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PubMed1991

Kupffer cell tumor necrosis factor-alpha production is suppressed during liver regeneration.

Mammalian liver regeneration following resection invokes intrinsic hepatic responses which result in rapid tissue repair. The role of soluble immune cytokines in this phenomenon is not known. The capacity of Kupffer cells (KC) from regenerating liver to produce the potent cytokine TNF-alpha was evaluated. Twenty-four hours after 70% partial hepatectomy (PHx) or sham operation, Kupffer cells were harvested from collagenase-digested Wistar-Furth rat livers and purified (greater than 95% by phagocytosis) by adherence. Following overnight culture with or without the cyclooxygenase inhibitor indomethacin (10 microM), 5 x 10(5) KC were repleted with fresh media with or without 2.5 micrograms/ml lipopolysaccharide (LPS). Supernatant TNF-alpha activities (units/ml) were measured using the L929 fibroblast lysis assay. With LPS, sham KC TNF-alpha levels were significantly higher (P less than 0.001) than those for PHx KC. Indomethacin significantly increased PHx KC TNF-alpha levels, but did not affect those for sham KC, suggesting autoregulation by arachidonic acid cyclooxygenase metabolites following PHx. We conclude that KC TNF-alpha production is suppressed following PHx by a mechanism apparently regulated by eicosanoid metabolism. During the stress of hepatic regeneration, a coordinated limitation of excessive TNF-alpha responses by PHx liver KC may naturally protect the host.

Animals↗
PubMed1993

Cyclin and cyclin-dependent kinase 1 mRNA expression in models of regenerating liver and human liver diseases.

There is compelling evidence that the eukaryotic cell cycle is controlled by a family of proteins called cyclins, which complex with cyclin-dependent kinases (CDK) to modulate key events during cell division. We have examined the regulation of these genes in models of experimental liver regeneration and their expression in human liver diseases. Seventy percent partial hepatectomy (PH) was performed on rats and normal BALB/c and athymic nude mice to determine patterns of cyclin and CDK1 mRNA expression. It has been previously shown by [3H]thymidine incorporation that athymic nude mice manifest impaired regeneration after PH. Our results demonstrate a sequential pattern of cyclin and CDK1 transcript expression in each of the models. Cyclin D1 was the most abundant mRNA steady-state transcript in the regenerating livers. CDK1 and cyclins associated with later stages of the cell cycle showed delayed and diminished expression in nude mice compared with normals. Nuclear run-off assays performed at key time points post-PH revealed little change in transcription rates, suggesting that steady-state mRNA expression of the cyclin genes is regulated primarily by posttranscriptional events. Human liver tissue from various acute and chronic hepatic diseases showed increased expression of cyclins A and D1. We conclude that the regenerating liver post-PH offers an excellent in vivo model for studying cyclin and CDK gene expression. Impaired regeneration in the nude mouse is associated with altered cyclin and CDK1 mRNA transcript expression. Furthermore, cyclins may eventually provide clinically relevant molecular markers of regenerative activity in human liver diseases.

Adolescent↗
PubMed1992

[The kinetic changes in murine lymphocyte subsets in regenerating liver].

The regeneration of the liver is frequently observed after the resection of liver tumor and partial liver transplantation, and it is assumed that the modification of the hematolymphoid system in the liver will occur during this process and influence not only the progress of the primary disease but also liver regeneration itself. In this study, we investigated by flow cytometric analysis the modification of the cell subpopulation in the peripheral blood lymphocytes (PBL), intrahepatic lymphocytes fraction 1, which come into marginal contact with the liver (IHL Fr. 1), and intrahepatic lymphocytes fraction 2, which come into close contact with the liver (IHL Fr.2). (1) The positive cells of each antigen (Thy 1.2, alpha beta TCR, gamma delta TCR, CD4 and CD8) exist in the normal liver as PBL. (2) CD8/CD4 ratio is 0.3-0.4 in PBL and IHL Fr.1 and significantly higher in IHL Fr.2 (0.7). (3) Compared with other fractions, the ratio of alpha beta TCR dull positive cells to whole alpha beta TCR positive cells is low, while (4) the percentage of gamma delta TCR positive cells is high in IHL Fr.2. These facts suggest that lymphocyte populations in the liver differ from those of PBL. Furthermore, one day after partial hepatectomy, (5) the percentage of the alpha beta TCR dull positive cells decreases in PBL, but remarkably increases to 2.6 times the normal level in IHL Fr.2 and (6) the ratio of CD8/CD4 increases to 1.4 times in IHL Fr.2. (7) The percentage of gamma delta TCR positive cells decreases in PBL, but does not significantly change in IHL Fr. 2 during the liver regeneration. These findings reveal that lymphocyte populations different from PBL exist in the liver and respond to stimulus to the liver in different ways from PBL. The mechanism for the modification occurring in the IHL population during liver regeneration and its biological significance are discussed.

Animals↗
PubMed2002

The mystery of liver regeneration.

BACKGROUND: Partial hepatectomy is the strongest stimulator of hepatic regeneration. The process of initiation and the control of the final size of the regenerated liver have been the subject of research for many years. A better understanding of this process and the effect of disease may allow better selection of patients for partial hepatectomy. It may also allow an insight into the possible application of clinical stimulation of regeneration. METHODS: Data were reviewed from the published literature using the Medline database. RESULTS: Most knowledge comes from in vitro studies and the study of resection in the rat model. A variety of cytokines, hormones and growth factors are involved in regeneration but very few have been found capable of stimulating regeneration in vitro. The exact interactions are not known, but there is probably a cascade involving different factors at differing stages of regeneration. CONCLUSION: Further in vivo research should allow greater understanding of liver regeneration, thereby providing a potential therapeutic tool in patients for whom regeneration has failed, or is likely to fail. Such research is also important in respect of liver support devices, which may inhibit liver regeneration by filtration of many of the factors involved.

Cytokines↗
PubMed1995

Strain-dependent differences in DNA synthesis and gene expression in the regenerating livers of CB57BL/6J and C3H/HeJ mice.

C3H/HeJ (C3H) mice are approximately 50-fold more susceptible to liver-tumor induction than C57BL/6J (B6) mice. This difference is susceptibility is a consequence of allelic differences in hepatocarcinogen sensitivity (Hcs) genes that control the growth of preneoplastic lesions in the liver. We have shown previously that these two strains differ in their responses to partial hepatectomy, which acts as a promoter of hepatocarcinogenesis in B6 mice but not in C3H mice. To determine whether there are also strain-specific differences in normal regulation of hepatic growth, we compared liver regeneration in C3H and B6 mice at the levels of DNA synthesis and gene expression. Partial hepatectomy induced a cascade of controlled events resulting in the regeneration of the liver to its original mass 11 d after surgery. We observed a two-fold greater level of DNA synthesis in C3H mice relative to B6 mice during the first peak of DNA synthesis, which occurred 35 h after hepatectomy in both strains. While the c-fos transcript was readily induced in both strains, there was a reduction in the expression of the late response genes E2F1 and dihydrofolate reductase in the livers of B6 mice when compared with the expression of these transcripts in the livers of C3H mice. The differential regulation of E2F1 between B6 and C3H mice may indicate that the Hcs genes and E2F1 function in the same signal transduction pathway of normal growth control.

Animals↗
PubMed2006

Involvement of the tyrosine phosphatase early gene of liver regeneration (PRL-1) in cell cycle and in liver regeneration and fibrosis effect of halofuginone.

Tyrosine phosphatase PRL-1 is one of the immediate-early genes up-regulated during liver regeneration and is apparently involved in cell proliferation. Previously, we have demonstrated that halofuginone, an inhibitor of collagen type I synthesis, prevents liver fibrosis and improves cirrhotic liver regeneration. In this study, we evaluated the effect of halofuginone on PRL-1 expression, its cellular localization in vitro and during liver regeneration, and fibrosis progression in vivo. In culture, halofuginone increased PRL-1 expression in primary rat hepatocytes and in hepatocellular carcinoma (HCC) cell lines, the former being more sensitive to halofuginone. The halofuginone-dependent increase in PRL-1 gene expression was correlated with an increase in the transcription factor early growth response-1 (Egr-1) and inversely correlated with the inhibition of cell proliferation. Halofuginone arrested HepG2 and Huh7 cell lines at the G1 phase, whereas Hep3B cells were arrested at G2/M, probably because of a reduction in the synthesis of cyclins D1 and B1 in all HCC cells and increased cyclin A in Hep3B cells. Halofuginone also affected the PRL-1 sub-cellular localization that was cell-cycle-dependent. In addition, halofuginone augmented PRL-1 expression in the remnant liver after partial hepatectomy and in chemically induced fibrosis in rats; this was accompanied by increased expression of insulin-like growth factor binding protein 1 (IGFBP-1), another immediate-early gene of regeneration. The regulation of the expression of the early genes of regeneration such as PRL-1 and IGFBP-1 is thus part of the mode of action of halofuginone and results in the prevention of liver fibrosis and improved cirrhotic liver regeneration.

Animals↗
PubMed1994

Metallothionein expression during liver regeneration after partial hepatectomy in cadmium-pretreated rats.

Metallothionein is a low molecular mass protein inducible mainly by heavy metals, having high affinity for binding cadmium, zinc and copper. In the present study we investigated the expression of metallothionein in regenerating liver, at different time intervals, in cadmium pretreated partially hepatectomized rats. Liver metallothionein is highly expressed during regeneration induced by partial hepatectomy in rats, providing zinc within the rapidly growing tissue. Cadmium pretreatment caused inhibition of the first peak of liver regeneration, while metallothionein expression was markedly more prominent in the liver residues of cadmium-pretreated rats. These results demonstrate that although metallothionein able to bind temporarily metal ions as zinc and cadmium has been highly expressed, the liver regenerative process was inhibited possibly due to the effects of cadmium on other pivotal events necessary to the DNA replication.

Animals↗
PubMed2006

Disruption of the middle hepatic vein is not crucial for liver regeneration of the remnant liver after right hemihepatectomy for hepatic tumors.

BACKGROUND: To clarify the role of the middle hepatic vein (MHV) in liver regeneration of the remnant liver after right hemihepatectomy for hepatic tumors, we reviewed 29 patients to evaluate liver regeneration for up to 12 postoperative months. METHODS: Volume regeneration of the remnant liver was investigated by computed tomography at 3, 6, and 12 postoperative months. The remnant liver was divided into the following three areas: the medial section (segment IV), the lateral section (segments II and III), and segment I. The patients were divided into two groups: group A (n = 17), in which the MHV was preserved in the remnant liver, and group B (n = 12), in which the MHV was removed. RESULTS: Volume regeneration of each area continued until 6 postoperative months but did not increase thereafter. On univariate analysis, differences in the volume regeneration of each area between the groups were not significant at any measured time point. Furthermore, disruption of the MHV was determined to not be crucial to the volume regeneration of any liver area on multivariate analysis. Only the resection volume (percentage) significantly affected liver regeneration of the remnant liver. CONCLUSIONS: Disruption of the MHV does not decisively affect liver regeneration of remnant liver after right hemihepatectomy for hepatic tumors.

Female↗
PubMed2006

Platelet-derived serotonin mediates liver regeneration.

The liver can regenerate its volume after major tissue loss. In a mouse model of liver regeneration, thrombocytopenia, or impaired platelet activity resulted in the failure to initiate cellular proliferation in the liver. Platelets are major carriers of serotonin in the blood. In thrombocytopenic mice, a serotonin agonist reconstituted liver proliferation. The expression of 5-HT2A and 2B subtype serotonin receptors in the liver increased after hepatectomy. Antagonists of 5-HT2A and 2B receptors inhibited liver regeneration. Liver regeneration was also blunted in mice lacking tryptophan hydroxylase 1, which is the rate-limiting enzyme for the synthesis of peripheral serotonin. This failure of regeneration was rescued by reloading serotonin-free platelets with a serotonin precursor molecule. These results suggest that platelet-derived serotonin is involved in the initiation of liver regeneration.

5-Hydroxytryptophan↗
PubMed2005

Metal tissue kinetics in regenerating liver, thymus, spleen, and submandibular gland after partial hepatectomy in mice.

Liver regeneration after partial hepatectomy (pHx) is a well-defined process, which involves the concerted action of extra- and intracellular factors resulting in induction of cell replication and its inhibition at the time when the entire liver mass is restored. Concomitantly, the breakdown of previously maintained tolerance and the exposure of self-antigens lead to the activation of preimmune and immune repertoires, which participate in surveillance against aberrant cells and the re-establishment of previous morphostasis. Because, in these events, important biological function might have tissue minerals that are affecting the structural integrity and enzyme activities, transduction signals, transcription and replication factors during cell proliferation and apoptosis, as well as the development and maintenance of immune functions and cytokine production, in this study we analyzed tissue dynamics of zinc, iron, magnesium, and calcium in the liver, thymus, spleen, and submandibular gland in intact and pHx mice on the 1st, 2nd, 7th, and 15th d after one-third pHx, using microwave digestion and inductivity coupled plasma spectrometry. The data showed that pHx induces significant and interconnected changes in all of the estimated metals not only in the regenerating liver but also in the lymphatic tissues and submandibular gland, indicating their importance for the control of growth processes.

Animals↗
PubMedDate not supplied

Poly(ADP-ribose) polymerase activity in regenerating liver of hypothyroid rats.

The role of PARP, a nuclear enzyme involved in DNA synthesis, repair and cell transformation, was studies during liver regeneration in hypothyroid animals. Hypothyroidism was induced by in vivo administration of propylthiouracil. In regenerating euthyroid animals PARP activity is stimulated showing an early and significant increase at 1.5 h with a maximum at 6 h after partial hepatectomy. Such an increase returns to control values within 18 h preceding the onset of DNA synthesis. A markedly different behavior, with respect to euthyroids, has been evidenced in hypothyroid rats. At first, liver PARP level was about 2-fold higher in non regenerating hypothyroid rats with respect to control euthyroids. During regeneration, PTU-treated animals show a net decrease in PARP activity, with a minimum at 6-9 h after partial hepatectomy. The activity returns to control levels within 24 days. The minimum in PARP activity anticipates, also in this case, the onset of DNA synthesis, which exhibits a maximum at 15-18 h. During liver regeneration PARP activity shows modifications related to the beginning of de novo DNA synthesis. Furthermore, these variations in turn undergo the effects of hypothyroidism.

Animals↗
PubMed2000

Liver regeneration.

The liver can precisely regulate its growth and mass. Surgical resection of hepatic lobes or hepatocyte loss caused by viral or chemical injury triggers hepatocyte replication while enlarged liver mass is corrected by apoptosis. Hepatocytes have a great replicative capacity and are capable of repopulating the liver. However, "stem-like" cells proliferate when hepatocyte replication is blocked or delayed. Detailed studies of the mechanisms that regulate liver growth have been done in animals subjected to partial hepatectomy or chemical injury. Substantial progress has been achieved using appropriate transgenic and knockout mouse models for this work. Gene expression in the regenerating liver can be divided into several phases, starting with expression of a large number of immediate early genes. Hepatocytes need to be primed before they can fully respond to the growth factors HGF (Hepatocyte Growth Factor), TGFalpha (Transforming Growth Factor Alpha), and EGF (Epidermal Growth Factor) in vitro. Priming requires the cytokines TNF and IL-6 in addition to other agents that prevent cytotoxicity. Reactive Oxygen Species and glutathione content can determine whether the TNF effect on hepatocytes is proliferative or apoptotic. At least four transcription factors, NFkappaB, STAT3 (which are strongly induced by TNF), AP-1 and C/EBPbeta play major roles in the initiation of liver regeneration. In addition, extensive remodeling of the hepatic extracellular matrix occurs shortly after partial hepatectomy. Progression through the cell cycle beyond the initiation phase requires growth factors. The expression of Cyclin D1 probably establishes the stage at which replication becomes growth factor-independent and autonomous. Knowledge about the mechanisms of liver regeneration can now be applied to correct clinical problems caused by deficient liver growth.

Animals↗
PubMed1995

Liver regeneration. 2. Role of growth factors and cytokines in hepatic regeneration.

During liver regeneration quiescent hepatocytes undergo one or two rounds of replication and then return to a nonproliferative state. Growth factors regulate this process by providing both stimulatory and inhibitory signals for cell proliferation. EGF, TGF alpha, and HGF stimulate DNA synthesis in hepatocytes in vivo and in culture but the sensitivity of cultured hepatocytes to the mitogenic effects of these factors is much higher than that of quiescent hepatocytes in intact livers. We have proposed that after partial hepatectomy, hepatocytes enter a state of replicative competence ("priming") before they can fully respond to growth factors. The priming step is an initiating event in liver regeneration that involves the activation and DNA binding of NF-kappa B and other transcription factors, which could be induced by TNF or other cytokines. EGF, TGF alpha, and HGF have major effects on liver growth. TGF alpha expression correlates with hepatocyte DNA synthesis during liver development and growth and the constitutive expression of the factor confers proliferative activity to adult hepatocytes in vivo and in culture. The data indicate that the activity of stimulatory and inhibitory growth factors such as TGF beta 1 and activin is low in normal livers but that the expression of both types of factors increase during liver regeneration.

Adult↗
PubMed1992

[Down-regulation of liver regeneration by LAK cells--a study for effect of neuraminidase treated LAK cells on liver regeneration].

Both effect of LAK cells and neuraminidase treated LAK (N-LAK) cells on liver regeneration were investigated after 70% partial hepatectomy in mice. Intravenous transfusion of LAK cells suppressed the liver regeneration depending on cell numbers injected. N-LAK cells accumulated into regenerating liver 1.7 times in cell number compared with LAK cells. Injection of 5 x 10(7) LAK cells and N-LAK cells into hepatectomized mice suppressed the liver regeneration by 16.5% and 53.8% respectively. These results indicated that suppression of the liver regeneration by LAK cells was dependent upon the number of injected LAK cells and the degree of accumulation of LAK cells into the liver, namely, LAK cells down-regulate the regeneration of liver cells in the micro-milieu.

Animals↗
PubMedDate not supplied

Liver regeneration and restoration of liver function after partial hepatectomy: the relation of fibrosis of the liver parenchyma.

BACKGROUND/AIMS: Patients who survive partial hepatectomy sometimes have unsatisfactory liver regeneration and restoration of liver function. Although the extent of resection should be adjusted to attain favorable liver regeneration and restoration of liver function, a guiding principle for this has not been established. METHODOLOGY: Seventy patients with hepatic tumors associated with liver disorders of various severity who underwent hepatectomy were studied. We calculated the removal rate of the liver and the regeneration rate of the remnant liver using computed tomography. The liver function was investigated using ICG R-15 (retention rate of indocyanine green). Liver disorder was classified into 4 groups, according to the severity of fibrosis. RESULTS: The regeneration rates of the remnant liver indicated a significant decline in patients with severe fibrosis. In the no fibrosis and mild fibrosis groups, an increased removal rate was associated with increased regeneration rate, and post-operative ICG R-15 improved with time. However, in the moderate fibrosis and severe fibrosis groups, an increased removal rate was not associated with increased regeneration rate, and post-operative ICG R-15 showed no change or became worse with time. CONCLUSIONS: Severe fibrosis of the liver parenchyma is associated with poorer regeneration of the remnant liver leading to poor restoration of post-operative liver function. The severity of fibrosis is useful as a predictive factor for liver regeneration and restoration of liver function after partial hepatectomy.

Adult↗
PubMed1977

Inhibitory effects of jaundice on regenerating liver.

The effects of partial hepatectomy on the energy charge (ATP + 1/2ADP/ATP + ADP + AMP) and mitochondrial oxidative phosphorylation were studied in normal and jaundiced rats. In normal rats and energy charge levels of the remnant liver decreased only slightly with a rise in the phosphorylative activity of the mitochondria at an early stage after hepatectomy, and then rapidly returned to normal. In jaundiced rats subjected to the common bile duct ligation the energy the energy charge levels of the liver decreased to approximately 0.800 from 0.849 of normal value, though their mitochondrial oxidative phosphorylation was within normal limits. In jaundiced rats the energy charge levels of the remnant liver after partial hepatectomy decreased markedly without a return toward normal. The mitochondrial phosphorylative activity increased to only about 50% of hepatectomized normal rats after partial hepatectomy. More than 70% of jaundice rats died within 24 hours after partial hepatectomy. It was suggested that the jaundice inhibits an enhancement of ATP generation to provide sufficient energy for high energy demand rather than the enery-requiring biosynthetic process in an early process of liver regeneration.

Adenine Nucleotides↗
PubMed2001

Effects of ethanol administration on hepatocellular ultrastructure of regenerating liver induced by partial hepatectomy.

Acute ethanol administration partially inhibits DNA and protein syntheses during liver regeneration (LR) induced by partial hepatectomy (PH) in rats. Previous findings that the magnitude of ethanol's deleterious effects on LR are related to the route and timing of its administration led us to perform studies at the ultrastructural level, comparing ethanol effects on PH-induced LR, as a consequence of its administration route. PH promoted alterations on the endoplasmic reticulum and mitochondria, accompanied by decreased glycogen and increased lipid content in cytoplasm. Structural nuclear and nucleolar activities were also evident. Intragastric ethanol administration practically abolished the adaptative changes found in PH-promoted regenerating hepatocytes, whereas its administration through the intraperitoneal route induced later ultrastructural modifications, indicating cellular proliferation. These results suggest that ethanol, under certain conditions, could stimulate liver proliferation triggered by PH. The mechanism underlying this surprising effect of ethanol on LR remains to be elucidated. However, it is suggested that an altered ethanol metabolism by rats subjected to PH could be involved.

Alcoholism↗
PubMed1998

Putrescine administration reverses cadmium-associated inhibition of liver regeneration.

The liver is of central importance in the metabolism of essential and toxic metals such as cadmium. Cadmium pretreatment suppressed the liver regenerative response to partial hepatectomy, due to the inhibition of the enzymatic activity of thymidine kinase. Exogenous putrescine administration has been reported to stimulate liver regeneration in animal models of acute liver failure. The purpose of this study was to document whether the administration of this polyamine enhances the impaired regenerative capacity of hepatocytes in cadmium-pretreated partially hepatectomized rats. The intraperitoneal administration of putrescine (1 or 10 mg/kg body weight), at the time of surgery and at 4 and 8 hr postoperatively partly restored the suppressed hepatocyte deoxyribonucleic acid (DNA) biosynthesis and thymidine kinase activity in cadmium-pretreated partially hepatectomized rats. Mitotic activity and the percentage of hepatocytes positive for proliferating cell nuclear antigen nuclei were in accordance with the liver proliferative status. Our results showed that exogenous putrescine administration is able to improve diminished liver regeneration after partial hepatectomy in this animal model of acute hepatic injury.

Animals↗