Liver regeneration after injury: Mechanisms, cellular interactions and therapeutic innovations.

The liver possesses a distinctive capacity for regeneration within the human body. Under normal circumstances, liver cells replicate themselves to maintain liver function. Compensatory replication of healthy hepatocytes is sufficient for the regeneration after acute liver injuries. In the late stage of chronic liver damage, a large number of hepatocytes die and hepatocyte replication is blocked. Liver regeneration has more complex mechanisms, such as the transdifferentiation between cell types or hepatic progenitor cells mediated. Dysregulation of liver regeneration causes severe chronic liver disease. Gaining a more comprehensive understanding of liver regeneration mechanisms would facilitate the advancement of efficient therapeutic approaches. This review provides an overview of the signalling pathways linked to different aspects of liver regeneration in various liver diseases. Moreover, new knowledge on cellular interactions during the regenerative process is also presented. Finally, this paper explores the potential applications of new technologies, such as nanotechnology, stem cell transplantation and organoids, in liver regeneration after injury, offering fresh perspectives on treating liver disease.

Liver Extracellular Vesicles and Particles Enriched ß-Sitosterol Effectively Promote Liver Regeneration in Mice.

Background: The liver's regenerative capacity allows it to repair itself after injury. Extracellular vesicles and particles (EVPs) in the liver's interstitial space are crucial for signal transduction, metabolism, and immune regulation. Understanding the role and mechanism of liver-derived EVPs in regeneration is significant, particularly after partial hepatectomy, where the mechanisms remain unclear. Methods: A 70% hepatectomy model was established in mice, and EVPs were isolated and characterized using electron microscopy, nanocharacterization, and Western blot analysis. Combined metabolomic and transcriptomic analyses revealed ß-sitosterol enrichment in EVPs and activation of the Hedgehog signaling pathway during regeneration. The role of ß-sitosterol in EVPs on the Hedgehog pathway and its targets were identified using qRT-PCR, Western blot analysis. The regulation of carnitine synthesis by this pathway was determined using a dual luciferase assay. The effect of a ß-sitosterol diet on liver regeneration was verified in mice. Results: After 70% hepatectomy, the liver successfully regenerated without liver failure or death. At 24 hours post-surgery, tissue staining showed transient regeneration-associated steatosis (TRAS), with increased Ki67 positivity at 48 hours. EVPs displayed a spherical lipid bilayer structure with particle sizes of 70-130 nm. CD9, CD63, and CD81 in liver-derived EVPs were confirmed. Transcriptomic and metabolomic analyses showed EVPs supplementation significantly promoted carnitine synthesis and fatty acid oxidation. Tissue staining confirmed accelerated TRAS resolution and enhanced liver regeneration with EVP supplementation. Mass spectrometry identified ß-sitosterol in EVPs, which binds to Smo protein, activating the Hedgehog pathway. This led to the nuclear transport of Gli3, stimulating Setd5 transcription and inducing carnitine synthesis, thereby accelerating fatty acid oxidation. Mice with increased ß-sitosterol intake showed faster TRAS resolution and liver regeneration compared to controls. Conclusion: Liver-derived EVPs promote regeneration after partial hepatectomy. ß-sitosterol from EVPs accelerates fatty acid oxidation and promotes liver regeneration by activating Hedgehog signaling pathway.

Carbon monoxide-loaded red blood cells ameliorate metabolic dysfunction-associated steatohepatitis progression via enhancing AMP-activated protein kinase activity and inhibiting Kupffer cell activation.

Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive form of nonalcoholic fatty liver disease characterised by fat accumulation, inflammation, oxidative stress, fibrosis, and impaired liver regeneration. In this study, we found that heme oxygenase-1 (HO-1) is induced in both MASH patients and in a MASH mouse model. Further, hepatic carbon monoxide (CO) levels in MASH model mice were >2-fold higher than in healthy mice, suggesting that liver HO-1 is activated as MASH progresses. Based on these findings, we used CO-loaded red blood cells (CO-RBCs) as a CO donor in the liver, and evaluated their therapeutic effect in methionine-choline deficient diet (MCDD)-induced and high-fat-diet (HFD)-induced MASH model mice. Intravenously administered CO-RBCs effectively delivered CO to the MASH liver, where they prevented fat accumulation by promoting fatty acid oxidation via AMP-activated protein kinase (AMPK) activation and peroxisome proliferator-activated receptor induction. They also markedly suppressed Kupffer cell activation and their corresponding anti-inflammatory and antioxidative stress activities in MASH mice. CO-RBCs also helped to restore liver regeneration in mice with HFD-induced MASH by activating AMPK. We confirmed the underlying mechanisms by performing in vitro experiments in RAW264.7 cells and palmitate-stimulated HepG2 cells. Taken together, CO-RBCs show potential as a promising cellular treatment for MASH.

Value of gadoxetic acid-enhanced MR imaging for preoperative prediction of future liver regeneration after hemihepatectomy.

PURPOSE: Liver resection is currently considered the most effective treatment for patients with liver cancer. To the best of our knowledge, no study has investigated the association between gadoxetic acid-enhanced magnetic resonance imaging (MRI) findings and liver regeneration in patients who underwent hemihepatectomy. We aimed to clarify the relationship between the signal intensity (SI) of the liver parenchyma on gadoxetic acid-enhanced MRI and the degree of liver regeneration in patients who underwent hemihepatectomy. MATERIALS AND METHODS: Forty-one patients who underwent gadoxetic acid-enhanced MRI before hemihepatectomy were enrolled. We calculated the liver-to-erector spinae muscle SI ratio (LMR) in the hepatobiliary phase and the precontrast images. ΔLMR was calculated using the following equation: ΔLMR = (LMR in the hepatobiliary phase-LMR in the precontrast image)/LMR in the precontrast image. The preoperative and postoperative remnant liver volumes (LVs) were calculated using CT volumetry. We calculated the resection rate (RR) and liver regeneration index (LRI) using the following formulas: RR = Resected LV/Total LV × 100 and LRI = (postoperative remnant LV-preoperative remnant LV)/preoperative remnant LV × 100. The relationships among LRI, imaging, and clinicopathological factors were analyzed. RESULTS: Univariate analysis showed RR and ΔLMR showed a positive correlation with LRI (ρ = 0.4133, p = 0.0072 and ρ = 0.7773, p < 0.001, respectively). Spleen volume showed a negative correlation with LRI (ρ = -0.3138, p = 0.0486). Stepwise multiple regression analysis showed ΔLMR and RR were independently correlated with LRI (ß coefficient = 44.8771, p = 0.0198 and ß coefficient = 1.9653, p < 0.001, respectively). CONCLUSION: ΔLMR may serve as a preoperative predictor of liver regeneration in patients undergoing hemihepatectomy.

Liver fibrosis as a predictor of liver failure and outcome following ALPPS among patients with primary liver cancer.

The influence of liver fibrosis on the rate of liver regeneration and complications following ALPPS has yet to be fully understood. This study aimed to scrutinize the effects of liver fibrosis on the postoperative complications, and prognosis subsequent to ALPPS. Clinical data were collected from patients with primary liver cancer who underwent ALPPS at Peking Union Medical College Hospital between May 2014 and October 2022. The degree of liver fibrosis was assessed using haematoxylin-eosin staining and Sirius red staining. This study encompassed thirty patients who underwent ALPPS for primary liver cancer, and there were 23 patients with hepatocellular carcinoma, 5 with cholangiocarcinoma, and 2 with combined hepatocellular-cholangiocarcinoma. The impact of severe liver fibrosis on the rate of liver regeneration was not statistically significant (P = 0.892). All patients with severe complications belonged to the severe liver fibrosis group. Severe liver fibrosis exhibited a significant association with 90 days mortality (P = 0.014) and overall survival (P = 0.012). Severe liver fibrosis emerges as a crucial risk factor for liver failure and perioperative mortality following the second step of ALPPS. Preoperative liver function impairment is an important predictive factor for postoperative liver failure.

Effect of Placental Derived Nucleoproteins on liver regeneration in DEN-induced liver fibrosis model.

BACKGROUND: Placental Derived Nucleoproteins (PDNs) is commonly associated with the process of angiogenesis, and doesn't affect the healthy vasculature. PDNs are clinically estimated for the treatment of cancer cases and severe hepatic injuries. Thus, the pathophysiological effects of PDNs targeting liver fibrosis is a concern. OBJECTIVES: To assess the molecular, histopathological, and chemical impact of PDNs on liver regeneration in Diethylnitrosamine (DEN)-induced mice liver fibrosis. METHODS: Normal untreated reference group of ten mice and two groups of induced liver cirrhosis using the recommended weekly dose of Diethylnitrosamine in total of eleven doses, initially 20 mg/kg body weight, and then 30 mg/kg in the third week, followed by 50 mg/kg for the last eight weeks, one of them combined treatment aligned with injection with total dose of extracted PDNs 25 mg/kg, in comparison to PDNs only treated group. An autopsy was performed after 22 weeks of the initial dose of DEN in each group. Molecular characterization of Alpha smooth muscle actin, TGFß and NF-κB biomarkers for liver then liver function panel were analyzed and finally hepatopathological changes were observed using H&E stain and Sirius red stain. RESULTS: Liver enzymes, total bilirubin and total proteins in tissue in PDNs-DEN treated models were controlled in the direction of normal group and 50 % reduction of fibrosis in comparing to DEN-treated models. The cellular arrangement of fibrosis in the DEN entire groups were differentiated with high significant impact on the survival of mice. Increased levels of the biochemical markers in liver homogenate, loss of tissue architecture, and proliferation were observed in induced groups and down regulation of alpha smooth muscle actin, TGFß and NF-κB. CONCLUSION: This finding demonstrates an improvement of Liver tissue induced fibrosis using DEN combined with PDNs. This strategy is to generate an animal model with a lower occurrence of fibrosis in a short time treatment regarding liver regeneration.

Development of a hepatic cryoinjury model to study liver regeneration.

The liver is a remarkable organ that can regenerate in response to injury. Depending on the extent of injury, the liver can undergo compensatory hyperplasia or fibrosis. Despite decades of research, the molecular mechanisms underlying these processes are poorly understood. Here, we developed a new model to study liver regeneration based on cryoinjury. To visualise liver regeneration at cellular resolution, we adapted the CUBIC tissue-clearing approach. Hepatic cryoinjury induced a localised necrotic and apoptotic lesion characterised by inflammation and infiltration of innate immune cells. Following this initial phase, we observed fibrosis, which resolved as regeneration re-established homeostasis in 30 days. Importantly, this approach enables the comparison of healthy and injured parenchyma with an individual animal, providing unique advantages to previous models. In summary, the hepatic cryoinjury model provides a fast and reproducible method for studying the cellular and molecular pathways underpinning fibrosis and liver regeneration.

Restoring energy metabolism by NAD+ supplement prevents alcohol-induced liver injury and boosts liver regeneration.

Our previous clinical metabolomics study illustrated that energy metabolism disorder is an underlying pathogenesis mechanism for the development of alcoholic liver disease (ALD). Supplementation of nicotinamide (NAM), the precursor of nicotinamide adenine dinucleotide (NAD+), may restore the energy metabolism homeostasis of ALD and thus serves as potential therapeutics to treat ALD. In this bedside-to-bench study, the protective effect of NAM against ALD was investigated by using the NIAAA mice model (chronic-plus-binge ethanol), and the liver regeneration boosting capability of NAM was evaluated by the partial hepatectomy mice model. Our results showed that NAM supplements not only protected the liver from alcohol-induced injury and improved alcohol-induced mitochondrial structure and function change, but also boosted liver regeneration in postpartial hepatectomy mice by increasing liver NAD+ content. These findings suggested that NAM, a water-soluble form of vitamin B3, can promote liver regeneration and improves liver function by alleviating alcohol-induced energy metabolism disorder.

Fenofibrate-promoted hepatomegaly and liver regeneration are PPARα-dependent and partially related to the YAP pathway.

Fenofibrate, a peroxisome proliferator-activated receptor α (PPARα) agonist, is widely prescribed for hyperlipidemia management. Recent studies also showed that it has therapeutic potential in various liver diseases. However, its effects on hepatomegaly and liver regeneration and the involved mechanisms remain unclear. Here, the study showed that fenofibrate significantly promoted liver enlargement and regeneration post-partial hepatectomy in mice, which was dependent on hepatocyte-expressed PPARα. Yes-associated protein (YAP) is pivotal in manipulating liver growth and regeneration. We further identified that fenofibrate activated YAP signaling by suppressing its K48-linked ubiquitination, promoting its K63-linked ubiquitination, and enhancing the interaction and transcriptional activity of the YAP-TEAD complex. Pharmacological inhibition of YAP-TEAD interaction using verteporfin or suppression of YAP using AAV Yap shRNA in mice significantly attenuated fenofibrate-induced hepatomegaly. Other factors, such as MYC, KRT23, RAS, and RHOA, might also participate in fenofibrate-promoted hepatomegaly and liver regeneration. These studies demonstrate that fenofibrate-promoted liver enlargement and regeneration are PPARα-dependent and partially through activating the YAP signaling, with clinical implications of fenofibrate as a novel therapeutic agent for promoting liver regeneration.

Dexmedetomidine facilitates autophagic flux to promote liver regeneration by suppressing GSK3ß activity in mouse partial hepatectomy.

INTRODUCTION: Dexmedetomidine (DEX), a highly selective α2-adrenergic receptor agonist, is widely used for sedation and anesthesia in patients undergoing hepatectomy. However, the effect of DEX on autophagic flux and liver regeneration remains unclear. OBJECTIVES: This study aimed to determine the role of DEX in hepatocyte autophagic flux and liver regeneration after PHx. METHODS: In mice, DEX was intraperitoneally injected 5 min before and 6 h after PHx. In vitro, DEX was co-incubated with culture medium for 24 h. Autophagic flux was detected by LC3-II and SQSTM1 expression levels in primary mouse hepatocytes and the proportion of red puncta in AML-12 cells transfected with FUGW-PK-hLC3 plasmid. Liver regeneration was assessed by cyclinD1 expression, Edu incorporation, H&E staining, ki67 immunostaining and liver/body ratios. Bafilomycin A1, si-GSK3ß and Flag-tagged GSK3ß, α2-ADR antagonist, GSK3ß inhibitor, AKT inhibitor were used to identify the role of GSK3ß in DEX-mediated autophagic flux and hepatocyte proliferation. RESULTS: Pre- and post-operative DEX treatment promoted liver regeneration after PHx, showing 12 h earlier than in DEX-untreated mice, accompanied by facilitated autophagic flux, which was completely abolished by bafilomycin A1 or α2-ADR antagonist. The suppression of GSK3ß activity by SB216763 and si-GSK3ß enhanced the effect of DEX on autophagic flux and liver regeneration, which was abolished by AKT inhibitor. CONCLUSION: Pre- and post-operative administration of DEX facilitates autophagic flux, leading to enhanced liver regeneration after partial hepatectomy through suppression of GSK3ß activity in an α2-ADR-dependent manner.

Boiling histotripsy exhibits anti-fibrotic effects in animal models of liver fibrosis.

Liver fibrosis is a hallmark of chronic liver disease which could lead to liver cirrhosis or liver cancer. However, there is currently lack of a direct treatment for liver fibrosis. Boiling histotripsy (BH) is an emerging non-invasive high-intensity focused ultrasound technique that can be employed to mechanically destruct solid tumour at the focus via acoustic cavitation without significant adverse effect on surrounding tissue. Here, we investigated whether BH can mechanically fractionate liver fibrotic tissue thereby exhibiting an anti-fibrotic effect in an animal model of liver fibrosis. BH-treated penumbra and its identical lobe showed reduced liver fibrosis, accompanied by increased hepatocyte specific marker expression, compared to the BH-untreated lobe. Furthermore, BH treatment improved serological liver function markers without notable adverse effects. The ability of BH to reduce fibrosis and promote liver regeneration in liver fibrotic tissue suggests that BH could potentially be an effective and reliable therapeutic approach against liver fibrosis.

[Characteristics of liver volume and pathological changes with different stages of liver fibrosis in chronic liver disease].

Objective: To measure the overall and lobulated volume of the liver with different degrees of liver fibrosis and to further observe pathological changes such as liver microvasculature, hepatocyte apoptosis, and regeneration in order to understand the macroscopic volume changes of the liver during liver fibrosis and its relationship with liver tissue microscopic pathology in patients with chronic liver disease. Methods: 53 patients with chronic hepatitis B, alcoholic fatty liver disease, autoimmune liver disease, nonalcoholic fatty liver disease, and drug-induced chronic liver disease who underwent both liver biopsy tissue and abdominal magnetic resonance imaging were collected. Patients were divided into early (F1-2), middle (F3-4), and late (F5-6) in accordance with the Ishak fibrosis stage and Masson stain. The liver and spleen volumes were measured using ITK-SNAP software. CD31 immunohistochemical staining was used to reflect intrahepatic angiogenesis. Ki67 and HNF-4α multiplex immunohistochemical staining were used to reflect hepatocyte regeneration. GS staining was used to determine parenchymal extinction lesions. TUNEL staining was used to observe hepatocyte apoptosis. Spearman correlation analysis was used to analyze the relationship between liver volume changes and liver histopathological changes. Results: As liver fibrosis progressed, the total liver volume and right lobe liver volume gradually decreased (P<0.05), while the spleen volume gradually increased (P<0.05). The expression of CD31 and GS gradually increased (P<0.05), and the expression of Ki67 first increased and then decreased (P<0.05). The positivity rate of CD31 was negatively correlated with the right lobe liver volume (r=-0.609, P<0.001) and the total liver volume (r=-0.363, P=0.017). The positivity rate of Ki67 was positively correlated with the right lobe liver volume (r=0.423, P=0.018), while the positivity rate of apoptotic cells was significantly negatively correlated with the total liver volume (r=-0.860, P<0.001). The positivity rate of GS was negatively correlated with the right lobe liver volume (r=-0.440, P=0.002), and the number of PELs was negatively correlated with RV (r=-0.476, P=0.013). The CD31 positive staining area was negatively correlated with the Ki67 positive staining area(r=-0.511, P=0.009). Conclusion: As liver fibrosis progresses, patients with chronic liver disease have a depletion in total liver volume and right lobe liver volume, and this is mainly in correlation with fewer liver cells and liver tissue microvasculature disorders.

Transcriptomic Characterization of Key Factors and Signaling Pathways for the Regeneration of Partially Hepatectomized Liver in Zebrafish.

Liver regeneration induced by partial hepatectomy (PHx) has attracted intensive research interests due to the great significance for liver resection and transplantation. The zebrafish (Danio rerio) is an excellent model to study liver regeneration. In the fish subjected to PHx (the tip of the ventral lobe was resected), the lost liver mass could be fully regenerated in seven days. However, the regulatory mechanisms underlying the liver regeneration remain largely unknown. In this study, gene expression profiles during the regeneration of PHx-treated liver were explored by RNA sequencing (RNA-seq). The genes responsive to the injury of PHx treatment were identified and classified into different clusters based on the expression profiles. Representative gene ontology (GO) enrichments for the early responsive genes included hormone activity, ribosome biogenesis and rRNA processing, etc., while the late responsive genes were enriched in biological processes such as glutathione metabolic process, antioxidant activity and cellular detoxification. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichments were also identified for the differentially expressed genes (DEGs) between the time-series samples and the sham controls. The proteasome was overrepresented by the up-regulated genes at all of the sampling time points. Inhibiting proteasome activity by the application of MG132 to the fish enhanced the expression of Pcna (proliferating cell nuclear antigen), an indicator of hepatocyte proliferation after PHx. Our data provide novel insights into the molecular mechanisms underlying the regeneration of PHx-treated liver.

Ammonia and urea metabolism in acute liver failure: A multicentre cohort study.

BACKGROUND & AIMS: Ammonia is metabolized into urea in the liver. In acute liver failure (ALF), ammonia has been associated with survival. However, urea variation has been poorly studied. METHODS: Observational cohort including ALF patients from Curry Cabral Hospital (Lisbon, Portugal) and Clinic Hospital (Barcelona, Spain) between 10/2010 and 01/2023. The United States ALF Study Group cohort was used for external validation. Primary exposures were serum ammonia and urea on ICU admission. Primary endpoint was 30-day transplant-free survival (TFS). Secondary endpoint was explanted liver weight. RESULTS: Among 191 ALF patients, median (IQR) age was 46 (32; 57) years and 85 (44.5%) were males. Overall, 86 (45.0%) patients were transplanted and 75 (39.3%) died. Among all ALF patients, following adjustment for age, sex, body weight, and aetiology, higher ammonia or lower urea was independently associated with higher INR on ICU admission (p < .009). Among all ALF patients, following adjustment for sex, aetiology, and lactate, higher ammonia was independently associated with lower TFS (adjusted odds ratio (95% confidence interval [CI]) = 0.991 (0.985; 0.997); p = .004). This model predicted TFS with good discrimination (area under receiver operating curve [95% CI] = 0.78 [0.75; 0.82]) and reasonable calibration (R2 of 0.43 and Brier score of 0.20) after external validation. Among transplanted patients, following adjustment for age, sex, actual body weight, and aetiology, higher ammonia (p = .024) or lower (p < .001) urea was independently associated with lower explanted liver weight. CONCLUSIONS: Among ALF patients, serum ammonia and urea were associated with ALF severity. A score incorporating serum ammonia predicted TFS reasonably well.

Integrative analysis of the transcriptome and metabolome reveals the importance of hepatokine FGF21 in liver aging.

Aging is a contributor to liver disease. Hence, the concept of liver aging has become prominent and has attracted considerable interest, but its underlying mechanism remains poorly understood. In our study, the internal mechanism of liver aging was explored via multi-omics analysis and molecular experiments to support future targeted therapy. An aged rat liver model was established with d-galactose, and two other senescent hepatocyte models were established by treating HepG2 cells with d-galactose and H2O2. We then performed transcriptomic and metabolomic assays of the aged liver model and transcriptome analyses of the senescent hepatocyte models. In livers, genes related to peroxisomes, fatty acid elongation, and fatty acid degradation exhibited down-regulated expression with aging, and the hepatokine Fgf21 expression was positively correlated with the down-regulation of these genes. In senescent hepatocytes, similar to the results found in aged livers, FGF21 expression was also decreased. Moreover, the expressions of cell cycle-related genes were significantly down-regulated, and the down-regulated gene E2F8 was the key cell cycle-regulating transcription factor. We then validated that FGF21 overexpression can protect against liver aging and that FGF21 can attenuate the declines in the antioxidant and regenerative capacities in the aging liver. We successfully validated the results from cellular and animal experiments using human liver and blood samples. Our study indicated that FGF21 is an important target for inhibiting liver aging and suggested that pharmacological prevention of the reduction in FGF21 expression due to aging may be used to treat liver aging-related diseases.

Transcriptional Control: A Directional Sign at the Crossroads of Adult Hepatic Progenitor Cells' Fates.

Hepatic progenitor cells (HPCs) have a bidirectional potential to differentiate into hepatocytes and bile duct epithelial cells and constitute a second barrier to liver regeneration in the adult liver. They are usually located in the Hering duct in the portal vein region where various cells, extracellular matrix, cytokines, and communication signals together constitute the niche of HPCs in homeostasis to maintain cellular plasticity. In various types of liver injury, different cellular signaling streams crosstalk with each other and point to the inducible transcription factor set, including FoxA1/2/3, YB-1, Foxl1, Sox9, HNF4α, HNF1α, and HNF1ß. These transcription factors exert different functions by binding to specific target genes, and their products often interact with each other, with diverse cascades of regulation in different molecular events that are essential for homeostatic regulation, self-renewal, proliferation, and selective differentiation of HPCs. Furthermore, the tumor predisposition of adult HPCs is found to be significantly increased under transcriptional factor dysregulation in transcriptional analysis, and the altered initial commitment of the differentiation pathway of HPCs may be one of the sources of intrahepatic tumors. Related transcription factors such as HNF4α and HNF1 are expected to be future targets for tumor treatment.

Secondary bile acids in portal blood contribute to liver regeneration in a rat model of partial hepatectomy.

Gut metabolites via the portal vein affect several liver functions, including regeneration. Here, we investigated gut microbiota-derived metabolites in portal and peripheral serum during liver regeneration. We developed rat models of 70% partial hepatectomy (PHx) with and without prior gut microbiota modulation by three-week antibiotic (Abx) treatment. Sham without Abx were used as controls and compared to sham with Abx. Liver regeneration at day 2 following PHx was assessed by expression of proliferating cell nuclear antigen (PCNA) protein in liver tissues and cyclin genes in primary hepatocytes. High pressure liquid chromatography-mass spectrometry (HPLC-MS) based portal and peripheral venous serum metabolomics was performed to identify differentially altered metabolites (DAMs). Compared to controls, rat livers at day 2 post-PHx showed significant upregulation in the average number of PCNA-positive cells, which positively correlated with the expression of cell cycle genes in hepatocytes. In Abx-treated PHx, we observed reduced PCNA-positivity and downregulation in gene expression of various cyclins in hepatocytes compared to PHx. We identified 224 DAMs between controls vs PHx and 189 DAMs between Abx-treated PHx vs PHx in portal serum. Many common DAMs showed opposite expression trends in PHx vs controls and then Abx+PHx vs PHx in portal serum, such as sphingosine-1-phosphate and deoxycholic acid. In vitro studies with deoxycholic acid demonstrated that it enhanced the viability and proliferation of primary hepatocytes and hepatocyte organoids. The study underscores the critical role of deoxycholic acid in portal blood in enhancing hepatocyte proliferation and subsequently, liver regeneration.

Characterization of a model of liver regeneration: Role of hedgehog signaling in experimental hepatic amoebiasis.

The development of amoebic liver abscess (ALA) leads to liver necrosis, accompanied by an exacerbated inflammatory response and the formation of multiple granulomas. Adequate management of the infection through the administration of treatment and the timely response of the organ to the damage allows the injury to heal with optimal regeneration without leaving scar tissue, which does not occur in other types of damage such as viral hepatitis that may conducts to fibrosis or cirrhosis. The Hedgehog signaling pathway (Hh) is crucial in the embryonic stage, while in adults it is usually reactivated in response to acute or chronic injuries, regeneration, and wound healing. In this work, we characterized Hh in experimental hepatic amoebiasis model, with the administration of treatment with metronidazole, as well as a pathway inhibitor (cyclopamine), through histological and immunohistochemical analyses including an ultrastructure analysis through transmission electron microscopy. The results showed an increase in the percentage of lesions obtained, a decrease in the presence of newly formed hepatocytes, a generalized inflammatory response, irregular distribution of type I collagen accompanied by the presence of fibroblast-type cells and a decrease in effector cells of this pathway. These results constitute the first evidence of the association of the activation of Hh with the liver regeneration process in experimental amebiasis.

Vitamin D Receptor Regulates Liver Regeneration After Partial Hepatectomy in Male Mice.

Vitamin D signals through the vitamin D receptor (VDR) to induce its end-organ effects. Hepatic stellate cells control development of liver fibrosis in response to stressors and vitamin D signaling decreases fibrogenesis. VDR expression in hepatocytes is low in healthy liver, and the role of VDR in hepatocyte proliferation is unclear. Hepatocyte-VDR null mice (hVDR) were used to assess the role of VDR and vitamin D signaling in hepatic regeneration. hVDR mice have impaired liver regeneration and impaired hepatocyte proliferation associated with significant differential changes in bile salts. Notably, mice lacking hepatocyte VDR had significant increases in expression of conjugated bile acids after partial hepatectomy, consistent with failure to normalize hepatic function by the 14-day time point tested. Real-time PCR of hVDR and control livers showed significant changes in expression of cell-cycle genes including cyclins D1 and E1 and cyclin-dependent kinase 2. Gene expression profiling of hepatocytes treated with vitamin D or control showed regulation of groups of genes involved in liver proliferation, hepatitis, liver hyperplasia/hyperproliferation, and liver necrosis/cell death. Together, these studies demonstrate an important functional role for VDR in hepatocytes during liver regeneration. Combined with the known profibrotic effects of impaired VDR signaling in stellate cells, the studies provide a mechanism whereby vitamin D deficiency would both reduce hepatocyte proliferation and permit fibrosis, leading to significant liver compromise.