Effect of serotonin receptor 2 blockage on liver regeneration after partial hepatectomy in the rat liver.

The effect of serotonin receptor 2 blockade (5-HT(2)) on liver regeneration after 30-34% and 60-70% partial hepatectomy in the rat liver was investigated. Materials and methods: Male Wistar rats were subjected to 60-70% (group I) and 30-34% (group II) partial hepatectomy. Serotonin receptor 2 blockade was exerted by intraperitoneal administration of ketanserin at different doses and time points after partial hepatectomy. The rats of all groups were killed at different time points until 96 h after partial hepatectomy. The rate of liver regeneration was evaluated by the mitotic index in hematoxylin and eosin sections, the immunochemical detection of Ki67 and proliferating cell nuclear antigens, the rate of [(3)H]-thymidine incorporation into hepatic DNA and liver thymidine kinase enzymatic activity. Results: Liver regeneration peaked at 24 and 32 h after partial hepatectomy in 60-70% hepatectomized rats. In 30-34% hepatectomized rats liver regeneration peaked at 60 h, whereas low rates of regenerative activity were observed between 24 and 72 h after partial hepatectomy. Ketanserin administration arrested liver regeneration only when administered at 16 h after 60-70% partial hepatectomy. Ketanserin also abrogated the observed peak of regenerative activity at 60 h in 30-34% hepatectomized rats when administered at 52 h after partial hepatectomy. All indices of liver regeneration were affected by ketanserin administration. Conclusions: Serotonin receptor 2 blockade can arrest liver regeneration only when administered close to G1/S transition point, and that while serotonin may be a cofactor for DNA synthesis, it does not play a role in initiation of liver regeneration.     

Hepatic collagen synthesis and degradation during liver regeneration after partial hepatectomy

To elucidate hepatic collagen metabolism during liver regeneration after partial hepatectomy, we measured collagen content, collagen synthesis, and collagen-degrading enzyme activity in the remnant livers of rats 3, 5, 7, and 14 days after a partial hepatectomy of 68%. Hepatic collagen synthesis was significantly higher 3, 5, and 7 days after partial hepatectomy than it was in sham-operated control rats, but there was no such difference 14 days after surgery, the maximal hepatic collagen synthesis being observed 5 days after surgery. Although the collagen concentration in the remnant liver was similar to that in the control liver, the total collagen content of the remnant liver increased rapidly with liver regeneration until 7 days after partial hepatectomy. Hepatic collagenase activity was similar to the control; however, hepatic cathepsin B and cathepsin L activity and the intracellular degradation of newly synthesized collagen were markedly decreased 3, 5, and 7 days after partial hepatectomy compared with the controls. Hepatic collagen synthesis was significantly and inversely correlated with cathepsin L activity and with the intracellular degradation of newly synthesized collagen. These findings suggest that a combination of increased collagen synthesis and decreased intracellular collagen degradation contributes to the rapid supply of collagen that is observed during the early phase of liver regeneration.     

Regional Hepatic Regeneration After Liver Resection Correlates Well with Preceding Changes in the Regional Portal Circulation in Humans

Background and Aims

While portal hemodynamics largely affects the liver regeneration after partial hepatectomy, whether the remnant liver homogeneously regenerates is unclear, especially in humans. We hypothesized that change in flow distribution varies in each remnant portal branch after liver resection in humans and the liver consequently regenerates heterogeneously.

Methods

Twenty-two patients who underwent anatomical hepatic resection preserving intact drainage veins were analyzed. Based on perioperative contrast-enhanced computed tomography, the regional hepatic regeneration in each segment was analyzed using a region growing software. The perioperative change in the distribution of blood flow in each portal branch was assessed using the computational flow dynamics technique. The correlation between the change in the portal flow distribution and the later regional hepatic regeneration was investigated.

Results

The distribution of portal blood flow in each remnant branch largely changed at 2 weeks (71–389 %). Each remnant segment also heterogeneously regenerated at 3 months (85–204 %). Meanwhile, a good correlation between the regional regeneration rate at 3 months and the relative change in the flow distribution in each circulating portal branch at 2 weeks was detected in each patient (r = 0.74–0.99).

Conclusions

After partial hepatectomy, the change in blood flow varies in each remnant portal branch and the liver heterogeneously regenerates in humans. The good correlation between the earlier change in the portal flow distribution and the later regional hepatic regeneration strongly suggests that the portal venous flow most likely regulates the non-uniform liver regeneration after hepatic resection in humans.     

Erythropoietin promotes hepatic regeneration after extended liver resection in rats

Background and Aim:  It has been proven in various animal studies that recombinant human erythropoietin (rHuEPO) protects renal, cardiac and neuronal, as well as hepatic, tissue from ischemia, and promotes regeneration of adult central nervous system neurons. To date, no data are available as to whether rHuEPO has the ability to stimulate liver regeneration after liver resection.
Methods:  Rats undergoing 70% or 90% hepatectomy received an intraportalvenous administration (i.p.) of rHuEPO prior to resection or a subcutaneous injection (s.c.) for 3 days postoperatively, control animals were treated with surgery and saline injection only. Regeneration capacity of remnant livers was studied over 7 days by histology and immunohistochemistry (Ki-67, proliferating cell nuclear antigen [PCNA]). Polymerase chain reaction was carried out to measure transforming growth factor β (TGF-β), hypoxia induced factor (HIF), signal transducing activator 3 and vascular endothelial growth factor.
Results:  Ten-day survival in rats undergoing 90% hepatectomy significantly increased in i.p.-pretreated animals. After 70% hepatectomy the mitotic index was significantly increased in both rHuEPO-treated groups. These data were confirmed by PCNA and Ki-67 expression, which was significantly increased in the treated groups 24 h and 2 days after liver resection. TGF-β and HIF mRNA both were upregulated in control animals 3 h after surgery.
Conclusion:  rHuEPO effectively increased liver regeneration in rats after 70% liver resection and enhanced survival after 90% hepatectomy. Thus, rHuEPO may increase the regenerative capacity after major hepatectomy.     

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.     

Ischemic preconditioning improves liver regeneration by sustaining energy metabolism after partial hepatectomy under ischemia in rats.

BACKGROUND: The protective effect of ischemic preconditioning (IPC) has been reported on improvement of survival, reduction of liver necrosis and enhancement of the regenerative capacity of hepatocytes after partial hepatectomy. This study was undertaken to confirm that IPC has a significant impact on regeneration of hepatocytes after partial hepatectomy in ischemically damaged liver. In addition, we sought to examine the role of adenine nucleotides in this process. METHODS: Wistar rats were subjected to 60 min of total hepatic ischemia, followed by 70% hepatectomy. The animals were subdivided into an IPC (10/15 min) group and a non-IPC (control) group. Liver function tests and arginase activity were analyzed. Hepatic adenosine triphosphate (ATP), adenosine diphosphate and adenosine monophosphate were measured using gradient high-performance liquid chromatography. The liver regeneration was identified using relative liver weight and proliferating cell nuclear antigen (PCNA) labeling index. RESULTS: IPC treatment improved serum liver enzymes and tissue arginase activity (P<0.05) when compared with the control group. The preconditioned livers were associated with upregulation of ATP expression and also increased tissue energy charge. Regenerated liver weight in the IPC group was significantly higher than in the control group (P<0.05). The PCNA labeling index in the remnant livers in the IPC group was also significantly increased at 24 and 48 h after partial hepatectomy (P<0.05). CONCLUSION: These results suggest that IPC-augmented liver regeneration after hepatectomy, probably due to the stabilization of energy metabolism in rats.     

Liver regeneration and the effect of exogenous putrescine on regenerative activity after partial hepatectomy in cirrhotic rats.

There are conflicting data regarding the ability of the liver to regenerate after partial hepatectomy in animals and humans with cirrhosis. The purpose of this study was to document liver regeneration after partial hepatectomy in a carbon tetrachloride rat model of cirrhosis and to determine whether exogenous putrescine, a polyamine that has been reported to stimulate liver regeneration in animal models of acute liver failure, enhances regenerative activity in cirrhosis. Liver fibrosis and cirrhosis were produced by weekly intragastric gavage with carbon tetrachloride in 130 adult male rats. Vehicle-gavaged rats (n = 12) served as healthy controls. At surgery and at 4 and 8 hr after 70% hepatectomy, rats received normal saline solution or 1 or 10 mg/kg putrescine by intraperitoneal injection. Another group (n = 32) of carbon tetrachloride-treated rats was given putrescine (100 mg/kg) or normal saline solution twice daily for 10 days before partial hepatectomy and at 0, 4 and 8 hr after partial hepatectomy. Liver regeneration was documented 24 and 48 hr after partial hepatectomy on the basis of restitution of liver mass, ornithine decarboxylase activity and [3H]thymidine incorporation into liver DNA. Automated image analysis of the resected liver specimens separated carbon tetrachloride-treated rats into two subgroups: those with bridging fibrosis (fibrotic group) and those with micronodular cirrhosis (cirrhotic group). Restitution of liver mass and ornithine decarboxylase activity at 24 and 48 hr after partial hepatectomy were similar to carbon tetrachloride-treated rats (both fibrotic and cirrhotic) and vehicle-treated healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of ursodeoxycholic acid on liver regeneration after partial hepatectomy in rats with non-alcoholic fatty liver disease

Aim:  To investigate the effect of ursodeoxycholic acid (UDCA) on liver regeneration following partial hepatectomy in rats with non-alcoholic fatty liver disease (NAFLD).
Methods:  UDCA was administered to seven rats (group 1) and physiological saline was administered both to seven rats (group 2) with NAFLD and to seven rats with normal livers (group 3). All rats underwent two-thirds hepatectomy and the remnant liver tissues were removed 48 h later. Mitotic index (MI) and levels of proliferating cell nuclear antigen (PCNA), glutathione (GSH) and malondialdehyde (MDA) were assayed.
Results:  MI and PCNA levels in group 2 were significantly lower than in groups 1 and 3, but the values in groups 1 and 3 were similar. The GSH levels of group 2 were significantly lower than those of group 3 in the hepatectomy tissues, and lower than those of groups 1 and 3 in the remnant tissues. The differences between GSH levels in groups 1 and 3 were not significant. MDA levels in hepatectomy and remnant tissues were significantly higher in group 2 compared to groups 1 and 3; values in groups 1 and 3 were similar.
Conclusion:  UDCA increases regeneration after partial hepatectomy in rats with NAFLD, possibly due to an attenuating effect on oxidative stress.     

Impaired liver regeneration after synchronous liver and colon resection in rats

BACKGROUND/AIMS: Hepatectomy combined with colectomy is the preferred treatment for patients with synchronous colorectal cancer and hepatic metastasis. However, the effects on hepatic reserve function of combining colectomy with hepatectomy are unclear. The purpose of this study was to determine liver regeneration and functions after hepatectomy with and without colectomy. METHODOLOGY: 23 rats underwent 70% hepatectomy (Hx group) and 23 rats underwent 70% hepatectomy with ileocecal resection (HCx group), and 6 rats just after surgery (day 0) underwent simple celiotomy. On days 0, 1, 2, 3 and 7 after surgery, the remnant liver weight, DNA synthesis rate, malondialdehyde concentration, hepatic Adenosine monophosphate, ADP, ATP, serum hyaluronic acid concentration and endotoxin level in the portal blood were measured. RESULTS: In HCx group, the hepatic DNA synthesis rate on day 1 (p < 0.01) and the liver weight on day 7 (p < 0.05) were significantly lower, hepatic malondialdehyde concentration on days 1 and 2 (p < 0.05) was significantly higher and serum hyaluronic acid and portal endotoxin levels on day 1 were significantly higher (p < 0.01 and p < 0.05, respectively). CONCLUSION: Addition of colectomy to hepatectomy impairs regeneration and endothelial cell function of the remnant liver; the impairment is associated with increased levels of portal endotoxin and hepatic lipoperoxide.     

Effect of angiotensin-converting enzyme inhibitors on liver regeneration in rats

BACKGROUND/AIMS: We previously reported that bradykinin augments liver regeneration in rats. The angiotensin-converting enzyme is also a powerful bradykinin-degrading enzyme. METHODOLOGY: Adult rats received lisinopril, captopril, enalaprilat, or saline solution, intraperitoneally, for 5 days before 70% partial hepatectomy, and daily after surgery. They received also losartan and bradykinin. Rats were sacrificed at 12, 24, 36, 48, 72, and 120 hours after hepatectomy. Liver regeneration was evaluated in terms of the restoration of liver weight in proportion to body weight, liver DNA content and immunostaining for proliferating cell nuclear antigen. RESULTS: The proliferating cell nuclear antigen labeling index was higher in the lisinopril-treated group than in the control group at all time points after hepatectomy, except 120 hours. The remnant liver dry weight was higher in lisinopril-treated rats than in control rats at early time points after surgery. The liver DNA content was higher in three angiotensin-converting enzyme inhibitor-treated groups than in the control group at 36 hours after hepatectomy. The bradykinin-induced regenerative response was similar to the lisinopril-induced response, and losartan induced a lower hepatocyte labeling index in comparison to the control group at 36 hours after hepatectomy. CONCLUSIONS: The present results provide evidence that angiotensin-converting enzyme inhibitors remarkably enhance liver regeneration.     

Liver regeneration and restoration of liver function after partial hepatectomy in patients with liver tumors

Liver regeneration and restoration of liver function were studied in six patients who underwent partial hepatectomy with removal of 30-70% of the liver. Liver volume and liver regeneration were studied by single-photon computed tomography (SPECT), using 99mTc-colloid as tracer. The method was assessed in 11 patients by comparing the pre- and post-operative volume measurements with the volume of the resected liver mass. The correlation coefficient between these methods was 0.899 (P less than 0.01). Liver function was determined by measuring the galactose elimination capacity and the caffeine clearance. After a postoperative follow-up period of 50 days the liver had regenerated maximally to a volume of 75 +/- 2% of the preoperative liver mass. Maximal restoration of liver function was achieved 120 days after operation and amounted to 75 +/- 10% for the caffeine clearance and to 100 +/- 25% for the galactose elimination capacity. This study shows that SPECT is a useful method for assessing liver regeneration in patients after partial hepatectomy. Our study furthermore shows that caffeine clearance correlates well with total liver volume, whereas the galactose elimination capacity overestimates total liver volume after partial hepatectomy.     

Serum 7alpha-hydroxycholesterol levels during liver regeneration after hepatectomy in humans

BACKGROUND/AIMS: Changes in bile acid synthesis during liver regeneration after hepatectomy is little known in humans. Since it has been reported that the serum 7 alpha-hydroxycholesterol levels reflect the hepatic bile acid synthesis and that the determination of bile acid synthesis is useful to assess the liver regeneration rate, we determined the serum 7 alpha-hydroxycholesterol level during liver regeneration after hepatectomy in clinical patients. METHODOLOGY: The serum 7 alpha-hydroxycholesterol levels were determined by gas-liquid chromatography-mass spectrometry-selected ion monitoring method before and on days 1, 3, 5, 7, 14 and 21 after hepatectomy in twenty consecutive patients. RESULTS: The 7 alpha-hydroxycholesterol levels became lower between days 1 and 7, were increased on day 14, and then decreased on day 21 after hepatectomy. The patients with preoperative external biliary drainage showed a higher serum 7 alpha-hydroxycholesterol level than those without biliary drainage before hepatectomy. The former showed lower serum 7 alpha-hydroxycholesterol levels than the latter throughout the 21 days after hepatectomy. In patients whose liver resection rate was more than 50%, the serum 7 alpha-hydroxycholesterol levels were kept lower until 21 days after hepatectomy compared with those whose liver was excised less than 50%. CONCLUSIONS: It is concluded that the patients who had preoperative biliary drainage or major hepatic resection seem to have less hepatic reserve capacity for bile acid synthesis after hepatectomy.     

Liver regeneration in response to partial hepatectomy in rats treated with retrorsine: a kinetic study

BACKGROUND/AIM: We have designed an experimental model in which transplantation of normal hepatocytes into rats previously treated with retrorsine (a naturally-occurring pyrrolizidine alkaloid) results in near-complete replacement of the recipient liver by donor-derived cells. Two/thirds partial hepatectomy was found to be essential for this process to occur. To probe this finding, in the present study we describe the kinetics of liver regeneration in response to partial hepatectomy in rats given retrorsine. METHODS: Six-weeks-old male Fisher 344 rats received retrorsine (2 injections of 30 mg/kg each, i.p., 2 weeks apart), or the vehicle. Four weeks after the last injection, partial hepatectomy was performed and rats were killed at 1, 2, 3, 6, and 15 days thereafter. RESULTS: At time zero, i.e. prior to partial hepatectomy, liver weight and total liver DNA content were significantly lower in retrorsine-treated animals compared to controls (DNA content: 19.2+/-1.7 vs. 25.7+/-1.1 mg/liver). Diffuse megalocytosis (enlarged hepatocytes) was present in the group exposed to retrorsine. By day 3 post-partial hepatectomy liver DNA content in control animals had more than doubled compared to day 1 values (20.2+/-1.5 vs. 8.8+/-1.2), while very little increase was seen in retrorsine-treated rats at the same time points (7.6+/-0.4 vs. 6.1+/-0.2). At 2 weeks after partial hepatectomy, total DNA content returned close to normal levels in the control group (26.9+/-1.0 mg/liver); however, the value was still very low in animals receiving retrorsine (9.1+/-0.7). Data on BrdU labeling were consistent with this pattern and indicated that DNA synthesis following partial hepatectomy was largely inhibited in the retrorsine group. Similarly, no mitotic response was observed in hepatocytes following partial hepatectomy in animals exposed to retrorsine. CONCLUSIONS: These results clearly indicate that retrorsine exerts a strong and persistent cell cycle block on hepatocyte proliferation. Further, these results are in agreement with the hypothesis that selective proliferation of transplanted hepatocytes in retrorsine-treated animals is dependent, at least in part, on the persistent cell cycle block imposed by the alkaloid on endogenous parenchymal cells.     

Liver regeneration is impaired in lipodystrophic fatty liver dystrophy mice

We previously reported that mice subjected to partial hepatectomy exhibit rapid development of hypoglycemia followed by transient accumulation of fat in the early regenerating liver. We also showed that disrupting these metabolic alterations results in impaired liver regeneration. The studies reported here were undertaken to further characterize and investigate the functional importance of changes in systemic adipose metabolism during normal liver regeneration. The results showed that a systemic catabolic response is induced in each of two distinct, commonly used experimental models of liver regeneration (partial hepatectomy and carbon tetrachloride treatment), and that this response occurs in proportion to the degree of induced hepatic insufficiency. Together, these observations suggest that catabolism of systemic adipose stores may be essential for normal liver regeneration. To test this possibility, we investigated the hepatic regenerative response in fatty liver dystrophy (fld) mice, which exhibit partial lipodystrophy and have diminished peripheral adipose stores. The results showed that the development of hypoglycemia and hepatic accumulation of fat was attenuated and liver regeneration was impaired following partial hepatectomy in these animals. The fld mice also exhibited increased hepatic p21 expression and diminished plasma levels of the adipose-derived hormones adiponectin and leptin, which have each been implicated as regulators of liver regeneration. Conclusion: These data suggest that the hypoglycemia that develops after partial hepatectomy induces systemic lipolysis followed by accumulation of fat derived from peripheral stores in the early regenerating liver, and that these events may be essential for initiation of normal liver regeneration.     

Serum alkaline phosphatase after extensive liver resection: a study in patients with biliary tract carcinoma.

BACKGROUND/AIMS: To clarify a correlation between serum alkaline phosphatase (ALP) levels and liver function and regeneration after major hepatectomy. METHODOLOGY: Post-operative changes in serum ALP levels were retrospectively examined in 91 non-cirrhotic patients with biliary tract carcinoma who underwent right hepatic lobectomy or more extensive liver resection. In addition, changes in liver volume after resection were assessed in 31 patients who underwent computed tomography before surgery and within 1 month after resection. RESULTS: Serum ALP levels reached its nadir on post-operative day 1, followed by a gradual increase until post-operative day 28. In patients with post-hepatectomy liver failure (n = 32), serum ALP levels were significantly lower on days 1, 7, 10, 14, 21, and 28 after resection than in those without such failure (n = 59). Unexpectedly, the volumetric study of the liver showed no significant difference between the two groups in the remnant liver volume after resection. CONCLUSIONS: Serum ALP levels can function as an indicator of liver function after hepatectomy, but not reflect morphological regeneration of the liver. Thus, increased ALP levels after hepatectomy may not reflect the cellular proliferation process itself.     

FK 506 ameliorates the hepatic injury associated with ischemia and reperfusion in rats.

The effect of FK 506 on regeneration of the liver was studied in rats after a two-thirds partial hepatectomy after 60 min of ischemia of the unresected liver. The animals were divided into three distinct groups of 10 rats each. Group 1 (controls) received 0.5 ml saline solution intravenously 30 min after the induction of ischemia. Groups 2 and 3 were injected with FK 506 (0.3 mg/kg) intravenously 30 min after and 24 min before the induction of hepatic ischemia, respectively. The hepatic content of ATP and serum levels of ALT and lactate dehydrogenase were determined on each animal. In addition, the histological appearance and mitotic activity of the remnant liver was determined at regular 24-hr intervals after hepatic ischemia. All 10 control animals died within 72 hr. Treatment with FK 506 resulted in improved survival in groups 2 and 3 (30% and 80%, respectively). The improved survival seen in the FK 506-treated animals was reflected by a restoration of hepatic ATP content, a reduction in the serum levels of ALT and lactate dehydrogenase, an amelioration of hepatic necrosis and neutrophilic infiltration and an increase in the mitotic activity of the liver. These results suggest that FK 506 ameliorates the hepatic injury associated with ischemia/reperfusion and has a potent stimulatory effect on liver cell regeneration that may make it valuable as a hepatoprotective agent when administered to organ donors before graft harvesting.     

Changes in circulating cytokine levels and lymphocyte subsets in healthy liver donors after partial hepatectomy

Aim: Studies of animal models have determined that liver regeneration after partial hepatectomy is mediated by a various cytokines. The aim of the present study was to evaluate the levels of these cytokines and subsets of circulating lymphocytes in healthy humans after partial hepatectomy. Methods: Four individuals underwent partial hepatectomy for living-related donor liver transplantation. We also evaluated for comparison, three patients with myoma uteri who underwent hysterectomy. Blood samples were obtained before surgery and on postoperative days (PD) 1, 3, and 7. Serum levels of hepatocyte growth factor, interleukin (IL)-6, -10, and plasma levels of transforming growth factor beta were measured. Results: Increased circulating levels of hepatocyte growth factor and transforming growth factor beta were observedafter hepatectomy. The levels of IL-6 and IL-10 peaked on PD 1. Circulating white blood cell counts increased remarkably, whereas lymphocyte count decreased particularly on PD 1 and 3. CD4/CD8 and T-helper cell (Th)1/Th2 ratios were still decreased on PD 7. The percentage of natural killer cells was increased on PD 1. Partial hepatectomy in healthy humans leads not only to decreased lymphocyte counts, but also to remarkable changes in lymphocyte subsets. Conclusion: These findings suggest that immune suppression after partial hepatectomy involves decreases in CD4(+) helper T cells, particularly Th1 cells.