Paediatric liver transplantation for metabolic disorders. Part 2: Metabolic disorders with liver lesions

Modelling urea cycle disorders using iPSCs

The urea cycle is a liver-based pathway enabling disposal of nitrogen waste. Urea cycle disorders (UCDs) are inherited metabolic diseases caused by deficiency of enzymes or transporters involved in the urea cycle and have a prevalence of 1:35,000 live births. Patients present recurrent acute hyperammonaemia, which causes high rate of death and neurological sequelae. Long-term therapy relies on a protein-restricted diet and ammonia scavenger drugs. Currently, liver transplantation is the only cure. Hence, high unmet needs require the identification of effective methods to model these diseases to generate innovative therapeutics. Advances in both induced pluripotent stem cells (iPSCs) and genome editing technologies have provided an invaluable opportunity to model patient-specific phenotypes in vitro by creating patients' avatar models, to investigate the pathophysiology, uncover novel therapeutic targets and provide a platform for drug discovery. This review summarises the progress made thus far in generating 2- and 3-dimensional iPSCs models for UCDs, the challenges encountered and how iPSCs offer future avenues for innovation in developing the next-generation of therapies for UCDs.

Long-term outcomes in pediatric patients who underwent living donor liver transplantation for biliary atresia

BACKGROUND

There is no consensus about long-term outcomes in patients with biliary atresia. We retrospectively reviewed the long-term outcomes in pediatric patients who underwent living donor liver transplantation for biliary atresia.

METHODS

Between May 2001 and December 2020, 221 (73%) of 302 pediatric patients who underwent living donor liver transplantation had biliary atresia. The median age at living donor liver transplantation was 1.2 (range 0.2-16.5) years, and follow-up was 10.3 ± 5.5 years.

RESULTS

The 10-year graft survival rates in patients with and without biliary atresia were 94% and 89%, respectively (P = .019). The 10-year graft survival was significantly poorer in patients ≥12 years of age (84%) versus those <12 years of age at living donor liver transplantation (0-2 years: 95%; 2-12 years: 96%) (P = .016). The causes of graft failure in patients with biliary atresia included late-onset refractory rejection (n = 6), bowel perforation (n = 2), and acute encephalitis (n = 2), as well as cerebral hemorrhage, hepatic vein thrombosis, and sepsis (n = 1 for all). All 7 patients with graft failure due to refractory rejection and hepatic vein thrombosis underwent repeated liver transplantation and are alive in 2021. The rates of post-transplant portal vein complications and early-onset acute cellular rejection in patients with biliary atresia were higher than in those without biliary atresia (P = .042 and P = .022, respectively). In 2021, of 60 adolescents with biliary atresia, 14 (23%) reported medication nonadherence. The rate of liver dysfunction due to late-onset acute cellular rejection and graft failure due to late-onset refractory rejection in patients with nonadherence was higher than in patients with satisfactory adherence (P = .009).

CONCLUSION

The long-term prognosis after living donor liver transplantation in pediatric patients with biliary atresia is quite good. However, long-term support to enhance medication adherence is required in adolescents with biliary atresia.

Outcomes After Living Donor Liver Transplantation in Pediatric Patients with Inherited Metabolic Diseases

BACKGROUND There is no consensus about the long-term prognosis of pediatric patients with a variety of rare liver diseases but with inherited metabolic diseases (IMDs). We retrospectively reviewed the developmental outcomes of patients with IMDs undergoing living donor liver transplantation (LDLT). MATERIAL AND METHODS Between May 2001 and December 2020, of 314 pediatric patients who underwent LDLT, 44 (14%) had IMDs. The median age at LDLT was 3.0 years old (range 0-15.0 years). Associations between the post-transplant complications and graft survival rate in patients with IMDs and biliary atresia (BA) were calculated. We evaluated the safety of LDLT from heterozygous carrier donors, the prognosis of patients with IMDs who have metabolic defects expressed in other organs, and developmental outcomes of patients with IMDs. RESULTS The 10-year graft survival rates in patients with IMDs and BA were 87% and 94%, respectively (P=0.041), and the causes of graft failure included pneumocystis pneumonia, acute lung failure, hemophagocytic syndrome, hepatic vein thrombosis, portal vein thrombosis, and sepsis. The rate of post-transplant cytomegalovirus viremia in patients with IMDs was higher than that of patients with BA (P=0.039). Of 39 patients with IMDs, 15 patients (38%) had severe motor and intellectual disabilities in 4 patients, intellectual developmental disorders including epilepsy in 2, and attention-deficit hyperactivity disorder in 2. Of 28 patients with IMDs, 13 (46%) needed special education. CONCLUSIONS The long-term outcomes of LDLT in patients with IMDs are good. However, further long-term social and educational follow-up regarding intellectual developmental disorders is needed.

Living Related Liver Transplantation for Metabolic Liver Diseases in Children

ABSTRACT

Metabolic liver diseases (MLDs) are a heterogeneous group of inherited conditions for which liver transplantation can provide definitive treatment. The limited availability of deceased donor organs means some who could benefit from transplant do not have this option. Living related liver transplant (LrLT) using relatives as donors has emerged as one solution to this problem. This technique is established worldwide, especially in Asian countries, with shorter waiting times and patient and graft survival rates equivalent to deceased donor liver transplantation. However, living donors are underutilized for MLDs in many western countries, possibly due to the fear of limited efficacy using heterozygous donors. We have reviewed the published literature and shown that the use of heterozygous donors for liver transplantation is safe for the majority of MLDs with excellent metabolic correction. The use of LrLT should be encouraged to complement deceased donor liver transplantation (DDLT) for treatment of MLDs.

Evolving Trends in Liver Transplant for Metabolic Liver Disease in the United States

Indications for liver transplantation (LT) in metabolic disease are evolving. We reviewed the US experience with primary LT for metabolic disease in the Scientific Registry for Transplant Recipients (October 1987 to June 2017) to determine the following: temporal changes in indications, longterm outcomes, and factors predicting survival. Patients were grouped by the presence of structural liver disease (SLD) and whether the defect was confined to the liver. There were 5996 patients who underwent LT for metabolic disease, 2354 (39.3%) being children. LT for metabolic disease increased in children but not in adults. Children experienced a 6-fold increase in LT for metabolic disease without SLD. Indications for LT remained stable in adults. Living donor liver transplantation increased between era 1 and era 3 from 5.6% to 7.6% in children and 0% to 4.5% in adults. Patient and graft survival improved with time. The latest 5-year patient survival rates were 94.5% and 81.5% in children and adults, respectively. Outcomes were worse in adults and in those with extrahepatic disease (P < 0.01), whereas SLD did not affect outcomes. Survival improved with younger age at LT until age <2 years. On multivariate analysis, diagnostic category, inpatient status, age at LT, and transplant era significantly predicted outcomes in all ages with male sex predicting survival in childhood only. Children without structural disease were less likely to die awaiting LT and had improved post-LT survival compared with children with chronic liver disease. In conclusion, LT for metabolic disease is increasingly used for phenotypic correction in children; extrahepatic manifestations significantly impact survival at all ages; where indicated, transplantation should not be unnecessarily delayed; and the development of new allocation models may be required.

Pediatric Liver Transplantation: Unique Concerns for the Critical Care Team

Liver transplantation originated in children more than 50 years ago, and these youngest patients, while comprising the minority of liver transplant recipients nationwide, can have some of the best and most rewarding outcomes. The indications for liver transplantation in children are generally more diverse than those seen in adult patients. This diversity in underlying cause of disease brings with it increased complexity for all who care for these patients. Children, still being completely dependent on others for survival, also require a care team that is able and ready to work with parents and family in addition to the patient at the center of the process. In this review, we aim to discuss diagnoses of particular uniqueness or importance to pediatric liver transplantation. We also discuss the evaluation of a pediatric patient for liver transplant, the system for allocating them a new liver, and also touch on postoperative concerns that are unique to the pediatric population.

Long-term outcomes in Ornithine Transcarbamylase deficiency: a series of 90 patients

Background

The principal aim of this study was to investigate the long-term outcomes of a large cohort of patients with ornithine transcarbamylase deficiency (OTCD) who were followed up at a single medical center.

Methods

We analyzed clinical, biochemical and genetic parameters of 90 patients (84 families, 48 males and 42 females) with OTCD between 1971 and 2011.

Results

Twenty-seven patients (22 boys, 5 girls) had a neonatal presentation; 52 patients had an “intermediate” late-onset form of the disease (21 boys, 31 girls) that was revealed between 1 month and 16 years; and 11 patients (5 boys, 6 girls) presented in adulthood (16 to 55 years). Patients with a neonatal presentation had increased mortality (90% versus 13% in late-onset forms) and peak plasma ammonium (mean value: 960 μmol/L versus 500 μmol/L) and glutamine (mean value: 4110 μmol/L versus 1000 μmol/L) levels at diagnosis. All of the neonatal forms displayed a greater number of acute decompensations (mean value: 6.2/patient versus 2.5 and 1.4 in infants and adults, respectively). In the adult group, some patients even recently died at the time of presentation during their first episode of coma. Molecular analyses identified a deleterious mutation in 59/68 patients investigated. Single base substitutions were detected more frequently than deletions (69% and 12%, respectively), with a recurrent mutation identified in the late-onset groups (pArg40 His; 13% in infants, 57% in adults); inherited mutations represented half of the cases. The neurological score did not differ significantly between the patients who were alive in the neonatal or late-onset groups and did not correlate with the peak ammonia and plasma glutamine concentrations at diagnosis. However, in late-onset forms of the disease, ammonia levels adjusted according to the glutamine/citrulline ratio at diagnosis were borderline predictors of low IQ (p = 0.12 by logistic regression; area under the receiver operating characteristic curve of 76%, p <0.05).

Conclusions

OTCD remains a severe disease, even in adult-onset patients for whom the prevention of metabolic decompensations is crucial. The combination of biochemical markers warrants further investigations to provide additional prognostic information regarding the neurological outcomes of patients with OTCD.