Characterization of human xenoreactive antibodies in liver failure patients exposed to pig hepatocytes after bioartificial liver treatment: an ex vivo model of pig to human xenotransplantation

BACKGROUND

There are limited experimental data on the nature of the humoral response elicited in humans against pig antigens. In this study, we have examined the xenoantibody (XAb) response in eight patients with acute liver failure exposed to pig hepatocytes after treatment with the bioartificial liver (BAL).

METHODS

Patients' plasma samples obtained before and after BAL treatment were tested for IgM and IgG XAbs, IgG subclasses, and XAb cytotoxicity, using enzyme-linked immunosorbent assay and flow-cytometric assays. The characterization of pig aortic endothelial cell (PAEC) surface xenoantigens was analyzed by immunoprecipitation.

RESULTS

We observed by day 10, a strong anti-pig IgG and IgM XAb response in patients undergoing two or more BAL treatments, with a significant increase in all the IgG subclasses; in contrast, XAb titers did not change if the patients received only one BAL treatment. The majority of the XAbs produced to porcine antigens were primarily specific for the alphaGal epitope. Both IgG and IgM XAbs were cytotoxic to PAECs, and the cytotoxic activity of IgG was associated with high levels of IgG1 and IgG3 subclasses, known to be efficient on complement activation. The characterization of porcine surface antigens demonstrated that IgM human XAbs, before and after BAL exposure, recognized xenoantigens on PAECs with similar molecular weights, suggesting that the same population of XAbs were present in the patients before and after exposure to pig antigens.

CONCLUSIONS

Repetitive exposure of humans to porcine antigens after BAL treatment, results in a strong IgG and IgM XAb responses that are primarily directed against the alphaGal epitope. These XAbs are cytotoxic to PAECs and the IgG toxicity correlates with high IgG1 and IgG3 levels. Our data also suggest that no new XAb specificity emerges after porcine exposure.

Artificial liver: review and Cedars-Sinai experience

During the past decade, whole organ transplantation has become the only clinically effective method of treating fulminant hepatic failure and chronic liver failure due to specific genetic, hepatocellular, and anatomic defects of liver function. However, wider application of liver transplantation is restricted by shortage of organ donors, high cost, relatively high morbidity, and need for life-long immunosuppression. As a result, investigators have attempted to develop alternative methods to treat liver insufficiency. These ranged from use of plasma exchange to utilization of detoxification columns and extracorporeal devices loaded with various liver tissue preparations. Recently, advances in hepatocyte isolation and culture techniques, improved understanding of hepatocyte-matrix interactions, availability of new biomaterials, improved hollow-fiber technology, and better understanding of flow and mass transport across semipermeable membranes have resulted in the development of a new generation of liver assist devices. Some of these devices, including the one developed by the authors, are currently being tested in the clinical setting. In this paper, the past experience with liver support systems is reviewed, the present status of the field is critically examined, and the results of a phase I clinical trial with the bioartificial liver, utilizing primary porcine hepatocytes, are summarized.

Liver assist systems: state of the art

Attempts to develop liver support systems for the treatment of patients with liver failure have ranged from use of plasma exchange to utilization of charcoal columns and extracorporeal devices loaded with liver tissue. However, no system has achieved wide clinical use and - in the absence of liver transplantation - severe hepatic failure continues to be associated with significant morbidity and mortality. In this paper, the authors review the current status of liver assist systems and summarize their clinical experience with a xenogeneic cell based-bioartificial liver.

Intrasplenic transplantation of allogeneic hepatocytes prolongs survival in anhepatic rats

To examine whether hepatocytes transplanted in the spleen can function as an ectopic liver, we performed hepatocyte transplantation in rats that were rendered anhepatic. Total hepatectomy was performed by using a novel single-stage technique. Following hepatectomy, Group 1 rats (n = 16) were monitored until death to determine survival time without prior intervention. Group 2 anhepatic rats (n = 20) were sacrificed at various times to measure blood hepatocyte growth factor (HGF) and transforming growth factor beta1 (TGF-beta1) levels. Group 3 (n = 16) rats received intrasplenic injection of isolated hepatocytes (2.5 x 10(7) cells/rat) followed by total hepatectomy after 3 days. Group 4 (n = 12) sham-transplanted rats received intrasplenic saline infusion, and after 3 days they were rendered anhepatic. Group 2, 3, and 4 rats were maintained on daily Cyclosporine A (10 mg/kg; intramuscularly). Group 1 anhepatic rats survived for 22.4 +/- 5.2 hours (standard deviation). The anhepatic state was associated with a progressive and statistically significant rise in blood HGF and TGF-beta1 levels. Rats that received hepatocyte transplantation before total hepatectomy had a significantly longer survival time than sham-transplanted anhepatic controls (34.1 +/- 8.5 vs. 15.5 +/- 4.8 hrs, P < .01). Additionally, at 12 hours post-hepatectomy, transplanted rats had significantly lower blood ammonia, prothrombin time, international normalized ratio, and TGF-beta1 levels when compared with sham-transplanted controls. In conclusion, intrasplenic transplantation of allogeneic hepatocytes prolonged survival, improved blood chemistry, and lowered blood TGF-beta1 levels in rats rendered anhepatic.

Novel human malignancy-associated gene (MAG) expressed in various tumors and in some tumor preexisting conditions

We have identified a novel human malignancy-associated gene (MAG) expressed in various malignant tumors including glioblastomas and hepatocellular carcinomas (HCCs) and in tumor preexisting conditions such as hepatitis C virus- and hepatitis B virus-induced liver cirrhosis. The expression of MAG was characterized using reverse transcription-PCR (RT-PCR), rapid amplification of cDNA ends PCR, RNA dot blotting, RNase protection assay, and Northern blot analysis. Rapid amplification of cDNA ends PCR yielded a 536-bp MAG fragment in HCC, macroregenerative liver nodules with dysplasia, and liver cirrhosis but not in normal liver or placenta. By RT-PCR, MAG expression was not found in 12 different normal tissues but found in 46 of 51 (90%) premalignant and malignant tissues of various sites. Embryonic liver and brain were positive for MAG expression together with tumors from the same organs, but the corresponding normal adult tissues were negative. By RNase protection assay, MAG mRNA was expressed in the HepG2 liver tumor cell line and in an ovarian carcinoma but not in normal liver. The estimated transcript size from Northern blot analysis was 8.8 kb. This novel gene may play a role in the progression of premalignant conditions and in the development of HCC and other cancers.

In vitro morphological and functional characterization of isolated porcine hepatocytes for extracorporeal liver support: bile acid uptake and conjugation

Recently, researchers have focused on the use of bioartificial liver (BAL) to support patients with fulminant hepatic failure (FHF). We have developed a cell-based BAL, consisting of porcine hepatocytes in a hollow-fiber bioreactor. To better characterize BAL metabolic functions in vitro, bioreactors were inoculated with 48-h-cultured, microcarrier-attached hepatocytes and perifused with recirculating human plasma that contained either 1 microCi of [24-14C] plasma-enriched cholate or 1 microCi of [24-14C] plasma-enriched taurocholate. Bile acids were sampled hourly and separated into four fractions (unconjugated, glycoconjugated, tauroconjugated, and sulfated) for radioactivity determination. Following 3 h perifusion, the glycoconjugated and sulfated bile acid fractions in the bioreactor extrafiber space were significantly elevated when compared to the recirculating plasma. During perifusion with taurocholate-enriched plasma, a relative decrease in the tauroconjugated fraction and an increase in the glycoconjugated fraction were observed. Cholate was accumulated by hepatocytes to a level threefold lower than taurocholate; however, a significant proportion of radioactivity (<25%) was detected in the glycoconjugated fraction. Ultrastructural examination of microcarrier-attached hepatocytes illustrated that the features typical of metabolically active liver cells were maintained. Our data demonstrate the ability of BAL to clear bile acids from the circulation, to accumulate cholate and taurocholate, and to conjugate a substantial amount of cholic acid.

Transplantation of hepatocytes for prevention of intracranial hypertension in pigs with ischemic liver failure

Intracranial hypertension leading to brain stem herniation is a major cause of death in fulminant hepatic failure (FHF). Mannitol, barbiturates, and hyperventilation have been used to treat brain swelling, but most patients are either refractory to medical management or cannot be treated because of concurrent medical problems or side effects. In this study, we examined whether allogeneic hepatocellular transplantation may prevent development of intracranial hypertension in pigs with experimentally induced liver failure. Of the two preparations tested--total hepatectomy (n = 47), and liver devascularization (n = 16)--only pigs with liver ischemia developed brain edema provided, however, that animals were maintained normothermic throughout the postoperative period. This model was then used in transplantation studies, in which six pigs received intrasplenic injection of allogeneic hepatocytes (2.5 x 10(9) cells/pig) and 3 days later acute liver failure was induced. In both models (anhepatic state, liver devascularization), pigs allowed to become hypothermic had significantly longer survival compared to those maintained normothermic. Normothermic pigs with liver ischemia had, at all time points studied, ICP greater than 20 mmHg. Pigs that received hepatocellular transplants had ICP below 15 mmHg until death; at the same time, cerebral perfusion pressure (CPP) in transplanted pigs was consistently higher than in controls (45 +/- 11 mmHg vs. 16 +/- 18 mmHg; p < 0.05). Spleens of transplanted pigs contained clusters of viable hepatocytes (hematoxylin-eosin, CAM 5.2). It was concluded that removal of the liver does not result in intracranial hypertension; hypothermia prolongs survival time in both anhepatic pigs and pigs with liver devascularization, and intrasplenic transplantation of allogeneic hepatocytes prevents development of intracranial hypertension in pigs with acute ischemic liver failure.

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 x100 higher and after 10 days in culture x20 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 x13.8 with EGF, x18.5 with transforming growth factor alpha (TGF-alpha), and x7.6 with hepatocyte growth factor (HGF). For fetal hepatocytes, the increase was twofold with either EGF, TGF-alpha or HGF. EGF-, TGF-alpha- and HGF-dependent DNA synthesis was inhibited by transforming growth factor beta-1 (TGF-beta1) in both fetal and adult hepatocyte cultures; this antiproliferative effect was significantly stronger in adult hepatocyte cultures. With cyclosporine, EGF-, TGF-alpha- 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-beta1. It was also found that cyclosporine suppresses proliferation of cultured fetal hepatocytes.

Growth of intraportally transplanted islets under liver regeneration stimulus and restoration of normoglycemia in streptozocin-diabetic rats

BACKGROUND

Limitation of beta-cell growth after intraportal islet transplantation plays an important role in graft failure. To induce transplanted beta-cell proliferation, we studied the effect of compensatory liver growth in diabetic rats that had a subtherapeutic islet mass previously injected into the liver.

METHODS

Syngeneic rats were used as islet donors or recipients; diabetes was induced by streptozocin. Three groups of streptozocin-treated rats were studied. In group 1, 250 islets were selectively transplanted into the posterior liver lobes and 10 days later anterior portal branch ligation (PBL) was performed (n = 18); in group 2, 250 islets were transplanted into the posterior lobes and 10 days later sham PBL was performed (n = 13); in group 3, rats underwent a sham transplantation and PBL (n = 6). Nonfasting blood glucose levels and body weight were monitored. Six rats in groups 1 and 2 were killed 48 hours after PBL, liver sections were stained for proliferating cell nuclear antigen, and islet cell labeling index was calculated. The remaining rats were killed 30 days later. Liver compensatory growth or atrophy was calculated and morphometric determination of beta-cell area was assessed on insulin-immunostained sections of the liver.

RESULTS

In group 1 rats killed 48 hours after PBL, islet cell labeling index was significantly higher than in group 2 (p < 0.0001). After PBL, we observed normalization of nonfasting blood glucose levels in 10 of 12 rats. At 30 days, posterior liver lobes showed compensatory growth (218.5% +/- 18.6%) accompanied by atrophy of the anterior lobes; morphometric study of liver-engrafted islets showed a significant increase of individual beta-cell area, compared with group 2 (p < 0.0001). In groups 2 and 3, normoglycemia was not achieved.

CONCLUSIONS

In streptozocin-diabetic rats, normoglycemia was restored after transplantation of a sub-therapeutic islet mass, followed by PBL-induced liver regeneration. Histologic and morphometric results indicating islet cell proliferation suggest that compensatory liver growth might have induced a hypertrophic/hyperplastic response in the intraportally transplanted beta-cells.

Treatment of severe liver failure with a bioartificial liver

Orthotopic liver transplantation (OLT) is the definitive therapy for severe liver failure. However, many patients die before an organ becomes available, mostly from cerebral edema. To provide temporary liver support, we developed a bioartificial liver (BAL) based on porcine hepatocytes and a charcoal column. Fifty-four consecutive BAL treatments were carried out in three groups of patients: Group I (n = 15) patients presented with FHF were listed for emergent OLT, Group II (n = 3) patients with primary non-function (PNF) of their liver grafts required urgent re-transplantation and Group III (n = 10) patients with acute exacerbation of chronic liver disease were not candidates for OLT. Patients were managed in a critical care unit receiving maximal standard support. Each BAL treatment was conducted for 6 hours. In Group I, all patients showed significant neurologic improvement, intracranial pressure (ICP) decreased and cerebral perfusion pressure (CPP) increased; other significant improvements, included lowered plasma ammonia and liver enzymes and increased glucose. One patient recovered spontaneously without OLT, all other patients were "bridged" to OLT, and recovered. Group II: PNF patients showed similar benefits. Group III: Chronic liver patients demonstrated transient beneficial effects after BAL treatment(s), however, most (n = 8) eventually succumbed to sepsis and multiple organ failure as they were not candidates for OLT; two patients, recovered, later were successfully transplanted and survived. Our clinical experience demonstrates that the BAL can serve as a bridge to OLT in patients with acute liver failure.

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.

Loss and recovery of liver regeneration in rats with fulminant hepatic failure

We earlier described a model of fulminant hepatic failure (FHF) in the rat where partial hepatectomy is combined with induction of right liver lobes necrosis. After this procedure, lack of regenerative response in the residual viable liver tissue (omental lobes) was associated with elevated plasma hepatocyte growth factor (HGF) and transforming growth factor beta (TGF-beta1) levels and delayed expression of HGF and c-met mRNA in the remnant liver. Here, we investigated whether syngeneic isolated hepatocytes transplanted in the spleen will prolong survival and facilitate liver regeneration in FHF rats. Inbred male Lewis rats were used. Group I rats (n = 46) received intrasplenic injection of 2 x 10(7) hepatocytes and 2 days later FHF was induced. Group II FHF rats (n = 46) received intrasplenic injection of saline. Rats undergoing partial hepatectomy of 68% (PH; n = 30) and a sham operation (SO; n = 30) served as controls. In 20 FHF rats (10 rats/group), survival time was determined. The remaining 72 FHF rats (36 rats/group) were used for physiologic studies (liver function and regeneration and plasma growth factor levels). In Group I rats survival was longer than that of Group II controls (73 +/- 22 hr vs. 33 +/- 9 hr; P < 0. 01). During the first 36 hr, Group I rats had lower blood ammonia, lactate, total bilirubin, PT, and PTT values, lower activity of liver enzymes, and higher monoethylglycinexylidide (MEGX) production than Group II rats. In Group I rats, livers increased in weight at a rate similar to that seen in PH controls and showed distinct mitotic and DNA synthetic activity (incorporation of bromodeoxyuridine and proliferation cell nuclear antigen expression). Plasma HGF and TGF-beta1 levels in these rats decreased and followed the pattern seen in PH rats; additionally, c-met expression in the remnant liver was accelerated. Hepatocyte transplantation prolonged survival in FHF rats and facilitated liver regeneration. Even though the remnant liver increased in weight four times reaching 30% of the original liver mass, the transplant-bearing rats expired due to inability of the regenerating liver to support the rat.

Lack of hepatocyte growth factor receptor (c-met) gene expression in fulminant hepatic failure livers before transplantation

To gain insight into liver regeneration mechanisms in fulminant hepatic failure, we compared gene expression of hepatocyte growth factor, its receptor c-met, c-myc, and albumin in human normal (4 cases) and fulminant (14 cases) livers by reverse transcription-polymerase chain reaction. In normal livers, hepatocyte growth factor gene was not expressed, whereas c-met, c-myc and albumin genes were always expressed. In fulminant hepatic failure, hepatocyte growth factor gene was expressed in 1 of 14 cases, c-met in none of 14 cases, c-myc in 10 of 14 cases, and albumin in 3 of 14 cases. By immunofluorescence, c-met protein was revealed in normal but not in fulminant hepatic failure liver tissue. Liver tissue is unlikely to account for high hepatocyte growth factor plasma levels typical for fulminant hepatic failure. Lack of its receptor (c-met) expression may explain a poor response of fulminant hepatic failure livers to exogenous hepatocyte growth factor that normally promotes liver growth and regeneration.

Clinical experience with a bioartificial liver in the treatment of severe liver failure. A phase I clinical trial

OBJECTIVE

The purpose of this study was to develop a bioartificial liver (BAL) to treat patients with severe liver failure until they can be either transplanted or recover spontaneously.

SUMMARY BACKGROUND DATA

Severe acute liver failure is associated with high mortality. Liver transplantation has emerged as an effective therapy for patients who did not respond to standard management. However, because of the donor organ shortage and urgent need for transplantation, many patients die before they can be transplanted and others do not survive after transplantation, primarily because of intracranial hypertension.

METHODS

Three groups of patients with severe acute liver failure were treated with the BAL. In group 1 (n = 18) were patients with fulminant hepatic failure (FHF), in group 2 (n = 3) were patients with primary nonfunction (PNF) of a transplanted liver, and in group 3 (n = 10) were patients with acute exacerbation of chronic liver disease. Patients in groups 1 and 2 were candidates for transplantation at the time they entered the study, whereas patients in group 3 were not.

RESULTS

In group 1, 16 patients were "bridged" successfully to transplantation, 1 patient was bridged to recovery without a transplant, and 1 patient died because of concomitant severe pancreatitis. In group 2, all patients were bridged successfully to retransplantation. In group 3, two patients were supported to recovery and successful transplants at later dates; the other eight patients, although supported temporarily with the BAL, later died because they were not candidates for transplantation.

CONCLUSIONS

The authors' clinical experience with the BAL has yielded encouraging results. A randomized, controlled, prospective trial (phase II-III) is being initiated to determine the efficacy of the system.

Intracranial pressure. Effects of pneumoperitoneum in a large-animal model

BACKGROUND

The effects of pneumoperitoneum on intracranial pressure (ICP) have received relatively little attention. This study was undertaken to investigate the changes in ICP occurring as a result of increased intraabdominal pressure (IAP) and positioning in animals with normal and elevated ICP.

METHOD

Five pigs (average weight 60 lb) were studied. A subarachnoid screw was placed for ICP monitoring. End tidal CO2 was monitored. Ventilation was performed to keep PCO2 between 30 and 50 mmHg. Measurements of arterial blood gases, mean arterial blood pressure, and ICP were recorded at four different levels of intraabdominal pressure (IAP 0, 8, 16, and 24 mmHg), both in the supine and Trendelenburg positions. A Foley catheter was introduced into the subarachnoid space to elevate the intracranial pressure, and the same measurements were performed.

RESULTS

There was a significant and linear increase in ICP with increased IAP and Trendelenburg position. The combination of increased IAP of 16 mmHg and Trendelenburg position increased ICP 150% over control levels.

CONCLUSIONS

Patient positioning and level of IAP should be taken into consideration when performing laparoscopy on patients with head trauma, cerebral aneurysms, and other conditions associated with increased ICP.

Repeated intraportal injections of subtherapeutic islet cell isografts restore normoglycemia in streptozotocin-diabetic rats

Poor engraftment and consequent loss of beta-cell mass could be one of the factors that are responsible for function loss after intraportal islet transplantation (Tx). Streptozotocin-diabetic rats were transplanted with syngeneic islets, which were injected into the portal vein via an indwelling catheter connected to a subcutaneous port. In Group I (n = 6), 1,000 islets were injected in a single dose into the liver. In Group II (n = 6), five doses of 200 islets were repeatedly injected over a period of 14 days, for a total of 1,000 islets. In Group III (n = 4), five decreasing doses of islets were injected over a period of 14 days, for a total of 750 islets. Nonfasting blood glucose (n-FBG) and body weight (b.wt.) were determined twice a week and an intravenous glucose tolerance test (IVGTT) was performed at 30 and 90 days. In Group I, n-FBG decreased in 2 wk from the time of first islet injection, averaging 110 +/- 21.9 mg/dl at 1 mo (p < 0.05 vs. normal controls); this value was maintained throughout the 3-mo duration of the study. In Group II, n-FBG was normalized in 2 wk averaging 90.2 +/- 25 mg/dL on day 12 (p = NS vs. normal controls) and 75.8 +/- 14.6 mg/dL at 1 month (p = NS vs. normal controls); this value was maintained throughout the 3-mo duration of the study. In Group III, n-FBG decreased to normal values in 2 wk, averaging 77 +/- 15.7 mg/dL at 1 mo (p = NS vs. normal controls), but normoglycemia was maintained for 40 days and then followed by a progressive increase. Only in Group II, KG (percent/min decline in glucose level) was not significantly different from that of normal controls (1.702 +/- 0.531 at 1 mo and 1.676 +/- 0.891 at 3 mo), while it was significantly lower than normal controls in both Group I and III animals. Body weight increase after Tx correlated with the number of transplanted islets and at 90 days, Group III rats showed less increase than Groups I and II (p < 0.05), while no significant differences in b.wt. were recorded between Group I and II. The findings indicate that intraportal islet Tx, injected repeatedly and in small doses, produced better metabolic effects than injection of the same total number of islets in a single dose.

Expression of HGF, its receptor c-met, c-myc, and albumin in cirrhotic and neoplastic human liver tissue

Hepatocellular carcinoma (HCC) is a common type of cancer, with approximately 260,000 new cases each year, and liver cirrhosis is generally considered a major predisposing factor for HCC. However, specific changes of gene expression in liver cirrhosis and HCC remain obscure. The expression of genes for hepatocyte growth factor (HGF), its receptor c-met proto-oncogene, c-myc proto-oncogene, and albumin was analyzed. Gene expression was studied by PCR in seven normal human livers, nine cases of hepatitis C cirrhosis, 12 cases of alcoholic cirrhosis, two cases of liver adenoma, and 12 cases of HCC. HGF and c-met protein were revealed by immunofluorescent staining. HGF mRNA was not expressed in normal livers but was detected in adenomas, in 80% of HCC, and in some cirrhoses. Paraffin-embedded and fresh-frozen tissue samples yielded similar results. Immunohistochemical data correlated with PCR results regarding the overexpression of the HGF/c-met system in HCC. Albumin gene expression was decreased in HCC vs normal livers, consistent with altered function of tumor hepatocytes. The elevated expression of the HGF/c-met system in HCC may play a role in tumor development and/or progression. Tissue localization studies of HGF and its receptor c-met protein support the existence of both autocrine and paracrine mechanisms of action of HGF in HCC vs only a paracrine mechanism in normal liver.

Fulminant hepatic failure in rats: survival and effect on blood chemistry and liver regeneration

A reproducible experimental animal model of fulminant hepatic failure (FHF) resembling the clinical condition is needed. We have developed such a model in the rat by combining resection of the two anterior liver lobes (68% liver mass) with ligation of the right lobes pedicle (24% liver mass), resulting in liver necrosis; the remaining two omental lobes (8% liver mass) are left intact. Adult Sprague-Dawley rats (250-300 g) were used. Survival time was determined in 60 rats. Because maintenance of body temperature at 37 degrees C shortened survival time by half, FHF rats were not warmed during the postinduction period and were allowed to gradually enter a state of mild to moderate hypothermia (29-32 degrees C). Additionally, 42 FHF rats were killed in batches of six rats each 2, 6, 12, 18, 24, 30, and 36 hours postoperatively to evaluate changes in blood chemistry (glucose, lactate, liver function tests, prothrombin time) and to assess liver regenerative response in the residual omental liver lobes (weight, protein content, incorporation of bromodeoxyuridine [BrdU], expression of proliferation cell nuclear antigen [PCNA], mitotic activity), plasma levels of hepatocyte growth factor (HGF) and transforming growth factor beta (TGF-beta1), and tissue expression of the HGF and it's receptor c-met. Rats undergoing partial hepatectomy of 68% (PH; n = 42) and a sham operation (SO; n = 42) served as controls. All SO and PH controls survived. PH rats showed only transient decreases in body temperature, signs of modest early hepatic dysfunction (hyperlactemia, hyperammonemia, prolonged PT time), and normal restitution of liver mass. All FHF rats became comatose by 24 hours postoperatively. Most animals (90%) died within 24-48 hours postoperatively (mean, 39 +/- 11 hours). Changes in blood chemistry reflected rapid development of liver failure. Plasma HGF levels were markedly elevated and at all time points were higher than in PH controls (P < .05). At the same time, expression of HGF and c-met messenger RNA in the remnant liver was delayed. Plasma TGF-beta1 levels increased early (18 hours) and remained twofold to threefold higher than that of PH and SO controls (P < .05). There was only a 20% increase in the weight of the remnant liver lobes due to swelling. No hepatocytes stained positively for BrdU and PCNA, and none showed mitotic figures. In contrast, all PH controls showed vigorous liver regeneration. In conclusion, we have developed and characterized a novel model of FHF in rats that has a number of physiological and biochemical features seen clinically in FHF, including severely impaired ability of the residual liver tissue to regenerate.