Early cell transplantation in LEC rats modeling Wilson's disease eliminates hepatic copper with reversal of liver disease

Toward Transplantation of Liver Organoids: From Biology and Ethics to Cost-effective Therapy

Liver disease is a common cause of morbidity and mortality, and many patients would benefit from liver transplantation. However, because of a shortage of suitable donor livers, even of those patients who are placed on the donor liver waiting list, many do not survive the waiting time for transplantation. Therefore, alternative treatments for end-stage liver disease need to be explored. Recent advances in organoid technology might serve as a solution to overcome the donor liver shortage in the future. In this overview, we highlight the potential of organoid technology for cell therapy and tissue engineering approaches. Both organoid-based approaches could be used as treatment for end-stage liver disease patients. Additionally, organoid-based cell therapy can also be used to repair liver grafts ex vivo to increase the supply of transplantable liver tissue. The potential of both approaches to become clinically available is carefully assessed, including their clinical, ethical, and economic implications. We provide insight into what aspects should be considered further to allow alternatives to donor liver transplantation to be successfully clinically implemented.

ATP7B gene therapy of autologous reprogrammed hepatocytes alleviates copper accumulation in a mouse model of Wilson's disease

BACKGROUND AND AIMS

Wilson's disease (WD) is a rare hereditary disorder due to ATP7B gene mutation, causing pathologic copper storage mainly in the liver and neurological systems. Hepatocyte transplantation showed therapeutic potential; however, this strategy is often hindered by a shortage of quality donor cells and by allogeneic immune rejection. In this study, we aimed to evaluate the function and efficacy of autologous reprogrammed, ATP7B gene-restored hepatocytes using a mouse model of WD.

APPROACH AND RESULTS

Sufficient liver progenitor cells (LPCs) were harvested by reprogramming hepatocytes from ATP7B^-/- mice with small molecules, which exhibited strong proliferation and hepatic differentiation capacity in vitro. After lentivirus-mediated mini ATP7B gene transfection and redifferentiation, functional LPC-ATP7B-derived hepatocytes (LPC-ATP7B-Heps) were developed. RNA sequencing data showed that, compared with LPC-green fluorescent protein-Heps (LPC-GFP-Heps) with enrichment of genes that were mainly in pathways of oxidative stress and cell apoptosis, in LPC-ATP7B-Heps under high copper stress, copper ion binding and cell proliferation pathways were enriched. LPC-ATP7B-Heps transplantation into ATP7B^-/- mice alleviated deposition of excess liver copper with its associated inflammation and fibrosis, comparable with those observed using normal primary hepatocytes at 4 months after transplantation.

CONCLUSIONS

We established a system of autologous reprogrammed WD hepatocytes and achieved ATP7B gene therapy in vitro. LPC-ATP7B-Heps transplantation demonstrated therapeutic efficacy on copper homeostasis in a mouse model of WD.

Novel Gene-Correction-Based Therapeutic Modalities for Monogenic Liver Disorders

The majority of monogenic liver diseases are autosomal recessive disorders, with few being sex-related or co-dominant. Although orthotopic liver transplantation (LT) is currently the sole therapeutic option for end-stage patients, such an invasive surgical approach is severely restricted by the lack of donors and post-transplant complications, mainly associated with life-long immunosuppressive regimens. Therefore, the last decade has witnessed efforts for innovative cellular or gene-based therapeutic strategies. Gene therapy is a promising approach for treatment of many hereditary disorders, such as monogenic inborn errors. The liver is an organ characterized by unique features, making it an attractive target for in vivo and ex vivo gene transfer. The current genetic approaches for hereditary liver diseases are mediated by viral or non-viral vectors, with promising results generated by gene-editing tools, such as CRISPR-Cas9 technology. Despite massive progress in experimental gene-correction technologies, limitations in validated approaches for monogenic liver disorders have encouraged researchers to refine promising gene therapy protocols. Herein, we highlighted the most common monogenetic liver disorders, followed by proposed genetic engineering approaches, offered as promising therapeutic modalities.

Long-Term Correction of Copper Metabolism in Wilson's Disease Mice with AAV8 Vector Delivering Truncated ATP7B

Wilson's disease (WD) is an autosomal recessive disorder of copper metabolism caused by mutations in the ATP7B gene encoding a liver active copper transport enzyme. Gene therapy with adeno-associated virus (AAV) carrying full-length ATP7B, which is about 4.4 kb, was shown to rescue copper metabolism disorder in WD mouse model. However, due to its relatively large size, the AAV vector containing full-length ATP7B could be oversized for its packaging capacity, which could lead to inefficient packaging. To this purpose, we engineered a truncated ATP7B mutant (tATP7B) that is about 3.3 kb in length and used for AAV gene therapy for WD mice. In vitro test showed that the excretion of copper outside the cells could be achieved with tATP7B as efficient as the full-length ATP7B. In vivo delivery of tATP7B to WD mice by AAV8 vectors corrected their copper metabolisms and significantly rescued copper accumulation-related syndromes, including reduced urinary copper excretion, increased serum ceruloplasmin, and improved liver damages. Thus, our study demonstrated that AAV gene therapy based on truncated ATP7B is a promising strategy in the treatment of WD.

Functional analyses of copper transporter genes in the human liver cell line HepG2

Copper (Cu) is an essential element regulated by four genes (hCTR1, hATOX1, hATP7A, and hATP7B in humans and zctr1, zatox1, zatp7a, and zatp7b in zebrafish) in copper uptake, distribution, and transport in animal cells. Zebrafish (Danio rerio) shows a higher endogenous ratio of zatp7a to zatp7b in the liver, is relatively intolerant to copper ions and has a different zatp7a and zatp7b expression patterns in different organs. As high-affinity copper transporters, both zctr1 and hCTR1 increased copper toxicity, whereas hATOX1 and zatox1 slightly reduced copper toxicity in HepG2 cells after copper administration for 24 h. The transfected zatp7b functioned in HepG2 cells as effectively as hATP7B after both 24-h and 96-h copper exposure, but zatp7a failed to function in HepG2 cells as effectively as hATP7A. Our findings suggest that ATP7A dysfunction would increase cytotoxicity in the liver; the reason for zebrafish's copper intolerance could be the bulk dysfunction and abnormal localization of zATP7A.

Determination of copper poisoning in Wilson's disease using laser ablation inductively coupled plasma mass spectrometry

Copper (Cu) is an essential trace element that is vital to the health of all living organisms. As a transition metal, it is involved in a myriad of biological processes. Balance studies estimated that the adult human requirement for copper is in the range of 1.3 to 2 mg per day. Cu deficiency alters immune function, neuropeptide synthesis and antioxidant defense, while the excess in Cu results in oxidative stress and progressive structural damage of mitochondrial and clinically in hepatic and/or neurological symptoms. This becomes particularly visible in Wilson's disease (WD) representing a rare autosomal recessive inherited disorder with a disease prevalence of about 1 in 30,000 people. The affected gene, i.e., ATP7B, belongs to the class of ATP-dependent, P-type Cu-transporting ATPases. To understand the pathomechanism in WD, several experimental models for studying WD were established. Independent studies performed in these models showed that the inactivation of the Atp7b gene results in a gradual increase in Cu in many organs during life span. However, the exact distribution of Cu and the potential impact of elevated Cu concentrations on other metals within the tissue are only sparely analyzed. Recently, novel laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)-based protocols for metal bio-imaging in liver and brain were established. In the present review, we will discuss the methodological background of this innovative technique and summarize our experiences using LA-ICP-MS imaging in biological monitoring, exact measurement, and spatial assignment of metals within tissue obtained from Atp7b null mice and clinical specimens taken from patients suffering from genetically confirmed WD. Using WD as an example, the data discussed demonstrates that LA-ICP-MS has multi-element capability, allowing precise measurement and visualization of metals in the tissue with high spatial resolution, sensitivity, quantification ability, and exceptional reproducibility.

Genes and Pathways Promoting Long-Term Liver Repopulation by Ex Vivo hYAP-ERT2 Transduced Hepatocytes and Treatment of Jaundice in Gunn Rats

Hepatocyte transplantation is an attractive alternative to liver transplantation. Thus far, however, extensive liver repopulation by adult hepatocytes has required ongoing genetic, physical, or chemical injury to host liver. We hypothesized that providing a regulated proliferative and/or survival advantage to transplanted hepatocytes should enable repopulation in a normal liver microenvironment. Here, we repopulated livers of DPPIV⁻ (dipeptidyl peptidase‐4) rats and Ugt1a1 (uridinediphosphoglucuronate glucuronosyltransferase 1a1)‐deficient Gunn rats (model of Crigler‐Najjar syndrome type 1), both models without underlying liver injury, for up to 1 year by transplanting lenti‐hYAP‐ERT2 (mutated estrogen receptor ligand‐binding domain 2)‐transduced hepatocytes (YAP‐Hc). Yap (yes‐associated protein) nuclear translocation/function in YAP‐Hc was regulated by tamoxifen. Repopulating YAP‐Hc and host hepatocytes were fluorescence‐activated cell sorting–purified and their transcriptomic profiles compared by RNAseq. After 1 year of liver repopulation, YAP‐Hc clusters exhibited normal morphology, integration into hepatic plates and hepatocyte‐specific gene expression, without dysplasia, dedifferentiation, or tumorigenesis. RNAseq analysis showed up‐regulation of 145 genes promoting cell proliferation and 305 genes suppressing apoptosis, including hepatocyte growth factor and connective tissue growth factor among the top 30 in each category and provided insight into the mechanism of cell competition that enabled replacement of host hepatocytes by YAP‐Hc. In Gunn rats transplanted with YAP‐Hc+tamoxifen, there was a 65%‐81% decline in serum bilirubin over 6 months versus 8%‐20% with control‐Hc, representing a 3‐4‐fold increase in therapeutic response. This correlated with liver repopulation as demonstrated by the presence of Ugt1a1‐positive hepatocyte clusters in livers and western blot analysis of tissue homogenates. Conclusion: Tamoxifen‐regulated nuclear translocation/function of hYAP‐ERT2 enabled long‐term repopulation of DPPIV^−/− and Gunn rat livers by hYAP‐ERT2‐transduced hepatocytes without tumorigenesis. This cell transplantation strategy may offer a potential therapy for most of the inherited monogenic liver diseases that do not exhibit liver injury.

Hepatocyte Transplantation in the Long Evans Cinnamon Rat Model of Wilson's Disease

Wilson's disease (WD), caused by a mutation in the P-type copper transporting ATPase (Atp7b) gene, results in excessive accumulation of copper in the liver. Long Evans Cinnamon rats (LEC) bear a mutation in the atp7b gene and share clinical characteristics of human WD. To explore hepatocyte transplantation (HT) as therapy for metabolic liver diseases, 8-week-old LEC rats (n = 12) were transplanted by intrasplenic injection of hepatocytes from donor Long Evans (LE) rats. Immunosuppression was maintained with intraperitoneal tacrolimus. The success of HT was monitored at 24 weeks of life. Serum aminotransferases and bilirubin peaked at 14–21 weeks in both HT rats and nontransplanted controls, but at 24 weeks, survival was 97% in LEC-HT versus 63% in controls. All transplanted rats showed restored biliary copper excretion and reduced liver iron concentration associated with increased ceruloplasmin oxidase activity. Liver tissue expressed atp7b mRNA (11.9 ± 13.6%) indicative of engraftment of normal cells in 7 of 12 HT rats, associated with a reduced liver copper concentration compared to untreated LEC rats. Periportal islets of normal appearing hepatocytes, recognized by atp7b antibody, were observed in transplanted livers while lobular host cells showed persistent pleomorphic changes and inflammatory infiltrates. In conclusion, transplantation of normal hepatocytes prevented fulminant hepatitis, reduces chronic inflammation, and improved 6-month survival in LEC rats. Engraftment of transplanted cells, which express atp7b mRNA, repopulated the recipient liver with normal functional capacity.

Demonstrating Potential of Cell Therapy for Wilson's Disease with the Long-Evans Cinnamon Rat Model

Wilson's disease (WD) is characterized by the inability to excrete copper (Cu) from the body with progressive tissue injury, especially in liver and brain. The molecular defect in WD concerns mutations in ATP7B gene leading to loss of Cu transport from the hepatocyte to the bile canaliculus. While drugs, e.g., Cu chelators, have been available for several decades, these must be taken lifelong, which can be difficult due to issues of compliance or side effects. Many individuals may require liver transplantation, which can also be difficult due to donor organ shortages. Therefore, achieving permanent cures via cell or gene therapy are of great interest for WD. Cell therapy is feasible because transplanted hepatocytes can integrate in liver parenchyma and restore deficient functions, including transport of Cu into bile. The availability of authentic animal models that recapitulate hepatic WD, especially the Long-Evans Cinnamon (LEC) rat, has advanced cell transplantation research in WD. We describe requirements for cell therapy in animal models with several standardized methods for studies to test or refine cell therapy strategies in WD.

Efficient liver repopulation of transplanted hepatocyte prevents cirrhosis in a rat model of hereditary tyrosinemia type I

Hereditary tyrosinemia type I (HT1) is caused by a deficiency in the enzyme fumarylacetoacetate hydrolase (Fah). Fah-deficient mice and pigs are phenotypically analogous to human HT1, but do not recapitulate all the chronic features of the human disorder, especially liver fibrosis and cirrhosis. Rats as an important model organism for biomedical research have many advantages over other animal models. Genome engineering in rats is limited till the availability of new gene editing technologies. Using the recently developed CRISPR/Cas9 technique, we generated Fah(-/-) rats. The Fah(-/-) rats faithfully represented major phenotypic and biochemical manifestations of human HT1, including hypertyrosinemia, liver failure, and renal tubular damage. More importantly, the Fah(-/-) rats developed remarkable liver fibrosis and cirrhosis, which have not been observed in Fah mutant mice or pigs. Transplantation of wild-type hepatocytes rescued the Fah(-/-) rats from impending death. Moreover, the highly efficient repopulation of hepatocytes in Fah(-/-) livers prevented the progression of liver fibrosis to cirrhosis and in turn restored liver architecture. These results indicate that Fah(-/-) rats may be used as an animal model of HT1 with liver cirrhosis. Furthermore, Fah(-/-) rats may be used as a tool in studying hepatocyte transplantation and a bioreactor for the expansion of hepatocytes.

Long-term metabolic correction of Wilson's disease in a murine model by gene therapy

BACKGROUND & AIMS

Wilson's disease (WD) is an autosomal recessively inherited copper storage disorder due to mutations in the ATP7B gene that causes hepatic and neurologic symptoms. Current treatments are based on lifelong copper chelating drugs and zinc salts, which may cause side effects and do not restore normal copper metabolism. In this work we assessed the efficacy of gene therapy to treat this condition.

METHODS

We transduced the liver of the Atp7b(-/-) WD mouse model with an adeno-associated vector serotype 8 (AAV8) encoding the human ATP7B cDNA placed under the control of the liver-specific α1-antitrypsin promoter (AAV8-AAT-ATP7B). After vector administration we carried out periodic evaluation of parameters associated with copper metabolism and disease progression. The animals were sacrificed 6months after treatment to analyze copper storage and hepatic histology.

RESULTS

We observed a dose-dependent therapeutic effect of AAV8-AAT-ATP7B manifested by the reduction of serum transaminases and urinary copper excretion, normalization of serum holoceruloplasmin, and restoration of physiological biliary copper excretion in response to copper overload. The liver of treated animals showed normalization of copper content and absence of histological alterations.

CONCLUSIONS

Our data demonstrate that AAV8-AAT-ATP7B-mediated gene therapy provides long-term correction of copper metabolism in a clinically relevant animal model of WD providing support for future translational studies.

The history and use of human hepatocytes for the treatment of liver diseases: the first 100 patients

Orthotopic liver transplantation remains the only curative treatment for many end-stage liver diseases, yet the number of patients receiving liver transplants remains limited by the number of organs available for transplant. There is a need for alternative therapies for liver diseases. The transplantation of isolated hepatocytes (liver cells) has been used as an experimental therapy for liver disease in a limited number of cases. Recently, the 100th case of hepatocyte transplantation was reported. This review discusses the history of the hepatocyte transplant field, the major discoveries that supported and enabled the first hepatocyte transplants, and reviews the cases and outcomes of the first 100 clinical transplants. Some of the problems that limit the application or efficacy of hepatocyte transplantation are discussed, as are possible solutions to these problems. In conclusion, hepatocyte transplants have proven effective particularly in cases of metabolic liver disease where reversal or amelioration of the characteristic symptoms of the disease is easily quantified. However, no patients have been completely corrected of a metabolic liver disease for a significant amount of time by hepatocyte transplantation alone. It is likely that future developments in new sources of cells for transplantation will be required before this cellular therapy can be fully implemented and available for large numbers of patients.

Cell therapy to remove excess copper in Wilson's disease

To achieve permanent correction of Wilson's disease by a cell therapy approach, replacement of diseased hepatocytes with healthy hepatocytes is desirable. There is a physiological requirement for hepatic ATP7B-dependent copper (Cu) transport in bile, which is deficient in Wilson's disease, producing progressive Cu accumulation in the liver or brain with organ damage. The ability to repopulate the liver with healthy hepatocytes raises the possibility of cell therapy in Wilson's disease. Therapeutic principles included reconstitution of bile canalicular network as well as proliferation in transplanted hepatocytes, despite toxic amounts of Cu in the liver. Nonetheless, cell therapy studies in animal models elicited major differences in the mechanisms driving liver repopulation with transplanted hepatocytes in Wilson's disease versus nondiseased settings. Recently, noninvasive imaging was developed to demonstrate Cu removal from the liver, including after cell therapy in Wilson's disease. Such developments will help advance cell/gene therapy approaches, particularly by offering roadmaps for clinical trials in people with Wilson's disease.

Regulation of copper transport crossing brain barrier systems by Cu-ATPases: effect of manganese exposure

Regulation of cellular copper (Cu) homeostasis involves Cu-transporting ATPases (Cu-ATPases), i.e., ATP7A and ATP7B. The question as to how these Cu-ATPases in brain barrier systems transport Cu, i.e., toward brain parenchyma, cerebrospinal fluid (CSF), or blood, remained unanswered. This study was designed to characterize roles of Cu-ATPases in regulating Cu transport at the blood-brain barrier (BBB) and blood-CSF barrier (BCB) and to investigate how exposure to toxic manganese (Mn) altered the function of Cu-ATPases, thereby contributing to the etiology of Mn-induced parkinsonian disorder. Studies by quantitative real-time RT-PCR (qPCR), Western blot, and immunocytochemistry revealed that both Cu-ATPases expressed abundantly in BBB and BCB. Transport kinetic studies by in situ brain infusion and ventriculo-cisternal (VC) perfusion in Sprague Dawley rat suggested that the BBB was a major site for Cu entry into brain, whereas the BCB was a predominant route for Cu efflux from the CSF to blood. Confocal evidence showed that the presence of excess Cu or Mn in the choroid plexus cells led to ATP7A relocating toward the apical microvilli facing the CSF, but ATP7B toward the basolateral membrane facing blood. Mn exposure inhibited the production of both Cu-ATPases. Collectively, these data suggest that Cu is transported by the BBB from the blood to brain, which is mediated by ATP7A in brain capillary. By diffusion, Cu ions move from the interstitial fluid into the CSF, where they are taken up by the BCB. Within the choroidal epithelial cells, Cu ions are transported by ATP7B back to the blood. Mn exposure alters these processes, leading to Cu dyshomeostasis-associated neuronal injury.

Therapeutic hepatocyte transplant for inherited metabolic disorders: functional considerations, recent outcomes and future prospects

The applications, outcomes and future strategies of hepatocyte transplantation (HTx) as a corrective intervention for inherited metabolic disease (IMD) are described. An overview of HTx in IMDs, as well as preclinical evaluations in rodent and other mammalian models, is summarized. Current treatments for IMDs are highlighted, along with short- and long-term outcomes and the potential for HTx to supplement or supplant these treatments. Finally, the advantages and disadvantages of HTx are presented, highlighted by long-term challenges with interorgan engraftment and expansion of transplanted cells, in addition to the future prospects of stem cell transplants. At present, the utility of HTx is represented by the potential to bridge patients with life-threatening liver disease to organ transplantation, especially as an adjuvant intervention where severe organ shortages continue to pose challenges.

Functional ultrasound imaging for assessment of extracellular matrix scaffolds used for liver organoid formation

A method of 3D functional ultrasound imaging has been developed to enable non-destructive assessment of extracellular matrix scaffolds that have been prepared by decellularization protocols and are intended for recellularization to create organoids. A major challenge in organ decellularization is retaining patent micro-vascular structures crucial for nutrient access and functionality of organoids. The imaging method described here provides statistical distributions of flow rates throughout the tissue volumes, 3D vessel network architecture visualization, characterization of microvessel volumes and sizes, and delineation of matrix from vascular circuits. The imaging protocol was tested on matrix scaffolds that are tissue-specific, but not species-specific, matrix extracts, prepared by a process that preserved >98% of the collagens, collagen-associated matrix components, and matrix-bound growth factors and cytokines. Image-derived data are discussed with respect to assessment of scaffolds followed by proof-of-concept studies in organoid establishment using Hep3B, a human hepatoblast-like cell line. Histology showed that the cells attached to scaffolds with patent vasculature within minutes, achieved engraftment at near 100%, expressed liver-specific functions within 24 h, and yielded evidence of proliferation and increasing differentiation of cells throughout the two weeks of culture studies. This imaging method should prove valuable in analyses of such matrix scaffolds.

Wilson's disease: update on integrated Chinese and Western medicine

Wilson's disease (WD), or hepatolenticular degeneration, is an autosomal recessive inheritance disorder of copper metabolism caused by ATP7B gene mutation. As WD is an inherited disease of the nervous system that is not curable; early diagnosis with early and life-long treatment leads to better prognoses. Currently, the recommended treatment for WD is integrated Chinese and Western medicine. A number of studies indicate that treatment of integrative medicine can not only enforce the de-copper effect but also improve liver function, intelligence, and other factors. This article reviewed in detail the advantages of WD treated with Chinese and Western medicine together.

Repeated transplantation of hepatocytes prevents fulminant hepatitis in a rat model of Wilson's disease

The outcome of consecutive hepatocyte transplants was explored in a rat model of Wilson's disease before the onset of fulminant hepatitis without preconditioning regimens. Rats received a high-copper diet in order to induce a rapid induction of liver failure. Sham-operated rats (15/15) developed jaundice and fulminant hepatitis, and they died within 4 weeks of first transplantation. Despite the continuation of a high dietary copper challenge, long-term survival was observed for a notable proportion of the transplanted animals (7/18). All survivors displayed normalized levels of hepatitis-associated serum markers and ceruloplasmin oxidase activity by posttransplant days 50 and 98, respectively. The liver copper concentrations, the liver histology, and the expression of marker genes were significantly restored within 4 months of transplantation in comparison with the control group. The high expression of a copper transporter gene (ATPase Cu++ transporting beta polypeptide) in the livers of the survivors indicated a high rate of repopulation by donor hepatocytes. Our data suggest that repeated cell transplantation can overcome the limitations of a single therapy session in rats with severe hepatic disease by functionally restoring the host liver without preconditioning.

The nude mouse as model for liver deficiency study and treatment and xenotransplantation

We aimed at reviewing the various uses of Nude mouse for the development of liver deficiency models and evaluation of efficacy of hepatic cell xenotransplantation. The first part records the large range of liver deficiency models that can be developed in Nude mice: surgical partial hepatectomy, acute toxic liver deficiency, chronic cirrhosis, and transgenic liver injury. The second part tackles the outcome of rat hepatocyte as well as human cell transplantation, both mature hepatocyte and hepatic progenitor, into Nude mouse submitted to liver injury. Results are discussed and compared to other available immunodeficient mouse models. The issue of humanized liver creation is also addressed. Altogether, these results show that Nude mouse appears to be a suitable small animal model to expand our insight into liver cell engraftment and regeneration.

Early gestational gene transfer with targeted ATP7B expression in the liver improves phenotype in a murine model of Wilson's disease

The ideal gene therapy for metabolical liver disorders would target hepatocytes before the onset of disease and be durable, non-toxic and non-immunogenic. Early gestational gene transfer can achieve such goals. Here, we demonstrate that prenatal gene transfer of human Atp7b reduces liver pathology and improves biochemical markers in Atp7b(-/-) mice, a murine model of Wilson's disease (WD). Following prenatal injection of lentivirus vector containing the human Atp7b gene under the transcriptional control of a liver-specific promoter, the full-length ATP7B was detectable in mouse livers for the entire duration of experiments (20 weeks after birth). In contrast to a marked pathology in non-injected animals, livers from age-matched treated mice consistently demonstrated normal gross and histological morphology. Hepatic copper content was decreased in the majority of treated mice, although remaining copper levels varied. Improvement of hepatic copper metabolism was further apparent from the presence of copper-bound ceruloplasmin in the sera and normalization of the mRNA levels for HMG CoA-reductase. With this approach, the complete loss of copper transport function can be ameliorated, as evident from phenotypical improvement in treated Atp7b(-/-) mice. This study provides proof of principle for in utero gene therapy in WD and other liver-based enzyme deficiencies.

Wilson's disease

In the almost 100 years since Wilson's description of the illness that now bears his name, tremendous advances have been made in our understanding of this disorder. The genetic basis for Wilson's disease - mutation within the ATP7B gene - has been identified. The pathophysiologic basis for the damage resulting from the inability to excrete copper via the biliary system with its consequent gradual accumulation, first in the liver and ultimately in the brain and other organs and tissues, is now known. This has led to the development of effective diagnostic and treatment modalities that, although they may not eliminate the disorder, do provide the means for efficient diagnosis and effective amelioration if carried out in a dedicated and persistent fashion. Nevertheless, Wilson's disease remains both a diagnostic and treatment challenge for physician and patient. Its protean clinical manifestations make diagnosis difficult. Appropriate diagnostic evaluations to confirm the diagnosis and institute treatment can be confusing. In this chapter, the clinical manifestations, diagnostic evaluation, and treatment approaches for Wilson's disease are discussed.

Early stage transplantation of bone marrow cells markedly ameliorates copper metabolism and restores liver function in a mouse model of Wilson disease

Background

Recent studies have demonstrated that normal bone marrow (BM) cells transplantation can correct liver injury in a mouse model of Wilson disease (WD). However, it still remains unknown when BM cells transplantation should be administered. The aim of this study was to investigate the potential impact of normal BM cells transplantation at different stages of WD to correct liver injury in toxic milk (tx) mice.

Methods

Recipient tx mice were sublethally irradiated (5 Gy) prior to transplantation. The congenic wild-type (DL) BM cells labeled with CM-DiI were transplanted via caudal vein injection into tx mice at the early (2 months of age) or late stage (5 months of age) of WD. The same volume of saline or tx BM cells were injected as controls. The DL donor cell population, copper concentration, serum ceruloplasmin oxidase activity and aspartate aminotransferase (AST) levels in the various groups were evaluated at 1, 4, 8 and 12 weeks post-transplant, respectively.

Results

The DL BM cells population was observed from 1 to 12 weeks and peaked by the 4^th week in the recipient liver after transplantation. DL BM cells transplantation during the early stage significantly corrected copper accumulation, AST across the observed time points and serum ceruloplasmin oxidase activity through 8 to 12 weeks in tx mice compared with those treated with saline or tx BM cells (all P < 0.05). In contrast, BM cells transplantation during the late stage only corrected AST levels from 4 to 12 weeks post-transplant and copper accumulation at 12 weeks post-transplant (all P < 0.05). No significant difference was found between the saline and tx BM cells transplantation groups across the observed time points (P > 0.05).

Conclusions

Early stage transplantation of normal BM cells is better than late stage transplantation in correcting liver function and copper metabolism in a mouse model of WD.

Rodent models of liver repopulation

The liver has an extraordinary faculty to regenerate. Hepatocytes are highly differentiated cells that, despite a resting G0 state in the normal quiescent liver, can re-enter the cell cycle to reconstitute the organ after an injury. However, the first cell therapy approaches trying to harness this specific characteristic of the hepatocytes came up against the competition with resident hepatocytes in the ability to proliferate. This review will describe the different rodent models that have been developed in the last 15 years to demonstrate the concept of liver repopulation with transplanted cells harbouring a selective advantage over resident hepatocytes. Examples will then be given to show how these models demonstrated the therapeutic efficiency of cell transplantation in specific disorders. The transplantation of human hepatocytes into some of these mouse models led to the creation of humanized livers. These humanized mice provide a powerful tool to study the physiopathology of human hepatotropic pathogens and to develop drugs against them. Finally, emphasis will be placed on the role of these rodent models in the demonstration of the hepatocytic potential of stem cells.

Biosafety in ex vivo gene therapy and conditional ablation of lentivirally transduced hepatocytes in nonhuman primates

Ex vivo gene therapy is an interesting alternative to orthotopic liver transplantation (OLT) for treating metabolic liver diseases. In this study, we investigated its efficacy and biosafety in nonhuman primates. Hepatocytes isolated from liver lobectomy were transduced in suspension with a bicistronic liver-specific lentiviral vector and immediately autotransplanted (SLIT) into three cynomolgus monkeys. The vector encoded cynomolgus erythropoietin (EPO) and the conditional suicide gene herpes simplex virus-thymidine kinase (HSV-TK). Survival of transduced hepatocytes and vector dissemination were evaluated by detecting transgene expression and vector DNA. SLIT was safely performed within a day in all three subjects. Serum EPO and hematocrit rapidly increased post-SLIT and their values returned to baseline within about 1 month. Isoforms of EPO detected in monkeys' sera differed from the physiological renal EPO. In liver biopsies at months 8 and 15, we detected EPO protein, vector mRNA and DNA, demonstrating long-term survival and functionality of transplanted lentivirally transduced hepatocytes. Valganciclovir administration resulted in complete ablation of the transduced hepatocytes. We demonstrated the feasibility and biosafety of SLIT, and the long term (>1 year) functionality of lentivirally transduced hepatocytes in nonhuman primates. The HSV-TK/valganciclovir suicide strategy can increase the biosafety of liver gene therapy protocols by safely and completely ablating transduced hepatocytes on demand.

Bile salt-induced pro-oxidant liver damage promotes transplanted cell proliferation for correcting Wilson disease in the Long-Evans Cinnamon rat model

Insights into disease-specific mechanisms for liver repopulation are needed for cell therapy. To understand the efficacy of pro-oxidant hepatic perturbations in Wilson disease, we studied Long-Evans Cinnamon (LEC) rats with copper toxicosis under several conditions. Hepatocytes from healthy Long-Evans Agouti (LEA) rats were transplanted intrasplenically into the liver. A cure was defined as lowering of copper to below 250 microg/g liver, presence of ATPase, Cu++ transporting, beta polypeptide (atp7b) messenger RNA (mRNA) in the liver and improvement in liver histology. Treatment of animals with the hydrophobic bile salt, cholic acid, or liver radiation before cell transplantation produced cure rates of 14% and 33%, respectively; whereas liver radiation plus partial hepatectomy followed by cell transplantation proved more effective, with cure in 55%, P < 0.01; and liver radiation plus cholic acid followed by cell transplantation was most effective, with cure in 75%, P < 0.001. As a group, cell therapy cures in rats preconditioned with liver radiation plus cholic acid resulted in less hepatic copper, indicating greater extent of liver repopulation. We observed increased hepatic catalase and superoxide dismutase activities in LEC rats, suggesting chronic oxidative stress. After liver radiation or cholic acid, hepatic lipid peroxidation levels increased, indicating further oxidative injury, although we did not observe overt additional cytotoxicity. This contrasted with healthy animals in which liver radiation and cholic acid produced hepatic steatosis and loss of injured hepatocytes. We concluded that pro-oxidant perturbations were uniquely effective for cell therapy in Wilson disease because of the nature of preexisting hepatic damage.

Cell-based therapies for metabolic liver disease

Liver transplantation is an important therapeutic option for many individuals with metabolic liver disease. Nevertheless, the invasive nature of surgery and limitations of donor organ availability have led to the search for alternatives to whole-organ transplantation. Cell-based therapies have been a particularly active area of investigation in recent years. Hepatocyte transplantations have been performed for a variety of indications, including acute liver failure, end-stage liver disease, and inborn errors of metabolism. Individuals with inborn errors of metabolism who have undergone hepatocyte transplantation have shown clinical improvement and partial correction of the underlying metabolic defect. In most cases, sustained benefits have not been observed. This may be related to inadequate cell dose, variations in the quality of hepatocyte preparations, rejection of the transplanted cells, or senescence of transplanted hepatocytes. Though initial proof of concept with hepatocyte transplantation has been demonstrated by a number of investigators, wide application of this technology has been hindered by the inability to secure a reliable and well-characterized cell source(s) for transplantation and by the challenges of sustained engraftment and expansion of transplanted cells in vivo. Cell-based therapies, including those based on stem cells or more differentiated progenitor cells, may represent the future of cell transplantation for treatment of metabolic liver disease.

Copper-transporting ATPases ATP7A and ATP7B: cousins, not twins

Copper plays an essential role in human physiology and is indispensable for normal growth and development. Enzymes that are involved in connective tissue formation, neurotransmitter biosynthesis, iron transport, and others essential physiological processes require copper as a cofactor to mediate their reactions. The biosynthetic incorporation of copper into these enzymes takes places within the secretory pathway and is critically dependent on the activity of copper-transporting ATPases ATP7A or ATP7B. In addition, ATP7A and ATP7B regulate intracellular copper concentration by removing excess copper from the cell. These two transporters belong to the family of P(1)-type ATPases, share significant sequence similarity, utilize the same general mechanism for their function, and show partial colocalization in some cells. However, the distinct biochemical characteristics and dissimilar trafficking properties of ATP7A and ATP7B in cells, in which they are co-expressed, indicate that specific functions of these two copper-transporting ATPases are not identical. Immuno-detection studies in cells and tissues have begun to suggest specific roles for ATP7A and ATP7B. These experiments also revealed technical challenges associated with quantitative detection of copper-transporting ATPases in tissues, as illustrated here by comparing the results of ATP7A and ATP7B immunodetection in mouse cerebellum.

Liver repopulation and carcinogenesis: two sides of the same coin?

Liver repopulation by transplanted normal hepatocytes has been described in a number of experimental settings. Extensive repopulation can also occur from the selective proliferation of endogenous normal hepatocytes, both in experimental animals and in the human liver. This review highlights the intriguing association between clinical and experimental conditions related to liver repopulation and an increased risk for development of hepatocellular carcinoma. It is suggested that any microenvironment that is able to sustain the clonal growth of normal transplanted (or endogenous) hepatocytes is also geared to select for the emergence of rare resistant cells with an altered phenotype. Whereas the first pathway leads to liver repopulation with normal histology, the latter results in the growth of focal proliferative lesions and carries an increased risk of neoplastic disease. The implications of this association are discussed, both in terms of pathogenetic significance and possible therapeutic exploitation.

Development of cell therapy strategies to overcome copper toxicity in the LEC rat model of Wilson disease

Aims: Therapeutic replacement of organs with healthy cells requires disease-specific strategies. As copper toxicosis due to ATP7B deficiency in Wilson disease produces significant liver injury, disease-specific study of transplanted cell proliferation will offer insights into cell and gene therapy mechanisms. Materials & methods: We used Long–Evans Cinnamon (LEC) rats to demonstrate the effects of liver preconditioning with radiation and ischemia reperfusion, followed by transplantation of healthy Long–Evans Agouti rat hepatocytes and analysis of hepatic atp7b mRNA, bile copper, liver copper and liver histology. Results: LEC rats without cell therapy or after transplantation of healthy cells without liver conditioning accumulated copper and showed liver disease during the study period. Liver conditioning incorporating hepatic radiation promoted transplanted cell proliferation and reversed Wilson disease parameters, although with interindividual variations and time lags for improvement, which were different from previous results of liver repopulation in healthy animals. Conclusion: Cell therapy will correct genetic disorders characterized by organ damage. However, suitable mechanisms for inducing transplanted cell proliferation will be critical for therapeutic success.

Transplantation of fetal liver epithelial progenitor cells ameliorates experimental liver fibrosis in mice

AIM: To investigate the effect of transplanted fetal liver epithelial progenitor (FLEP) cells on liver fibrosis in mice.

METHODS: FLEP cells were isolated from embryonal day (ED) 14 BALB/c mice and transplanted into female syngenic BALB/c mice (n = 60). After partial hepatectomy (PH), diethylnitrosamine (DEN) was administered to induce liver fibrosis. Controls received FLEP cells and non-supplemented drinking water, the model group received DEN-spiked water, and the experimental group received FLEP cells and DEN. Mice were killed after 1, 2, and 3 mo, and alanine aminotransferase (ALT), aspartate aminotransferase (AST), hyaluronic acid (HA), and laminin (LN) in serum, and hydroxyproline (Hyp) content in liver were assessed. Alpha-smooth muscle actin (α-SMA) of liver was tested by immunohistochemistry. Transplanted male mice FLEP cells were identified by immunocytochemistry for sry (sex determination region for Y chromosome) protein.

RESULTS: Serum ALT, AST, HA, and LN were markedly reduced by transplanted FLEP cells. Liver Hyp content and α-SMA staining in mice receiving FLEP cells were lower than that of the model group, which was consistent with altered liver pathology. Transplanted cells proliferated and differentiated into hepatocytes and bile duct epithelial cells with 30%-50% repopulation in the liver fibrosis induced by DEN after 3 mo.

CONCLUSION: Transplanted FLEP cells proliferate and differentiate into hepatocytes and bile duct epithelial cells with high repopulation capacity in the fiberized liver induced by DEN, which restores liver function and reduces liver fibrosis.

Liver repopulation trial using bone marrow cells in a retrorsine-induced chronic hepatocellular injury model

OBJECTIVES

The aim of this study was to determine the potential of bone marrow derived cells to participate in liver repopulation. In this model, the injected cells had a "selective growth advantage" compared to the native hepatocytes whose proliferation was blocked by retrorsine.

METHODS

Total bone marrow cells were isolated from male Fisher 344 rats not deficient in dipeptidyl peptidase activity (F344, DPP IV+). The animals were given an injection of retrorsine and were divided in 2 groups: 1/group R (N=13): female F344 rats received 4.106 male cells at day 0 (labeled by chromosome Y). 2/group RH (N=19): Male F344 DPP IV- rats received 4.106 male DPP IV+ cells after hepatectomy at day 0 (labelled by DPP IV activity).

RESULTS

Group R: no male cell was detected by PCR at day 14, 28, 56 and 84. Group RH: isolated DPP IV+ transplanted cells were observed at days 14 and 28 in the periportal areas. Later, these cells were no longer visible. Liver regeneration occurred by proliferation of small clusters of hepatocytes.

CONCLUSIONS

In this experimental model the capacity of transplanted bone marrow cells to repopulate the liver was tested against the same capacity of native liver stem cells. Liver regeneration occurred via native liver cells seen as small hepatocytes. In this model the small hepatocytes may be considered as hepatic stem cells.

Lentiviral gene transfer ameliorates disease progression in Long-Evans cinnamon rats: an animal model for Wilson disease

OBJECTIVE

Wilson disease is a copper storage disorder caused by mutations in the ATP7B gene leading to liver cirrhosis. It has previously been shown that lentiviral vectors can govern an efficient delivery and stable expression of a transgene. The aim of this pilot study was to prove the principle of a lentiviral gene transfer in the Long-Evans cinnamon (LEC) rat, an animal model of Wilson disease.

MATERIAL AND METHODS

LEC rats were treated either by systemic application of lentiviral vectors or by intrasplenic transplantation of LEC-rat hepatocytes lentivirally transduced with ATP7B. The ATP7B gene expression was analyzed by RT-PCR and immunofluorescence analysis. The therapeutic effect was assessed by analysis of liver histology, serum ceruloplasmin oxidase activity, and liver copper content.

RESULTS

Hepatic expression of the transgene was detected at different time-points post-treatment and lasted for up to 24 weeks (end of experiment). Liver copper levels were lowered in all treatment groups compared to untreated LEC rats. Twenty-four weeks after treatment, the area of the examined liver-tissue sections occupied by fibrosis was 48.3-57.9% in untreated LEC rats and 10.7-19.8% in rats treated with cell therapy. In systemically treated rats, only small fibrous septa could be observed.

CONCLUSIONS

These data prove for the first time that lentiviral ATP7B gene transfer is feasible in Wilson disease. In our pilot study the systemic approach was more promising in ameliorating disease progression than the transplantation of lentivirally transduced hepatocytes.

Development of liver regenerative therapy using glycoside-modified bone marrow cells

Several recent studies have reported that bone marrow cells (BMCs) have the ability to generate functional hepatocytes. However, the efficiency at which BMC transplantation generates functional hepatocytes is rather low. We assumed that if BMCs accumulated directly in liver, the functional BMC-derived hepatocytes should increase efficiently. We tried to increase the accumulation of BMCs directly in liver through the interaction between hepatic asialoglycoprotein receptor and desialylated BMCs. Desialylated BMCs were produced with treatment of neuraminidase. Desialylated BMCs that expressed green fluorescent protein (GFP) were injected into Long Evans Cinnamon (LEC) rats, a human Wilson's disease model, intravenously. At 3 and 5 months after transplantation, GFP-expressing hepatocyte nodules appeared in the liver of these BMC-transplanted LEC rats. These findings suggest that the functional BMC-derived hepatocytes can be generated by the direct accumulation of BMCs and that this strategy is new BMC therapy for liver regeneration.

Characteristics of rat bone marrow cells differentiated into a liver cell lineage and dynamics of the transplanted cells in the injured liver

BACKGROUND

Bone marrow cells (BMCs) have been shown to differentiate into a liver cell lineage, but little is known about their dynamics following transplantation. BMCs were cultured to investigate the expression of liver-specific genes in vitro and transplanted into in vivo liver-injury models to elucidate their dynamics in the liver.

METHODS

The mRNA expression of various liver-specific genes in BMCs cocultured with hepatocytes was analyzed using reverse transcription-polymerase chain reaction. BMCs from transgenic rats expressing green fiuorescent protein were transplanted into the spleen of rat liver-injury models induced with 2-acetylaminofiuorene (2-AAF) or carbon tetrachloride (CCl4). BMCs were also transplanted directly into livers treated with CCl4 to determine which route is better for transplantation.

RESULTS

BMCs differentiated into a liver cell lineage in vitro and expressed mRNAs consistent with mature hepatocytes, including albumin. The transplanted BMCs were found in the liver in the CCl4-induced injury model, but not in the 2-AAF-induced model. The hepatocyte growth factor and fibroblast growth factor mRNA levels in the liver were significantly higher in the CCl4-induced model than in the 2-AAF-induced model. Migration of BMCs to the liver was more effective following injection into the liver, rather than into the spleen.

CONCLUSIONS

Cultured BMCs differentiated into a liver cell lineage are a potential source for cell transplantation. Transplantation is successful in the severely injured liver with a high level of expression of mRNAs for growth factors. Injection of BMCs directly into the liver is the preferred route of administration.

Experimental models of acute and chronic liver failure in nude mice to study hepatocyte transplantation

Although hepatocyte transplantation is a promising therapy for acute liver failure in human, there is still a lack of animal models suffering from hepatic injury in which the benefits of hepatocyte transplantation could be evaluated solely, without the bias caused by immunosuppression. As a consequence, the aim of the study was first to develop reproducible models of partial hepatectomy and of thioacetamide (TA)- or Jo2-induced acute liver failure in nude mice. Chronic liver disease was also investigated by repeated injections of sublethal doses of thioacetamide. Survival rates, routine histologic observations, alanin aminotransferase sera content, Ki67, and caspase 3 immunodetection were investigated both after 40% partial hepatectomy and after toxic-induced damages. Liver injuries were more severe and/or precocious in nude mice than in Balb/c mice for a given treatment with a maximum of acute injury obtained 24 h after single toxic injection, and were found to be transitory and reversible within 10 days. Toxics induced apoptosis followed by necrosis, confirming recent published data. Onset of fibrosis leading to reproducible chronic cirrhosis in nude mice correlated with increasing number of Ki67-positive cells, indicating that high levels of cell proliferation occurred. Chronic cirrhosis progressively reversed to fibrosis when the treatment ceased. Preliminary results demonstrated that engrafted xenogeneic hepatocytes could be detected in the host liver by anti-MHC class I immunohistochemistry. Fractions enriched in 2n or 4n hepatocytes by cell sorting using a flow cytometer were equivalent to the unpurified fraction in terms of engraftment in control nude mice or in nude mice subjected to PH. However, in mice suffering from liver injury 24 h after Jo2 or TA treatment, the engraftment of 2n hepatocytes was about twice that of an unpurified hepatocyte population or of a population enriched in 4n hepatocytes.

Diminution of toxic copper accumulation in toxic milk mice modeling Wilson disease by embryonic hepatocyte intrasplenic transplantation

AIM: To observe the therapeutic effect of intrasplenic transplantation with embryonic hepatocytes on amelioration of hereditary copper accumulation in toxic milk (TX) mouse modeling Wilson disease.

METHODS: Donor hepatocytes were harvested from 14-d fetal liver of a pregnant homogeneous DL mouse. These cells were successively cultured, labeled with fluorescein dye Hoechst 33342 for 24 h, and sequentially infused into the spleen parenchyma of the recipient TX mice. No host immunosuppression measures were taken. Two and four weeks after transplantation, the recipients were killed for routine histologic investigation and immunohistochemistry study up to 4 wk after transplantation. The serum copper and ceruloplasmin concentrations of the recipient mice were determined by graphite furnace atomic absorption spectroscopy.

RESULTS: In the following 2^nd and 4^th wk after transplantation, the donor hepatocytes could be visualized in the livers of 47.3% recipients. The serum ceruloplasmin and copper concentrations increased by 1.6-fold after 2 wk and 2.0-fold times after 4 wk respectively, which ultimately rose from about 30% of the normal level to nearly 60% (P<0.01). The hepatic copper concentration decreased 7.2%, 4 wk after transplantation. Pathologic examination showed that there were many actively proliferative hepatocyte precursor cells with specific embryonic hepatocyte marker AFP migrated into hepatic sinusoids of the recipients. A large number of cells carrying hepatocytes marker and albumin were observed in the recipient spleen tissues.

CONCLUSION: Embryonic hepatocytes are capable of differentiating into mature hepatocytes in vivo. After transplantation, the hereditary abnormalities of copper metabolism in TX mice could be corrected partially by intrasplenic transplantation of homogeneous embryonic hepatocytes.

Long-term extensive expansion of mouse hepatic stem/progenitor cells in a novel serum-free culture system

BACKGROUND & AIMS

The liver has high regenerative potential. We attempted to establish a novel culture system for extensive expansion of fetal mouse hepatic stem/progenitor cells and to characterize cultured cells.

METHODS

Hepatic spheroids collected from 6-day floating cultures were cultured on collagen-coated dishes in serum-free conditions in medium containing growth factors. Cultured cells were mainly characterized by immunocytochemistry and flow cytometry or transplanted into adult mice.

RESULTS

Approximately 400 expanding hepatic spheroids were generated from every 1 x 10(6) fetal liver cells. Subsequently, highly replicative colonies were subcultured with maintaining colony formation on collagen-coated dishes. These colonies consisted of small immature alpha-fetoprotein-positive cells and hepatocytic and cholangiocytic lineage-committed cells. The immature alpha-fetoprotein-positive cells could be expanded in a reproducible manner at least 5 x 10(5)-fold (which involved at least 30 passages over >6 months) without losing differentiation potential. Flow cytometric analysis showed that all cultured cells expressed CD49f, but not CD34, Thy-1, c-kit, or CD45. Nearly 15% of the cells expressed Sca-1, and approximately 5%-20% of the cells were side population cells. Both sorted side population cells and Sca-1-positive cells (especially side population cells) produced a large number of alpha-fetoprotein-positive cells and lineage-committed cells. Expanded cells had bidirectional differentiation potential and improved serum albumin levels in mice with severe liver damage.

CONCLUSIONS

Long-term extensive expansion of transplantable hepatic stem/progenitor cells was reproducibly achieved in a novel serum-free culture system. Moreover, this culture system yielded side population and Sca-1-positive cell populations that included hepatic stem/progenitor cells with differentiation and proliferation properties.

Wilson disease: new insights into pathogenesis, diagnosis, and future therapy

Wilson disease is caused by disease-specific mutations of the copper transporting ATPase, ATP7B. The diagnosis is established by clinical and biochemical means, though advances in molecular diagnostics will someday permit de novo diagnosis. The patient may present with hepatic, neurologic, or psychiatric symptoms, or a combination of these. Both environmental and extragenic effects contribute to the varied phenotypic presentations of this disease. Patients can be treated effectively with chelating agents or zinc salts, or with liver transplantation. Liver cell transplant and gene therapy offer potential cures for this disorder, but at present only data from preclinical studies on animal models are available. Future advances in immunotolerization and gene therapy will likely enable human trials for treatment of this disorder and other genetic disorders of hepatic metabolism.

Emerging insights into liver-directed cell therapy for genetic and acquired disorders

Treatment of acute or chronic liver diseases by cell transplantation is an attractive prospect because organ shortages greatly restrict liver transplantation. Moreover, a variety of genetic deficiency states affecting extrahepatic organs are amenable to liver-directed cell therapy. While the initial clinical experience with liver cell transplantation has been encouraging, further advances in several areas are necessary to improve these results. Insights into how engraftment and proliferation of transplanted cells may be modulated to obtain therapeutically effective masses of transplanted cells will be important in this pursuit. Studies of cell therapy in animal models of specific diseases have provided insights into the development of clinically relevant strategies for various disorders. Also, identification of suitable cell types, including stem/progenitor cells that could be expanded and manipulated in cell culture conditions, has begun to provide important new information for cell therapy. Similarly, advances in cryopreservation of cells and prevention of allograft rejection offer ways to accomplish cell therapy in an effective manner. Taken together, these advances indicate that liver-directed cell therapy will be well positioned in the near future to play significant roles in transplantation medicine.

Wilson disease: pathophysiology, diagnosis, treatment, and screening

Wilson disease is an autosomal recessive condition of copper metabolism that was once considered fatal. The identification of the gene for Wilson disease has led to a better understanding of the molecular defect underlying this disorder and has impacted on disease diagnosis for some individuals. Medical therapy with chelating agents or zinc salts remains the mainstay of therapy for most patients, and liver transplant is lifesaving for those with advanced disease refractory to medical therapy or with fulminant hepatic failure. Future cell-based and genetic therapies may provide a cure for this disorder.

Liver cell transplantation leads to repopulation and functional correction in a mouse model of Wilson's disease

BACKGROUND AND AIM

The toxic milk (tx) mouse is a non-fatal animal model for the metabolic liver disorder, Wilson's disease. The tx mouse has a mutated gene for a copper-transporting protein, causing early copper accumulation in the liver and late accumulation in other tissues. The present study investigated the efficacy of liver cell transplantation (LCT) to correct the tx mouse phenotype.

METHODS

Congenic hepatocytes were isolated and intrasplenically transplanted into 3-4-month-old tx mice, which were then placed on various copper-loaded diets to examine its influence on repopulation by transplanted cells. The control animals were age-matched untransplanted tx mice. Liver repopulation was determined by comparisons of restriction fragment length polymorphism ratios (DNA and mRNA), and copper levels were measured by atomic absorption spectroscopy.

RESULTS

Repopulation in recipient tx mice was detected in 11 of 25 animals (44%) at 4 months after LCT. Dietary copper loading (whether given before or after LCT, or both) provided no growth advantage for donor cells, with similar repopulation incidences in all copper treatment groups. Overall, liver copper levels were significantly lower in repopulated animals (538 +/- 68 microg/g, n = 11) compared to non-repopulated animals (866 +/- 62 microg/g, n = 14) and untreated controls (910 +/- 103 microg/g, n = 6; P < 0.05). This effect was also seen in the kidney and spleen. Brain copper levels remained unchanged.

CONCLUSION

Transplanted liver cells can proliferate and correct a non-fatal metabolic liver disease, with some restoration of hepatic copper homeostasis after 4 months leading to reduced copper levels in the liver and extrahepatic tissues, but not in the brain.

Regional and transient ischemia/reperfusion injury in the liver improves therapeutic efficacy of allogeneic intraportal hepatocyte transplantation in low-density lipoprotein receptor deficient Watanabe rabbits

BACKGROUND/AIMS

Hepatocyte transplantation has the potential to become an alternative to organ transplantation for the treatment of hereditary liver disease. Currently used hepatocyte transplantation techniques are often not sufficient for phenotypic correction. In a pre-clinical model we investigated the effect of regional transient ischemia reperfusion injury and repeated infusions of allogeneic hepatocytes on LDL cholesterol levels in LDL receptor deficient hyperlipidemic Watanabe rabbits.

METHODS

A catheter was surgically inserted into the inferior mesenteric vein. Blood supply to the right liver lobe was transiently interrupted. Nine infusions of 2.5x10(7) adult allogeneic hepatocytes from white New Zealand rabbits were applied over a period of 2 months.

RESULTS

Compared to pretreatment levels LDL cholesterol decreased significantly in Watanabe rabbits with transient ischemia reperfusion injury and repeated hepatocyte transplantation (-42+/-3%). Repeated hepatocyte transplantation without transient ischemia reperfusion injury decreased LDL cholesterol levels only moderately (-11+/-4%). LDL receptor messenger RNA and proteins were detected in hepatocyte transplanted liver but not in the liver of sham treated animals.

CONCLUSIONS

Our data indicate that transient ischemia reperfusion injury of the recipient liver is safe and significantly improves the therapeutic efficacy of allogeneic hepatocyte transplantation in hyperlipidemic rabbits with congenital LDL receptor deficiency.

Polyphenols from Camellia sinenesis attenuate experimental cholestasis-induced liver fibrosis in rats

Accumulation of hydrophobic bile acids during cholestasis leads to generation of oxygen free radicals in the liver. Accordingly, this study investigated whether polyphenols from green tea Camellia sinenesis, which are potent free radical scavengers, decrease hepatic injury caused by experimental cholestasis. Rats were fed a standard chow or a diet containing 0.1% polyphenolic extracts from C. sinenesis starting 3 days before bile duct ligation. After bile duct ligation, serum alanine transaminase increased to 760 U/l after 1 day in rats fed a control diet. Focal necrosis and bile duct proliferation were also observed after 1-2 days, and fibrosis developed 2-3 wk after bile duct ligation. Additionally, procollagen-alpha1(I) mRNA increased 30-fold 3 wk after bile duct ligation, accompanied by increased expression of alpha-smooth muscle actin and transforming growth factor-beta and the accumulation of 4-hydroxynenonal, an end product of lipid peroxidation. Polyphenol feeding blocked or blunted all of these bile duct ligation-dependent changes by 45-73%. Together, the results indicate that cholestasis due to bile duct ligation causes liver injury by mechanisms involving oxidative stress. Polyphenols from C. sinenesis scavenge oxygen radicals and prevent activation of stellate cells, thereby minimizing liver fibrosis.

Sestamibi is a substrate for MDR1 and MDR2 P-glycoprotein genes

Technetium-99m sestamibi has attracted interest for assessment of the function of P-glycoproteins, which are well expressed in the liver and have roles in biliary transport and the removal of chemotherapeutic drugs. To further examine the cross-reactivity of (99m)Tc-sestamibi for P-glycoprotein family members, we conducted studies in animals. Hepatobiliary secretion of (99m)Tc-sestamibi was determined in normal FVB/N mice, mutant mice with specific P-glycoprotein deficiencies in the FVB/N background, normal Long-Evans Agouti (LEA) rats, and Long-Evans Cinnamon (LEC) rats with abnormal copper transport and liver disease but intact P-glycoprotein expression. After intrasplenic injection, (99m)Tc-sestamibi was rapidly incorporated in the mouse and rat liver, with maximal accumulation after 102+/-31 and 109+/-16 s, respectively ( P=NS). In normal mice and rats, 55%+/-11% and 55%+/-6%, respectively, of the maximal sestamibi activity was retained in the liver after 1 h ( P=NS). In double knockout mice lacking both mdr1a and mdr1b homologs of the human MDR1 ( ABCB1) gene, 88%+/-11% of maximal sestamibi activity was retained in the liver after 1 h ( P<0.001). In knockout mice deficient in either mdr1a gene or mdr2 ( ABCB4) gene, biliary sestamibi excretion was also impaired, although this impairment was relatively less pronounced in ABCB4-deficient mice than in double knockout mice lacking both ABCB1 gene homologs ( P<0.03). Hepatobiliary sestamibi excretion in LEC rats was not different from that in control normal rats, despite the presence of significant liver disease in the former. Hepatobiliary sestamibi excretion requires P-glycoproteins and is unperturbed in chronic liver disease. Sestamibi appears to be a substrate for both ABCB1 and ABCB4 genes, although the former utilizes it far more efficiently. Assessment of P-glycoprotein activity with sestamibi should consider how regulation of ABCB1 and related family members might modulate sestamibi incorporation.