Period Of Liver Regeneration Research Articles

Four Waves of Hepatocyte Proliferation Linked with Three Waves of Hepatic Fat Accumulation during Partial Hepatectomy-Induced Liver Regeneration

Partial hepatectomy (PH) triggers hepatocyte proliferation–mediated liver repair and is widely used to study the mechanisms governing liver regeneration in mice. However, the dynamics of the hepatocyte proliferative response to PH remain unclear. We found that PH-induced mouse liver regrowth was driven by four consecutive waves of hepatocyte replication. The first wave exhibited the highest magnitude followed by two moderate waves and one minor wave. Underlying this continuous hepatocyte replication was persistent activation of cell cycle components throughout the period of liver regeneration. Hepatocyte mitotic activity in the first three proliferative cycles showed a circadian rhythm manifested by three corresponding mitosis peaks, which were always observed at Zeitgeber time 0. The Bmal1-Clock/Wee1/Cdc2 pathway has been proposed by others to govern the circadian rhythm of hepatocyte mitosis during liver regeneration. However, we did not observe the correlations in the expression or phosphorylation of these proteins in regenerating livers. Notably, Bmal1 protein displayed frequent changes in hepatic distribution and cellular localization as the liver regrowth progressed. Further, three waves of hepatic fat accumulation occurred during hepatic regeneration. The first started before and lasted through the first round of hepatocyte proliferation, whereas the second and third occurred concomitantly with the second and third mitotic peaks, respectively.ConclusionPH-induced liver regeneration consists of four continuous waves of hepatocyte proliferation coupled with three waves of hepatic fat accumulation. Bmal1, Wee1, and Cdc2 may not form a pathway regulating the circadian rhythm of hepatocyte mitosis during liver regeneration.

Selenomethionine effects on polyamine catabolism in renal tissue of hepatectomized rats

Background/Aims. Selenium metabolism and polyamine biosynthesis are linked in their common requirement for Sadenosylmethionine. During the period of liver regeneration, many growth factors that affect kidney metabolism appear in circulation. The idea of the present study was to elucidate the influence of Se-Met on polyamine metabolism in renal tissue of hepatectomized rats.Methods: Male albino Wister rats, were used for this study. Partial hepatectomy was performed by the resection of two-thirds of liver tissue mass (67%). One group of hepatectomized animals received Se-Metionine intraperitoneally, in a single daily dose of 2.5 g per 100g body weight, and the other, as well as control group, received 0.9 NaCl instead of the drug for seven days. The last dose of selenomethionine was applicated on the 7 day after hepatectomy, one hour before sacrificing. Results: The supplementation of Se-methionine to hepatectomized animals causes the decrease of PAO activity in renal tissue. The amount of MDA follows PAO activity; it increases after operation in kidney tissue and decreases under SeMet treatment. Diamine oxidase activity increases under the influence of Se-methionine in renal tissue of hepatectomized rats. Conclusion: During regeneration, polyamine metabolism in renal tissue modifies. Se-methionine suplementation has a protective effect.

肝再生早期における血小板の役割の検討―血小板と肝細胞の接触の意義について―

肝再生早期における血小板の役割の検討―血小板と肝細胞の接触の意義について―

Influence of hepatic regeneration after partial hepatectomy on theophylline pharmacokinetics in rats

The influence of hepatic regeneration after partial hepatectomy on theophylline pharmacokinetics has been studied on the rat. At different times after partial hepatectomy, theophylline was administered intravenously as a single dose of 6 mg/Kg. Drug plasma levels were determined by HPLC and pharmacokinetic parameters were obtained. Physiological parameters were also measured. Following hepatectomy, an increase in mass liver was observed and 15 days after surgery, liver mass was 78% of nonhepatectomized rats. Initial theophylline concentrations varied during the regeneration period, as well as the distribution volume at steady-estate (Vss). Elimination half-life (t 1/2), notably increased after hepatectomy (7.27+/-1.38 h), decreased with time (6.70+/-1.18 h, 6.47+/-0.69 and 5.17+/-0.87 h after 24 h, 3 days and 15 days post-hepatectomy, respectively) to reach a value close to that of the control group (4.30+/-1.37 h). The increase in elimination half-life led to a decrease in the mean residence time during the period of liver regeneration. However, the intrinsic clearance hardly varied during regeneration period. We could establish the following relationship between liver weight (LW) and the elimination half-life: t 1/2 (h)=-0.358*LW (g)+8.6168 (R2=0.9906). For the mean residence time (MRT) this relationship was: MRT (h) =-0.5173*LW (g)+12.433 (R2=0.991).

Two-stage hepatectomy: A planned strategy to treat irresectable liver tumors.

To assess feasibility, risks, and patient outcomes in the treatment of colorectal metastases with two-stage hepatectomy. Some patients with multiple hepatic colorectal metastases are not candidates for a complete resection by a single hepatectomy, even when downstaged by chemotherapy, after portal embolization, or combined with a locally destructive technique. In two-stage hepatectomy, the highest possible number of tumors is resected in a first, noncurative intervention, and the remaining tumors are resected after a period of liver regeneration. In selected patients with irresectable multiple metastases not amenable to a single hepatectomy procedure, two-stage hepatectomy might offer a chance of long-term remission. Of consecutive patients with conventionally irresectable colorectal metastases treated by chemotherapy, 16 of 398 (4%) became eligible for curative two-stage hepatectomy combined with chemotherapy and adjuvant nonsurgical interventions as indicated. Two-stage hepatectomy was feasible in 13 of 16 patients (81%). There were no surgical deaths. The postoperative death rate (2 months or less) was 0% for the first-stage procedure and 15% for the second-stage one. Postoperative complication rates were 31% and 45%, respectively, with only one complication leading to reoperation. The 3-year survival rate was 35%, with four patients (31%) disease-free at 7, 22, 36, and 54 months. Median survival was 31 months from the second hepatectomy and 44 months from the diagnosis of metastases. Two-stage hepatectomy combined with chemotherapy may allow a long-term remission in selected patients with irresectable multiple metastases and increases the proportion of patients with resectable disease.

Hepatocyte growth-factor-scatter factor can stimulate post-operative tumor-cell proliferation in childhood hepatoblastoma

Rapid growth of residual tumor after partial hepatectomy has been observed during the period of liver regeneration in children with malignant embryonal hepatoblastoma. The aim of this study was to elucidate the role of hepatocyte growth-factor-scatter factor (HGF-SF) in this phenomenon. Markedly increased serum levels of HGF-SF up to 15 ng/ml were found in 13/18 patients after liver resection and in 6/16 patients with regressive tumors after chemotherapy, in comparison with 15 patients with non-pre-treated hepatoblastoma and 20 healthy children of the same age group. In the tumors, epithelial tumor cells highly expressed the HGF-SF receptor c-met, as shown by immunohistochemistry and m-RNA RT-PCR. The hepatoblastoma cell lines HepT1, HepT3 and HUH6 reacted with significantly increased proliferation to rhHGF-SF in these concentrations (1-15 ng/ml). In the tumors, HGF-SF was found to be expressed in the stromal fibroblasts. In culture, hepatoblastoma cells (HepT3, HUH6) stimulated secretion of the factor by human fibroblasts, indicating the paracrine fashion of intratumoral HGF-SF production. Cultured hepatoblastoma cells ceased to proliferate at 20-50 ng/ml HGF-SF, and they underwent cell death at ≥100 ng/ml. In contrast, the hepatocellular-carcinoma cell line HepG2 decreased growth under HGF-SF in a dose-dependent manner. We conclude that post-operatively secreted and intratumorally produced HGF-SF can function as a growth factor for hepatoblastoma, while the same agent has a cytostatic effect in unphysiologically high concentrations. Int. J. Cancer 85:151–159, 2000. ©2000 Wiley-Liss, Inc.

Hepatocyte growth-factor-scatter factor can stimulate post-operative tumor-cell proliferation in childhood hepatoblastoma.

Rapid growth of residual tumor after partial hepatectomy has been observed during the period of liver regeneration in children with malignant embryonal hepatoblastoma. The aim of this study was to elucidate the role of hepatocyte growth-factor-scatter factor (HGF-SF) in this phenomenon. Markedly increased serum levels of HGF-SF up to 15 ng/ml were found in 13/18 patients after liver resection and in 6/16 patients with regressive tumors after chemotherapy, in comparison with 15 patients with non-pre-treated hepatoblastoma and 20 healthy children of the same age group. In the tumors, epithelial tumor cells highly expressed the HGF-SF receptor c-met, as shown by immunohistochemistry and m-RNA RT-PCR. The hepatoblastoma cell lines HepT1, HepT3 and HUH6 reacted with significantly increased proliferation to rhHGF-SF in these concentrations (1-15 ng/ml). In the tumors, HGF-SF was found to be expressed in the stromal fibroblasts. In culture, hepatoblastoma cells (HepT3, HUH6) stimulated secretion of the factor by human fibroblasts, indicating the paracrine fashion of intratumoral HGF-SF production. Cultured hepatoblastoma cells ceased to proliferate at 20-50 ng/ml HGF-SF, and they underwent cell death at >/=100 ng/ml. In contrast, the hepatocellular-carcinoma cell line HepG2 decreased growth under HGF-SF in a dose-dependent manner. We conclude that post-operatively secreted and intratumorally produced HGF-SF can function as a growth factor for hepatoblastoma, while the same agent has a cytostatic effect in unphysiologically high concentrations.

Cytokines, nitric oxide synthesis and liver regeneration.

During the prereplicative period of liver regeneration the changes in the levels of mRNA for tumour necrosis factor-alpha (TNF-alpha) and its receptors were nearly synchronous. The mRNA levels reached their maximum 1-3 h after operation and exceeded the values for intact animals about ten-fold. Lipopolysaccharide stimulation induced an increase in TNF-alpha and TNF receptor production comparable with that occurring during regeneration. Nitric oxide (NO) production in the regenerating liver was determined by electron paramagnetic resonance (EPR) spectroscopy. The first increase in NO production occurred approximately 1 h after partial hepatectomy (PHE). The second and more pronounced peak of NO production was observed about 6 h after PHE when the hepatocytes entered the first cell cycle; it originated mainly from these cells. The consequent minimum of NO synthesis coincided with the maximal rate of DNA synthesis. The third gradual rise of NO production was seen at the transit from the first to the second cell cycle of the hepatocytes and the entrance of the non-parenchymal cells into proliferation. Hepatocytes, Kupffer and endothelial cells were isolated from livers after PHE. They were found to start their main NO production in the described sequence at the times corresponding to their respective entrance into the cell cycle. The maxima of NO synthesis were inversely correlated to the DNA-synthesizing activity of the individual cell type.

Levels of rna for TNF-α and receptors during the prereplicative period of liver regeneration

Levels of rna for TNF-α and receptors during the prereplicative period of liver regeneration

Morphology of nuclear ribonucleoproteins in the early period of liver regeneration after irradiation.

Cytochemical study of hepatocytes nuclei of the liver irradiated with a dose of 650 rad and irradiated after partial hepatectomy was performed. Morphological exponents of the intensive synthesis of preribosomal RNA in the nucleolus, as well as the transcription of heterogeneous RNA contained in perichromatin fibrils were revealed under the ionizing radiation effect. The behavior of perichromatin granules in the course of the experiment suggests delay in the transport of messenger RNA to cytoplasm, influenced by gamma radiation. Nuclear bodies were observed very often in nuclei of hepatocytes of irradiated animals.

Multiple esterase forms in isolated hepatocytes and Kupffer cells of partially hepatectomized rats.

The esterase patterns of isolated parenchymal liver cells of rats consisted of 6 bands of enzymatic activity, whereas the patterns of iron-loaded Kupffer cells showed 5 bands. Both patterns become simpler in the early prereplicative period of liver regeneration. Dukring simultaneous replication of DNA, i.e. 24 h after partial liver removal, an additional band of esterase activity appears in patterns of hepatocytes and Kupffer cells. At the moment of maximum hepatocyte mitotic rate, i.e. 36 h after partial hepatectomy, both esterase patterns lose the single band of activity again. 2 or 3 days after surgery the initial esterase patterns in hepatocytes return whereas the patterns of Kupffer cells remain incomplete.

UDP-N-acetylglucosamine-glycoprotein N-acetylglucosaminyltransferase in regenerating rat liver.

The assay condition for N-acetylglucosaminyltransferase activities in rat liver microsomal fraction was developed. The enzyme activities towards endogenous acceptors within 48 h after partial hepatectomy were lower than in controls, exceeding the control level by 96 h, and then higher than in controls up to 240 h after the operation. The changes in N-acetylglucosaminyltransferase activities towards exogenous acceptor (UDP-2-acetamido-2-deoxy-D-glucose: glycoprotein 2-acetamido-2-deoxy-D-glucosyltransferase, EC 2.4.1.51) were consistent with those in the enzyme activities towards endogenous acceptors at 144 h, but not at 48 h, after the operation. The contents of protein and the levels of protein-bound hexosamine in the liver microsomes were decreased at early period of liver regeneration. These results suggest that the acceptor capacity of liver microsomal proteins is diminished during first 48 h of the regeneration. This may be responsible for the decreased transfer of the amino sugar to nascent glycoproteins. However, the enzyme activity was enhanced at 144 h and the level of endogenous acceptors may increase.

Thyroid hormone metabolism during liver regeneration in rats.

The metabolism of thyroid hormones was studied during the prereplicative period of liver regeneration. After partial hepatectomy, serum thyroxine (T4) and triiodothyronine (T3) levles progressively fell, and reached a nadir at 12 h proportional to the quantity of liver tissue exised. The diminution (60-80%) in serum iodothyronines was related specifically to partial hepatectomy because laparotomy, ether anesthesia, and other stressful surgical procedures did not induce similar changes. At least 3 phenomena appear to be involved: 1) increased utilization and turnover of thyroid hormone by the regenerating liver remmant. 2) diminished hormone secretion by the thyroid gland between 6-12 h after surgery, and 3) a slightly reduced concentration of serum iodothyronine carrier proteins. The results support the concept that the liver participates in the metabolic regulation of T2 and T4 which in turn, control hepatocellular growth. It is suggested, however, that additional unknown factors control increased hepatic thyroid hormone turnover after partial hepatectomy.

Increased levels of rat hepatic nuclear free and engaged RNA polymerase activities during liver regeneration

Rat liver nuclei, seventeen hours after partial hepatectomy, showed a two to three-fold increase in total RNA synthesis in vitro over the sham operated controls. When tested with exogenous synthetic template, this was found to be mainly a reflection of increased levels of both the nuclear free and engaged RNA polymerase activities per se . It was also observed that there was a greater stimulation of the species of RNA polymerase that are α-amanitin resistant than sensitive (3.2 μg/ml). This observation was further confirmed by DEAE-Sephadex column chromatography of the solubilized nuclear free and engaged RNA polymerases and found RNA polymerase I and IIIa were the major species greatly stimulated during this period of liver regeneration. These data suggest not only that there exists a sensitive equilibrium between the nuclear free and engaged RNA polymerases; they also suggest the possibility that RNA polymerase itself may play a positive role in the regulation of gene expression.

Modification of ribosomal proteins during liver regeneration

Analysis of the 2D gel electrophoretic pattern of ribosomal proteins from both the small and large subunit of rat liver were made at various times following partial hepatectomy. No changes were observed in the electrophoretic mobility of proteins from the 60S subunit during periods of 2 hr. to 72 hr. of liver regeneration. Changes were observed, however, in two proteins of the 40S subunit a short time after partial hepatectomy. Protein S 6 disappeared from its normal position and a new spot appeared as a more negative form as early as 2 hr. post regeneration. This modification persisted for at least 18 hr. At 72 hr., S 6 returned to its normal position. Protein S 2, on the other hand, underwent a different pattern of change during the early stages of liver regeneration. S 2 was observed to migrate as 2 spots at 2 hr. after partial hepatectomy and this pattern was preserved at the 4 hr. period. At 8 hr., the pattern was further modified to 2 spots which was distinct from the earlier change. This pattern was similar at 12 hr. At 18 hr. only the normal S 2 protein was observed. No further change in S 2 migration was observed at the 72 hr. period of liver regeneration.