Long-Term Correction of Albumin Levels in the Nagase Analbuminemic Rat: Repopulation of the Liver by Transplanted Normal Hepatocytes under a Regeneration Response

Response of Cultured Fetal and Adult Rat Hepatocytes to Growth Factors and Cyclosporine

Hepatocyte transplantation is a promising alternative to orthotopic liver transplantation in experimental animal models with genetic disorders of liver metabolism and liver failure. Fetal hepatocytes have several characteristics that make them potentially suitable as donor cells. In contrast to adult hepatocytes, fetal hepatocytes are thought to be highly proliferative, which may facilitate engraftment, expansion of transplanted cell population, and gene transfer requiring active DNA synthesis. The present study was undertaken to evaluate the proliferative capacity of fetal and adult rat hepatocytes under standardized culture conditions. Fetal (20 days of gestation) and adult hepatocytes were cultured in serum-free media at low densities and treated with growth factors. Proliferation was assessed by [3H]-thymidine incorporation and cell cycle analysis by flow cytometry. In nonstimulated cells, DNA synthesis at 4 h was about × 100 higher and after 10 days in culture ×20 higher in fetal compared to adult hepatocytes. When epidermal growth factor (EGF) was added, maximal DNA synthesis in fetal hepatocytes was seen at 48 h, whereas in adult hepatocytes at 72 h. For adult hepatocytes, the average increase compared to untreated cells was × 13.8 with EGF, ×18.5 with transforming growth factor alpha (TGF-α), and ×7.6 with hepatocyte growth factor (HGF). For fetal hepatocytes, the increase was twofold with either EGF, TGF-α or HGF. EGF-, TGF-α- and HGF-dependent DNA synthesis was inhibited by transfroming growth factor beta-1 (TGF-β1) in both fetal and adult hepatocyte cultures; this antiproliferative effect was significantly stronger in adult hepatocyte cultures. With cyclosporine, EGF-, TGF-α- and HGF-dependent DNA synthesis in fetal hepatocyte cultures decreased by 36–46%, whereas in adult hepatocytes by 19–27%. These results show that in contrast to adult hepatocytes, fetal hepatocytes have high spontaneous proliferative activity independently of growth factors and are relatively resistant to the inhibitory effect of TGF-β1. It was also found that cyclosporine suppresses proliferation of cultured fetal hepatocytes.

Regional Transient Portal Ischemia and Irradiation as Preparative Regimen for Hepatocyte Transplantation

Hepatocyte transplantation is regarded as a promising option to correct hereditary metabolic liver disease. This study describes a novel method involving regional transient portal ischemia (RTPI) in combination with hepatic irradiation (IR) as a preparative regimen for hepatocyte transplantation. The right lobules of rat livers (45% of liver mass) were subjected to RTPI of 30–120 min. Liver specimens and serum samples were analyzed for transaminase levels, DNA damage, apoptosis, and proliferation. Repopulation experiments involved livers of dipeptidylpeptidase IV (DPPIV)-deficient rats preconditioned with RTPI (60–90 min) either with or without prior partial hepatic IR (25 Gy). After reperfusion intervals of 1 and 24 h, 12 million wild-type (DPPIV positive) hepatocytes were transplanted into recipient livers via the spleen. RTPI of 60–90 min caused limited hepatic injury through necrosis and induced a distinct regenerative response in the host liver. Twelve weeks following transplantation, small clusters of donor hepatocytes were detected within the portal areas. Quantitative analysis revealed limited engraftment of 0.79% to 2.95%, whereas control animals (sham OP) exhibited 4.16% (determined as relative activity of DPPIV when compared to wild-type liver). Repopulation was significantly enhanced (21.43%) when IR was performed prior to RTPI, optimum preconditioning settings being 90 min of ischemia and 1 h of reperfusion before transplantation. We demonstrate that RTPI alone is disadvantageous to donor cell engraftment, whereas the combination of IR with RTPI comprises an effective preparative regimen for liver repopulation. The method described clearly has potential for clinical application.

Hepatocytes isolated from neoplastic liver-immunomagnetic purging as a new source for transplantation

AIM: To investigate whether hepatocytes isolated from macroscopically normal liver during hepatic resection for neoplasia could provide a novel source of healthy hepatocytes, including the development of reliable protocols for malignant cells removal from the hepatocyte preparation.

METHODS: Hepatocytes were procured from resected liver of 18 patients with liver tumors using optimised digestion and cell-enrichment protocols. Suspensions of various known quantities of the HT-29 tumor cell line and patient hepatocytes were treated or not with Ep-CAM-antibody-coated immunomagnetic beads in order to investigate the efficacy of tumor-purging by immunomagnetic depletion, using a semi-quantitative RT-PCR method developed to detect tumor cells. Immunomagnetic bead-treated or bead-untreated tumor cell-hepatocyte suspensions were transplanted intra-peritoneally in Balb/C nude mice to assess the rates of tumor development.

RESULTS: Mean viable hepatocyte yield was 9.3 x 10⁶ cells per gram of digested liver with mean viability of 70.5%. Immunomagnetic depletion removed tumor cells to below the RT-PCR detection-threshold of 1 tumor cell in 10⁶ hepatocytes, representing a maximum tumor purging efficacy of greater than 400 000-fold. Transplanted, immunomagnetic bead-purged tumor cell-hepatocyte suspensions did not form peritoneal tumors in Balb/C nude mice. Co-transplantation of hepatocytes with tumor cells did not increase tumorigenesis of the tumor cells.

CONCLUSION: Immunomagnetic depletion appears to be an effective method of purging contaminating tumor cells to below threshold for likely tumorigenesis. Along with improved techniques for isolation of large numbers of viable hepatocytes, normal liver resected for neoplasia has potential as another clinically useful source of hepatocytes for transplantation.

Efficient Hepatocyte Engraftment in a Nonhuman Primate Model After Partial Portal Vein Embolization

BACKGROUND

Hepatocyte transplantation could be an alternative to whole liver transplantation for the treatment of metabolic liver diseases. However, the results of clinical investigations suggest that the number of engrafted hepatocytes was insufficient to correct metabolic disorders. This may partly result from a lack of proliferation of transplanted hepatocytes. In rodents, portal ligation enhances hepatocyte engraftment after transplantation. We investigated the effects of partial portal ligation and embolization on engraftment and proliferation of transplanted hepatocytes in primates.

METHODS

Hepatocyte autotransplantation was performed in Macaca monkeys. The left lateral lobe was resected for hepatocyte isolation. The first group of monkeys underwent surgical ligation of the left and right anterior portal branches; in the second group, the same portal territories were obstructed by embolization with biological glue. To evaluate the proportion of cell engraftment hepatocytes were Hoechst-labeled and transplanted via the portal vein. Cell proliferation was measured by BrdU incorporation.

RESULTS

Hepatocyte proliferation was induced by both procedures but it was significantly higher after partial portal embolization (23.5% and 11.2% of dividing hepatocytes on days 3 and 7) than after ligation (3% and 0.8%). Hepatocytes engrafted more efficiently after embolization than after ligation. They proliferated and participated to liver regeneration representing 10% of the liver mass on day seven and their number remained constant on day 15.

CONCLUSIONS

These data suggest that partial portal embolization of the recipient liver improves engraftment of transplanted hepatocytes in a primate preclinical model providing a new strategy for hepatocyte transplantation.

Human hepatocyte transplantation: worldwide results

The conception and animal modeling of hepatocyte transplantation along with a partial listing of human hepatocyte infusions over the last 13 years have been detailed in authoritative reviews. However, to adequately best represent the worldwide effort of moving from highly successful clinical solid liver transplants "back to" isolated hepatocyte therapy requires repeating important concepts with explanations of how or why not animal experimental data translate to human experience. This overview summarizes 78 human clinical hepatocyte transplant experiences authenticated by the authors. The human cell infusion experiences are categorized by liver disease treated (metabolic, chronic, and acute liver failure), and these are accompanied by seminal in vitro and in vivo experimental data.

Tissue distribution of fetal liver cells following in utero transplantation in mice

Transplantation of hepatic stem cells in utero has been advanced as a potential clinical approach to a variety of diseases, including deficiencies of coagulation factors. Although syngeneic transplantation has met with some success, consideration needs to be given to the potential for transplanted cells to colonize nontarget tissues. Liver cells were harvested from Rosa26 embyros at embryonic age 12.5 days postconception (pc) and transplanted into the peritoneal cavity of syngeneic recipients in utero. Tissues were harvested from tissue recipients at various time points ranging from 1 to 328 days pc, and tissues were stained for beta-galactosidase to identify the existence of cells derived from Rosa26 donors. Beta-galactosidase-positive cells were found in the lung, liver, and brain as early as 20 days pc and through 328 days pc. Positive cells in these tissues existed as islands of cells that were morphologically similar to hepatocytes. In the spleen, individual beta-galactosidase-positive cells of both leukocytic and erythrocytic lineages were present, and suggest that hematopoietic cells were transferred to recipients along with hepatocytes. The lack of an inflammatory response to the beta-galactosidase-positive cells suggests that the donor cells were immunologically tolerated. In summary, the possibility that cells administered in utero may inadvertently colonize nontarget tissues suggests that clinical application of this method will need to be approached with diligence.

Liver repopulation: a new concept of hepatocyte transplantation

Hepatocyte transplantation has been recognized as an alternative strategy for organ transplantation because the supply of donor livers is limited. However, in conventional hepatocyte transplantation, only 1%-10% of the liver replaced with transplanted hepatocytes. Recently a novel concept termed "liver repopulation" has been established, where the whole recipient liver can be replaced by a small number of donor hepatocytes. To induce liver repopulation, growth advantage of the donor hepatocytes against the host liver seems to be required according to the data of previous studies. Additionally, various cell sources, including bone marrow cells and other stem cells, could potentially be used as donor cells for liver repopulation. In this article, we discuss recent progress and future perspectives of this emerging technology.

Treatment of fulminant liver failure by transplantation of microencapsulated primary or immortalized xenogeneic hepatocytes

BACKGROUND

The aim of this study was to evaluate in vitro and in vivo functions of isolated hepatocytes after immortalization, cryopreservation, encapsulation and xenotransplantation into mice with fulminant liver failure (FLF).

METHODS

Rat and human hepatocytes were isolated from normal liver tissue by collagenase digestion. Human hepatocytes were immortalized using lentiviral vectors coding for SV 40 large T antigen, Bmi-1 and telomerase. Rat and immortalized human hepatocytes (IHH) were encapsulated in 400 micron alginate-PLL-alginate membranes and cryopreserved using a computerized device. In vitro, encapsulated hepatocytes (cryopreserved or freshly isolated) were cultured in albumin-free medium and albumin production was measured by enzyme-linked immunosorbent assay (ELISA). In vivo, a model of FLF was established in C57/BL6 mice by acetaminophen administration (700 mg/kg i.p.) followed 15 h later by a 30% hepatectomy. Microencapsulated (cryopreserved or freshly isolated) hepatocytes were transplanted intraperitoneally to mice with FLF and the following experimental groups were performed: group 1 (n = 10) Tx of empty capsules; group 2 (n = 12) Tx of free primary rat hepatocytes; group 3 (n = 12) Tx of cryopreserved encapsulated rat hepatocytes; group 4 (n = 10) Tx of fresh encapsulated rat hepatocytes; group 5 (n = 9) Tx of cryopreserved encapsulated IHH; group 6 (n = 10) Tx of fresh encapsulated IHH. Animals were killed at regular intervals and histopathology of microcapsules and liver tissue was obtained.

RESULTS

In vitro, cryopreserved or fresh encapsulated rodent hepatocytes showed a progressively decreasing albumin secretion over 1 week in culture. In contrast, cryopreserved or fresh encapsulated IHH showed minimal, but stable albumin secretion. In vivo, FLF was achieved by combination of acetaminophen with 30% hepatectomy, resulting in a reproducible survival of 23% +/- 5%. In groups 1 and 2, survival rates were not improved significantly compared with untreated mice. In groups 3 and 4, Tx of cryopreserved or fresh encapsulated rat hepatocytes significantly increased survival rate to 66% and 80%, respectively (P < 0.01). In groups 5 and 6, Tx of cryopreserved or fresh encapsulated IHH improved survival to 50% and 55%, respectively (P < 0.05). Histopathology revealed that encapsulated hepatocytes were viable up to 2 weeks post-Tx.

CONCLUSIONS

Primary rodent hepatocytes maintained synthetic functions after encapsulation and cryopreservation short-term. IHH showed minimal albumin secretion in the absence of encapsulation and cryopreservation, suggesting that hepatocytes loose specific functions after immortalization. After induction of FLF in mice, intraperitoneal Tx of encapsulated (primary or immortalized, fresh or cryopreserved) xenogeneic hepatocytes significantly improved survival. These results indicate that naïve and genetically modified hepatocytes can successfully be encapsulated, stored using cryopreservation, and be transplanted into xenogeneic recipients with liver failure and sustain liver metabolic functions.

Liver gene therapy: advances and hurdles

Liver gene therapy is being developed as an alternative to orthotopic liver transplantation, which is the only effective therapy for many liver diseases. The liver has unique features that make it attractive for in vivo and ex vivo gene transfer. In vivo approach is far less invasive than ex vivo approach, although in most cases, host immune response directed against the transgene product and/or vector particles severely impairs the efficiency of gene transfer, and precludes long-term transgene expression after in vivo gene delivery. Ex vivo approach allows for an elective targeting of the hepatocytes, avoiding that the transgene be expressed in professional antigen-presenting, but is faced with the low in vitro proliferative ability of hepatocytes, and to the low in vivo liver repopulating ability of transplanted cells. In some specific situations where immune response was controlled or transplanted cells had a strong growth advantage over host hepatocytes, gene transfer resulted in long-term and complete correction of a liver genetic defect. In this review, we will outline the liver diseases that may benefit from gene therapy, the vector technology under investigation, the advances and the problems to be overcome.

In utero transplantation of wild-type fetal liver cells rescues factor X-deficient mice from fatal neonatal bleeding diatheses

Factor X (FX)-deficient embryos suffer partial embryonic lethality with approximately 30% of the embryos arresting at midgestation. The remaining animals survive to term but die perinatally mainly from abdominal or intracranial hemorrhage. We have rescued FX-deficient mice by transplanting fetal liver cells from FX+/+, Rosa26 fetuses into midgestation embryos derived from FX+/- heterozygous crosses. FX-/- embryos were born at the expected frequency and approximately 50% of the FX-/- neonates survived longer than 4 months. FX-/- embryos receiving saline injections that survived to term died perinatally similar to untreated FX-deficient mice. The plasma levels of FX in the rescued 16-week-old FX-/- mice were approximately 1-6% of wild-type levels. beta-Galactosidase-staining cells derived from the donor Rosa26 fetal liver cells were detected in 47% of the livers of adult mice. In addition, donor-derived cells were also recovered in the bone marrow, spleen, lung, and occasionally in the brain and testis. These results suggest that in utero cell transplantation could be an effective therapeutic strategy to treat pathologies resulting from the deficiency of hepatic-expressed factors.

Transplantation of hepatocytes in nonhuman primates: a preclinical model for the treatment of hepatic metabolic diseases

BACKGROUND

The transplantation of isolated hepatocytes in large animals, including nonhuman primates, must be evaluated before clinical trials are performed. However, in the absence of large transgenic animals and large-animal (as opposed to small-animal) models of genetic deficiencies, it is difficult to evaluate the fate of transplanted hepatocytes, their localization, survival, and function within the parenchyma of the host liver. In this work, we aimed to develop a technique for delivering hepatocytes to the liver of a nonhuman primate and to evaluate their localization and functionality in the short term.

METHODS

A 20% hepatectomy was performed in 34 cynomolgus monkeys (Macaca fascicularis) and hepatocytes were isolated. Hepatocytes were labeled in vitro with a recombinant retrovirus expressing the beta-galactosidase gene and returned to the liver by infusion through a portal catheter left in place. Liver biopsies were performed 4 and 7 d after transplantation.

RESULTS

Twenty-four monkeys underwent surgery to define the necessary technical adjustments and to optimize conditions. Six monkeys died. The whole protocol, including the transplantation of genetically marked hepatocytes and procurement of liver biopsies, was performed in the remaining 10 monkeys. In eight monkeys, transplanted hepatocytes expressing the beta-galactosidase gene were widely distributed in the portal tracts, sinusoids, and hepatocyte plates of the host liver 4 and 7 d after transplantation.

CONCLUSIONS

We have developed an experimental nonhuman primate model for the evaluation of hepatocyte transplantation. We demonstrated the engraftment and functioning of transplanted hepatocytes in the host liver 4 and 7 d after transplantation.

Hepatocyte transplantation in a model of toxin-induced liver disease: variable therapeutic effect during replacement of damaged parenchyma by donor cells

To provide long-term therapy in patients with severe toxin-induced hepatic parenchymal damage, donor hepatocytes would need to replicate and replace a large portion of the damaged parenchyma. Using a mouse model developed to reproduce this type of hepatic injury, we found that hepatocyte transplantation only slightly improved survival after transplantation despite the fact that many non-survivors showed moderate liver repopulation by donor cells. Perhaps accounting for this outcome, donor parenchyma in non-survivors did not have typical lobular organization. These results indicate that the re-creation of functional parenchyma by transplanted hepatocytes requires time, during which donor cells proliferate and then establish normal parenchymal architecture.

Extracorporeal support and hepatocyte transplantation in acute liver failure and cirrhosis

The relative shortage of donor organs and lack of immediate availability mean that many patients with acute liver failure die before orthotopic liver transplantation can be performed. An effective temporary liver support system could improve the chance of survival with or without a transplant being ultimately carried out. Recent technological advances resulting in improved maintenance of hepatocyte viability and function in culture and bioreactor designs which facilitate adequate perfusion of the cellular component and removal of products of cellular metabolism have led to the development of a number of bioartificial devices for liver support. Three such devices have undergone preliminary clinical evaluation in the setting of acute liver failure, with a statistically significant reduction in raised intracerebral pressure along with improvements in consciousness level and some biochemical parameters associated with treatment with one of these. Several other devices with different characteristics have shown promise in vitro and/or in animal models but await clinical evaluation. Several new totally artificial systems have also been described, along with the emergence of isolated hepatocyte transplantation, with reports of successful 'bridging' to liver transplantation. Controlled trials on a multicentre basis in well-defined patient groups and with standardized outcome measures will be required to properly evaluate the clinical value of each of these approaches to providing liver support in acute liver failure and cirrhosis. A better understanding of mechanisms underlying multiorgan failure and of factors inhibiting liver regeneration, thereby allowing a more targeted approach, will be essential to the further development of effective liver support strategies in these settings.

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.

Fetal rat hepatocytes: isolation, characterization, and transplantation in the Nagase analbuminemic rats

BACKGROUND

In contrast to adult hepatocytes, fetal hepatocytes (FH) are thought to be highly proliferative, less immunogenic, and resistant to cryopreservation and ischemic injury. These qualities could enhance FH engraftment, proliferation, and gene transfer requiring active DNA synthesis.

METHODS

Rat FH were obtained using the nonperfusion collagenase/DNase digestion method. Free and cultured cells were studied using electron microscopy, fluorescence-activated cell sorting, and Northern analysis using alpha-fetoprotein and albumin as markers of hepatocyte lineage. DNA synthetic activity was measured in quiescent and mitogen-stimulated fetal and adult hepatocytes by [3H]thymidine incorporation. Susceptibility of cultured FH to retrovirally mediated gene transfer was studied using an amphotropic retroviral vector carrying the Escherichia coli lac-Z gene. Nagase analbuminemic rats were used as recipients to study the effects of intraportal FH transplantation. Analysis of serum albumin was carried out by enzyme-linked immunosorbent assay.

RESULTS

In fetal liver, 87+/-2% of the cells showed morphological and molecular features of hepatocytes. DNA synthetic activity in nonstimulated cultured FH was 10 times greater than the maximal hepatocyte growth factor-driven response in adult rat hepatocytes. A total of 5-15% FH stained positive for X-gal; results of transduction in adult hepatocyte cultures were negative. In Nagase analbuminemic rat recipients, FH produced significant amounts of albumin only when a hepatic regenerative stimulus was applied. Immunohistochemistry confirmed presence of albumin-positive hepatocytes.

CONCLUSIONS

Fetal rat liver from the late gestation period is highly enriched with hepatocyte progenitors. They are highly proliferative and susceptible to retroviral transduction and can engraft and function in the adult rat liver if transplanted under a hepatic regenerative stimulus.

Massive repopulation of rat liver by transplantation of hepatocytes into specific lobes of the liver and ligation of portal vein branches to other lobes

An important consideration in application of hepatocyte transplantation is whether the number of engrafted hepatocytes is sufficient to achieve the desired effect. Here we have evaluated the proliferative potential of transplanted primary hepatocytes during regeneration of hepatic lobes. Two million hepatocytes isolated from congeneic normal Wistar-RHA rats were injected into the main portal vein of deficient, jaundiced Gunn rats. The right branch of the portal vein was ligated 24 hr before hepatocyte transplantation (group A) or transiently clamped during hepatocyte injection (group B) or 24 hr after hepatocyte injection (group C). In these groups, the three lobes supplied by the right branch of the portal vein rapidly atrophied and disappeared in 4 days, whereas the remaining lobes proliferated, as shown by size increase and 5-bromo-2-deoxy-uridine uptake. Two control groups received 2 million (group D) or 20 million hepatocytes (group E) without ligation. Hepatocyte engraftment occurred in all groups. The greatest hypobilirubinemic effect was observed in group A, in which serum bilirubin concentrations were reduced to 1.7+/-0.45 mg/dl from pretransplantation levels of 6.9+/-1.2 mg/dl. This effect was even greater than that observed after transplantation of 20 times more hepatocytes without ligation (group E). Specific endonuclease digestion of a polymerase chain reaction-amplified segment of the ugt1 gene from hepatic DNA showed that up to 25% of the DNA was of donor origin. This paralleled the hepatic bilirubin-UDP-glucuronosyltransferase activity, which was above 50% of normal. The results indicate that the transplanted hepatocytes proliferate preferentially within the regenerating lobes, replacing more than 20% of the liver mass with the progeny of the transplanted phenotypically normal hepatocytes.

Treatment of hypercholesterolemia in the Watanabe rabbit using allogeneic hepatocellular transplantation under a regeneration stimulus

Numerous studies have reported successful allotransplantation of hepatocytes. However, none have shown long-term correction of a liver-related metabolic defect. In this study, we used a method of regional hepatocyte transplantation and subsequent induction of transplanted cell proliferation by regeneration response in the transplant-bearing liver lobes. New Zealand White rabbits were used as cell donors and Watanabe heritable hyperlipidemic (WHHL) rabbits were used as cell recipients (2 x 10(8) cells/rabbit). All recipient rabbits were maintained on daily cyclosporine. Two weeks after baseline serum cholesterol determination, group I WHHL rabbits (n = 7) received an infusion of cells into the right lateral liver lobe, and a loose ligature was placed around the portal venous branch supplying the anterior lobe. After 1 week, to allow engraftment, the portal venous branch was ligated, which resulted in the atrophy of the affected liver parenchyma and induction of hyperplasia in the transplant-bearing liver tissue. Group II rabbits (n = 6) were transplanted with New Zealand White hepatocytes without portal branch ligation (PBL) and group III rabbits (n = 4) were subjected to sham transplantation (saline) and PBL. The experimental period extended to 150 days after transplantation. All WHHL rabbits transplanted with normal hepatocytes showed reduction in serum cholesterol and low-density lipoprotein (LDL) levels. Group I (PBL-stimulated) recipients demonstrated a more pronounced and sustained effect than group II animals (P < 0.05). Group III controls showed only a slight, typical for aging decrease in serum cholesterol. Group I recipient livers perfused with LDL labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl indocarbocyanine perchlorate (DiI) showed much higher numbers of DiI-LDL-positive hepatocytes than those of group II recipients. In conclusion, a liver regeneration stimulus enhanced the population of transplanted hepatocytes and their functional effect in a large animal model of inborn error of liver metabolism.