Hepatocyte transplantation. Advancing biology and treating children

Tracking of Primary Human Hepatocytes with Clinical MRI: Initial Results with Tat-Peptide Modified Superparamagnetic Iron Oxide Particles

The transplantation of primary human hepatocytes is a promising approach in the treatment of specific liver diseases. However, little is known about the fate of the cells following application. Magnetic resonance imaging (MRI) could enable real-time tracking and long-term detection of transplanted hepatocytes. The use of superparamagnetic iron oxide particles as cellular contrast agents should allow for the non-invasive detection of labelled cells on high-resolution magnetic resonance images. Experiments were performed on primary human hepatocytes to transfer the method of detecting labelled cells via clinical MRI into human hepatocyte transplantation. For labelling, Tat-peptide modified nano-sized superparamagnetic MagForce particles were used. Cells were investigated via a clinical MR scanner at 3.0 Tesla and the particle uptake within single hepatocytes was estimated using microscopic examinations. The labelled primary human hepatocytes were clearly detectable by MRI, proving the feasibility of this new concept. Therefore, this method is a useful tool to investigate the effects of human hepatocyte transplantation and to improve safety aspects of this method.

Human heterologous liver cells transiently improve hyperammonemia and ureagenesis in individuals with severe urea cycle disorders

BACKGROUND

Urea cycle disorders (UCDs) still have a poor prognosis despite several therapeutic advancements. As liver transplantation can provide a cure, liver cell therapy (LCT) might be a new therapeutic option in these patients.

METHODS

Twelve patients with severe UCDs were included in this prospective clinical trial. Patients received up to six infusions of cryopreserved human heterologous liver cells via a surgically placed catheter in the portal vein. Portal vein pressure, portal vein flow, and vital signs were monitored continuously. Calcineurin inhibitors and steroids were used for immunosuppression. In four patients, ureagenesis was determined with stable isotopes. Number and severity of hyperammonemic events and side effects of immunosuppression were analyzed during an observation period of up to 2 years.

RESULTS

No study-related mortality was observed. The application catheter dislocated in two children. No significant side effects of catheter application or cell infusion were noted in the other ten patients. The overall incidence of infections did not differ significantly from a historical control group, and no specific side effects of immunosuppression were found. Seven patients were treated per protocol and could be analyzed for efficacy. Severe metabolic crises could be prevented in all of these patients, moderate crises in four of seven. Ureagenesis increased after cell infusion in all patients investigated.

CONCLUSIONS

We found a favorable safety profile with respect to catheter placement, intraportal liver cell infusion, and immunosuppression. More than half of the children treated per protocol experienced metabolic stabilization and could be safely bridged to liver transplantation.

Monitoring of intraportal liver cell application in children

Despite recent advances and promising results in children, liver cell transplantation (LCT) should still be regarded as an experimental therapy. Several substantial complications are known from animal studies and individual patients. However, safety data on liver cell infusion in children are scarce. We used LCT in four children of different ages (3 weeks to 11 years, 3-40 kg) and underlying diseases [acute liver failure (n = 1), urea cycle disorders (n = 2), and Crigler-Najjar syndrome (n = 1)]. Vital parameters, portal vein flow (PVF), portal vein pressure (PVP), and liver enzymes were measured every 5 min during cell application and hourly thereafter between applications. An application protocol with discontinuation rules depending on changes in PVF and PVP was developed and successfully applied. Application was feasible in all children despite the catastrophic overall condition of the patient with acute liver failure. No application-related changes in vital parameters were found, and none of the children experienced clinical signs of portal vein thrombosis, pulmonary embolism, or anaphylactic reactions. Time courses for changes in PVF, PVP, and liver enzymes were obtained. Thorough monitoring of portal vein pressure and duplex sonography according to a defined protocol is likely to increase safety of cell application in pediatric LCT.

Liver, liver cell and stem cell transplantation for the treatment of urea cycle defects

Despite advances in pharmacological therapy of urea cycle disorders (UCDs), the overall long-term prognosis is poor, especially for neonatal manifestations. Transplantation of liver tissue or isolated cells appears suitable for transfer of the missing enzyme. Liver transplantation (LT) for UCDs has an excellent 5-year survival rate of approximately 90% and is the only way to completely cure the disease. However, major neurological damage can only be prevented if the operation is performed during the first months of life. Unfortunately, such early LTs have a substantial risk for peri- and postoperative complications, mostly caused by a relatively large liver graft. Liver cell transplantation (LCT) is less invasive than LT, but has still to be regarded as an experimental therapy with about 100 patients treated since its first use in 1993. UCDs are a model disease for LCT, because of the poor prognosis, mainly hepatic enzyme defects, and excellent outcome after LT. So far, 10 children underwent LCT for UCDs with very few technical complications and encouraging clinical results. A first prospective study on its use in severe neonatal UCDs has recently started. However, availability of hepatocytes is limited by the scarcity of donor livers; therefore the use of stem cells is under investigation. Several different cell types may be regarded as liver stem cells, and in vivo transformation into hepatocyte-like cells has been shown in animal studies. However, a clear proof of principle in animal models of human metabolic disease is still missing, which is the prerequisite for clinical application in humans.

Liver transplantation for non-hepatotoxic inborn errors of metabolism

Hepatic-based inborn errors of metabolism are targets for treatment with liver transplantation in children, in whom the metabolic defect causes irreversible damage to the liver. However, certain metabolic defects originate with enzyme deficiencies localized in the liver but then give rise to toxic intermediates that damage extrahepatic organs without any significant compromise of general liver function. Here, the rationale of using liver transplantation to replace an organ that is functioning normally except for a specific metabolic pathway raises difficult questions about indications for transplantation, timing, amount of replacement tissue needed to correct the defect, and whether heterozygote parents are suitable living donors for liver transplantation in their affected children. This review explores these questions and others, including the role of hepatocyte transplantation, in this select group of disorders. Until the promise of specific gene or enzyme replacement therapy is realized, liver and hepatocyte transplantation offers the best chance of achieving metabolic control in these challenging patients.

Hepatocytes transplantation in rats with acute hepatic failure

AIM: To study the effect of allogeneic hepatocytes transplantation (HcT) intraperitoneally, intrasplenically or through vena portae in rats with acute hepatic failure (AHF) induced by D-galactosamine (D-gal).

METHODS: AHF rats were induced by D-gal. HcT was carried out 60h after intoxication, and all rats were divided into six groups: GroupⅠ received 2×10¹⁰/L hepatocytes 1 mL intraperitoneally with cyclosporin A (CsA) at 10 mg/kg simultaneously; Group Ⅱ received 1 mL normal saline (NS) intraperitoneally with CsA10 mg/kg; Group Ⅲ received 2×10¹⁰/L hepatocytes 1 mL through vena portae; Group Ⅳreceived 1mL NS through vena portae; Group Ⅴreceived 2×10¹⁰/L hepatocytes 1 mL intrasplenically; Group Ⅵ received 1 mL NS intrasplenically. After 1 wk the survival rates, liver function and liver histology of all rats were observed.

RESULTS: The survival rate of Group Ⅰ was higher than that of GroupⅡ (60 % vs 20%, P < 0.01), and their liver function and liver histology were obviously improved as compared with GroupⅡ. Similarly, the survival rate of Group Ⅴ was higher than that of Group Ⅵ (47% vs 20%, P < 0.05), and the liver function and liver histology were also improved in GroupⅤas compared with Group Ⅵ. On the other hand, the survival rate of Group Ⅲ was similar to that of GroupⅥ (20% vs 13.3%, P > 0.05), and their liver function and liver histology were also not improved significantly as compared with Group Ⅱ.

CONCLUSION: After HcT intraperitoneally or intrasplenically, the survival rates of AHF rats intoxicated with D-gal are increased, and the liver function and histology are also improved. On the contrary, the survival rate, liver function and liver histology of AHF rats through vena portae HcT are not improved.

Common diagnostic problems in pediatric liver pathology

The role of the pathologist in dealing with common problems of liver disease in children is likely to change dramatically as the molecular genetic revolution progresses. For example, microchip arrays for genes involved in bile salt synthesis and transport will pinpoint the specific mutations responsible for infantile cholestasis and similar methods will sort out infectious agents of acute and chronic hepatitis. But even as biochemistry, microbiology, and immunology laboratories already provide essential diagnostic information in such settings, informed histopathologic interpretation will continue to guide investigations of etiology and therapeutics and will remain an important medical necessity [95,96,100,102,104].