Hepatic microenvironment affects oval cell localization in albumin-urokinase-type plasminogen activator transgenic mice

Participation of liver stem cells in cholangiocarcinogenesis after aflatoxin B1 exposure of glutathione S-transferase A3 knockout mice

Aflatoxin B1, arguably the most potent human carcinogen, induces liver cancer in humans, rats, trout, ducks, and so on, but adult mice are totally resistant. This resistance is because of a detoxifying enzyme, mouse glutathione S-transferase A3, which binds to and inactivates aflatoxin B1 epoxide, preventing the epoxide from binding to DNA and causing mutations. Glutathione S-transferase A3 or its analog has not been detected in any of the sensitive species, including humans. The generation of a glutathione S-transferase A3 knockout (represented as KO or -/-) mice has allowed us to study the induction of liver cancer in mice by aflatoxin B1. In contrast to the induction of hepatocellular carcinomas in other species, aflatoxin B1 induces cholangiocarcinomas in GSTA3-/- mice. In other species and in knockout mice, the induction of liver cancer is preceded by extensive proliferation of small oval cells, providing additional evidence that oval cells are bipolar stem cells and may give rise to either hepatocellular carcinoma or cholangiocarcinoma depending on the nature of the hepatocarcinogen and the species of animal. The recent development of mouse oval cell lines in our laboratory from aflatoxin B1-treated GSTA3-/- mice should provide a new venue for study of the properties and potential of putative mouse liver stem cells.

A spontaneous myoepithelial carcinoma in the mammary gland of an aged female ICR (CD-1) mouse

We report a female Crlj:CD1(ICR) mouse with a spontaneous mammary gland tumor composed of biphasic tumor cells, i.e., epithelioid and spindle-shaped myoepithelial cells. Macroscopically, a subcutaneous mass, approximately 3 cm in diameter was found in the lumbodorsal region. Histopathologically, the epithelioid cells proliferated in an alveolar or nest-like growth pattern, occasionally forming glandular-like structures. On the other hand, the spindle-shaped cells proliferated in a sarcomatous pattern. Normal mammary gland was observed in the vicinity of the tumor. Both types of tumor cells showed immunoreactivity for cytokeratin (wide spectrum screening), vimentin, S100, and p63. In addition, the epithelioid cells and spindle-shaped cells were immunopositive for glial fibrillary acidic protein and smooth muscle actin, respectively. Moderate atypia, high proliferative activity, massive necrosis, and partial infiltration to the surrounding tissues were also observed. We made a diagnosis of myoepithelial carcinoma, which is extremely rare in ICR mice.

Genes inducing iPS phenotype play a role in hepatocyte survival and proliferation in vitro and liver regeneration in vivo

Reprogramming factors have been used to induce pluripotent stem cells as an alternative to somatic cell nuclear transfer technology in studies targeting disease models and regenerative medicine. The neuronal repressor RE-1 silencing transcription factor (REST) maintains self-renewal and pluripotency in mouse embryonic stem cells by maintaining the expression of Oct3/4, Nanog, and cMyc. We report that primary hepatocytes express REST and most of the reprogramming factors in culture. Their expression is up-regulated by hepatocyte growth factor (HGF) and epidermal growth factor (EGF). REST inhibition results in down-regulation of reprogramming factor expression, increased apoptosis, decreased proliferation, and cell death. The reprogramming factors are also up-regulated after 70% partial hepatectomy in vivo.

CONCLUSION

These findings show that genes inducing the iPS phenotype, even though expressed at lower levels than embryonic stem cells, nonetheless are associated with control of apoptosis and cell proliferation in hepatocytes in culture and may play a role in such processes during liver regeneration.

The role of stem cells in liver repair and fibrosis

In response to liver injury or loss of liver mass, proliferation of mature liver cells is the first-line defense to restore liver homeostasis. In the setting of chronic liver disease, however, the ability of hepatocytes and cholangiocytes to proliferate is blocked and small bipotential progenitor cells are activated. Recent studies have established the role of these facultative progenitor cells in injury repair and fibrosis in patients with chronic liver disease and in experimental models. Several signaling pathways linking progenitor cell activation and fibrosis have been identified, and there is increasing evidence that cross-talk (both physical and via soluble factors) between progenitor cells and myofibroblasts is essential for both fibrosis and parenchymal regeneration. Even more exciting are new data examining the cellular components of the progenitor cell niche, demonstrating that both resident liver cells and circulating cells from the bone marrow can function as stem cells, suggesting that there is a surprising degree of phenotypic plasticity such that progenitor cells can contribute to the myofibroblast population and vice versa. We highlight here recent findings from the literature demonstrating the cellular and functional complexity of the progenitor cell niche, and emphasize some of the important questions that remain to drive future research.

Hepatocyte transplantation and the differentiation fate of host oval cells in acute severe hepatic injury

Oval cells and hepatocytes rarely proliferate simultaneously. This study aimed to determine the impacts of hepatocyte transplantation on the response and fate of oval cells that are activated to proliferate in acute severe hepatic injury. Retrorsine + D-galactosamine (R+D-gal) treatment was used to induce acute hepatic injury and to elicit extensive activation of oval cells in male dipeptidyl peptidase IV-deficient F344 rats. These rats were then randomized to receive wild-type hepatocyte transplantation or vehicle intraportally. The kinetics of oval cell response and their differentiation fate were analyzed. Results showed that oval cells were activated early and differentiated into hepatocytes in R+D-gal-treated rats without hepatocyte transplantation. With hepatocyte transplantation, the oval cells were recruited later and continued to proliferate in parallel with the massive proliferation of transplanted hepatocytes. They formed ductules and differentiated into biliary cells. When hepatocytes were transplanted at the day when oval cells were at their peak response, the numerous activated oval cells ceased to differentiate into hepatocytes and remained in ductular form. The ductular oval cells were capable of differentiating into hepatocytes again when the donor hepatocytes were inhibited to proliferate. We conclude that hepatocyte transplantation changes the mechanism of liver reconstitution and affects the differentiation fate of host oval cells in acute severe hepatic injury.

Relation between liver progenitor cell expansion and extracellular matrix deposition in a CDE-induced murine model of chronic liver injury

In chronic liver injury, liver progenitor cells (LPCs) proliferate in the periportal area, migrate inside the lobule, and undergo further differentiation. This process is associated with extracellular matrix (ECM) remodeling. We analyzed LPC expansion and matrix accumulation in a choline-deficient, ethionine-supplemented (CDE) model of LPC proliferation. After day 3, CDE induced collagen deposits in the periportal area. Expansion of LPCs as assessed by increased number of cytokeratin 19 (CK19)-positive cells was first observed at day 7, while ECM accumulated 10 times more than in controls. Thereafter, LPCs and ECM increased in parallel. Furthermore, ECM not only accumulates prior to the increase in number of LPCs, but is also found in front of LPCs along the porto-venous gradient of lobular invasion. Double immunostaining revealed that LPCs are embedded in ECM at all times. Moreover, LPCs infiltrating the liver parenchyma are chaperoned by alpha-smooth muscle actin (alpha-SMA)-positive cells. Gene expression analyses confirmed these observations. The expression of CK19, alpha-fetoprotein, E-cadherin, and CD49f messenger RNA (mRNA), largely overexpressed by LPCs, significantly increased between day 7 and day 10. By contrast, at day 3 there was a rapid burst in the expression of components of the ECM, collagen I and laminin, as well as in alpha-SMA and connective tissue growth factor expression.

CONCLUSION

Our data demonstrate that, in a CDE model, ECM deposition and activation of matrix-producing cells occurred as an initial phase, prior to LPC expansion, and in front of LPCs along the porto-venous gradient of lobular invasion. Those observations may reveal a fundamental role for the established hepatic microenvironment or niche during the process of activation and differentiation of liver progenitor cells.

Intrahepatic transplantation of hepatic oval cells for fulminant hepatic failure in rats

AIM: To evaluate the effect of intrahepatic trans-plantation of hepatic oval cells (HOC) on fulminant hepatic failure (FHF) in rats.

METHODS: HOC obtained from rats were labeled with green fluocescent protein (GFP) or 5, 6-carboxyfluorescein diacetate succinmidyl ester (CFDA-SE). Cell fluorescence was observed under fluorescent microscope at 6, 24, 48 and 72 h after labeling. CFDA-SE labeled HOC (5 × 10⁶ cells each rat) were injected into livers of rats with FHF induced by D-galactosamine. Serum albumin (ALB), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBil) levels were measured at different time points. Liver function of rats was examined on days 3, 7, 14 and 21 after HOC transplantation.

RESULTS: The positive rate of GFP and CFDA-SE labeled HOC was 10% and 90%, respectively, with no significant change in cell viabilities. The survival rate was higher in HOC transplantation group than in control group, especially 48 (9/15 vs 6/15) and 72 h (9/15 vs 4/15) after HOC transplantation. The serum ALT, AST and TBil levels were decreased while the serum Alb level was increased after HOC transplantation. Fluorescence became faded and diffused in liver tissues, suggesting that proliferation and differentiation occur in transplanted HOC.

CONCLUSION: CFDA-SE is superior to GFP in labeling HOC, although fluorescence intensity is decreased progressively with cell division. HOC transplantation can improve the liver function and increase the survival rate of recipients.

Hepatic non-parenchymal cells and extracellular matrix participate in oval cell-mediated liver regeneration

AIM: To elucidate the interaction between non-parenchymal cells, extracellular matrix and oval cells during the restituting process of liver injury induced by partial hepatectomy (PH).

METHODS: We examined the localization of oval cells, non-parenchymal cells, and the extracellular matrix components using immunohistochemical and double immunofluorescent analysis during the proliferation and differentiation of oval cells in N-2-acetylaminofluorene (2-AAF)/PH rat model.

RESULTS: By day 2 after PH, small oval cells began to proliferate around the portal area. Most of stellate cells and laminin were present along the hepatic sinusoids in the periportal area. Kupffer cells and fibronectin markedly increased in the whole hepatic lobule. From day 4 to 9, oval cells spread further into hepatic parenchyma, closely associated with stellate cells, fibronectin and laminin. Kupffer cells admixed with oval cells by day 6 and then decreased in the periportal zone. From day 12 to 15, most of hepatic stellate cells (HSCs), laminin and fibronectin located around the small hepatocyte nodus, and minority of them appeared in the nodus. Kupffer cells were mainly limited in the pericentral sinusoids. After day 18, the normal liver lobule structures began to recover.

CONCLUSION: Local hepatic microenvironment may participate in the oval cell-mediated liver regeneration through the cell-cell and cell-matrix interactions.

Rescue of fertility in homozygous mice for the urokinase plasminogen activator transgene by the transplantation of mouse hepatocytes

Development of the urokinase plasminogen activator/SCID (uPA/SCID) transgenic mouse model has opened new perspectives for the study of different biological mechanisms such as liver regeneration, stem cell differentiation, and human hepatic pathogens. We observed that homozygous uPA/SCID mice (uPA+/+/SCID) had a small offspring, indicating a fertility defect. The goal of this study was thus to rescue the fertility of homozygous uPA mice. A deregulation of ovarian function with an absence of corpus luteum was observed in female uPA+/+/SCID mice. In male uPA+/+/SCID mice, a decrease of the weight of the testes, epididymis, seminal vesicle, and prostate was measured. This was associated with an absence of seminal and prostatic secretions and a reduction in testicular sperm production. We hypothesized that the infertility of mice was the consequence of uPA-induced liver injury. Thus, in order to rescue liver function, hepatocytes from mice negative for the uPA transgene were transplanted into uPA+/+/SCID mice. Thirty days after cell transplantation, the livers of transplanted uPA+/+/SCID mice were totally repopulated and presented a normal morphology. Furthermore, transplantation restored normal body weight, life span, and reproductive organ function. In conclusion, we demonstrated that the transplantation of uPA+/+/SCID mice with healthy hepatocytes was sufficient to rescue the reproductive capacity of female and male uPA homozygous animals, highlighting the importance of normal liver function to reproductive capability.

What fires prometheus? The link between inflammation and regeneration following chronic liver injury

Liver progenitor cells (LPCs) play a major role in the regeneration process after chronic liver damage, giving rise to hepatocytes and cholangiocytes. Thus, they provide a cell-based therapeutic alternative to organ transplant, the current treatment of choice for end-stage liver disease. In recent years, much attention has focused on unravelling the cytokines and growth factors that underlie this response. Liver regeneration following acute damage is achieved by proliferation of mature hepatocytes; yet similar cytokines, most related to the inflammatory process, are implicated in both acute and chronic liver regeneration. Thus, many recent studies represent attempts to identify LPC-specific factors. This review summarises our current understanding of LPC biology with a particular focus on the liver inflammatory response being associated with the induction of LPCs in the liver. We will describe: (i) the pathways of liver regeneration following acute and chronic damage; (ii) the similarities and differences between the two pathways; (iii) the liver inflammatory environment; (iv) the unique features of liver immunology as well as (v) the interactions between liver immune cells and LPCs. Combining data from studies on the LPC-driven regeneration process with the knowledge in the field of liver immunology will improve our understanding of the LPC response and allow us to regulate these cells in vivo and in vitro for future therapeutic strategies to treat chronic liver disease.

Long-term production of major coagulation factors and inhibitors by primary human hepatocytes in vitro: perspectives for clinical application

BACKGROUND/AIMS

Patients with coagulation factor disorders require lifelong symptomatic treatment. This is associated with limited efficacy and transmission risks. From a clinical point of view, hepatocyte transplantation offers a rational alternative but is currently being hampered by lack of functional stability of engrafted cells. It was the aim of our study to devise culture conditions providing stable cell polarity, attachment and growth factor stimulation to improve longevity and coagulation factor production.

METHODS

Human hepatocytes (HC) were plated on different extracellular matrices, inside collagen gel or Matrigel. HC were grown inside growth factor-enriched serum-free medium (SFM) or exposed to media switching from differentiation (DM) to dedifferentiation (DeDM).

RESULTS

Over more than 30 days in vitro human HC synthesized coagulation factors (factors VII, VIII, IX, fibrinogen) and coagulation inhibitors (antithrombin III, protein C). Protein synthesis was augmented when HC were grown inside a 3D collagen type I matrix, while Matrigel showed no additional benefit. Soluble growth factors improved coagulation factor production when applied in SFM or in sequential DM/DeDM. Coagulation factor levels ranged from 3% to 12% in the first week to 2.5-5% after 4 weeks, reaching biologically relevant levels.

CONCLUSION

Preserved synthesis and secretion of coagulation factors in balanced proportion by human HC in this model may offer new perspectives for HC transplantation in coagulation defects of patients.

E-cadherin as a reliable cell surface marker for the identification of liver specific stem cells

Oval cells are liver-specific bipotent stem cells which accumulate in injured liver when proliferation of mature hepatocytes and/or cholangiocytes is impaired. They represent an intermediary cell type with phenotypical characteristics of both, hepatocytes and cholangiocytes. Oval cells express specific cell surface proteins allowing their identification in situ. Most of these cell surface proteins, however, are recognized by antibodies in mouse liver tissue that are not commercially available or work only on frozen sections. We show herein the unequivocal identification of oval cells in paraffin-embedded mouse liver samples based on strong E-cadherin expression different from that of hepatocytes and bile duct cells. By comparing the pattern of E-cadherin expression with that of both, A6-antigen and CD44, we suggest a tight control of E-cadherin expression depending on the differentiation stage of the progenitor cells. In human cirrhotic liver samples E-cadherin expression was found as a common feature of both, typical and atypical reactions, and, thus, can also serve as an indication of the progenitor cell compartment activation.

Separate origins of hepatitis B virus surface antigen-negative foci and hepatocellular carcinomas in transgenic HBsAg (alb/psx) mice

We have examined the development and transgene expression in liver lesions of transgenic mice bearing the hepatitis B surface antigen (HBsAg) gene of hepatitis B virus under the control of the albumin promoter (alb/psx) to study liver regeneration and hepatocellular carcinoma (HCC) associated with hepatitis B virus infection. Storage of the HBsAg in the endoplasmic reticulum precedes loss of liver cells and regenerative hyperplastic nodules that do not express HBsAg. Histological analysis indicated that HBsAg-negative foci and nodules arose from liver progenitor cells in the portal zone and lacked mRNA expression. Genomic DNA from eight of nine HBsAg-negative laser capture-excised liver foci showed loss of part of the alb/psx gene, whereas no loss of the actin gene was observed. The alb/psx DNA was intact in adjacent HBsAg-positive tissue. Sequencing of polymerase chain reaction products suggested that alterations in the HBsAg transgene in HBsAg-negative foci occurred via large-scale deletions as opposed to single-site mutations. Southern blot analysis of HCC from 2-year-old transgenic HBsAg mice, however, revealed an intact alb/psx gene. Thus, HBsAg-negative progenitor cells with deletions in the transgene appear to be responsible for compensatory regeneration of the liver, whereas HCCs arise from clonal expansion of hepatocytes with intact alb/psx transgenes.

Progenitor cells in liver regeneration: molecular responses controlling their activation and expansion

Although normally quiescent, the adult mammalian liver possesses a great capacity to regenerate after different types of injuries in order to restore the lost liver mass and ensure maintenance of the multiple liver functions. Major players in the regeneration process are mature residual cells, including hepatocytes, cholangiocytes and stromal cells. However, if the regenerative capacity of mature cells is impaired by liver-damaging agents, hepatic progenitor cells are activated and expand into the liver parenchyma. Upon transit amplification, the progenitor cells may generate new hepatocytes and biliary cells to restore liver homeostasis. In recent years, hepatic progenitor cells have been the subject of increasing interest due to their therapeutic potential in numerous liver diseases as alternative or supportive/complementary tools to liver transplantation. While the first investigations on hepatic progenitor cells have focused on their origin and phenotypic characterization, recent attention has focused on the influence of the hepatic microenvironment on their activation and proliferation. This microenvironment comprises the extracellular matrix, epithelial and non-epithelial resident liver cells, and recruited inflammatory cells as well as the variety of growth-modulating molecules produced and/or harboured by these elements. The cellular and molecular responses to different regenerative stimuli seem to depend on the injury inflicted and consequently on the molecular microenvironment created in the liver by a certain insult. This review will focus on molecular responses controlling activation and expansion of the hepatic progenitor cell niche, emphasizing similarities and differences in the microenvironments orchestrating regeneration by recruitment of progenitor cell populations or by replication of mature cells.

Development of an HSV-tk transgenic mouse model for study of liver damage

The herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system that selectively depletes cells expressing HSV-tk upon treatment with GCV has provided a valuable tool for developing a new animal model expressing the desired tissue damage. In this paper, an HSV-tk vector with an albumin promoter/enhancer was constructed. Based on the favourable killing effect on Hep-G2 cells by the recombinant construct, the HSV-tk transgenic mouse strains were developed. One strain of the TK transgenic mouse (TK5) was studied intensively. Integration of the target gene was confirmed primarily by PCR. Fluorescence in situ hybridization following G-banding analysis demonstrated that the insertion site was located at 2F1-G3. The hepatocyte-specific transcription and expression of HSV-tkwas verified by reverse transcription (RT)-PCR as well as by immunohistochemical staining. When two second-generation mice (TK5-F1 and TK5-F2) were injected with GCV, the pathogenic alterations in the liver were readily identified, including the appearance of vaculation in the hepatocytes with inflammatory infiltration in the liver, and diffuse proliferation of hepatocytes. In addition, the blood test demonstrates a significant increase of serum alanine aminotransferase, aspartate aminotransferase and total bilirubin. In conclusion, the transgenic mouse model with hepatocyte-specific expressed HSV-tk developed hepatitis with administration of GCV, had morphological and clinical chemical characteristics indicative of hepatocellular disease and should be useful for the the study of inducible liver-specific diseases.

Donor-Derived, Liver-Specific Protein Expression after Bone Marrow Transplantation

BACKGROUND

Bone marrow transplantation (BMT) may represent a novel mechanism to deliver a functional gene to a deficient liver. Bone marrow-derived hepatocytes are rare and without a defined contribution to liver function. Consequently, the clinical significance of BMT to treat liver disease is unclear. We sought to quantify bone marrow-derived hepatocyte protein expression after BMT and determine whether the process is inducible with liver injury.

METHODS

Mice transgenic for human alpha-1 antitrypsin (hAAT) under a hepatocyte-specific promoter were used as bone marrow donors. Adenoviral transduction of modified urokinase plasminogen activator (Ad-muPA) was used to induce liver injury. Eight weeks after lethal irradiation and BMT, recipients were stratified into two groups: BMT alone (n = 5) and BMT + Ad-muPA (n= 10). Both groups of animals were bled before (t = 0) and at 2, 4, 8, and 16 weeks after Ad-muPA administration, and the serum samples were assessed for hAAT by enzyme-linked immunosorbent assay.

RESULTS

Transgenic donor mice expressed 5 to 10 mg/mL of hAAT. Recipients of BMT alone expressed less than 80 ng/mL of hAAT over all time periods. Animals receiving BMT + Ad-muPA showed sustained and stable hAAT expression of approximately 200 ng/mL. Differences were statistically significant at each time point.

CONCLUSION

Serum protein levels from liver-specific transgene expression are detectable and persist after BMT. Expression is low, but inducible with liver injury. We are currently developing strategies to augment donor-derived, liver-specific protein expression after BMT.

Hepatic progenitor cells in human liver cirrhosis: Immunohistochemical, electron microscopic and immunofluorencence confocal microscopic findings

AIM: To investigate whether hepatic progenitor cells (HPC), that reveal the features of oval cells in rodents and small epithelial cells (SEC) in certain human liver disease, were also found in human liver cirrhosis (HLC).

METHODS: Surgical liver specimens from 20 cases of hepatitis B virus-positive HLC (15 cases containing hepatocellular carcinoma) were investigated by light microscopic immunohistochemistry (LM-IHC). Among them specimens from 15 cases were investigated by electron microscopy (EM) and those from 5 cases by immunofluorencence confocal laser scanning microscopy (ICLSM). Antibodies against cytokeratin 7 and albumin were used and single and/or double labelling were performed respectively.

RESULTS: LM-IHC showed that at the margins of regenerating nodules and in the fibrous septae, a small number of cells in the proliferating bile ductules were positive for CK7 and albumin. At the EM level these HPC were morphologically similar to the SEC described previously, and also similar to the oval cells seen in experimental hepatocarcinogenesis. They were characterized by their small size, oval shape, a high nucleus/cytoplasm ratio, a low organelle content in cytoplasm, and existence of tonofilaments and intercellular junctions. ICLSM revealed that HPC expressed both cytokeratin 7 and albumin.

CONCLUSION: HPC with ultrastructural and immunophenotypical features of oval cells, i.e., hepatic stem cell-like cells as noted in other liver diseases, were found in HLC. These findings further support the hypothesis that bipotent hepatic stem cells, that may give rise to biliary epithelial cells and hepatocytes, exist in human livers.

Sympathetic nervous system inhibition increases hepatic progenitors and reduces liver injury

Recovery from liver damage might be enhanced by encouraging repopulation of the liver by endogenous hepatic progenitor cells. Oval cells are resident hepatic stem cells that promote liver regeneration and repair. Little is known about the mediators that regulate the accumulation of these cells in the liver. Parasympathetic nervous system inhibition reduces the number of oval cells in injured livers. The effect of sympathetic nervous system (SNS) inhibition on oval cell number is not known. Adrenergic inhibition mobilizes hematopoietic precursors into the circulation and has also been shown to promote liver regeneration. Thus, we hypothesized that SNS inhibition would promote hepatic accumulation of oval cells and reduce liver damage in mice fed antioxidant-depleted diets to induce liver injury. Our results confirm this hypothesis. Compared with control mice that were fed only the antioxidant-depleted diets, mice fed the same diets with prazosin (PRZ, an alpha-1 adrenoceptor antagonist) or 6-hydroxydopamine (6-OHDA, an agent that induces chemical sympathectomy) had significantly increased numbers of oval cells. Increased oval cell accumulation was accompanied by less hepatic necrosis and steatosis, lower serum aminotransferases, and greater liver and whole body weights. Neither PRZ nor 6-OHDA affected the expression of cytokines, growth factors, or growth factor receptors that are known to regulate progenitor cells. In conclusion, stress-related sympathetic activity modulates progenitor cell accumulation in damaged livers and SNS blockade with alpha-adrenoceptor antagonists enhances hepatic progenitor cell accumulation.

Biological characteristics of rat hepatic oval cells

AIM

To observe the morphological parameters, phenotypes and evolution of hepatic oval cells in rats.

METHODS

Rat models for hepatic oval cell proliferation were established, and cell image analysis and immunohistochemical staining of hepatic oval cells were performed on the tissue sections.

RESULTS

Hepatic oval cells were characterized by small size, oval shape and ovoid nuclei. The plasma of the cells was positive for cytokeratin (CK) 19, OV6, alfa-fetal protein (AFP) and vimentin staining, and negative for leucocyte common antigen (LCA) staining. The nuclei were positive for proliferating cell nuclear antigen (PCNA). Some hepatocyte-like cells were discerned around the portal tracts and these cells were positive for CK19 and OV6 staining.

CONCLUSION

Hepatic oval cells differ from hepatocytes morphologically and express the phenotypes of ductular cells and hepatocytes. Hepatocyte-like cells are most likely the intermediate transition cells between hepatic oval cells and hepatocytes.