Hepatic regeneration and growth factors

Role of estrogen in hepatocellular carcinoma: is inflammation the key?

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and accounts for the third-leading cause of cancer-related deaths. Over the past decades, advances have been made in the field of surgery, but effective treatment of HCC is lacking. Due to a marked male predominance in morbidity and mortality in HCC patients, it has long been considered that sex hormones play a role in HCC development. Recently estrogen has been proven to exert protective effects against HCC through IL-6 restrictions, STAT3 inactivation and tumour-associated macrophage inhibition. While IL-6-dependent STAT3 activation is considered a key event in inflammation-induced liver cancer, the anti-inflammation effect of estrogen is well documented. The roles of the estrogen receptor and aromatase and interactions between microRNAs and estrogen in HCC have been investigated. In this review, we present a novel model to elucidate the mechanism of estrogen-mediated inhibition of HCC development through an anti-inflammation effect and provide new insights into the roles of estrogen in liver disease.

Genomics of liver transplant injury and regeneration

While improved surgical techniques, post-operative care, and immunosuppression regimens have reduced morbidity and mortality associated with orthotopic liver transplantation (OLT), further improvement of outcomes requires personalized treatment and a better understanding of genomic mechanisms involved. Gene expression profiles of ischemia/reperfusion (I/R) injury, regeneration, and rejection, may suggest mechanisms for development of better predictive tools and treatments. The liver is unique in its regenerative potential, recovering lost mass and function after injury from ischemia, resection, and rejection. I/R injury, an inevitable consequence of perfusion cessation, cold storage, and reperfusion, is regulated by the interaction of the immune system, inflammatory cytokines, and reduced microcirculatory blood flow in the liver. Rejection, a common post-operative complication, is mediated by the recipient's immune system through T-cell-dependent responses activating proinflammatory and apoptotic pathways. Characterizing distinctive gene expression signatures for these events can identify therapies to reduce injury, promote regeneration, and improve outcomes. While certain markers of liver injury and regeneration have been observed in animals, many of these are unverified in human studies. Further investigation of these genomic signatures and mechanisms through new technology offers promise, but continues to pose a significant challenge. An overview of the current fund of knowledge in this area is reviewed.

The association between circulating oestradiol levels and severity of liver disease in males with hepatitis B virus infection

BACKGROUND

Males have a strikingly increased risk of advanced liver disease. This study was designed to investigate the association between sex hormone levels and different disease states in hepatitis B virus (HBV)-infected male patients.

METHODS

Two hundred and fifty-two male patients, including 30 with acute hepatitis B (AHB), 127 with chronic hepatitis B (CHB) and 95 with chronic severe hepatitis B (CSHB), and 48 healthy controls (HCs) were enroled in this study. All patients were followed for 4 months. The primary end point was in-hospital mortality at the end of 90 days. At study entry, a blood sample was collected from all subjects to examine liver function, renal function and sex hormone levels (serum total testosterone and oestradiol). A total of nine clinical chemistry and biochemical variables were analyzed for possible association with outcomes by using Cox proportional hazards and multiple regression models.

RESULTS

We demonstrated that in CSHB and CHB patients, oestradiol levels were significantly increased compared with HCs and AHB patients, whereas no significant differences were observed in AHB patients and HCs. All male patients had normal levels of testosterone which were not significantly different compared with those of HCs. Increased oestradiol levels were clinically associated with severe liver disease, and increased 3-month mortality rate. Multivariate analysis demonstrated that oestradiol and the model for end-stage liver disease (MELD) score were independent predictors for mortality (both P < 0.001).

CONCLUSION

Oestradiol levels are significantly increased in male patients with hepatitis B, and were associated with the severity of liver disease. Moreover, elevation of oestradiol is an independent predictive factor for the 3-month mortality rate in male patients with hepatitis B.

Tumor-specific expression of microRNA-26a suppresses human hepatocellular carcinoma growth via cyclin-dependent and -independent pathways

MicroRNA-26a (miR-26a) is a tumor suppressor that is reduced in hepatocellular carcinoma (HCC). Increasing evidence indicates that the liver is a hormone-responsive organ like the breast. The purpose of this study was to investigate whether miR-26a, regulated by a human α-fetoprotein (hAFP) and human telomerase reverse transcriptase (hTERT) dual promoter, could be specifically expressed in liver tumor cells to suppress their growth and to clarify whether estrogen receptor-α (ERα) is regulated by miR-26a and involved in the HCC process. Our data show that miR-26a expression driven by a hAFP-TERT dual promoter was tumor-specific and decreased the viability of tumor cells by regulating ERα, progesterone receptor (PR) and P53 except for cyclin D2 or cyclin E2 in vitro and in vivo. Our data also show that estradiol (E2) promotes the growth of liver cancer cells similar to breast cancer cells partly via the E2-ERα pathway and that miR-26a significantly down regulates ERα and prevents the stimulation of hepatoma cell growth by E2. These data suggest that ERα, which is regulated by miR-26a, is important for liver tumor cell growth. Moreover, hAFP-TERT dual promoter-mediated miR-26a expression could specifically exert potential antitumor activity and provide a novel targeting approach for cancer therapy.

Role of sex hormones in the modulation of cholangiocyte function

Over the last years, cholangiocytes, the cells that line the biliary tree, have been considered an important object of study for their biological properties which involves bile formation, proliferation, injury repair, fibrosis and angiogenesis. Cholangiocyte proliferation occurs in all pathologic conditions of liver injury where it is associated with inflammation and regeneration. During these processes, biliary cells start to secrete different cytokines, growth factors, neuropeptides and hormones which represent potential mechanisms for cross talk with other liver cells. Several studies suggest that hormones, and in particular, sex hormones, play a fundamental role in the modulation of the growth of this compartment in the injured liver which functionally conditions the progression of liver disease. Understanding the mechanisms of action and the intracellular pathways of these compounds on cholangiocyte pathophysiology will provide new potential strategies for the management of chronic liver diseases. The purpose of this review is to summarize the recent findings on the role of sex hormones in cholangiocyte proliferation and biology.

Sex hormones and risk of liver tumor

The liver is morphologically and functionally modulated by sex hormones. Long-term use of oral contraceptives (OCs) and anabolic androgenic steroids (AASs) can induce both benign (hemangioma, adenoma, and focal nodular hyperplasia [FNH]) and malignant (hepatocellular carcinoma [HCC]) hepatocellular tumors. Hepatic adenomas (HAs) are rare, benign neoplasms usually occurring in young women, the development and the complications of which have been related to the strength of OCs and the duration of their use. HA incidence has fallen since the introduction of pills containing smaller amounts of estrogens. FNH is a benign lesion, most commonly seen in young women, which is thought to represent a local hyperplastic response of hepatocytes to a vascular abnormality. Because of the female predominance and the young age at onset, a role of female hormones has been suggested. Furthermore, a large proportion of women with FNH (50-75%) are OC users. Liver hemangiomas (LHs) are the most common benign liver tumors and are seen more commonly in young adult females. The female predilection and clinical observations of LH growth under conditions of estrogenic exposure suggest a possible role for estrogen in the pathogenesis of LHs. HCC has become one of the most widespread tumors in the world in recent years, representing the sixth leading cancer and the third most common cause of death from cancer. Apart from liver cirrhosis, numerous other factors responsible for its onset have been proposed: hepatitis infections from virus B (HBV) and C (HCV), alcohol, smoking, and aflatoxin. However, regardless of etiology, chronic liver diseases progress at unequal rates in the two sexes, with the major sequelae, such as cirrhosis and HCC, being more frequent in men than in women. These epidemiological data have prompted researchers to investigate the relationship between sex hormones and liver tumors. The human liver expresses estrogen and androgen receptors and experimentally both androgens and estrogens have been implicated in stimulating hepatocyte proliferation and may act as liver tumor inducers or promoters.

Insights on augmenter of liver regeneration cloning and function

Hepatic stimulator substance (HSS) has been referred to as a liver-specific but species non-specific growth factor. Gradient purification and sequence analysis of HSS protein indicated that it contained the augmenter of liver regeneration (ALR), also known as hepatopoietin (HPO). ALR, acting as a hepatotrophic growth factor, specifically stimulated proliferation of cultured hepatocytes as well as hepatoma cells in vitro, promoted liver regeneration and recovery of damaged hepatocytes and rescued acute hepatic failure in vivo. ALR belongs to the new Erv1/Alr protein family, members of which are found in lower and higher eukaryotes from yeast to man and even in some double-stranded DNA viruses. The present review article focuses on the molecular biology of ALR, examining the ALR gene and its expression from yeast to man and the biological function of ALR protein. ALR protein seems to be non-liver-specific as was previously believed, increasing the necessity to extend research on mammalian ALR protein in different tissues, organs and developmental stages in conditions of normal and abnormal cellular growth.

Expression of augmenter of liver regeneration (ALR) in human liver cirrhosis and carcinoma

AIMS

To determine the expression of a protein termed augmenter of liver regeneration (ALR), recently found to have a specific and beneficial effect on the process of liver regeneration in normal and diseased human liver.

METHODS AND RESULTS

ALR expression in normal and cirrhotic human livers with various underlying diseases as well as in tissue samples of hepatocellular carcinoma (HCC) and cholangiocellular carcinoma (CCC) was analysed by immunohistochemistry and quantitative reverse transciptase-polymerase chain reaction (RT-PCR). Expression analysis of ALR in total liver protein extracts by Western blotting showed mainly dimeric ALR protein. Immunohistochemically, cytosolic and perinuclear immunosignals were found in hepatocytes and cholangiocytes in normal, cirrhotic or cancerous liver tissue and only weak signals in some endothelial cells in normal livers. Quantitative mRNA analysis revealed significantly increased ALR expression in cirrhosis compared with normal liver tissue. In HCC and CCC ALR mRNA expression was also significantly enhanced compared with normal liver tissue, but expression levels did not differ from the matching non-neoplastic tissue in the same patient.

CONCLUSIONS

The findings suggest an important role for ALR in hepatocellular regeneration in liver cirrhosis as well as in hepatocarcinogenesis and therefore its potential value in the clinical diagnosis of hepatic cirrhosis and cancer.

Influence of ursodeoxycholate-enriched diet on liver tumor growth in HBV transgenic mice

Hepatitis B virus (HBV) transgenic mice (official designation, Tg [Alb-1 HBV] Bri 44) invariably develop macroscopically evident tumors within the 20th month of life. Sustained proliferative activity seems to play an important role in the development of these lesions. We previously showed that ursodeoxycholate (UDC) stimulates hepatocyte proliferation in various experimental settings. Herein, we tested the assumption that biological factors able to further increase liver cell proliferation, such as UDC, could accelerate tumor development in this animal model. For this study, 22 eight-week-old male transgenic mice were divided into 2 groups; 11 animals received a standard diet, and 11 received a UDC-enriched diet. The 2 groups were further divided into 2 subgroups of 5 and 6 animals each and were sacrificed at 3 and 15 months of age, respectively. These different times were chosen to exclude diet-related toxicity (in 3-month-old mice) and evaluate tumor growth (in 15-month-old mice). In addition, hepatocyte proliferation was assessed in all animals. In 3-month-old mice receiving UDC, cholestatic and cytolytic indices as well as liver histology were comparable to those in controls. At 15 months, all UDC-treated mice showed large multinodular tumors whereas only 33% of controls developed smaller uninodular neoplasms. Hepatocyte proliferation was increased in all animals receiving UDC compared with controls. In conclusion, the increase in serum UDC (undetectable in mice fed a standard diet), in the absence of any toxic effect on the liver, suggests the involvement of this bile salt in the stimulation of hepatocyte proliferation and tumor growth.

Sex hormones and liver cancer

Hepatocellular carcinoma (HCC) is one of the most common malignancy in the world and it usually occurs in individuals with chronic liver disease. The neoplasm is predominant in the male gender, where it is characterized also by a worst prognosis than in females. The pathogenesis of HCC is obscure. Because of its striking male predominance, androgens have been investigated as potential factors able to induce or at least promote hepatic carcinogenesis; this hypothesis has been also supported by the ability of androgens of inducing liver neoplasms in experimental models. On the other hand, due to the fact that HCC occurs predominantly in male cirrhotics who present a characteristic hormone imbalance with a relative hyperestrogenic state, the potential role of estrogen in liver cancer has been studied as well. In this paper, the potential role of sex hormones in liver carcinogenesis has been reviewed.

Regenerative capacities of normal and cirrhotic livers following 70% hepatectomy in rats and the effect of alpha-tocopherol on cirrhotic regeneration

BACKGROUND

The regeneration of normal and cirrhotic liver has been very well demonstrated after partial hepatectomy; although the tissue regenerated by cirrhotic liver is also cirrhotic. The structural differences of the regenerated tissues between normal and cirrhotic livers may also indicate different regeneration capacities. The objective of this study was to compare the regeneration capacities of normal and cirrhotic livers by bromodeoxyuridine (BrdU) incorporation and proliferating cell nuclear antigen (PCNA) labeling indices in replicating nuclei and mitotic figures in cells in partially hepatectomized normal and cirrhotic rats and to study the effect of alpha-tocopherol on cirrhotic liver regeneration.

METHODS

Five groups of adult Wistar rats comprised normal livers, cirrhotic livers, regenerated normal livers, regenerated cirrhotic livers, and alpha-tocopherol-treated regenerated cirrhotic livers. Cirrhosis was induced by intragastric administration of carbon tetrachloride and phenobarbital in the drinking water of the rats. Liver regeneration capacities in normal and cirrhotic rats and following partial hepatectomy in normal and cirrhotic rats and cirrhotic rats that were administered alpha-tocopherol were evaluated through BrdU incorporation, PCNA labeling, and mitotic indices.

RESULTS

BrdU and PCNA labeling and mitotic indices were zero for normal rats and 4.3 +/- 3.5, 6.5 +/- 5, and 2.5 +/- 1.5 for cirrhotic rats, respectively. The values after partial hepatectomy in normal and cirrhotic rats were 46.2 +/- 8.7 and 27.8 +/- 7.5 for BrdU labeling, 83.7 +/- 6.5 and 51.3 +/- 6.8 for PCNA labeling, and 31.8 +/- 4.2 and 18.6 +/- 3.4 for mitotic index, respectively. For the fifth group comprising cirrhotic rats that were administered alpha-tocopherol and had undergone partial hepatectomy, BrdU incorporation, PCNA labeling, and mitotic indices were 37.5 +/- 6.3, 76.5 +/- 6.2, and 27.2 +/- 4.2, respectively. When the cirrhotic liver regeneration group was compared with the normal liver regeneration group, rates of liver regeneration in the cirrhotic group were significantly depressed (P < 0.01). Although the BrdU incorporation and PCNA labeling indices of the alpha-tocopherol-administered cirrhotic liver regeneration group indicated significantly lower rates of liver regeneration when compared with the normal liver regeneration group (P < 0.05), the liver regeneration rates of the alpha-tocopherol-administered cirrhotic group were also significantly higher than those of the cirrhotic liver regeneration group that was not administered alpha-tocopherol (P < 0.01).

CONCLUSIONS

Cirrhotic livers revealed a significantly depressed capacity for regeneration following partial hepatectomy. alpha-Tocopherol administration seemed to improve the rates of regeneration in cirrhotic rats with respect to the BrdU incorporation, PCNA labeling, and mitotic indices.

Molecular mechanisms of augmenter of liver regeneration as immunoregulator: its effect on interferon-gamma expression in rat liver

BACKGROUND

We have shown that the administration of exogenous Augmenter of Liver Regeneration protein in intact rats i) regulates mitochondrial gene expression by inducing the transcription and translation of the nuclear-encoded mitochondrial transcription factor A, and ii) inhibits the lytic activity of liver-resident Natural Killer cells.

AIMS

The present investigation was carried out to study the effect, in intact rats, of exogenous administration of Augmenter of Liver Regeneration protein on Interferon-gamma, a cytokine produced by activated Natural Killer cells and known to control the expression of mitochondrial transcription factor A, a nuclear gene responsible for mitochondrial metabolism.

METHODS

Interferon-gamma was measured as messenger RNA in liver-derived mononuclear leukocytes and as protein in liver-derived Natural Killer cells after a single injection of Augmenter of Liver Regeneration protein.

RESULTS

The data obtained demonstrate that: i) in intact rats, Augmenter of Liver Regeneration protein administration induces a reduction of Interferon-gamma in the liver-resident Natural Killer cells and ii) the administration of Interferon-gamma in 70% hepatectomized rats is followed by a significant reduction both of the mitochondrial transcription factor A expression and of liver regeneration.

CONCLUSIONS

These data demonstrate the pivotal role of Augmenter of Liver Regeneration as Growth Factor and as immunoregulator by controlling, through Interferon-gamma levels, the mitochondrial transcription factor A expression and the lytic activity of liver-resident Natural Killer cells.

A mutant for the yeast scERV1 gene displays a new defect in mitochondrial morphology and distribution

The yeast scERV1 gene is the best characterized representative of a new gene family found in different lower and higher eukaryotes. The gene product is essential for the yeast cell and has a complex influence on different aspects of mitochondrial biogenesis. The homologous mammalian ALR(Augmenter of Liver Regeneration) genes from man, mouse and rat are important at different developmental stages of the organism as, for example, in spermatogenesis and liver regeneration. In this study the influence of scERV1 on the morphology of mitochondria and its submitochondrial localization are investigated. A temperature-sensitive mutant of the gene was stained with a mitochondria-specific dye and fluorescence was inspected at the permissive and restrictive temperature. A new phenotype for morphological defects of mitochondria was identified. Already at the permissive temperature mitochondrial vesicles accumulate at defined positions in the cell. After shift to the restrictive temperature, morphological changes, and finally complete loss of mitochondrial structures, are observed. Ultrastructural studies confirm these findings and demonstrate the loss of the mitochondrial inner membrane and at the final stage a drastic reduction or complete absence of mitochondria from the cell. GFP fusion experiments with the scERV1 gene and subcellular localization by fractionation experiments identify the gene product inside mitoplasts and the cytosol. Re-investigation of the mutant phenotype demonstrates that after longer incubation of the mutant at the restrictive temperature an irreversible defect of the cells, even on glucose complete medium, is found that is in accordance with a complete loss or irreversible damage of mitochondria.

A fresh look at augmenter of liver regeneration in rats

Augmenter of liver regeneration (ALR) is a hepatotrophic protein originally identified by bioassay in regenerating rat and canine livers following partial hepatectomy and in the hyperplastic livers of weanling rats, but not in resting adult livers. The ALR gene and gene product were subsequently described, but little is known about the cellular/subcellular sites of ALR synthesis in the liver, or about the release and dissemination of the peptide. To obtain this information in rats, we raised antibodies in rabbits against rat ALR for development of an enzyme-linked immunosorbent assay (ELISA). ALR concentrations were then determined in intact livers of unaltered weanling and adult rats; in regenerating residual liver after partial hepatectomy; in cultured hepatocytes and nonparenchymal cells (NPCs); and in culture medium and serum. ALR in the various liver cells was localized with immunohistochemistry. In addition, hepatic ALR and ALR mRNA were assayed with Western blotting and reverse-transcriptase polymerase chain reaction (RT-PCR), respectively. The hepatocyte was the predominant liver cell in which ALR was synthesized and stored; the cultured hepatocytes secreted ALR into the medium in a time-dependent fashion. Contrary to previous belief, the ALR peptide and ALR mRNA were present in comparable concentrations in the hepatocytes of both weanling and resting adult livers, as well as in cultured hepatocytes. A further unexpected finding was that hepatic ALR levels decreased for 12 hours after 70% hepatectomy in adult rats and then rose with no corresponding change in mRNA transcripts. In the meantime, circulating (serum) ALR levels increased up to 12 hours and declined thereafter. Thus, ALR appears to be constitutively expressed in hepatocytes in an inactive form, and released from the cells in an active form by unknown means in response to partial hepatectomy and under other circumstances of liver maturation (as in weanling rats) or regeneration.

Levels of hepatic stimulator substance in liver regenerating process of partially hepatectomized rats pretreated with a single dose of carbon tetrachloride

Liver regeneration after injury with carbon tetrachloride (CCl4) followed by partial hepatectomy is a complex model involving toxicological, inflammatory, and necrotic processes. In the present study, the time-course of hepatic regenerative process was investigated in relation to hepatic stimulator substance (HSS) activity, administration of a single dose of CCl4 and partial (70%) hepatectomy in male rats. To evaluate liver injury events, the levels of serum aspartic aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) were measured. Hepatic DNA synthesis reached a maximum at 36 hr after hepatectomy in contrast to the reported 24-hr and 32-hr peaks observed in nontreated hepatectomized rats. On the other hand, HSS activity appeared to peak at 28, 40, and 44 hr after hepatectomy in CCl4-treated rats, and it was quite a lot lower at 24, 32, 36, 48, and 60 hr. The hypothesis that HSS promotes liver regeneration but it does not initiate it, as other factors have been found to do, is discussed.

Zinc and metallothioneins on cellular immune effectiveness during liver regeneration in young and old mice

Partial hepatectomy in young mice (pHx) induces thymic atrophy, disregulation of thymocytes subsets and a strong accumulation of zinc in thymic tissue after 1-2 days of liver regeneration. Zinc is relevant for good immune functioning. Restoration of zinc into both the thymus and thymocytes subsets in the late period of liver regeneration is observed in young pHx mice. These findings have suggested a link between the thymus and the liver influencing T-cell functions and involving zinc. This kind of link could be relevant in aging because thymic involution, negative crude zinc balance and crippled immune functions are constant events. The preminence of a liver extrathymic T-cell pathway after pHx or during aging has been suggested. Thus the study of pHx in young and old mice may offer a good model to better understand the role played both by thymic involution and by liver extrathymic T-cell pathway and the role of zinc in these physiological processes during aging. Young pHx mice after 1-2 days of liver regeneration show: reduced thymic endocrine activity, increment of double negative (DN) thymocytes subsets, impairment of peripheral immune efficiency (PHA, NK activity and IL-2) and negative crude zinc balance, which are all restored in the late period of liver regeneration. By contrast the thymic and peripheral immune defects and the negative crude zinc balance, already present in old sham mice, are not modified during liver regeneration in old pHx mice. Circulating leukocytes and lymphocytes are not significantly modified both in young and old pHx mice as compared to respective sham controls. Zinc may also be crucial for extrathymic T-cells pathway, being preminent in aging, rather than in young age, due to its metallothioneins (MT) binding capacity. MT are significantly increased in young pHx and in aging inducing a low zinc-free quota for thymic and peripheral immune efficiency in young pHx mice, and for extrathymic T-cell pathway, in old age. Thus low zinc bioavailability, due to MT, may play a pivotal role, not only for thymocytes but also for liver extrathymic T-cell pathway.

The in vivo effect of hepatotrophic factors augmenter of liver regeneration, hepatocyte growth factor, and insulin-like growth factor-II on liver natural killer cell functions

Fine balanced sequential changes of the levels of circulating hepatotrophic factors are essential for normal liver regeneration. Our recent studies have indicated that liver-resident natural killer (NK) cells are important regulators of liver regeneration and have raised the possibility that hepatotrophic factors might mediate their activities through NK cells. In the present study, we assessed the effects of in vivo administration of three hepatotrophic factors (augmenter of liver regeneration [ALR], insulin-like growth factor-II [IGF-II], and hepatocyte growth factor [HGF]) on NK cells in normal rats. Each of the three, given over a 1-day period in doses known to produce hepatotrophic activity, induced inhibition of NK cell cytotoxic activities in the population of mononuclear leukocytes (MNL) in the liver, but not in MNL from the spleen or peripheral blood. In contrast to these results obtained by the whole animal treatment, the three molecules had no effect on NK cell functions when added to cultures of MNL from the livers, spleens, or blood of untreated rats. These data support and extend our previously advanced hypothesis that ALR and other hepatotrophic factors play an important role in liver regeneration by regional regulation of NK cells through some as-yet-unknown intermediary mechanism.

The in vivo effect of hepatotrophic factors augmenter of liver regeneration, hepatocyte growth factor, and insulin-like growth factor-II on liver natural killer cell functions

Fine balanced sequential changes of the levels of circulating hepatotrophic factors are essential for normal liver regeneration. Our recent studies have indicated that liver-resident natural killer (NK) cells are important regulators of liver regeneration and have raised the possibility that hepatotrophic factors might mediate their activities through NK cells. In the present study, we assessed the effects of in vivo administration of three hepatotrophic factors (augmenter of liver regeneration [ALR], insulin-like growth factor-II [IGF-II], and hepatocyte growth factor [HGF]) on NK cells in normal rats. Each of the three, given over a 1-day period in doses known to produce hepatotrophic activity, induced inhibition of NK cell cytotoxic activities in the population of mononuclear leukocytes (MNL) in the liver, but not in MNL from the spleen or peripheral blood. In contrast to these results obtained by the whole animal treatment, the three molecules had no effect on NK cell functions when added to cultures of MNL from the livers, spleens, or blood of untreated rats. These data support and extend our previously advanced hypothesis that ALR and other hepatotrophic factors play an important role in liver regeneration by regional regulation of NK cells through some as-yet-unknown intermediary mechanism.

The effect of the pineal gland on liver regeneration in rats

BACKGROUND/AIMS

We investigated the influence of pinealectomy on liver regeneration after partial hepatectomy in rats.

METHODS

Thirty rats were allocated into four groups as follows: group 1 in which no operation was done (control), group 2 in which only midline scalp incision and craniotomy was performed (sham operation), group 3 in which pinealectomy was performed and group 4 in which the rats underwent pinealectomy and pineal transplantation. Eight weeks later all the rats underwent 70% hepatectomy.

RESULTS

Hepatic regenerative capacity was observed 24 h after PH by bromodeoxyuridine incorporation into DNA and the mitotic index of hepatocytes. The bromodeoxyuridine labeling indices were 45.4, 35.8, 19.9 and 36.8 in groups 1, 2, 3 and 4, respectively. The mitotic indices of the same groups were 31.2, 28.7, 8.3 and 13.4, respectively. Both the bromodeoxyuridine labeling and mitotic indices were significantly lower in the pinealectomized rats than in the control and sham operation groups.

CONCLUSIONS

These results suggest that the pineal gland stimulates liver regeneration after partial hepatectomy in rats.

Cloning and sequence analysis of the rat augmenter of liver regeneration (ALR) gene: expression of biologically active recombinant ALR and demonstration of tissue distribution

A full-length cDNA clone encoding a purified augmenter of liver regeneration (ALR) factor prepared from the cytosol of weanling rat livers was isolated. The 1.2-kb cDNA included a 299-bp 5' untranslated region, a 375-bp coding region, and a 550-bp 3' untranslated region. It encoded a protein consisting of 125 amino acids. The molecular weight of ALR calculated from the cDNA was 15,081, which is consistent with the size estimated by SDS/PAGE under reducing conditions. The molecular weight of the purified native ALR estimated by SDS/PAGE under nonreducing conditions was approximately 30,000; thus ALR apparently has a homodimeric structure. The recombinant ALR produced by expression of the cDNA in COS cells was tested in vivo in the canine Eck fistula model and found to have potency equivalent to the purified native ALR. The 125-aa sequence deduced from the rat ALR cDNA shows 50% homology to the amino acid sequence of the gene for oxidative phosphorylation and vegetative growth in the yeast Saccharomyces cerevisiae.