Hepatocyte ploidy in regenerating livers after partial hepatectomy, drug-induced necrosis, and cirrhosis

Mosaicism in health and disease - clones picking up speed

Post-zygotic variation refers to genetic changes that arise in the soma of an individual and that are not usually inherited by the next generation. Although there is a paucity of research on such variation, emerging studies show that it is common: individuals are complex mosaics of genetically distinct cells, to such an extent that no two somatic cells are likely to have the exact same genome. Although most types of mutation can be involved in post-zygotic variation, structural genetic variants are likely to leave the largest genomic footprint. Somatic variation has diverse physiological roles and pathological consequences, particularly when acquired variants influence the clonal trajectories of the affected cells. Post-zygotic variation is an important confounder in medical genetic testing and a promising avenue for research: future studies could involve analyses of sorted and single cells from multiple tissue types to fully explore its potential.

Effect of angiotensin-converting enzyme inhibitor, lisinopril on morphological and biochemical aspects of fibrotic liver regeneration

BACKGROUND/AIMS

Hepatic fibrosis results in defective liver regeneration following partial hepatectomy. Angiotensin converting enzyme (ACE) inhibitors can enhance liver regeneration and are also involved in the reduction of hepatic fibrosis. The present study has been conducted to evaluate the potential effect of an ACE inhibitor, lisinopril, on the morphological and biochemical aspects of fibrotic liver regeneration.

MATERIALS AND METHODS

Eight-week old female Sprague Dawley rats were made fibrotic by intragastric carbon tetrachloride treatment. Rats were given saline or lisinopril (1 mg/kg) orally for 1 week and were subjected to sham surgery or two-third partial hepatectomy. Liver regenerative and functional capacities were determined 48 hours post surgery.

RESULTS

Lisinopril administration did not affect the regeneration rate, proliferation cell nuclear antigen count, and hepatocellular area of fibrotic livers following partial hepatectomy. No statistically significant difference between treated and control rats regarding mitotic count, hepatocyte nuclear area, and binuclear hepatocyte frequency was observed. Serum biochemical analysis showed that lisinopril non-significantly decreased the partial hepatectomy induced elevated levels of alanine aminotransferase, aspartate transaminase, and alkaline phosphatase whereas lactate dehydrogenase and total bilirubin levels were significantly reduced. No marked reduction in hepatic collagen content and alpha smooth actin positive cells was observed by lisinopril treatment.

CONCLUSION

ACE inhibitor lisinopril did not produce major histomorphological alterations in regenerating fibrotic liver following partial hepatectomy, however, it may improve its functional capability.

Aneuploidy, polyploidy and ploidy reversal in the liver

Polyploidy has been described in the liver for over 100 years. The frequency of polyploid hepatocytes varies by age and species, but up to 90% of mouse hepatocytes and approximately 50% of human hepatocytes are polyploid. In addition to alterations in the entire complement of chromosomes, variations in chromosome copy number have been recently described. Aneuploidy in the liver is pervasive, affecting 60% of hepatocytes in mice and 30-90% of hepatocytes in humans. Polyploidy and aneuploidy in the liver are closely linked, and the ploidy conveyor model describes this relationship. Diploid hepatocytes undergo failed cytokinesis to generate polyploid cells. Proliferating polyploid hepatocytes, which form multipolar spindles during cell division, generate reduced ploidy progeny (e.g., diploid hepatocytes from tetraploids or octaploids) and/or aneuploid daughters. New evidence suggests that random hepatic aneuploidy can promote adaptation to liver injury. For instance, in response to chronic liver damage, subsets of aneuploid hepatocytes that are differentially resistant to the injury remain healthy, regenerate the liver and restore function. Future work is required to elucidate the mechanisms regulating dynamic chromosome changes in the liver and to understand how these processes impact normal and abnormal liver function.

Antioxidative, antiapoptotic, and proliferative effect of curcumin on liver regeneration after partial hepatectomy in rats

The aim of the present study was to assess the influence of curcumin on liver regeneration after partial hepatectomy (PH) in rats. A total of 24 male Sprague Dawley rats were divided into three groups: sham-operated (SH), PH, and PH + curcumin; each group contains eight animals. The rats in curcumin-treated groups were given curcumin (in a dose of 100 mg/kg body weight) once a day orally for 7 days, starting 3 days prior to hepatectomy operation. At 7 days after resection, liver samples were collected. The malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) levels were estimated in liver homogenates. Moreover, histopathological examination, mitotic index (MI), proliferating cell nuclear antigen labeling, proliferation index (PI), transferase-mediated 2'-deoxyuridine, 5'-triphosphate nick end-labeling assay, and apoptotic index (AI) were evaluated at 7 days after hepatectomy. As a result, curcumin significantly increased MI and PI and significantly decreased AI in PH rats. Additionally, curcumin remarkably inhibited MDA elevation, restored impaired antioxidant SOD activity and GSH level and also attenuated hepatic vacuolar degeneration and sinusoidal congestion. These results suggested that curcumin treatment had a beneficial effect on liver regenerative capacity of the remnant liver tissue after hepatectomy, probably due to its antioxidative, antiapoptotic, and proliferative properties.

Effects of bicyclol on liver regeneration after partial hepatectomy in rats

Bicyclol is a synthetic antihepatitis drug with antioxidative property. The present study was performed to investigate the effect of bicyclol on liver regeneration after partial hepatectomy in rats. Bicyclol (300 mg/kg) was given to rats subjected to 70% hepatectomy three times before operation. At 6, 24, and 48 h after resection, samples were collected for the measurement of serum alanine aminotransferase (ALT), total bilirubin (TBil), hepatic glycogen, malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH). Moreover, liver regeneration rate, proliferating cell nuclear antigen (PCNA) labeling, proliferation index, and histopathological examination were evaluated at 48 h after hepatectomy. As a result, bicyclol significantly increased regeneration rate, mitotic index (MI), PCNA labeling index, and proliferation index in PH rats. Additionally, bicyclol remarkably inhibited the elevation of serum ALT and TBil levels, alleviated the formation of liver MDA, restored impaired antioxidant SOD and GSH, increased hepatic glycogen content, and also attenuated hepatic vacuolar degeneration. These results suggested that bicyclol had a beneficial effect on liver regenerative capacity of the remnant liver tissue after hepatectomy, probably due to its antioxidative property.

Mechanism of plasmid delivery by hydrodynamic tail vein injection. II. Morphological studies

BACKGROUND

The efficient delivery of plasmid DNA (pDNA) to hepatocytes by a hydrodynamic tail vein (HTV) procedure has greatly popularized the use of naked nucleic acids. The hydrodynamic process renders onto the tissue increased physical forces in terms of increased pressures and shear forces that could lead to transient or permanent membrane damage. It can also trigger a series of cellular events to seal or reorganize the stretched membrane. Our goal was to study the uptake mechanism by following the morphological changes in the liver and correlate these with the fate of the injected plasmid DNA.

METHODS

We utilized both light microscopic (LM) and electron microscopic (EM) techniques to determine the effect of the HTV procedure on hepatocytes and non-parenchymal cells at various times after injection. The LM studies used paraffin-embedded livers with hematoxylin and eosin (H&E) staining. The immune-EM studies used antibodies labeled with sub-nanometer gold particles followed by silver enhancement to identify the location of injected pDNA at the subcellular level. The level of overall damage to liver cells was estimated based on alanine aminotransferase (ALT) release and clearance.

RESULTS

Both the LM and EM results showed the appearance of large vesicles in hepatocytes as early as 5 min post-injection. The number of vesicles decreased by 20-60 min. Plasmid DNA molecules often appeared to be associated with or inside such vesicles. DNA could also be detected in the space of Disse, in the cytoplasm and in nuclei. Non-parenchymal cells also contained DNA, but HTV-induced vesicles could not be observed in them.

CONCLUSIONS

Our studies suggest an alternative or additional pathway for naked DNA into hepatocytes besides direct entry via membrane pores. It may be difficult to prove which of these pathways lead to gene expression, but the membrane pore hypothesis alone appears insufficient to explain why expression happens preferentially in hepatocytes. Further study is needed to delineate the importance of each of these putative pathways and their interrelationship in enabling oligonucleotide (siRNA) activity and pDNA expression.

Tetraploidy/aneuploidy and stem cells in cancer promotion: The role of chromosome passenger proteins

While polyploidy, a state of having fully duplicated sets of chromosomes per cell, has been described in normally developing bone marrow megakaryocytes or as an adaptive response in other cell types, aneuploidy is never detected in normal cells. Tetraploidy or aneuploidy can be induced by several signals and it is highly prevalent in different forms of cancers, suggesting a role for this cell cycle state in promoting cellular transformation. Investigations suggested that loss of heterozygosity of cancer-related genes in stem cells might contribute to genetic instability in progeny cells and to subsequent cancer development. Deregulated expression of chromosome passenger proteins, such as Aurora kinases or Survivin, is a hallmark of various cancers, and experimentally induced changes in these regulators can promote tetraploidy or aneuploidy and loss of heterozygosity. Our studies described an induction of tetraploidy/aneuploidy by a stable form of Aurora-B, leading to acquisition of transformation properties. It is intriguing to speculate that in some cancers, tetraploidy/aneuploidy induced by deregulated expression of a mitotic regulator represents a primary event that leads to unbalanced expression of a cluster of crucial genes and to cellular transformation.

Experimental models of acute and chronic liver failure in nude mice to study hepatocyte transplantation

Although hepatocyte transplantation is a promising therapy for acute liver failure in human, there is still a lack of animal models suffering from hepatic injury in which the benefits of hepatocyte transplantation could be evaluated solely, without the bias caused by immunosuppression. As a consequence, the aim of the study was first to develop reproducible models of partial hepatectomy and of thioacetamide (TA)- or Jo2-induced acute liver failure in nude mice. Chronic liver disease was also investigated by repeated injections of sublethal doses of thioacetamide. Survival rates, routine histologic observations, alanin aminotransferase sera content, Ki67, and caspase 3 immunodetection were investigated both after 40% partial hepatectomy and after toxic-induced damages. Liver injuries were more severe and/or precocious in nude mice than in Balb/c mice for a given treatment with a maximum of acute injury obtained 24 h after single toxic injection, and were found to be transitory and reversible within 10 days. Toxics induced apoptosis followed by necrosis, confirming recent published data. Onset of fibrosis leading to reproducible chronic cirrhosis in nude mice correlated with increasing number of Ki67-positive cells, indicating that high levels of cell proliferation occurred. Chronic cirrhosis progressively reversed to fibrosis when the treatment ceased. Preliminary results demonstrated that engrafted xenogeneic hepatocytes could be detected in the host liver by anti-MHC class I immunohistochemistry. Fractions enriched in 2n or 4n hepatocytes by cell sorting using a flow cytometer were equivalent to the unpurified fraction in terms of engraftment in control nude mice or in nude mice subjected to PH. However, in mice suffering from liver injury 24 h after Jo2 or TA treatment, the engraftment of 2n hepatocytes was about twice that of an unpurified hepatocyte population or of a population enriched in 4n hepatocytes.

Dietary supplementation with monounsaturated and long-chain polyunsaturated fatty acids influences the liver structural recovery and hepatocyte binuclearity in female Wistar rats in experimental cirrhosis induced by thioacetamide

Oral administration of 300 mg/l thioacetamide (TAA) for 4 months causes hepatic lesions comparable to those described in alcoholic liver cirrhosis in humans and associated protein-energy malnutrition. In this sense, direct supplementation with monounsaturated fatty acids (MUFAs) and/or polyunsaturated fatty acids (PUFAs) might provide an advantage in the correction of the fatty acid deficiency in these patients. PUFAs are essential components of cell membranes maintaining its fluidity and function, important energy sources, and precursors of eicosanoids. Moreover, these fatty acids also modulate gene transcription, mRNA stability, and cellular differentiation.

METHODS

Fifty-four female Wistar rats (Interfauna Ibérica, Barcelona, Spain) weighing 110-120 g were used in this study. The animals were divided into two groups: one group was treated with 300 mg/l TAA dissolved in drinking water during 4 months, and the other group, which served as a control, was given water without TAA. To evaluate the changes induced by the administration of TAA for 4 months, TAA-treated (n = 7) and control animals (n = 5) were killed. Then, the TAA treatment was stopped and the rest of the animals in both TAA and control groups were divided into three experimental groups and three control groups which received for 2 weeks different type of diets. Using the TAA-induced liver cirrhosis model in rats, we analysed the effects of dietary supplementation with MUFAs and PUFAs on binuclearity and ultrastructure of hepatocytes. After TAA-induced cirrhosis, we analysed whether dietary supplementation with fatty acids may restore the normal percentage of binucleated cells, as well as the ultrastructure, nuclear area, and nuclear/cytoplasm index of hepatocytes.

RESULTS

Treatment with TAA causes cirrhosis characterized by the appearance of parenchyma nodules and fibrous septae, as well as qualitative and quantitative alterations in liver and plasma lipids. Our results indicate that dietary MUFAs support hepatocyte recovery regarding its ultrastructural and morphometric values. However, PUFAs-enriched diets (n-3 and n-3 + n-6) do not correct hepatomegaly, fibrosis or lipid accumulation. Thus, dietary PUFAs do not enhance hepatocyte recovery from morphological and ultrastructural alterations.

CONCLUSIONS

In our experimental model of cirrhosis, dietary supplementation with a high proportion of long-chain PUFAs (n-3 or n-6) negatively influences liver recovery. This negative effect was likely due to the increased susceptibility of cell membranes to lipid peroxidation, together with an alteration in lipid metabolism.

Gene expression difference in regenerating rat liver after 0-36-40-44h short interval successive partial hepatectomy

AIM: To identify genes related to rat liver regeneration (LR) after 0-36-40-44h short interval successive partial hepatectomy (SISPH) and to analyze their action and expression profile in LR.

METHODS: A cDNA microarray containing 551 elements (liver chip) was made to analyze extensively expression changes of them in 0-36-40-44h SISPH, which were selected from subtractive cDNA libraries of the LR. Cluster analysis of these gene expression profile was performed by Genemath.

RESULTS: Among the selected 551 cDNA, 157 were up- ordown-regulated more than twofold at one or more time points. Of the 157 elements, 86 were up-regulated and 71 down-regulated, and 70 were not reported and 87 were reported, which had not been previously reported to be involved in LR. By cluster analysis and generalization analysis, 6 distinct temporal induction or suppression patterns showed that immediate induction, intermediate induction, late induction, immediate suppression, intermediate suppression, and late suppression. Comparison of the gene expression in SISPH with after PH found that 38 genes were specially altered in SISPH, and the expression trends for other 119 genes were similar between SISPH and PH, except of the various abundance at the different time points.

CONCLUSION: In 0-36-40-44h SISPH, the numbers of the up-regulated and down-regulated genes show no apparent difference. The genes expressed lately are more than that immediately, and much more than that intermediately. The genes expressed abundantly are much less than that increased 2-5 folds.