Effects of tacrolimus and insulin in a liver regeneration model in growing animals with portal vein stenosis: immunohistochemical and molecular studies

The basis of liver regeneration: A systems biology approach

INTRODUCTION

Liver regeneration is a normal response to liver injury. The aim of this study was to determine the molecular basis of liver regeneration, through an integrative analysis of high-throughput gene expression datasets.

METHODS

We identified and curated datasets pertaining to liver regeneration from the Gene Expression Omnibus, where regenerating liver tissue was compared to healthy liver samples. The key dysregulated genes and pathways were identified using Ingenuity Pathway Analysis software. There were three eligible datasets in total.

RESULTS

In the early phase after hepatectomy, inflammatory pathways such as Nrf2 oxidative stress-mediated response and cytokine signaling were significantly upregulated. At peak regeneration, we discovered that cell cycle genes were predominantly expressed to promote cell proliferation. Using the Betweenness centrality algorithm, we discovered that Jun is the key central gene in liver regeneration. Calcineurin inhibitors may inhibit liver regeneration, based on predictive modeling.

CONCLUSION

There is a paucity of human literature in defining the molecular mechanisms of liver regeneration along a time continuum. Nonetheless, using an integrative computational analysis approach to the available high-throughput data, we determine that the oxidative stress response and cytokine signaling are key early after hepatectomy, whereas cell cycle control is important at peak regeneration. The transcription factor Jun is central to liver regeneration and a potential therapeutic target. Future studies of regeneration in humans along a time continuum are needed to better define the underlying mechanisms, and ultimately enhance care of patients with acute and chronic liver failure while awaiting transplant.

Hormonal Contribution to Liver Regeneration

An understanding of the molecular basis of liver regeneration will open new horizons for the development of novel therapies for chronic liver failure. Such therapies would solve the drawbacks associated with liver transplant, including the shortage of donor organs, long waitlist time, high medical costs, and lifelong use of immunosuppressive agents. Regeneration after partial hepatectomy has been studied in animal models, particularly fumarylacetoacetate hydrolase-deficient (FAH ^-/-) mice and pigs. The process of regeneration is distinctive, complex, and well coordinated, and it depends on the interplay among several signaling pathways (eg, nuclear factor κβ, Notch, Hippo), cytokines (eg, tumor necrosis factor α, interleukin 6), and growth factors (eg, hepatocyte growth factor, epidermal growth factor, vascular endothelial growth factor), and other components. Furthermore, endocrinal hormones (eg, norepinephrine, growth hormone, insulin, thyroid hormones) also can influence the aforementioned pathways and factors. We believe that these endocrinal hormones are important hepatic mitogens that strongly induce and accelerate hepatocyte proliferation (regeneration) by directly and indirectly triggering the activity of the involved signaling pathways, cytokines, growth factors, and transcription factors. The subsequent induction of cyclins and associated cyclin-dependent kinase complexes allow hepatocytes to enter the cell cycle. In this review article, we comprehensively summarize the current knowledge regarding the roles and mechanisms of these hormones in liver regeneration. Articles used for this review were identified by searching MEDLINE and EMBASE databases from inception through June 1, 2019.

Administration of Ginkgo biloba Extract (EGb761) Alone and in Combination with FK506 Promotes Liver Regeneration in a Rat Model of Partial Hepatectomy

Background:

Free radical damage is known to occur during liver regeneration. The Ginkgo biloba extract EGb761 has antioxidant properties due to its ability to scavenge free radicals. FK506 has been widely used as an immunosuppressant that stimulates hepatocyte proliferation following partial hepatectomy.

Aims:

To explore whether EGb761 enhances liver regeneration after hepatectomy in rats, we investigated the effects of EGb761 alone and in combination with FK506 on the liver regenerative process.

Study Design:

Animal experimentation.

Methods:

A total of 75 Wistar albino rats weighing 340.08±11.66 g were randomly divided into five experimental groups: sham, control, FK506, EGb761, and FK506 + EGb761. According to the study groups, rats were administered FK506 at a dose of 0.1 mg/kg/day and EGb761 at 25 mg/kg/day three times via the intraperitoneal route. Then, two-thirds hepatectomy was performed according to the Higgins and Anderson technique in all the rats. At postoperative 48 h, 53 surviving rats were sacrificed. Serum and plasma samples were collected for analyzing thymidine kinase and oxidative stress marker levels. The regenerated liver was entirely resected, weighed, and sectioned. The mitotic index was assessed using hematoxylin-eosin staining. The extent of liver regeneration was calculated using the Child’s formula. The data were statistically analyzed using ANOVA, with a significance level of 5% (p<0.05).

Results:

Rats who received EGb761 showed significantly higher levels of liver regeneration than those who received FK506 or FK506 + EGb761 (p<0.01). Thymidine kinase level and mitotic index were significantly higher in the EGb761 (p<0.005) and FK506 (p<0.05) groups than in the control and sham groups. In addition, the liver regeneration percentage was significantly higher in the EGb761 group than in the FK506 group (p<0.01). Myeloperoxidase and malondialdehyde levels were significantly correlated between the EGb761 and FK506 groups, even at lower levels in the EGb761 group (p<0.001).

Conclusion:

EGb761, which is an antioxidant, reduces liver damage and stimulates liver regeneration following partial hepatectomy in rats through its anti-inflammatory and antioxidative effects.