decisions based on single values or qualitative trends without quantitative aggregation or synthesis. We therefore aimed to derive and test a holistic ALT metric for the 5th post-transplant year (Yr 4-5) that may better guide clinical decision-making and/or population comparisons.

METHODS

We derived the "adjusted mean Yr 4-5 ALT" for children transplanted in 2005-2016 by averaging the median ALT from each month. Patients in quartiles (Q1-4) defined by the adjusted mean Yr 4-5 ALT were compared by clinical variables, Yr 5-8 outcomes, and tacrolimus standard deviation (MLVI).

RESULTS

For 97 children [49 male; 77 deceased donors; median (IQR) age at LT 2.5 (0.8-11.7) years], the 25th, 50th, and 75th percentile thresholds for adjusted mean Yr 4-5 ALT were 19, 28, and 47 U/L, respectively. Age, donor type, LT indication, rejection history, and mean tacrolimus levels did not differ between quartiles (Q). Children in Q4 had more Yr 4-5 acute rejection episodes (p < .01), higher Yr 4-5 MLVI (p < .01), and more Yr 5-8 for-cause liver biopsies (p < .01) than those in Q1 + Q2. Children in Q3 also had higher Yr 4-5 MLVI than Q1 + Q2 (p = .047). Rates of chronic rejection and therapeutic liver-related procedures were higher in Q4 but the difference did not reach significance.

CONCLUSION

An integrated ALT metric calculated utilizing all available ALT values correlates with MLVI and future for-cause biopsies. Further study of this novel ALT metric as a predictor of clinical outcomes and descriptor of populations is warranted.

Long-term Outcome of Pediatric Liver Transplant Recipients Who Have Reached Adulthood: A Single-center Experience

BACKGROUND

As long-term survival of pediatric liver transplant recipients increases, the assessment of physical, psychological, and social well-being becomes more important.

METHODS

In this retrospective analysis, 120 young adult patients (age ≥18 y) who underwent liver transplantation in childhood were studied. Patients with ideal outcome were defined as patients with perfect graft function, with no complications from the immunosuppressive medication, no late retransplantation, and no steroid treatment. Also, the patients' drug adherence and their psychosocial situation were assessed.

RESULTS

After a median follow-up of 19 y, only 16.7% of the patients (mean age: 26.5 y) were considered patients with ideal outcome. The main reasons precluding ideal outcome were chronic kidney disease (38.3%), elevated liver enzymes (33.3%), and arterial hypertension (31.7%). Ideal outcome decreased over time from 54% to 42%, 26%, and 8% at 10-, 15-, 20-, and 25-y follow-up, respectively. Reduced drug adherence was noted in 24.8% of patients and associated with a significantly higher prevalence of donor-specific antibodies class II ( P  = 0.015), elevated transaminases ( P  = 0.010), and chronic rejection ( P  < 0.001). Also, 15% of patients had a psychiatric disease, mainly depression.

CONCLUSIONS

The morbidity of young adults who underwent liver transplantation as children was high and increased over time. The majority developed complications from immunosuppression or chronic graft dysfunction. More than 1 in 7 patients had a psychiatric disease and 1 in 4 was not perfectly drug adherent. Therefore, immunosuppressive treatment and psychological care should be optimized for these particularly vulnerable patients.

Liver transplantation immunology: Immunosuppression, rejection, and immunomodulation

Outcomes after liver transplantation have continuously improved over the past decades, but long-term survival rates are still lower than in the general population. The liver has distinct immunological functions linked to its unique anatomical configuration and to its harbouring of a large number of cells with fundamental immunological roles. The transplanted liver can modulate the immunological system of the recipient to promote tolerance, thus offering the potential for less aggressive immunosuppression. The selection and adjustment of immunosuppressive drugs should be individualised to optimally control alloreactivity while mitigating toxicities. Routine laboratory tests are not accurate enough to make a confident diagnosis of allograft rejection. Although several promising biomarkers are being investigated, none of them is sufficiently validated for routine use; hence, liver biopsy remains necessary to guide clinical decisions. Recently, there has been an exponential increase in the use of immune checkpoint inhibitors due to the unquestionable oncological benefits they provide for many patients with advanced-stage tumours. It is expected that their use will also increase in liver transplant recipients and that this might affect the incidence of allograft rejection. Currently, the evidence regarding the efficacy and safety of immune checkpoint inhibitors in liver transplant recipients is limited and cases of severe allograft rejection have been reported. In this review, we discuss the clinical relevance of alloimmune disease, the role of minimisation/withdrawal of immunosuppression, and provide practical guidance for using checkpoint inhibitors in liver transplant recipients.

Quantification of extracellular matrix remodeling for the non-invasive identification of graft fibrosis after liver transplantation

Detecting patients with early post-transplant fibrosis after liver transplantation (LT) is very important. Non-invasive tests are needed to avoid liver biopsies. We aimed to detect fibrosis in liver transplant recipients (LTR) using extracellular matrix (ECM) remodeling biomarkers. ECM biomarkers for type III (PRO-C3), IV (PRO-C4), VI (PRO-C6) and XVIII (PRO-C18L) collagen formation and type IV collagen degradation (C4M) were measured by ELISA in prospectively collected, cryopreserved plasma samples (n = 100) of LTR with paired liver biopsies from a protocol biopsy program. Fibrosis ≥ F2 was present in 29% of patients (median 44 months post-LT). APRI and FIB-4 neither identified significant fibrosis nor were correlated with histopathological fibrosis scores, while ECM biomarkers (AUCs 0.67-0.74) did. The median levels of PRO-C3 (15.7 vs. 11.6 ng/ml; p = 0.002) and C4M (22.9 vs. 11.6 ng/ml; p = 0.006) levels were elevated in T-cell-mediated rejection compared to normal graft function. The median levels of PRO-C4 (178.9 vs. 151.8 ng/ml; p = 0.009) and C4M (18.9 vs. 16.8 ng/ml; p = 0.004) levels were increased if donor-specific antibodies were present. PRO-C6 had the highest sensitivity (100%), NPV (100%) and negative likelihood-ratio (0) for graft fibrosis. To conclude, ECM biomarkers are helpful in identifying patients at risk of relevant graft fibrosis.

Liver fibrosis in children: a comprehensive review of mechanisms, diagnosis, and therapy

Chronic liver disease incidence is increasing among children worldwide due to a multitude of epidemiological changes. Most of these chronic insults to the pediatric liver progress to fibrosis and cirrhosis to different degrees. Liver and immune physiology differs significantly in children from adults. Because most of pediatric liver diseases have no definitive therapy, a better understanding of population and disease-specific fibrogenesis is mandatory. Furthermore, fibrosis development has prognostic significance and often guide treatment. Evaluation of liver fibrosis continues to rely on the gold-standard liver biopsy. However, many high-quality studies put forward the high diagnostic accuracy of numerous diagnostic modalities in this setting. Herein, we summarize and discuss the recent literature on fibrogenesis with an emphasis on pediatric physiology along with a detailed outline of disease-specific signatures, noninvasive diagnostic modalities, and the potential for antifibrotic therapies.

The role of immunosuppression in long-term graft hepatitis and fibrosis after paediatric liver transplant - comparison of two treatment protocols

Background and aims

We have previously demonstrated high rates of chronic allograft hepatitis and fibrosis in liver transplant patients on long-term cyclosporine monotherapy. We subsequently changed practice to add low-dose prednisolone to maintenance treatment with tacrolimus post-transplant. The aim of the study was to assess the impact of the immunosuppression change on graft histopathology.

Methods

Patients treated in this era (Tac + Pred, 2000-2009, N = 128) were compared to a historical cohort, who had been maintained on a steroid-free, cyclosporine-based regime (CSA-Only, 1985-1996, N = 129). Protocol liver biopsies and laboratory tests were performed five- and ten-years post-transplant in both groups.

Results

Compared to CSA-Only, the Tac + Pred cohort had significantly lower rates of chronic hepatitis (CH) at five (20% vs. 44%, p < 0.001) and ten (15% vs. 67%, p < 0.001) years post-transplant, with similar trends observed in inflammation and fibrosis at five years. The Tac + Pred cohort also had significantly lower hepatic transaminases and IgG levels and was less likely to be autoantibody positive at both time points. However, the degree of graft fibrosis at ten years did not differ significantly between eras (p = 0.356).

Conclusion

Increased immunosuppression effectively reduced chronic allograft hepatitis and fibrosis at five years, suggesting it is an immunologically driven variant of rejection. However, there was no significant reduction in the degree of fibrosis at ten years, indicating a multifactorial origin for long term graft fibrosis.

Are protocol graft biopsies after pediatric liver transplantation useful? Experience in a single center over 20 years

BACKGROUND

The role of protocol liver biopsies (PLB) in the follow-up of pediatric liver transplant recipients remains questionable. This single-center retrospective study aimed to evaluate their clinical impact on the long-term management of pediatric liver transplant recipients.

METHODS

We described histopathological lesions and clinical consequences for patient management of PLB performed 1, 5, 10, 15, 20, and 25 years after pediatric liver transplantation (LT).

RESULTS

A total of 351 PLB performed on 133 patients between 1992 and 2021 were reviewed. PLB found signs of rejection in 21.7% of cases (76/351), and moderate to severe fibrosis in 26.5% of cases (93/351). Overall, 264 PLB (75.2%) did not cause any changes to patient care. Immunosuppression was enhanced after 63 PLB, including 23 cases of occult rejection. The 1-year PLB triggered significantly more changes, while biopsies at 15, 20, and 25 years produced the lowest rates of subsequent modifications. PLB had a significantly higher probability of inducing therapeutic changes if the patient had abnormal biological or imaging results (odds ratio [OR] 2.82 and 2.06), or a recent history of rejection or bacterial infection (OR 2.22 and 2.03).

CONCLUSION

Our results suggest that, although it often does not prompt any treatment changes, PLB could be performed because of its ability to detect silent rejection requiring an increase in immunosuppression. PLB could be carried out 1, 5, and 10 years after LT and then every 10 years in patients with normal biological and imaging results and no recent complications, while other patients could be kept on a 5-year protocol.

Positive autoantibodies in living liver donors

BACKGROUND

There is a nationwide shortage of organs available for liver transplantation. Living donors help meet this growing demand. Not uncommonly, donors will have positive autoantibodies. However, it is unclear whether donor positive autoantibodies are correlated with worse outcomes following living liver donor transplantations.

AIM

To analyze the significance of positive autoantibodies in donors on post-transplant outcomes in recipients.

METHODS

We performed a retrospective review of living liver donors who had undergone liver transplantation between January 1, 2012 and August 31, 2021. Demographic characteristics and pre-transplant data including antinuclear antibodies (ANA) and anti-smooth muscle antibody titers were collected in donors. Outcomes of interest were post-transplantation complications including mortality, biliary strictures, biliary leaks, infection, and rejection. Pediatric recipients and donors without measured pre-transplant autoantibody serologies were excluded from this study.

RESULTS

172 living donor liver transplantations were performed during the study period, of which 115 patients met inclusion criteria. 37 (32%) living donors were autoantibody-positive with a median ANA titer of 1:160 (range 1:80 to 1:1280) and median anti-SMA titer of 1:40 (range 1:20 to 1:160). There were no significant differences in baseline demographics between the autoantibody positive and negative donors. Post-transplantation rates of death (P value = 1), infections (P value = 0.66), and overall rates of complications (P value = 0.52) were similar between the autoantibody positive and negative groups. Higher incidences of anastomotic strictures and rejection were observed in the autoantibody positive group; however, these differences were not statistically significant (P value = 0.07 and P value = 0.30 respectively).

CONCLUSION

Isolated pre-transplant autoantibody positivity is not correlated to worse post-transplant outcomes in living liver donor transplants.

Minimal Development of Liver Fibrosis in Adult Tolerant Liver Transplant Recipients Late After Immunosuppressive Drug Weaning and Transplantation

BACKGROUND

Operationally tolerant liver transplant (LTx)-recipients can be weaned off immunosuppressive (IS) drugs without development of graft rejection. However, it is feared that liver fibrosis might develop after complete IS weaning. The purpose of this small single-center study was to assess liver fibrosis in adult tolerant LTx recipients long after LTx and IS weaning.

METHODS

Liver fibrosis was assessed in adult tolerant LTx-recipients (n = 9) using noninvasive transient elastography and measurements of multiple pro- and antifibrotic serum markers associated with liver fibrosis. The data was collected for 2 subsequent years; 8 and 9 years after IS weaning and 19 and 20 years after transplantation. Healthy individuals (n = 9) matched for age and sex were included as a reference for fibrosis-related serum markers. This study was conducted in accordance with the Declaration of Helsinki and approved by the medical ethics committee of our institution.

RESULTS

Transient elastography indicated that 7 of 9 tolerant LTx recipients had no or minimal liver fibrosis (F0-F1), whereas 2 recipients had moderate or severe liver fibrosis (F2-F3). Most fibrosis-related serum markers in tolerant LTx recipients were within or close to the range obtained for healthy individuals.

CONCLUSIONS

The results from this small, single-center study indicated that most adult tolerant LTx recipients have no or minimal liver graft fibrosis long after transplantation and IS weaning, and their fibrosis-related serum marker profile indicates an absence of a profibrotic status.

Standardizing the histological assessment of late posttransplantation biopsies from pediatric liver allograft recipients

Excellent short-term survival after pediatric liver transplantation (LT) has shifted attention toward the optimization of long-term outcomes. Despite considerable progress in imaging and other noninvasive modalities, liver biopsies continue to be required to monitor allograft health and to titrate immunosuppression. However, a standardized approach to the detailed assessment of long-term graft histology is currently lacking. The aim of this study was to formulate a list of histopathological features relevant for the assessment of long-surviving liver allograft health and to develop an approach for assessing the presence and severity of these features in a standardized manner. Whole-slide digital images from 31 biopsies obtained ≥4 years after transplantation to determine eligibility for an immunosuppression withdrawal trial were selected to illustrate a range of typical histopathological findings seen in children with clinically stable grafts, including those associated with alloantibodies. Fifty histological features were independently assessed and, where appropriate, scored semiquantitatively by six pathologists to determine inter- and intraobserver reproducibility of the histopathological features using unweighted and weighted kappa statistics; the latter metric enabled distinction between minor and major disagreements in parameter severity scoring. Weighted interobserver kappa statistics showed a high level of agreement for various parameters of inflammation, interface activity, fibrosis, and microvascular injury. Intraobserver agreement for these features was even more substantial. The results of this study will help to standardize the assessment of biopsies from long-surviving liver allografts, aid the recognition of important histological features, and facilitate international comparisons and clinical trials aiming to improve outcomes for children undergoing LT.

Long-term liver allograft fibrosis: A review with emphasis on idiopathic post-transplant hepatitis and chronic antibody mediated rejection

Liver transplantation (LT) is a life-saving surgical procedure and the current standard of care for most patients with end stage liver disease. With improvements in organ preservation techniques, perioperative care, and immunosuppression, there is better patient and graft survival following LT, and assessment of the liver allograft in long-term survivors is becoming increasingly important. Recurrent or de novo viral or autoimmune injury remains the most common causes of chronic hepatitis and fibrosis following liver transplantation in adults. However, no obvious cause can be identified in many adults with controlled recurrent disease and the majority of pediatric LT recipients, as they have been transplanted for non-recurrent liver diseases. Serial surveillance liver biopsies post LT have been evaluated in several adult and pediatric centers to identify long-term pathological changes. Pathological findings are frequently present in liver biopsies obtained after a year post LT. The significance of these findings is uncertain as many of these are seen in protocol liver biopsies from patients with clinically good allograft function and normal liver chemistry parameters. This narrative review summaries the factors predisposing to long-term liver allograft fibrosis, highlighting the putative role of idiopathic post-LT hepatitis and chronic antibody mediated rejection in its pathogenesis.

The New Challenge in Pediatric Liver Transplantation: Chronic Antibody-Mediated Rejection

Antibody-mediated rejection (AMR) of liver allograft transplantation was considered as anecdotal for many decades. However recently, AMR has gained clinical awareness as a potential cause of chronic liver injury, leading to liver allograft fibrosis and eventual graft failure. (1) Methods: Literature on chronic AMR (cAMR) in pediatric post-liver transplant patients was reviewed for epidemiologic data, physiopathology, diagnosis, and treatment approaches. (2) Results: Accurate incidence of cAMR in pediatric liver transplantation remains unknown. Diagnostic criteria of cAMR were suggested by the Banff Working Group in 2016 and are based on standardized histopathological findings, C4d staining pattern, associated with the presence of donor-specific antibodies (DSA). Physio-pathological mechanisms are not clear for the technically difficult-to-obtain animal models reproducing cAMR. Treatment protocols are not established, being limited to case reports and case series, based on experience in ABO incompatible transplantation and kidney transplantation. Immunosuppression compliance with adequate dose adjustment may prevent cAMR. Conversion of Cyclosporine to Tacrolimus may improve pathological findings if treated in early phase. The association of steroids, Mycophenolate Mofetil (MMF) and mTOR inhibitors have shown some synergistic effects. Second-line treatments such as intravenous immunoglobulin (IVIG) and plasma exchange may decrease antibody titers based on ABO incompatible transplant protocols. The use of anti-CD20 (Rituximab) and proteasome inhibitors (Bortezomib) is controversial due to the lack of qualified studies. Therefore, multicenter randomized trials are needed to establish the best therapeutic strategy. In refractory cases, re-transplantation is the only treatment for allograft failure. (3) Conclusions: This literature review collects recent clinical, histopathological, and therapeutical advances of cAMR in liver allograft transplantation of pediatric patients. There are many physio-pathological aspects of cAMR to be clarified. Further efforts with multicenter prospective protocols to manage patients with cAMR are needed to improve its outcome.

Accuracy of noninvasive fibrosis scores in predicting advanced fibrosis in pediatric patients after liver transplantation

BACKGROUND

Liver biopsy is the gold standard to stage fibrosis in liver disease. Several scoring systems have been studied to predict advanced fibrosis in liver disease. Those scores have not been validated in pediatric liver transplant patients.

AIM

Evaluate the performance of three fibrosis scores (FSc) in assessing the presence of advanced fibrosis (AF) in children after orthotopic liver transplantation (OLT).

METHODS

Patients < 20 years of age who underwent liver biopsy post-OLT with laboratory values within 1 month of the biopsy were included. Fibrosis was determined by an experienced pathologist (F0-4). We defined AF as F3-4. The following FSc were calculated: AST/ALT ratio, APRI, and FIB-4 index. Receiver operating characteristic curve analysis was done to assess the FSc performance in predicting AF.

RESULTS

A total of 232 biopsies were analyzed, of those 42 (18.1%) showed AF (F3-4). FIB-4 was significantly higher in patients with AF compared to those without AF [median value of 1.1 [0.7, 3.0] and 0.6 [0.2, 1.4], respectively (p = .02)]; however, FIB-4 had satisfactory accuracy to diagnose AF with significant overlap and AUC of 0.68 (CI 0.56-0.81). Cutoff points of 0.2 and 3.03 were used to rule in and rule out AF, respectively. AST/ALT and APRI were not significantly different between patients with and without AF.

CONCLUSION

Even though FIB-4 had satisfactory accuracy in detecting AF in pediatric transplant patients, noninvasive hepatic FSc developed in adults still performed poorly. Our results highlight the need to develop a reliable pediatric FSc.

Pediatric Liver Transplantation

Liver transplantation (LT) for children results in excellent short- and long-term patient and graft survival. LT is a lifesaving procedure in children with acute or chronic liver disease, hepatic tumors, and select genetic metabolic diseases in which it can significantly improve quality of life. In this article, the authors discuss the unique aspects of pediatric LT, including the indications, appropriate patient selection and evaluation, allocation of organs, transplant surgery including the use of variant grafts, posttransplant care including immunosuppression management, prognosis, and transition of care.

Clinical implications of serum autotoxin in regular follow up after pediatric living donor liver transplantation for biliary atresia

BACKGROUND

Pediatric patients sometimes develop graft fibrosis after living donor liver transplant (LDLT). Autotaxin is a recently developed serum marker for hepatic fibrosis. We studied the relationship between serum autotaxin levels and histological findings in patients after LDLT for biliary atresia (BA).

METHODS

Information on patients aged <19 years who received LDLT for BA and were followed for at least 1 year after LDLT was gathered. Autotaxin levels were compared with pathological fibrosis scores.

RESULTS

The study included 52 patients, of whom 4 patients had no fibrosis (F0), 36 patients had F1 fibrosis, and 12 patients had F2. The median serum autotaxin level was 0.89 mg/L. In patients with portal vein (PV) complications such as stenosis or thrombosis (n = 7), the mean autotoxin level was 1.25 mg/L compared with 0.95 mg/L in patients without PV complications (p = 0.004). Among patients without PV complications, the mean autotaxin level was 0.90, 0.88, and 1.18 mg/L in F0, F1, and F2 fibrosis, respectively. The mean autotaxin was higher in F2 fibrosis than in F0 or F1 fibrosis (p<0.05). Autotoxin had a high area under the curve (0.86) with the cut-off level of 0.897 mg/L.

CONCLUSION

Serum autotaxin is a novel marker for liver fibrosis in patients after pediatric LDLT for BA.

TYPE OF STUDY

Study of Diagnostic Test.

LEVEL OF EVIDENCE

Level II.

Graft Fibrosis Over 10 to 15 Years in Pediatric Liver Transplant Recipients: Multicenter Study of Paired, Longitudinal Surveillance Biopsies

Previous single-center, cross-sectional studies have reported a steep increase in the prevalence and severity of fibrosis through 10 to 15 years after pediatric liver transplantation. We report a multicenter study of paired surveillance biopsies in a contemporary cohort. Children who underwent liver transplant when younger than 6 years old and had paired surveillance liver biopsies were enrolled (n = 78, 35% girls, median 1.2 years old at transplant). A central pathologist graded inflammation, assessed rejection activity index, and staged fibrosis in the portal, sinusoidal, and perivenular compartments, allowing for calculation of the Liver Allograft Fibrosis Score (LAFSc). Analysis of variance tested associations between fibrosis progression and clinical parameters. The first biopsy, at a median 8.2 years (interquartile range, 5.9-11.6 years) after transplantation, showed absent to mild fibrosis (LAFSc 0-2) in 29%, moderate (LAFSc 3-5) in 56%, and severe (LAFSc 6-7) in 14% of patients. The second biopsy, at a median 4.7 years (IQR, 4.3-5.1 years) later, showed fibrosis progression (LAFSc increased by ≥3) in 10 (13%) and regression (LAFSc decreased by ≥3) in 4 (5%) patients. After adjusting for baseline LAFSc, younger age at transplant was the only risk factor for fibrosis progression. Although fibrosis prevalence and severity 6 to 12 years after transplant was similar to previous reports, fibrosis trajectory during the next 4 to 5 years was stable. Our data may be reassuring for children with consistently normal liver tests. A comprehensive understanding of factors determining allograft health during the very long term is essential to optimizing allograft and patient health.

Diagnostic performance of 2D-shear wave elastography and serum fibrosis markers for evaluation of hepatic graft fibrosis in pediatric liver-inclusive transplant recipients: A prospective pilot study

BACKGROUND

Liver biopsy is the gold standard for hepatic fibrosis staging, but it is invasive and has potential severe complications. We aimed to determine the diagnostic performance of 2D-SWE and serum markers to predict significant hepatic graft fibrosis (≥F2) in pediatric liver-inclusive transplant recipients.

METHODS

This prospective, cross-sectional pilot study included children younger than 19 years who had received a LT or LSBT and underwent a liver biopsy performed for clinical indications. LS was measured using 2D-SWE. The AUROC was calculated to evaluate the diagnostic performance of 2D-SWE and biomarkers (AST/ALT ratio, APRI, FIB4) for predicting significant fibrosis.

RESULTS

Twenty-two children (13 males, 8 LSBT) were included. Eighteen (81.8%) children received a whole liver graft. Thirteen (59.1%) patients had hepatic fibrosis (≥F1) and four (18.2%) had significant fibrosis. The AUROCs of AST/ALT ratio, APRI, and FIB4 for predicting significant hepatic graft fibrosis were 0.71 (p = .29), 0.85 (p = .0001), and 0.76 (p = .03), respectively. When FIB4 was calculated using the hepatic graft's age, its AUROC improved to 0.85 (p < .0001). The AUROC of 2D-SWE for predicting significant hepatic graft fibrosis was 0.80 (p = .046). When 2D-SWE was combined with APRI or FIB4, its AUROC improved to 0.82 (p = .08) and 0.87 (p = .002), respectively.

CONCLUSIONS

APRI and FIB4 can accurately predict significant hepatic graft fibrosis. 2D-SWE may serve as a valuable adjunct tool to detect significant graft fibrosis, especially when combined with these serum markers.

Clinical Value of Surveillance Biopsies in Pediatric Liver Transplantation

Although pediatric liver transplantation (LT) results in excellent long-term outcomes, a high incidence of early acute cellular rejection and late graft fibrosis persists. Routine measurement of allograft enzymes may not reliably detect rejection episodes, identify candidates for immunosuppression minimization, or indicate allograft fibrosis. Surveillance biopsies (SBs) can provide valuable information in this regard, but their role in pediatric LT is not fully established. A retrospective cohort of 236 pediatric LT recipients from a high-volume center was studied to characterize the risks and benefits of SB versus for-cause biopsies (FCBs). The study population was 47.1% male and 54.7% Hispanic, and 31% received living donor grafts. Our data suggest that patients in the SB group had better transplant outcomes (rejection-free, graft, and patient survival) compared with patients who had FCBs or who never underwent biopsy. Among 817 biopsies obtained from 236 patients, 150 (18.4%) were SBs. Only 6 patients had a biopsy-related complication, and none were observed in the SB subset. Graft biochemical blood tests did not accurately predict rejection severity on biopsy, with aspartate aminotransferase area under the receiver operating characteristic curve (AUROC) 0.66, alanine aminotransferase AUROC 0.65 (very poor predictions), and gamma-glutamyltransferase AUROC 0.58 (no prediction). SBs identified subclinical rejection in 18.6% of biopsies, whereas 63.3% of SBs had evidence of fibrosis. SBs prompted changes in immunosuppression including dose reduction. Our experience suggests that SB in pediatric LT is safe, offers valuable information about subclinical rejection episodes, and can guide management of immunosuppression, including minimization. Improved outcomes with SB were likely multifactorial, potentially relating to a more favorable early posttransplant course and possible effect of management optimization through SB. Further multicenter studies are needed to examine the role of SBs on long-term outcomes in pediatric LT.

Cold Ischemia Time and Graft Fibrosis Are Associated with Autoantibodies after Pediatric Liver Transplantation: A Retrospective Cohort Study of the European Reference Network TransplantChild

The reported prevalence of autoantibodies (AAB) (ANA, SMA, LKM, SLA) after pediatric liver transplantation (pLTX) varies considerably from 26-75%, but their clinical impact on outcome is uncertain. We aimed to study the prevalence of AAB after pLTX, their association with donor-, transplant-, and recipient-characteristics, and their relation to outcome. In our multicenter retrospective study, we aimed to clarify conflicting results from earlier studies. Six ERN TransplantChild centers reported data on 242 patients, of whom 61% were AAB positive. Prevalence varied across these centers. Independent of the interval between pLTX and AAB analysis, a one-hour increase in CIT resulted in an odds ratio (OR) of 1.37 (95% CI 1.11-1.69) for SMA positivity and an OR of 1.42 (95%CI 1.18-1.72) for ANA positivity. Steroid-free immunosuppression (IS) versus steroid-including IS (OR 5.28; 95% CI 1.45-19.28) was a risk factor for SMA positivity. Liver enzymes were not associated with ANA or SMA positivity. We did not observe an association of rejection activity index with ANA or SMA. However, the liver fibrosis score in follow-up biopsies was associated with ANA titer and donor age. In conclusion, this first multicenter study on AAB after pLTX showed high AAB prevalence and varied widely between centers. Longer CIT and prednisolone-free-IS were associated with AAB positivity, whereas AAB were not indicative of rejection, but instead were associated with graft fibrosis. The detection of AAB may be a marker of liver fibrosis and may be taken into consideration when indications for liver biopsy and immunosuppressive regimes, or reduction of immunosuppression in long-term follow-up, are being discussed. Prospective immunological profiling of pLTX patients, including AAB, is important to further improve our understanding of transplant immunology and silent graft fibrosis.

Allograft Fibrosis After Pediatric Liver Transplantation: Incidence, Risk Factors, and Evolution

Allograft fibrosis (AF) after pediatric liver transplantation (pLT) is frequent, but its dynamics are unclear. Our aim was to assess the evolution and risk factors of AF after pLT. A retrospective single-center analysis of pLT patients with a follow-up of ≥5 years who underwent protocol liver biopsies at 6 months, 1 year, 2 years, 5 years, and 10 years was performed. Fibrosis was assessed using the METAVIR and Ishak systems and the liver allograft fibrosis score (LAFs). Of 219 pLTs performed from 2008 to 2018, 80 (36.5%) pLTs were included, and 320 biopsies were reviewed. At 6 months after pLT, fibrosis was found in 54 (67.5%) patients by the METAVIR/Ishak systems and in 59 (73.8%) by the LAFs (P = 0.65). By 5 years, AF was detected in 67 (83.8%), 69 (86.3%), and 72 (90%) specimens using the METAVIR, Ishak, and LAFs systems, respectively (P = 0.54); mild (METAVIR, 51 [63.8%]; Ishak, 60 [75%]; LAFs, 65 [81.2%]) and moderate (METAVIR, 16 [20%]; Ishak, 9 [11.9%]; LAFs, 7 [8.8%]) stages were detected, but severe fibrosis was not found (P = 0.09). In the LAFs, fibrosis involved the portal (85%), sinusoidal (15%), and centrolobular (12%) areas. Of 18 patients with 10-year protocol biopsies, AF was present in 16 (90%), including 1 (5.5%) with severe fibrosis. In all systems, 36.3% of patients showed fibrosis progression from 2 years to 5 years after LT, but they remained stable at the 10-year biopsies without clinical implications. In multivariate analysis, only donor age >40 years was a risk factor for moderate AF at 5 years after LT (odds ratio, 8.3; 95% confidence interval, 1.6-42.1, P = 0.01). Cold ischemia time (CIT) >8 hours was associated with portal (P < 0.001)/sinusoidal fibrosis (P = 0.04), donor age >40 years was associated with sinusoidal (P = 0.01)/centrilobular (P = 0.04) fibrosis, and low tacrolimus trough level within 1 year after LT was associated with centrilobular fibrosis (P = 0.02). AF has a high incidence after pLT, occurring early after transplantation. In most cases, AF is mild or moderate and remains stable in the long run without clinical implications. Donor selection, short CIT, and immunosuppression adherence are crucial to reducing the risk of advanced AF.

Two-Dimensional Shear Wave Elastography Evaluation of Post-transplantation Complications in Pediatric Receipt: A Retrospective Cohort

BACKGROUND

The 20-year survival rate in pediatric patients after liver transplantation (LT) was no more than 70%. Hepatic fibrosis is one of the principal factors affecting the long-term prognosis. Imaging evaluation was the first-line examination for pediatric liver graft assessment. However, the sensitivity and specificity were insufficient. Thus, two-dimensional shear wave elastography (2D-SWE) was performed to evaluate liver graft stiffness and complication in post-transplant pediatric receipt.

MATERIALS AND METHODS

In this retrospective cohort, 343 pediatric recipients who underwent liver graft biopsy in our tertiary LT center were recruited between June 2018 and December 2020. The 2D-SWE evaluation, laboratory examination, routine post-transplant biopsy, and hepatic pathological assessment were performed.

RESULTS

Ninety-eight of the 343 pediatric patients were included according to the protocol. The Liver Stiffness Measurements (LSM) value of 2D-SWE was significantly elevated in post-transplant fibrosis (p < 0.0001). The LSM value of patients with post-transplant biliary complications (p < 0.0001) and biopsy-proven rejection (BPR, p = 0.0016) also rose compared to regular recovery patients. Concerning the sensitivity and specificity of 2D-SWE in diagnosing liver graft fibrosis, the area under the ROC curve (AUC) was 88%, and the optimal cutoff value was 10.3 kPa.

CONCLUSION

Pediatric LSM by 2D-SWE was efficient. Routine 2D-SWE evaluation could be optimal to predict significant liver graft fibrosis.

Protocol liver biopsies in stable long-term pediatric liver transplant recipients: risk or benefit?

BACKGROUND

Follow-up after pediatric liver transplantation (LTX) is challenging and needs to be refined to extend graft survival as well as general functional health and patients´ quality of life. Strategies towards individual immunosuppressive therapy seem to play a key role. Our aim was to evaluate protocol liver biopsies (PLB) as a tool in personalized follow up after pediatric LTX.

PATIENTS AND METHODS

Our retrospective analysis evaluates 92 PLB in clinically asymptomatic pediatric patients after LTX between 2009 and 2019. Histological findings were characterized using the Desmet scoring system. In addition to PLB, other follow-up tools like laboratory parameters, ultrasound imaging and transient elastography were evaluated. Risk factors for development of fibrosis or inflammation were analyzed.

RESULTS

PLB revealed a high prevalence of graft fibrosis (67.4%) and graft inflammation (47.8%). Graft inflammation was significantly (P = 0.0353*) more frequent within the first 5 years after transplantation compared to later time points. Besides conventional ultrasound, the measurement of liver stiffness using transient elastography correlate with stage of fibrosis (r = 0.567, P = <0.0001***). Presence of donor-specific anti-human leukocyte antigen antibodies in blood correlates with grade of inflammation in PLB (r = 0.6040, P = 0.0018 **). None of the patients who underwent PLB suffered from intervention-related complications. Histopathological results had an impact on clinical decision making in one-third of all patients after PLB.

CONCLUSION

PLB are a safe and useful tool to detect silent immune-mediated allograft injuries in the context of normal liver parameters.

Influence of early biliary complications on survival rates after pediatric liver transplantation-A positive outlook

BACKGROUND

Early biliary complications (EBC) constitute a burden after pediatric liver transplantation frequently requiring immediate therapy. We aimed to assess the impact of EBC on short- and long-term patient and graft survival as well as post-transplant morbidity.

METHODS

We analyzed 121 pediatric liver transplantations performed between 1984 and 2019 at the Medical University of Innsbruck for the occurrence of early (<90 days) biliary complications and investigated the influence of EBC on patient and graft survival.

RESULTS

Early biliary complications occurred in 30 (24.8%) out of the 121 pediatric liver transplant recipients. Patient survival at 15 years (89.2% vs. 84.2%, p = .65) and all-cause (82.5% vs. 74.0%) and death-censored graft survival (82.5% vs. 75.1%, p = .71) at 10 years were similar between the EBC and the non-EBC group. The EBC group had a significantly longer ICU (25 vs. 16 days, p < .001) and initial hospital stay (64 vs. 42 days, p = .002). Livers of patients with EBC were characterized by multiple bile ducts (33.3% vs. 13.2%, p = .027), and patients with EBC had a higher risk to develop late biliary complications (OR 2.821 [95% CI 1.049-7.587], p = .044) and bowel obstruction/perforation (OR 4.388 [95% CI 1.503-12.812], p = .007).

CONCLUSION

Early biliary complications after pediatric liver transplantation is frequent. The occurrence of EBC significantly increased post-transplant morbidity without affecting mortality. Multiple bile ducts were the only risk factor for the development of EBC in our cohort.

Liver Histopathology in Late Protocol Biopsies after Pediatric Liver Transplantation

Liver transplantation has become a routine treatment for children with end stage liver failure. Recently, the long term survival of pediatric patients after liver transplantation has improved, with a life expectancy much longer than that of adult recipients, but also with longer exposition of the graft to various injuries, including immunological, inflammatory and others. Biochemical tests, although important, do not always reflect graft injury. The aim of our study was to analyze the histopathology of the graft in late protocol biopsies and correlate it with the clinical and biochemical status of these patients. We analyzed 61 protocol liver biopsies taken from 61 patients. Biopsies were taken 9.03–17.09 years (mean 12.68, median 11.74 years) after transplantation. Liver specimens were examined particularly for the presence and stage of liver fibrosis, inflammation, steatosis, and acute or chronic cellular and humoral rejection. We did not find any abnormalities in 26 (42.6%) liver specimens. None of the patients had signs of cellular or antibody mediated rejection or chronic rejection. In 23 liver biopsies (37.7%), we found non-specific lymphoid infiltrates. Another problem was fibrosis (equal to or more than three on the Ishak scale)—we found it in 17 patients, including seven liver specimens (11.5%) with severe fibrosis (Ishak 5–6). Conclusions: Various pathomorphological abnormalities were found in more than half of patients with a median 11.74 years post-transplant follow-up. Most of them presented normal laboratory liver tests at the same time, suggesting a slow subclinical process leading to pathomorphological abnormalities. No single factor for the development of these abnormalities was found, but our study supports the need for protocol liver biopsies even in patients with normal/almost normal biochemical liver tests.

Post-transplant hepatic fibrosis in pediatric liver-small bowel transplant recipients: A single-center, retrospective, observational study

BACKGROUND

Little is known about the prevalence of hepatic graft fibrosis in combined LSBT children. We aimed to determine the prevalence of and identify potential predictors for hepatic graft fibrosis in LSBT children and to compare them with those in LT children.

METHODS

We retrospectively included children younger than 19 years who had received a primary LT/LSBT between 2000 and 2018 and had a liver biopsy performed at least 6 months post-transplant. A Cox proportional hazards regression model was used to determine predictors associated with significant hepatic graft fibrosis (≥F2) in LSBT vs LT children.

RESULTS

Ninety-six children (47 LSBT, 54 females) were included. The median post-transplant follow-up (years) was 12.8 in LT vs 10.5 in LSBT patients (P = .06). Hepatic graft fibrosis was found in 81.6% of LT vs 70.2% of LSBT children (P = .19), after a median time of 2.5 years and 2.6 years, respectively. On multivariate analyses, having post-transplant biliary complications was found to be associated with significant graft fibrosis in LT children, whereas AST/ALT ratio was found to predict significant hepatic graft fibrosis in LSBT children. The use of parenteral nutrition after transplant was not associated with significant hepatic graft fibrosis.

CONCLUSIONS

The prevalence of hepatic graft fibrosis in LSBT children did not significantly differ from that in LT children, but the predictors may differ. Future studies should investigate the role of post-transplant autoimmune antibodies and donor-specific antibodies in the development and progression of hepatic graft fibrosis in LSBT children.

Ultrasonographically guided percutaneous transhepatic liver biopsy after pediatric liver transplantation

BACKGROUND

Complications associated with ultrasonographically guided percutaneous transhepatic liver biopsy (PTLB) after liver transplantation (LT) have been rarely reported, and there is no consensus about its safety. We retrospectively reviewed the safety and outcomes of PTLB after pediatric LT.

METHODS

Between January 2008 and December 2019, 8/1122 (0.71%) pediatric patients who underwent ultrasonographically guided PTLB after LT developed complications. The median age at PTLB was 7.8 years (range 0.1-17.9). Grafts included left lobe/left lateral segment in 1050 patients and others in 72. PTLB was performed using local anesthesia±sedation in 1028 patients and general anesthesia in 94.

RESULTS

Complications after PTLB included acute cholangitis in 3 patients, sepsis in 2, respiratory failure due to over-sedation in 1, subcapsular hematoma in 1, and intrahepatic arterioportal fistula in 1. The incidence of complications of PTLB in patients with biopsy alone and those with simultaneous interventions was 0.49% and 3.19%, respectively (p = .023). Patients who developed acute cholangitis, respiratory failure, subcapsular hematoma, and arterioportal fistula improved with non-operative management. Of two patients with sepsis, one underwent PTLB and percutaneous transhepatic portal vein balloon dilatation and developed fever and seizures the following day. Sepsis was treated with antibiotic therapy. Another patient who underwent PTLB and exchange of percutaneous transhepatic biliary drainage catheter developed fever and impaired consciousness immediately. Sepsis was treated with antibiotic therapy, mechanical ventilation, and continuous hemofiltration.

CONCLUSIONS

Percutaneous transhepatic liver biopsy after pediatric LT is safe. However, combining liver biopsy with simultaneous procedures for vascular and biliary complications is associated with an increased risk of complications.

The role of the gut microbiome in graft fibrosis after pediatric liver transplantation

Liver transplantation (LT) is a life-saving option for children with end-stage liver disease. However, about 50% of patients develop graft fibrosis in 1 year after LT, with normal liver function. Graft fibrosis may progress to cirrhosis, resulting in graft dysfunction and ultimately the need for re-transplantation. Previous studies have identified various risk factors for the post-LT fibrogenesis, however, to date, neither of the factors seems to fully explain the cause of graft fibrosis. Recently, evidence has accumulated on the important role of the gut microbiome in outcomes after solid organ transplantation. As an altered microbiome is present in pediatric patients with end-stage liver diseases, we hypothesize that the persisting alterations in microbial composition or function contribute to the development of graft fibrosis, for example by bacteria translocation due to increased intestinal permeability, imbalanced bile acids metabolism, and/or decreased production of short-chain fatty acids (SCFAs). Subsequently, an immune response can be activated in the graft, together with the stimulation of fibrogenesis. Here we review current knowledge about the potential mechanisms by which alterations in microbial composition or function may lead to graft fibrosis in pediatric LT and we provide prospective views on the efficacy of gut microbiome manipulation as a therapeutic target to alleviate the graft fibrosis and to improve long-term survival after LT.

Efficacy and Safety of Immunosuppression Withdrawal in Pediatric Liver Transplant Recipients: Moving Toward Personalized Management

BACKGROUND AND AIMS

Tolerance is transplantation's holy grail, as it denotes allograft health without immunosuppression and its toxicities. Our aim was to determine, among stable long-term pediatric liver transplant recipients, the efficacy and safety of immunosuppression withdrawal to identify operational tolerance.

APPROACH AND RESULTS

We conducted a multicenter, single-arm trial of immunosuppression withdrawal over 36-48 weeks. Liver tests were monitored biweekly (year 1), monthly (year 2), and bimonthly (years 3-4). For-cause biopsies were done at investigators' discretion but mandated when alanine aminotransferase or gamma glutamyltransferase exceeded 100 U/L. All subjects underwent final liver biopsy at trial end. The primary efficacy endpoint was operational tolerance, defined by strict biochemical and histological criteria 1 year after stopping immunosuppression. Among 88 subjects (median age 11 years; 39 boys; 57 deceased donor grafts), 33 (37.5%; 95% confidence interval [CI] 27.4%, 48.5%) were operationally tolerant, 16 were nontolerant by histology (met biochemical but failed histological criteria), and 39 were nontolerant by rejection. Rejection, predicted by subtle liver inflammation in trial entry biopsies, typically (n = 32) occurred at ≤32% of the trial-entry immunosuppression dose and was treated with corticosteroids (n = 32) and/or tacrolimus (n = 38) with resolution (liver tests within 1.5 times the baseline) for all but 1 subject. No death, graft loss, or chronic, severe, or refractory rejection occurred. Neither fibrosis stage nor the expression level of a rejection gene set increased over 4 years for either tolerant or nontolerant subjects.

CONCLUSIONS

Immunosuppression withdrawal showed that 37.5% of selected pediatric liver-transplant recipients were operationally tolerant. Allograft histology did not deteriorate for either tolerant or nontolerant subjects. The timing and reversibility of failed withdrawal justifies future trials exploring the efficacy, safety, and potential benefits of immunosuppression minimization.

Autoantibodies and Donor-specific Antibodies are Associated With Graft Dysfunction in Pediatric Liver Transplantation

OBJECTIVES

Autoantibodies (AAb) and donor-specific HLA antibodies (DSA) are frequently present in pediatric liver transplant (LT) recipients. Their clinical significance remains incompletely understood. We aimed to investigate the prevalence of serum AAb and DSA in pediatric LT recipients and its correlation with patient characteristics and histological and biochemical parameters.

METHODS

We retrospectively reviewed the data from 62 pediatric LT patients in follow-up at Ghent University Hospital between January 2007 and February 2018. Blood samples with AAb measurement were taken systematically, liver biopsies (LB) were performed on clinical indication.

RESULTS

AAb were detected in 27 (43.3%) patients, with antinuclear antibodies (ANA) being the most frequently (24%) encountered AAb. There was an association between AAb positivity and female gender (P = 0,032) and deceased donor LT (P = 0,006). Patients with positive AAb underwent a higher number of LB during their follow-up (P < 0,001), and an association was found with the presence of nonspecific histologic alterations (P = 0,032) in the absence of de novo autoimmune hepatitis. Positive AAb were also associated with higher alkaline phosphatase (P < 0,001), ALT (P < 0,001), AST (P < 0,001), γ-GT (P = 0,001), IgG (P = 0,011) and lower albumin (P = 0,029). Fourteen out of 50 (28%) patients were DSA-positive, mostly anti-HLA class II. DSA positivity was associated with T-cell-mediated rejection (P = 0,019), higher total (P = 0,033), and direct (P = 0,012) bilirubin and γ-GT (P < 0,001).

CONCLUSIONS

The presence of AAb and DSA is associated with histological and biochemical parameters of graft dysfunction. Larger prospective studies are warranted to investigate the causal relationships between AAb and DSA development and outcome parameters post pediatric LT.

Recurrent Autoimmune Hepatitis and De Novo Autoimmune Hepatitis in the Liver Allograft

OBJECTIVES

Autoimmune hepatitis (AIH) is a form of severe hepatitis that can recur after orthotopic liver transplant (OLT). Presentation of AIH in patients with OLT who do not have a history of AIH is called de novo AIH (DNAIH). We evaluated the clinicopathologic characteristics of AIH and DNAIH.

METHODS

Clinicopathologic and outcome measures of 11 patients with recurrent AIH (RAIH) and 22 with DNAIH identified between 2000 and 2017 were compared.

RESULTS

Both cohorts showed female predominance. The mean clinical follow-up was 13 and 7.8 years in the in the RAIH and DNAIH groups, respectively (P = .1). Moderate portal inflammation was more common in patients with RAIH (64% vs 27%, P = .043). A trend was observed for more cases of DNAIH showing severe inflammation (36% vs 9%, P = .09) and submassive necrosis compared with RAIH (23% vs 0%, P = .086). A trend for more advanced fibrosis was also noted in the RAIH group (27% vs 5%, P = .059). Three patients with RAIH lost their grafts because of RAIH. Five-year disease-specific graft survival (GS) (P = .012) and overall GS (P = .015) were worse in patients with RAIH. Complement component 4d immunohistochemistry was positive in 2 patients with RAIH and 3 with DNAIH but showed no correlation with GS or other parameters.

CONCLUSIONS

RAIH seems to have a more aggressive clinical course than DNAIH and warrants closer clinical follow-up and aggressive treatment.

Profiling the liver graft

PURPOSE OF REVIEW

Achieving operational tolerance remains a priority in liver transplantation. Although several biomarkers of tolerance and rejection have been identified, few have been reproducible and validated across centers, and therefore have yet to reach clinical practice. Here we summarize findings from prior seminal studies and review current developments in profiling the liver allograft.

RECENT FINDINGS

Substantial efforts and progress have been made in the recent years towards the discovery of reliable biomarkers that can predict and guide successful immunosuppression withdrawal. Recent studies have also investigated the transcriptomic signatures underlying not only acute rejection but also subclinical inflammation and chronic allograft injury.

SUMMARY

As new genomic and sequencing technologies continue to develop, clinical trials are underway to validate biomarkers of tolerance, as well as better understand the mechanisms of both acute and subclinical rejection, with the goal of maximizing allograft survival. Altogether, this will hopefully enable the implementation of immunosuppression withdrawal protocols into clinical practice and make operational tolerance reliably attainable in the near future.

Evaluation of Graft Fibrosis, Inflammation and Donor-specific Antibodies at Protocol Liver Biopsies in Pediatric Liver Transplant Patients: a Single Center Experience

BACKGROUND

The impact of graft fibrosis and inflammation on the natural history of pediatric liver transplants (LT) is still debated. Our objectives were to evaluate the evolution of posttransplant fibrosis and inflammation over time at protocol liver biopsies (PLBs), risk factors for fibrosis, presence of donor-specific antibodies (DSAs) and/or their correlation with graft and recipient factors.

METHODS

A single-center, retrospective (2000-2019) cross-sectional study on pediatric LT recipients who had at least one PLB, followed by a longitudinal evaluation in those who had at least two PLBs, was conducted. Fibrosis was assessed by the Liver Allograft Fibrosis Semiquantitative score, inflammation by the Rejection Activity Index, DSAs by Luminex®.

RESULTS

A total of 134 PLBs from 94 patients were included. Fibrosis was detected in 87% (30% mild, 45% moderate, 12% severe), 80% in the portal tracts. There was an increase in fibrosis between the 1-3 and the 4-6 year group (p=0.01), then it was stable. Inflammation was observed in 44% (30% mild, 13% moderate, 1% severe), 90% in the portal tracts. Anti-HLA II (IgG) DSAs were detected in 14/40 (35%). Portal fibrosis was associated with portal inflammation in the 1-3 year group (p=0.04). Low immunosuppression levels were correlated with sinusoidal fibrosis (p=0.04) and DSA positivity (p-value=0.006). There was no statistically significant correlation between DSA positivity and the presence of graft fibrosis or inflammation.

CONCLUSIONS

This study corroborates the concept of an early evolution of silent graft fibrosis. Suboptimal immunosuppression may play a role in the development of fibrosis and DSAs.

Subclinical biliary strictures as a cause of long-term allograft dysfunction in children who underwent liver transplantation

We aimed to evaluate the role of liver biopsy to predict subclinical biliary strictures (BS) and assess the impact of BS on long-term allograft dysfunction following liver transplantation in children (LT). We reviewed all liver biopsies performed from 2012-2018. Percutaneous transhepatic cholangiography (PTC) was performed in patients presenting cholangiolar proliferation on cytokeratin-7 stained sections. We performed 271 biopsies in 161 children (86% with a left lateral segment); 44/161 (27%) presented with diffuse or multifocal cholangiolar proliferation. Among them, a tight BS was confirmed in 38/44 (86%, 24% of total) and it was managed by balloon dilatation. Cholangiolar proliferation showed a positive predictive value (PPV) for BS of 86.4%. Levels of alkaline phosphatase >325 IU/L predicted BS (P = .007). Dilatation of intrahepatic bile ducts on ultrasound was found only in 44% of patients with BS. Following a median follow-up of 9.2 years, only 15/38 (39%) patients resolved the BS. In conclusion subclinical BS is very common and probably underdiagnosed in these patients. Histological evidence of cholangiolar proliferation detectable by cytokeratin-7 immunostain should be preferred to liver function tests and ultrasound to suspect BS. BS in this setting should be regarded as a main cause of long-term allograft dysfunction.

Understanding, predicting and achieving liver transplant tolerance: from bench to bedside

In the past 40 years, liver transplantation has evolved from a high-risk procedure to one that offers high success rates for reversal of liver dysfunction and excellent patient and graft survival. The liver is the most tolerogenic of transplanted organs; indeed, immunosuppressive therapy can be completely withdrawn without rejection of the graft in carefully selected, stable long-term liver recipients. However, in other recipients, chronic allograft injury, late graft failure and the adverse effects of anti-rejection therapy remain important obstacles to improved success. The liver has a unique composition of parenchymal and immune cells that regulate innate and adaptive immunity and that can promote antigen-specific tolerance. Although the mechanisms underlying liver transplant tolerance are not well understood, important insights have been gained into how the local microenvironment, hepatic immune cells and specific molecular pathways can promote donor-specific tolerance. These insights provide a basis for the identification of potential clinical biomarkers that might correlate with tolerance or rejection and for the development of novel therapeutic targets. Innovative approaches aimed at promoting immunosuppressive drug minimization or withdrawal include the adoptive transfer of donor-derived or recipient-derived regulatory immune cells to promote liver transplant tolerance. In this Review, we summarize and discuss these developments and their implications for liver transplantation.

Pyruvate Kinase M2 Tetramerization Protects against Hepatic Stellate Cell Activation and Liver Fibrosis

Liver fibrosis is an increasing health problem worldwide, for which no effective antifibrosis drugs are available. Although the involvement of aerobic glycolysis in hepatic stellate cell (HSC) activation has been reported, the role of pyruvate kinase M2 (PKM2) in liver fibrogenesis still remains unknown. We examined PKM2 expression and location in liver tissues and primary hepatic cells. The in vitro and in vivo effects of a PKM2 antagonist (shikonin) and its allosteric agent (TEPP-46) on liver fibrosis were investigated in HSCs and liver fibrosis mouse model. Chromatin immunoprecipitation sequencing and immunoprecipitation were performed to identify the relevant molecular mechanisms. PKM2 expression was significantly up-regulated in both mouse and human fibrotic livers compared with normal livers, and mainly detected in activated, rather than quiescent, HSCs. PKM2 knockdown markedly inhibited the activation and proliferation of HSCs in vitro. Interestingly, the PKM2 dimer, rather than the tetramer, induced HSC activation. PKM2 tetramerization induced by TEPP-46 effectively inhibited HSC activation, reduced aerobic glycolysis, and decreased MYC and CCND1 expression via regulating histone H3K9 acetylation in activated HSCs. TEPP-46 and shikonin dramatically attenuated liver fibrosis in vivo. Our findings demonstrate a nonmetabolic role of PKM2 in liver fibrosis. PKM2 tetramerization or suppression could prevent HSC activation and protects against liver fibrosis.

Role of Innate Immunity in Pediatric Post-transplant Idiopathic Liver Fibrosis

Pediatric post-transplant idiopathic liver fibrosis is an unexplained graft fibrosis that occurs in symptom-free children without acute rejection and surgical complications. Despite a lack of consensus on the subject, the development of pediatric post-transplant idiopathic liver fibrosis is believed to be the result of multiple potential factors, including ischemia-reperfusion injury, allogeneic acute and chronic rejection, viral hepatitis recurrence, opportunistic infection, and drug-induced liver damage. Among them, there is growing evidence that innate immunity may also have a unique role in this progression. This study reviews the features of pediatric post-transplant idiopathic liver fibrosis and discusses current studies illustrating the potential mechanisms of liver allograft tolerance induced by intrahepatic innate immunity, the role of components including Toll-like receptors (TLRs), interferons (IFN), dendritic cells (DC), natural killer cells (NK cells), NKT cells, neutrophils, and Kupffer cells, as well as their possibly relevant role in the development of pediatric post-transplant idiopathic liver fibrosis.