Impaired liver regeneration after hepatectomy and bleeding is associated with a shift from hepatocyte proliferation to hypertrophy

BrdU does not induce hepatocellular damage in experimental Wistar rats

Bromodeoxyuridine (BrdU) is used in studies related to cell proliferation and neurogenesis. The multiple intraperitoneal injections of this molecule could favor liver function profile changes. In this study, we evaluate the systemic and hepatocellular impact of BrdU in male adult Wistar rats in 30 %-partial hepatectomy (PHx) model. The rats received BrdU 50 mg/Kg by intraperitoneal injection at 0.5, 1, 2, 3, 6, 9 and 16 days after 30 %-PH. The rats were distributed into four groups as follows, control, sham, PHx/BrdU(-) and PHx/BrdU(+). On day 16, we evaluated hepatocellular nuclei and analyzed histopathological features by haematoxylin-eosin stain and apoptotic profile was qualified by caspase-3 presence. The systemic effect was evaluated by liver markers such as alanine transferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), alkaline phosphatase (AP), bilirubin, total proteins and serum albumin content. The statistical analysis consisted of a student t-test and one-way ANOVA. BrdU did not induce apoptosis or hepatocellular damage in male rats. Multiple administrations of BrdU in male rats did not induce significant decrease body weight, but increased serum ALT and LDH levels were found. Our results show that the BrdU does not produce hepatocellular damage.

Peroxisome proliferator-activated receptor α agonist induces mouse hepatomegaly through the spatial hepatocyte enlargement and proliferation

Peroxisome proliferator-activated receptor alpha (PPARα) activation-induced hepatomegaly is accompanied by hepatocyte hypertrophy around the central vein (CV) area and hepatocyte proliferation around the portal vein (PV) area. However, the molecular mechanisms underlying this spatial change of hepatocytes remains unclear. In this study, we examined the characteristics and possible reasons for the zonation distinction of hypertrophy and proliferation during PPARα activation-induced mouse liver enlargement. Mice were injected with corn oil or a typical mouse PPARα agonist WY-14643 (100 mg·kg-1·d-1, i.p.) for 1, 2, 3, 5 or 10 days. At each time point, the mice were sacrificed after the final dose, and liver tissues and serum were harvested for analysis. We showed that PPARα activation induced zonal changes in hepatocyte hypertrophy and proliferation in the mice. In order to determine the zonal expression of proteins related to hepatocyte hypertrophy and proliferation in PPARα-induced liver enlargement, we performed digitonin liver perfusion to separately destroy the hepatocytes around the CV or PV areas, and found that PPARα activation-induced increase magnitude of its downstream targets such as cytochrome P450 (CYP) 4 A and acyl-coenzyme A oxidase 1 (ACOX1) levels around the CV area were higher compared with those around the PV area. Upregulation of proliferation-related proteins such as cell nuclear antigen (PCNA) and cyclin A1 (CCNA1) after WY-14643-induced PPARα activation mainly occurred around the PV area. This study reveals that the zonal expression of PPARα targets and proliferation-related proteins is responsible for the spatial change of hepatocyte hypertrophy and proliferation after PPARα activation. These findings provide a new insight into the understanding of PPARα activation-induced liver enlargement and regeneration.

The role of ubiquitin signaling pathway on liver regeneration in rats

The ubiquitin signalling pathway is a large system associated with numerous intracellular mechanisms. However, its function in the liver regeneration process remains unknown. This particular study investigates the intracellular effect mechanisms of the ubiquitin signalling pathway. It also determines the differences in the expression of 88 genes belonging to the ubiquitin pathway using the RT-PCR array method. To conduct this research, three genes-that differed in the expression analysis were selected. Moreover, their proteins were analysed by western blot analysis while using Ki67 immunohistochemical analysis that determines proliferation rates by hour. It was determined that BRCA1 and BARD1, which are effective in DNA repair, play an active role at PH24. Similarly, Ube2t expression, which belongs to the Fanconi anaemia pathway associated with DNA repair, was also found to be high at PH12-72 h. In addition, it was revealed that the expressions of Anapc2, Anapc11, Cdc20 belonging to the APC/C^Cdc20 complex, which participate in cell cycle regulation, differed at different hours after PH. Expression of Mul1, which is involved in mitochondrial biogenesis and mitophagy mechanisms, peaked at PH12 under the observation. Considering the Mul1 gene expression difference, MUL1-mediated mitophagy and mitochondrial fission mechanism may be associated with liver regeneration. It was also determined that PARKIN-mediated mitophagy mechanisms are not active in 0-72 h of liver regeneration since PARKIN expression did not show a significant change in PH groups.

Premature Macrophage Activation by Stored Red Blood Cell Transfusion Halts Liver Regeneration Post-Partial Hepatectomy in Rats

Liver resection is a common treatment for various conditions and often requires blood transfusions to compensate for operative blood loss. As partial hepatectomy (PHx) is frequently performed in patients with a pre-damaged liver, avoiding further injury is of paramount clinical importance. Our aim was to study the impact of red blood cell (RBC) resuscitation on liver regeneration. We assessed the impact of RBC storage time on liver regeneration following 50% PHx in rats and explored possible contributing molecular mechanisms using immunohistochemistry, RNA-Seq, and macrophage depletion. The liver was successfully regenerated after PHx when rats were transfused with fresh RBCs (F-RBCs). However, in rats resuscitated with stored RBCs (S-RBCs), the regeneration process was disrupted, as detected by delayed hepatocyte proliferation and lack of hypertrophy. The delayed regeneration was associated with elevated numbers of hemorrhage-activated liver macrophages (Mhem) secreting HO-1. Depletion of macrophages prior to PHx and transfusion improved the regeneration process. Gene expression profiling revealed alterations in numerous genes belonging to critical pathways, including cell cycle and DNA replication, and genes associated with immune cell activation, such as chemokine signaling and platelet activation and adhesion. Our results implicate activated macrophages in delayed liver regeneration following S-RBC transfusion via HO-1 and PAI-1 overexpression.

Impact of laparoscopic liver resection on liver regeneration

BACKGROUND

Liver regeneration after liver resection plays an important role in preventing posthepatectomy liver failure. In this study, we aimed to evaluate and compare the impact of laparoscopic liver resection (LLR) and open liver resection (OLR) on liver regeneration.

METHODS

Patients who underwent curative anatomical liver resection for hepatocellular carcinoma, cholangiocellular carcinoma, and colorectal liver metastases at our institution between January 2010 and December 2018 were included in this study. The patients were divided into the OLR and LLR groups. Preoperative liver volume (PLV), future remnant liver volume, resected liver volume (RLV), liver volume at 1 month after the surgery, and liver volume at 6 months after the surgery were calculated. The liver regeneration rate was defined as the increase in the rate of RLV, and the liver recovery rate was defined as the rate of return to the PLV.

RESULTS

The study included 72 patients. Among them, 43 were included in the OLR group and 29 were included in the LLR group. No differences were observed in the baseline characteristics and surgical procedures between the two groups. Moreover, no significant difference was observed in the liver regeneration rate at 1 month after the surgery (OLR vs. LLR: 68.9% vs. 69.0%, p = 0.875) and at 6 months after the surgery (91.8% vs. 93.2%, p = 0.995). Furthermore, the liver recovery rates were not significantly different between the two groups at 1 month after the surgery (90.3% vs. 90.6%, p = 0.893) and at 6 months after the surgery (96.9% vs. 98.8%, p = 0.986).

CONCLUSION

Liver regeneration after liver resection is not affected by the type of surgical procedure and both laparoscopic and open procedures yield similar regeneration and recovery rates.

Maternal high-fat diet consumption programs male offspring to mitigate complications in liver regeneration

In the last decades, obesity and nonalcoholic fatty liver disease (NAFLD) have become increasingly prevalent in wide world. Fatty liver can be detrimental to liver regeneration (LR) and offspring of obese dams (HFD-O) are susceptible to NAFLD development. Here we evaluated LR capacity in HFD-O after partial hepatectomy (PHx). HFD-O re-exposed or not to HFD in later life were evaluated for metabolic parameters, inflammation, proliferation, tissue repair markers and survival rate after PHx. Increasing adiposity and fatty liver were observed in HFD-O. Despite lower IL-6 levels, Ki67 labeling, cells in S phase and Ciclin D1/PCNA protein content, a lower impact on survival rate was found after PHx, even when re-exposed to HFD. However, no difference was observed between offspring of control dams (SC-O) and HFD-O after surgery. Although LR impairment is dependent of steatosis development, offspring of obese dams are programmed to be protected from the damage promoted by HFD.

Metabolic hallmarks of liver regeneration

Despite the crucial role of cell metabolism in biological processes, particularly cell division, metabolic aspects of liver regeneration are not well defined. Better understanding of the metabolic activity governing division of liver cells will provide powerful insights into mechanisms of physiological and pathological liver regeneration. Recent studies have provided evidence that metabolic response to liver failure might be a proximal signal to initiate cell proliferation in liver regeneration. In this review, we highlight how lipids, carbohydrates, and proteins dynamically change and orchestrate liver regeneration. In addition, we discuss translational studies in which metabolic intervention has been used to treat chronic liver diseases (CLDs).

Deletion of Golgi protein 73 delayed hepatocyte proliferation of mouse in the early stages of liver regeneration

BACKGROUND AND AIM

Golgi protein 73 (GP73) is a transmembrane protein that can promote the proliferation of cancer cells. However, the roles of GP73 in the proliferation of non-malignant hepatocytes have rarely been investigated.

METHODS

The wild-type (GP73+/+ ) and GP73 gene knockout mice (GP73-/- ) were subject to 70% partial hepatectomy (PHx) to explore the involvement of GP73 in liver regeneration.

RESULTS

After PHx, a significant increase of GP73 expression was observed in GP73+/+ mouse liver. Noticeably, promoted recovery of liver mass was observed in GP73-/- mouse at Day 1 after PHx, as showed by the liver/body weight ratio. RNA sequencing revealed that genes relevant to cell cycle and inflammation response in the residual liver tissues were severely suppressed with the deletion of GP73, particularly the inactivation of NF-κB signal pathway in early phase of liver regeneration. In line with this, we do see the downregulation of cell cycle-related protein including cyclin D1, p-cyclin D1, β-catenin, as well as interleukin 6, tumor necrosis factor-α, CCl2, and CXCl10. In contrast, activation of mTOR signaling pathway was documented, accompanied with the histological hypertrophy of hepatocytes in GP73-/- mouse.

CONCLUSIONS

Golgi protein 73 deletion leads to delayed response of liver regeneration and inflammation in the early stages of liver regeneration after PHx.

Caspase-3-related apoptosis prevents pathological regeneration in a living liver donor rat model

PURPOSE

The main goal of this study was to determine the relationship of cleaved-caspase-3 (C3)-related apoptosis and hepatic proliferation, during the liver repopulation in a living liver donor rat model.

MATERIAL/METHODS

Thirty-three animals were randomized into eleven groups and evaluated on postoperative from 3 ​h until 384 ​h after 30%-partial hepatectomy (30%-PHx). Liver sections (5 ​μm) were processed by hematoxylin-eosin, and immunostaining for C3, accompanied by hepatic function test. C3 content and the hepatic lobule enlargement were analyzed by optical density, followed by cell counting.

RESULTS

Transient variations of alanine transferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were found. Significant increase in the C3 levels, and cell nuclei number, were detected at 12 ​h and 48 ​h after 30%-PHx, evidencing a correlation of p ​= ​-0.3679.

CONCLUSION

In the 30%-PHx rat model, C3-related apoptosis prevents proliferative pathological conditions during the hepatic lobule re-modeling.

Modulation of Autophagy: A Novel "Rejuvenation" Strategy for the Aging Liver

Aging is a natural life process which leads to a gradual decline of essential physiological processes. For the liver, it leads to alterations in histomorphology (steatosis and fibrosis) and function (protein synthesis and energy generation) and affects central hepatocellular processes (autophagy, mitochondrial respiration, and hepatocyte proliferation). These alterations do not only impair the metabolic capacity of the liver but also represent important factors in the pathogenesis of malignant liver disease. Autophagy is a recycling process for eukaryotic cells to degrade dysfunctional intracellular components and to reuse the basic substances. It plays a crucial role in maintaining cell homeostasis and in resisting environmental stress. Emerging evidence shows that modulating autophagy seems to be effective in improving the age-related alterations of the liver. However, autophagy is a double-edged sword for the aged liver. Upregulating autophagy alleviates hepatic steatosis and ROS-induced cellular stress and promotes hepatocyte proliferation but may aggravate hepatic fibrosis. Therefore, a well-balanced autophagy modulation strategy might be suitable to alleviate age-related liver dysfunction. Conclusion. Modulation of autophagy is a promising strategy for "rejuvenation" of the aged liver. Detailed knowledge regarding the most devastating processes in the individual patient is needed to effectively counteract aging of the liver without causing obvious harm.

Longitudinal study of Pex1-G844D NMRI mouse model: A robust pre-clinical model for mild Zellweger spectrum disorder

Zellweger spectrum disorders (ZSD) are inborn errors of metabolism caused by mutations in PEX genes that lead to peroxisomal biogenesis disorder (PBD). No validated treatment is able to modify the dismal progression of the disease. ZSD mouse models used to develop therapeutic approaches are limited by poor survival and breeding restrictions. To overcome these limitations, we backcrossed the hypomorphic Pex1 p.G844D allele to NMRI background. NMRI mouse breeding restored an autosomal recessive Mendelian inheritance pattern and delivered twice larger litters. Mice were longitudinally phenotyped up to 6 months of age to make this model suitable for therapeutic interventions. ZSD mice exhibited growth retardation and relative hepatomegaly associated to progressive hepatocyte hypertrophy. Biochemical studies associated with RNA sequencing deciphered ZSD liver glycogen metabolism alterations. Affected fibroblasts displayed classical immunofluorescence pattern and biochemical alterations associated with PBD. Plasma and liver showed very long-chain fatty acids, specific oxysterols and C₂₇ bile acids intermediates elevation in ZSD mice along with a specific urine organic acid profile. With ageing, C₂₆ fatty acid and phytanic acid levels tended to normalize in ZSD mice, as described in patients reaching adulthood. In conclusion, our mouse model recapitulates a mild ZSD phenotype and is suitable for liver-targeted therapies evaluation.

Influence of the Glissonean Pedicle Transection Approach in Spiegel Lobe-Preserving Left Hepatectomy on Spiegel Lobe Volume and Remnant Liver Functions

BACKGROUND

The extrahepatic surgical technique in liver resection can be divided into glissonean pedicle transection and glissonean separated transection approaches. In this study, we compared remnant liver function and liver regeneration involving the Spiegel lobe between these two approaches regarding Spiegel lobe-preserving left hepatectomy.

METHODS

We enrolled 31 patients who underwent Spiegel lobe-preserving left hepatectomy for malignant hepatobiliary diseases between April 2008 and January 2020. The postoperative Spiegel lobe volume was measured using a volume analyzer at 3 and 6 months postoperatively.

RESULTS

Of the 31 patients, 22 and 9 were included in the glissonean separated transection and glissonean pedicle transection groups, respectively. There was no significant between-group difference in the preoperative Spiegel lobe volume. However, the volumes at 3 and 6 months postoperatively were significantly larger in the glissonean pedicle transection group than in the glissonean transection group (29.92 mL vs. 13.00 mL; P < 0.001 and 28.43 mL vs. 15.01 mL; P < 0.001, respectively). There was no significant between-group difference in postoperative remnant liver function.

CONCLUSIONS

The postoperative Spiegel lobe volume was larger, and liver regeneration was better with the glissonean pedicle transection approach because of transection for Spiegel branch of the portal vein. It is desirable to preserve Spiegel branch in possible cases when surgeons select the glissonean separated transection approach based on the location and size of the tumors.

Roles of mTOR Signaling in Tissue Regeneration

The mammalian target of rapamycin (mTOR), is a serine/threonine protein kinase and belongs to the phosphatidylinositol 3-kinase (PI3K)-related kinase (PIKK) family. mTOR interacts with other subunits to form two distinct complexes, mTORC1 and mTORC2. mTORC1 coordinates cell growth and metabolism in response to environmental input, including growth factors, amino acid, energy and stress. mTORC2 mainly controls cell survival and migration through phosphorylating glucocorticoid-regulated kinase (SGK), protein kinase B (Akt), and protein kinase C (PKC) kinase families. The dysregulation of mTOR is involved in human diseases including cancer, cardiovascular diseases, neurodegenerative diseases, and epilepsy. Tissue damage caused by trauma, diseases or aging disrupt the tissue functions. Tissue regeneration after injuries is of significance for recovering the tissue homeostasis and functions. Mammals have very limited regenerative capacity in multiple tissues and organs, such as the heart and central nervous system (CNS). Thereby, understanding the mechanisms underlying tissue regeneration is crucial for tissue repair and regenerative medicine. mTOR is activated in multiple tissue injuries. In this review, we summarize the roles of mTOR signaling in tissue regeneration such as neurons, muscles, the liver and the intestine.