Hepatocellular transplantation

Hepatocyte Transplantation in Man

Recent advances in liver transplantation have caused a serious shortage of donor livers, and a consensus on determining brain death has not been reached by the medical community in several countries, including Japan. To overcome these circumstances, hepatocellular transplantation (HCTX) has been attempted because HCTX requires no vascular anastomosis and donor hepatocytes are easy to obtain from living donors, and easy to preserve for a long time. In many experimental studies on HCTX some promising findings have been obtained, but clinically there has been little progress. Our success with survival of autotransplanted monkey hepatocytes and the development of a preparation of human hepatocytes has renewed interest in clinical HCTX. A multipuncture perfusion method or collagenase perfusion via the umbilical vein enables us to obtain approximately 1 × 108 hepatocytes from partially resected liver (60 g). The clinical trial of HCTX into the spleen was performed in 10 patients in Japan. A CT image, taken 1 mo after HCTX, showed a low density area corresponding to the inoculated site, which suggested that the transplanted hepatocytes survived and possessed hepatocellular function. One patient who sustained hepatic encephalopathy and massive ascites has now returned to work 11 mo after HCTX and hepatic artery ligation. However, there were no definite findings for functional support of damaged livers by HCTX in the spleen. We will review our experiments on HCTX, and describe the current and future aspects of HCTX.

Biliary fibrosis drives liver repopulation and phenotype transition of transplanted hepatocytes

BACKGROUND & AIMS

Current research focuses on developing alternative strategies to restore decreased liver mass prior to the onset of end-stage liver disease. Cell engraftment/repopulation requires regeneration in normal liver, but we have shown that severe liver injury stimulates repopulation without partial hepatectomy (PH). We have now investigated whether a less severe injury, secondary biliary fibrosis, would drive engraftment/repopulation of ectopically transplanted mature hepatocytes.

METHODS

Ductular proliferation and progressive fibrosis in dipeptidyl-peptidase IV (DPPIV)(-) F344 rats was induced by common bile duct ligation (BDL). Purified DPPIV(+)/green fluorescent protein (GFP)(+) hepatocytes were infused without PH into the spleen of BDL rats and compared to rats without BDL.

RESULTS

Within one week, transplanted hepatocytes were detected in hepatic portal areas and at the periphery of expanding portal regions. DPPIV(+)/GFP(+) repopulating cell clusters of different sizes were observed in BDL rats but not untreated normal recipients. Surprisingly, some engrafted hepatocytes formed CK-19/claudin-7 expressing epithelial cells resembling cholangiocytes within repopulating clusters. In addition, substantial numbers of hepatocytes engrafted at the intrasplenic injection site assembled into multicellular groups. These also showed biliary "transdifferentiation" in the majority of intrasplenic injection sites of rats that received BDL but not in untreated recipients. PCR array analysis showed upregulation of osteopontin (SPP1). Cell culture studies demonstrated increased Itgβ4, HNF1β, HNF6, Sox-9, and CK-19 mRNA expression in hepatocytes incubated with osteopontin, suggesting that this secreted protein promotes dedifferentiation of hepatocytes.

CONCLUSIONS

Our studies show that biliary fibrosis stimulates liver repopulation by ectopically transplanted hepatocytes and also stimulates hepatocyte transition towards a biliary epithelial phenotype.

Hepatocyte Transplantation Ameliorates the Metabolic Abnormality in a Mouse Model of Acute Intermittent Porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant disorder characterized by insufficient porphobilinogen deaminase (PBGD) activity. When hepatic heme synthesis is induced, porphobilinogen (PBG) and 5-aminolevulinic acid (ALA) accumulate, which causes clinical symptoms such as abdominal pain, neuropathy, and psychiatric disturbances. Our aim was to investigate if hepatocyte transplantation can prevent or minimize the metabolic alterations in an AIP mouse model. We transplanted wild-type hepatocytes into PBGD-deficient mice and induced heme synthesis with phenobarbital. ALA and PBG concentrations in plasma were monitored, and the gene transcriptions of hepatic enzymes ALAS1, PBGD, and CYP2A5 were analyzed. Results were compared with controls and correlated to the percentage of engrafted hepatocytes. The accumulation of ALA and PBG was reduced by approximately 50% after the second hepatocyte transplantation. We detected no difference in mRNA levels of PBGD, ALAS1, or CYP2A5. Engraftment corresponding to 2.7% of the total hepatocyte mass was achieved following two hepatocyte transplantations. A lack of precursor production in less than 3% of the hepatocytes resulted in a 50% reduction in plasma precursor concentrations. This disproportional finding suggests that ALA and PBG produced in PBGD-deficient hepatocytes crossed cellular membranes and was metabolized by transplanted cells. The lack of effect on enzyme mRNA levels suggests that no significant efflux of heme from normal to PBGD-deficient hepatocytes takes place. Further studies are needed to establish the minimal number of engrafted hepatocytes needed to completely correct the metabolic abnormality in AIP and whether amelioration of the metabolic defect by partial restoration of PBGD enzyme activity translates into a clinical effect in human AIP.

Cell delivery: from cell transplantation to organ engineering

Cell populations derived from adult tissue and stem cells possess a great expectation for the treatment of several diseases. Great efforts have been made to generate cells with therapeutic impact from stem cells. However, it is clear that the development of systems to deliver such cells to induce efficient engraftment, growth, and function is a real necessity. Biologic and artificial scaffolds have received significant attention for their potential therapeutic application when use to form tissues in vitro and facilitate engraftment in vivo. Ultimately more sophisticated methods for decellularization of organs have been successfully used in tissue engineering and regenerative medicine applications. These decellularized tissues and organs appear to provide bioactive molecules and bioinductive properties to induce homing, differentiation, and proliferation of cells. The combination of decellularized organs and stem cells may dramatically improve the survival, engraftment, and fate control of transplanted stem cells and their ultimate clinical utility, opening the doors to a new era of organ engineering.

Review of hepatocyte transplantation

BACKGROUND

Hepatocyte transplantation is a promising treatment for several liver diseases and can also be used as a "bridge" to liver transplantation in cases of liver failure. Although the first animal experiments with this technique began in 1967, it was first applied in humans only in 1992. Unfortunately, unequivocal evidence of transplanted human hepatocyte function has been obtained in only one patient with Crigler-Najjar syndrome type I and, even then, the amount of bilirubin-UDP-glucuronosyltransferase enzyme activity derived from the transplanted cells was not sufficient to eliminate the patient's eventual need for organ transplantation.

METHODS

A literature review was carried out using MEDLINE and library searches.

RESULTS

This review considers the following: (1) alternatives or bridges to orthotopic liver transplantation (OLT); (2) solutions to the shortage of organs-the shortage of organ donors has impeded the development of human hepatocyte transplantation, and immortalized hepatocytes in particular could provide an unlimited supply of transplantable cells in a nearly future; (3) future directions. We review these efforts along with hepatocyte transplantation over the last 13 years.

Hepatocyte transplantation

Numerous laboratory studies have shown that hepatocyte transplantation may serve as an alternative to organ transplantation for patients with life-threatening liver disease. Because of the successes of experimental hepatocyte transplantation, institutions have attempted to use this therapy in the clinic for the treatment of a variety of hepatic diseases. Unfortunately, unequivocal evidence of transplanted human hepatocyte function has been obtained in only one patient with Crigler-Najjar syndrome type I, and, even then, the amount of bilirubin-UGT enzyme activity derived from the transplanted cells was not sufficient to eliminate the patient's eventual need for organ transplantation. A roadmap for improving patient outcome following hepatocyte transplantation can be obtained by a re-examination of previous animal research. A better understanding of the factors that allow hepatocyte integration and survival in the liver and spleen is needed to help reduce the need for repeated cell infusions and multiple donors. Although clinical evidence of hepatocyte function can be used to indicate function of transplanted hepatocytes, definitive histologic evidence is difficult to obtain. In order to assess whether rejection is taking place in a timely fashion, a reliable way of detecting donor hepatocytes will be needed. The most important issue affecting transplantation, however, relates to donor availability. Alternatives to the transplantation of allogeneic human hepatocytes include transplantation of hepatocytes derived from fetal, adult or embryonic stem cells, engineered immortalized cells, or hepatocytes derived from other animal species.

Treatment of liver failure in rats with end-stage cirrhosis by transplantation of immortalized hepatocytes

The shortage of organ donors has impeded the development of human hepatocyte transplantation. Immortalized hepatocytes could provide an unlimited supply of transplantable cells. To determine whether immortalized hepatocytes could provide global metabolic support in end-stage liver disease, 35 immortalized rat hepatocyte clones were developed by transduction with the gene encoding the simian virus 40 T antigen (SV40Tag). The SV40Tag sequence and a suicide gene, herpes simplex virus thymidine kinase (HSV-tk), were flanked by loxP sequences so that they could be excised by Cre/lox recombination. When transplanted into the spleens of portacaval-shunted rats, 3 of the 35 immortalized hepatocyte clones prevented the development of hyperammonemia-induced hepatic encephalopathy. The protection was reversed by treatment with ganciclovir, which kills HSV-tk-expressing cells. Transplantation of alginate-encapsulated, immortalized hepatocytes into the spleens of cirrhotic rats resulted in significant improvement in prothrombin time, serum albumin and bilirubin levels, hepatic encephalopathy score, and duration of survival. The metabolic support provided by the immortalized cells equaled that observed after transplantation of primary rat hepatocytes. In conclusion, immortalized hepatocytes can function as well as primary hepatocytes following transplantation and can be engineered to contain safeguards that could make them clinically useful. Further investigation is warranted regarding the mechanisms of loss of mass or function of the transplanted hepatocytes over time and how the relatively few engrafted hepatocytes can ameliorate liver decompensation in cirrhosis.

Cyclophosphamide disrupts hepatic sinusoidal endothelium and improves transplanted cell engraftment in rat liver

To determine whether disruption of the hepatic sinusoidal endothelium will facilitate engraftment of transplanted cells, we treated Fischer 344 (F344) rats lacking dipeptidyl peptidase IV (DPPIV) activity with cyclophosphamide (CP). Electron microscopy showed endothelial injury within 6 hours following CP, and, after 24 and 48 hours, the endothelium was disrupted in most hepatic sinusoids. CP did not affect Kupffer cell function. Similarly, CP had no obvious effects on hepatocytes. Intrasplenic transplantation of F344 rat hepatocytes followed by their localization with DPPIV histochemistry showed 3- to 5-fold increases in the number of transplanted cells in CP-treated animals. Transplanted cells integrated in the liver parenchyma more rapidly in CP-treated animals, and hybrid bile canaliculi developed even 1 day after cell transplantation, which was not observed in control animals. To demonstrate whether improved cell engraftment translated into superior liver repopulation, recipient animals were conditioned with retrorsine and two-thirds partial hepatectomy (PH), which induces transplanted cell proliferation. CP treatment of these animals before cell transplantation significantly increased the number and size of transplanted cell foci. In conclusion, disruption of the hepatic sinusoidal endothelium was associated with accelerated entry and integration of transplanted cells in the liver parenchyma. These results provide insights into hepatocyte engraftment in the liver and will help in optimizing liver-directed cell therapy.

Hepatocyte transplantation in rats with decompensated cirrhosis

Hepatocyte transplantation improves the survival of laboratory animals with experimentally induced acute liver failure and the physiological abnormalities associated with liver-based metabolic deficiencies. The role of hepatocyte transplantation in treating decompensated liver cirrhosis, however, has not been studied in depth. To address this issue, cirrhosis was induced using phenobarbital and carbon tetrachloride (CCL(4)) and animals were studied only when evidence of liver failure did not improve when CCL(4) was held for 4 weeks. Animals received intrasplenic transplantation of syngeneic rat hepatocytes (G1); intraperitoneal transplantation of syngeneic rat hepatocytes (G2); intraperitoneal transplantation of a cellular homogenate of syngeneic rat hepatocytes (G3); intraperitoneal transplantation of syngeneic rat bone marrow cells (G4); or intrasplenic injection of Dulbecco's modified Eagle medium (DMEM) (G5). After transplantation, body weight and serum albumin levels deteriorated over time in all control (G2-G5) animals but did not deteriorate in animals receiving intrasplenic hepatocyte transplantation (G1) (P <.01). Prothrombin time (PT), total bilirubin, serum ammonia, and hepatic encephalopathy score were also significantly improved toward normal in animals receiving intrasplenic hepatocyte transplantation (P <. 01). More importantly, survival was prolonged after a single infusion of hepatocytes and a second infusion prolonged survival from 15 to 128 days (P <.01). Thus, hepatocyte transplantation can improve liver function and prolong the survival of rats with irreversible, decompensated cirrhosis and may be useful in the treatment of cirrhosis in humans.

Entry and integration of transplanted hepatocytes in rat liver plates occur by disruption of hepatic sinusoidal endothelium

To establish the process by which transplanted cells integrate into the liver parenchyma, we used dipeptidyl peptidase IV-deficient F344 rats as hosts. On intrasplenic injection, transplanted hepatocytes immediately entered liver sinusoids, along with attenuation of portal vein radicles on angiography. However, a large fraction of transplanted cells (>70%) was rapidly cleared from portal spaces by phagocyte/macrophage responses. On the other hand, transplanted hepatocytes entering the hepatic sinusoids showed superior survival. These cells translocated from sinusoids into liver plates between 16 and 20 hours after transplantation, during which electron microscopy showed disruption of the sinusoidal endothelium. Interestingly, production of vascular endothelial growth factor was observed in hepatocytes before endothelial disruptions. Portal hypertension and angiographic changes resulting from cell transplantation resolved promptly. Integration of transplanted hepatocytes in the liver parenchyma required cell membrane regenesis, with hybrid gap junctions and bile canaliculi forming over 3 to 7 days after cell transplantation. We propose that strategies to deposit cells into distal hepatic sinusoids, to disrupt sinusoidal endothelium for facilitating cell entry into liver plates, and to accelerate cell integrations into liver parenchyma will advance applications of hepatocyte transplantation.

Improvement of the effect of hepatocyte isograft in the Gunn rat by cotransplantation of islets of Langerhans

PURPOSE

Hepatocyte transplantation (HcTX) has been investigated for many years as an alternative therapy to orthotopic liver transplantation to treat hepatic congenital enzymatic deficiency disease. The animal model most used is the Gunn rat, which presents a hyperbilirubinemia caused by the lack of uridine-diphosphate-glucuronyl-transferase. Some investigators have clearly described a hepatotrophic effect mediated by islets of Langerhans (IL) when transplanted with hepatocytes (Hc). In this study, the functional effect of cotransplanted IL on hepatocytes (co-HcTX) in Gunn rats in an isograft model is assessed.

METHODS

Two groups are compared: group 1 (n = 6), HcTX to group 2 (n = 6), co-HcTX. Cells isolated by enzymatic digestion are transplanted directly into the splenic parenchyma. Blood samples are taken regularly until day 100 to measure the unconjugated bilirubin (UB). Histological examination of the spleen is performed at the end of the experiment.

RESULTS

Both groups show a significant decrease of the UB: group 1, 47%; group 2, 65%. The decrease is statistically more pronounced with co-HcTX. The histological analysis shows a trophic effect of the IL on the grafted hepatocytes in the co-HcTX group.

CONCLUSIONS

The HcTX and the co-HcTX correct partially the hyperbilirubinemia of the Gunn rat. A functional assessment has been performed to evaluate the effect of cotransplanted IL on HcTX.

Restoration of serum albumin levels in nagase analbuminemic rats by hepatocyte transplantation

Recently, we described a new strategy for hepatocyte transplantation, using retrorsine/partial hepatectomy (PH) in a DPPIV- mutant Fischer rat model. Treatment of rats with retrorsine, a pyrrolizidine alkaloid, blocks endogenous hepatocytes from proliferating, so that after exposure to this agent coupled with PH and hepatocyte transplantation, transplanted hepatocytes selectively repopulate the liver. In the present study, we determined whether this method of cell transplantation can restore biosynthetic and physiological function in the liver by transplanting normal hepatocytes into rats genetically deficient in albumin synthesis, the Nagase analbuminic rat (NAR). After hepatocyte transplantation, albumin mRNA and protein were identified in the liver by in situ hybridization and immunohistochemistry, respectively, and serum albumin levels were determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blot, and enzyme-linked immunosorbent assay (ELISA) methods. At 1 month posttransplantation, large clusters of cells expressing albumin mRNA and protein were identified in the liver, representing approximately 50% of hepatocytes for albumin mRNA and approximately 61% for protein. At 2 months' posttransplantation, cells expressing albumin mRNA represented approximately 77% of hepatocyte mass, and cells expressing albumin protein represented approximately 81% of total hepatocyte mass. Hepatocyte-transplanted NAR also exhibited normal or near-normal serum albumin levels (3.0 +/- 0.2 g/dL). High levels of serum albumin were sustained for the 2-month duration of experiments. These results demonstrate the ability of this protocol for hepatocyte transplantation to restore a major biosynthetic and physiological function of the liver, and suggest its potential use as a method to treat genetic-based or acquired liver diseases.

Non-viral ex vivo hepatic gene transfer by in situ lipofection of liver and intraperitoneal transplantation of hepatocytes

Perfusion of liver with plasmid DNA-lipofectin complexes via the portal vein results in efficient accumulation of the vector in hepatocytes. Such hepatocytes, when administered intraperitoneally into a hepatectomized rat, repopulate the liver and express the transgene efficiently. This procedure obviates the need for large-scale hepatocyte culture for ex vivo gene transfer. Further, intraperitoneal transplantation is a simple and cost-effective strategy of introducing genetically modified hepatocytes into liver. Thus, in situ lipofection of liver and intraperitoneal transfer of hepatocytes can be developed into a novel method of non-viral ex vivo gene transfer technique that has applications in the treatment of metabolic disorders of liver and hepatic gene therapy.

Hepatocellular transplantation into the lung in chronic liver failure following bile duct obstruction in the rat

Injection of hepatocytes or cell-free supernatant into the lung was able to prevent death from surgically induced fulminant hepatic failure in the rat in over 90% and 53% of subjects, respectively. The aim of this study was to investigate whether this technique can be applied in chronic liver failure. Chronic liver failure was induced in Lewis rats by ligation and transection of the common bile duct, which led to cirrhosis after 3-5 wk in all animals. Four groups of animals were formed: group 1 (n = 5), normal rats, serving as control; group 2 (n = 15), cirrhotic rats, no further treatment; group 3 (n = 14), hepatocyte transplantation by injection of cell suspension transcutaneously into the right lung of cirrhotic animals four wk after bile duct ligation; group 4 (n = 17), injection of 1 mL cell-free supernatant intravenously at two-day intervals, starting 4 wk after ligation. Liver function tests, prothrombin time and serum protein levels were measured weekly before and every two days after transplantation. In group 2 all animals had died 56 (49-69) days after ligation. Survival in groups 3 and 4 was similar: all rats had died from liver failure 61 (51-72) and 60 (49-76) days following bile duct ligation. Survival rates and laboratory investigations showed no significant differences between treated and untreated cirrhotic animals. These data suggest that hepatocyte transplantation into the lung as well as supernatant injection do not have any significant effect on chronic hepatic failure, at least in the rat model.

Membrane antigen expression of syngeneically but heterotopically transplanted hepatocytes in rats

The expression of membrane antigens on rat hepatocytes transplanted syngeneically and heterotopically was analyzed immunohistochemically using monoclonal antibodies against rat hepatocytes. Isolated adult and fetal hepatocytes were able to survive in the spleen, salivary gland, thymus, or subcapsular region of the kidney for various periods after transplantation. Fairly clear expression of HAM2, 4, and 8 antigens was observed on hepatocytes transplanted into syngeneic spleen, suggesting that the cells might be functionally equivalent to hepatocytes in situ. HAM4 antigen was localized specifically on the newly formed bile-canalicular faces of hepatocytes. The expression of HAM2 (MHC class I) antigen on the transplanted hepatocytes appeared much stronger on the side facing lymphoid tissues, than on the other faces, suggesting that some immunological reactions may take place between hepatocytes and lymphoid tissue. HAM8 antigen, which is localized on gap junctions between neighboring hepatocytes in rat liver, was also recognized between transplanted hepatocytes. In salivary glands where hepatocytes were transplanted, bile-canaliculus-like structures were observed not only between neighboring hepatocytes but also between hepatocytes and salivary acinar cells, suggesting good interaction between the two different epithelial cell types. Hepatocytes transplanted into thymus appeared viable, but most showed fatty degeneration. Some healthy hepatocytes survived in the interlobular connective tissue and the thymic cortical tissue. When fetal hepatocytes were transplanted heterotopically, they formed a mass consisting of hepatocytes and bile duct-like structures 7 wk after transplantation. The inoculated hepatocytes possessed HAM4 antigen, which was not recognized on fetal hepatocytes at day 14 of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Intrahepatic hepatocyte transplantation following subtotal hepatectomy in the recipient: a possible model in the treatment of hepatic enzyme deficiency

Orthotopic liver transplantation as treatment for hereditary enzyme deficiencies in the absence of cirrhosis suffers from significant operative risks, complications, and donor shortages. Transplantation of isolated hepatocytes (HTX) may offer opportunities for the treatment of these diseases and retain the recipient liver. Hepatocytes transplanted into the portal vein, spleen, or omentum lack an ideal growing environment for cell proliferation and maintenance. Therefore, we investigated a method combining 75% recipient hepatectomy with direct injection of hepatocytes into the remaining 25% of liver parenchyma to provide proliferative stimuli and a stable environment during and following liver regeneration. Recipient Gunn rats (glucuronyltransferase deficiency and hyperbilirubinemia) underwent hepatectomy before HTX by direct injection of 10(7) isolated hepatocytes into the remaining parenchyma. Inbred male Wistar and Gunn rats were used as normal and control hepatocyte donors and saline injection served as a sham transplant control. Isolation of donor hepatocytes was performed with a two-step collagenase digestive method (Seglen) with cell viability of 85% to 95%. Liver regeneration was complete by 2 weeks posttransplant. Four weeks following HTX, total serum bilirubin and qualitative bile analysis were performed. A significant decrease in total serum bilirubin levels was observed in Gunn rats receiving Wistar hepatocytes compared with those receiving Gunn hepatocytes and saline control. Bile analysis from HTX rats demonstrated a normal pattern containing bilirubin monoglucuronides and diglucuronides (conjugated bilirubin) in the rats receiving Wistar hepatocytes, whereas the control group receiving Gunn hepatocytes or saline injection demonstrated only unconjugated bilirubin. No differences in histological appearance were noted between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatocellular transplantation into the lung for temporary support of acute liver failure in the rat

Because hepatocyte transplantation into the spleen or the peritoneal cavity, although successful in rats, is more difficult and less successful in larger animals, the lung was chosen for its accessibility and its high oxygen content as a new site for hepatocyte implantation for treatment of acute hepatic failure. Acute hepatic failure was induced by a combination by a portocaval side-to-side shunt and an 80% liver resection, which was associated with a greater than 90% mortality. Hepatocyte transplantation was performed either by injection of 1 x 10(7) cells via the jugular vein (100% mortality) or 5-7 x 10(7) cells transcutaneously into the right lung (92% survival). After injection of the cell-free supernatant into the lung, 53.3% of the animals survived. If more than 90% of the liver was resected, none of the animals survived despite hepatocyte or supernatant injection. From these findings, it is concluded that the lung is a suitable home for hepatocytes. However, the hepatocytes survived only in cases of acute hepatic failure with some remaining vital liver parenchyma.

Intrasplenic hepatocellular transplantation corrects hepatic encephalopathy in portacaval-shunted rats

The aim of this work was to evaluate the effect of intrasplenic hepatocellular transplantation on hepatic encephalopathy in an experimental model of chronic liver failure induced by end-to-side portacaval shunt in the rat. Inbred male Wistar Furth rats were divided into three groups: rats subjected to portacaval shunt (n = 10), rats subjected to portacaval shunt and intrasplenic hepatocellular transplantation of 10(7) hepatocytes isolated from livers of syngeneic rats (n = 10) and sham-operated rats (n = 10). Behavior tests were performed in a blind fashion at 3 wk, at 2 mo and at 3 mo after surgery. Spontaneous activity and nose-poke exploration by individual rats were studied in automated open field boxes equipped with infrared cells. Each cell beam interruption was automatically recorded on a microcomputer and transformed into a score index (counts/hour). Plasma levels of amino acids, ammonia and total biliary acids were measured. Portacaval shunt rats showed reduced spontaneous activity and nose-poke exploration scores. Intrasplenic hepatocellular transplantation significantly increased spontaneous activity after 2 mo and improved nose-poke exploration after 3 wk. At 3 mo, spontaneous activity and nose-poke exploration in portacaval shunt/intrasplenic hepatocellular transplantation rats were not significantly different from those of sham rats. Increases in plasma ammonia levels after portacaval shunt were not corrected. Amino acid imbalance and bile acid concentration in plasma were partially corrected by intrasplenic hepatocellular transplantation. These data show that intrasplenic hepatocellular transplantation can correct the neurological symptoms of hepatic encephalopathy in an experimental model of chronic liver failure and suggest that intrasplenic hepatocellular transplantation might be of therapeutic interest in chronic liver failure.

Transplantation studies on human and duck hepatocytes in athymic nude mice

For determination of the most suitable tissue for heterotopic transplantation of exogenous hepatocytes, dissociated hepatocytes or small pieces of liver tissue were transplanted into the spleen, adipose tissue and inside the capsule of the kidney of BALB/c mice. Survival of syngeneic grafts of dissociated hepatocytes was highest in the spleen and that of pieces of liver tissue in the adipose tissue, but only the latter system was suitable for xenogeneic transplantation. Histological examination showed that a total of 50% of the human or duck liver tissue implants survived in the inguinal fat pad of athymic nude mice (BALB/c-nu). Histochemical analyses revealed that most hepatocytes transplanted into the fat pad gave positive reactions for glucose-6-phosphatase and with periodic acid-Schiff reagent at least 28 days after transplantation. Electron microscopic observation showed that these cells also maintained characteristic cellular organelles. This xenogeneic transplantation into adipose tissue should be useful in the studies on replication and infection of human hepatotropic viruses such as hepatitis B and C viruses.

Permanent engraftment and function of hepatocytes delivered to the liver: implications for gene therapy and liver repopulation

To examine the distribution of intrasplenically transplanted hepatocytes, we used HBsAg-producing G7 HBV transgenic hepatocytes or cells labeled with 111In. Most hepatocytes translocated to the liver (55% +/- 7%; mean +/- S.D.); the spleen retained a smaller fraction (15% +/- 3%); and some transplanted cells localized in lungs (3%) or pancreas (1%). Transplanted hepatocytes were rapidly assimilated into the liver lobule. Morphometrical quantitation indicated that the numbers of transplanted hepatocytes in the liver at 48 hr and at 9 mo after transplantation were similar. Serum HBsAg was detected in recipients of the G7 HBV hepatocytes during the 1-yr experiment. These results indicate that a large number of hepatocytes can be reproducibly delivered to the liver by transplantation into the spleen. Transplanted hepatocytes engraft rapidly, assimilate into host liver, maintain normal function and survive permanently. Systems for safe delivery and localization of hepatocytes in the liver represent a critical step toward successfully accomplishing hepatocyte-directed gene therapy and repopulation of the acutely devastated liver.

Intrasplenic hepatocyte transplantation: evaluation of DNA synthesis and proliferation in auxiliary transplanted cells

The value of isolated hepatocyte transplantation as a temporary support in acute hepatic failure remains controversial regarding the functional capacities of freshly isolated and transplanted hepatocytes. To evaluate the survival rate of intrasplenically transplanted liver cells and their response to a proliferation stimulus like partial hepatectomy, 3H-thymidine incorporation into hepatic and auxiliary transplanted hepatocyte DNA was determined. The survival rate of intrasplenically transplanted hepatocytes was evaluated by analyses of m-albumin-RNA within the splenic tissue and compared to the morphological findings. The histological results show a marked decrease (greater than x 100) of intrasplenically transplanted hepatocytes within 1 week after injection. The amount of surviving cells then remained constant for 3 months without any signs of proliferation. After partial hepatectomy a stimulation of hepatic regeneration was observed in the remaining liver tissue but not in auxiliary transplanted hepatocytes. M-albumin-RNA determination of auxiliary transplanted hepatocytes revealed a decrease of m-albumin-RNA concentration of greater than 100 times within 24 h after transplantation indicating early cell necrosis of the transplanted cells. Since intrasplenically transplanted hepatocytes underwent an early cell necrosis without any evidence for a directly postoperatively inducible cell proliferation, it is concluded that a sufficient metabolic support in acute hepatic failure cannot be taken into consideration.

Transplantation of isolated hepatocytes. A review of current ideas

Over the past decade there has been an increase in interest in studies of transplantation of isolated hepatocytes. The survival of hepatocytes in sites distant from the normal hepatic circulation has provided insights into cell proliferation and phenotypic expression of liver-specific functions. The possibility of treating liver insufficiency in disease has also been investigated. The present review is intended to give an account of the development of methods for the study of hepatocyte transplantation, techniques for assessment of graft function and future possibilities for application of the technique.

Transplantation of cryopreserved hepatocytes or liver cytosol injection in the treatment of acute liver failure in rats

Intraperitoneally injected cryopreserved hepatocytes or liver cytosol were used for the treatment of acute galactosamine-induced liver failure in rats. Both methods were similarly capable to improve the survival rates as compared to control groups. Furthermore, a new viability test for transplanted hepatocytes, using a nuclearmedical tracer technique, was evaluated in this study. This test demonstrated viability of intraperitoneally transplanted hepatocytes for at least 6 days after operation. Cytosol injection should be preferred to hepatocyte transplantation in the treatment of acute liver failure, avoiding the problems of cell storage and post-transplant immunosuppression.