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Introduction: Recent animal studies have shown that the alternate renin-angiotensin system (RAS) consisting of angiotensin-converting enzyme 2 (ACE2), angiotensin-(1–7) (Ang-(1–7)) and the Mas receptor is upregulated in cirrhosis and contributes to splanchnic vasodilatation and portal hypertension. To determine the potential relevance of these findings to human liver disease, we evaluated its expression and relationship to the patients’ clinical status in subjects with cirrhosis. Methods: Blood sampling from peripheral and central vascular beds was performed intra-operatively for cirrhotic patients at the time of liver transplantation (LT) or trans-jugular intra-hepatic portosystemic shunt (TIPS) procedures to measure angiotensin II (Ang II) and Ang-(1–7) peptide levels and ACE and ACE2 enzyme activity. Relevant clinical and hemodynamic data were recorded pre-operatively for all subjects and peripheral blood sampling was repeated 3 months or later post-operatively. Results: Ang-(1–-7) and ACE2 activity were up-regulated more than twofold in cirrhotic subjects both at the time of LT and TIPS and levels returned to comparable levels as control subjects post-transplantation. Ang-(1–7) levels correlated positively with the degree of liver disease severity, as measured by the model for an end-stage liver disease (MELD) and also with clinical parameters of pathological vasodilatation including cardiac output (CO). There were strong correlations found between the ACE2:ACE and the Ang-(1–7):Ang II ratio highlighting the inter-dependence of the alternate and classical arms of the RAS and thus their potential impact on vascular tone. Conclusions: In human cirrhosis, the alternate RAS is markedly upregulated and the activation of this system is associated strongly with features of the hyperdynamic circulation in advanced human cirrhosis.
Non-alcoholic fatty liver disease (NAFLD) is gaining in importance and is linked to obesity. Especially,thedevelopmentoffibrosisandportalhypertensioninNAFLDpatientsrequirestreatment. Transgenic TGR(mREN2)27 rats overexpressing mouse renin spontaneously develop NAFLD with portal hypertension but without obesity. This study investigated the additional role of obesity in this model on the development of portal hypertension and fibrosis. Obesity was induced in twelve-week old TGR(mREN2)27 rats after receiving Western diet (WD) for two or four weeks. Liver fibrosis was assessed using standard techniques. Hepatic expression of transforming growth factor-β1 (TGF-β1), collagen type Iα1, α-smooth muscle actin, and the macrophage markers Emr1, as well as the chemoattractant Ccl2, interleukin-1β (IL1β) and tumor necrosis factor-α (TNFα) were analyzed. Assessment of portal and systemic hemodynamics was performed using the colored microsphere technique. Asexpected,WDinducedobesityandliverfibrosisasconfirmedbySiriusRedandOilRed O staining. The expression of the monocyte-macrophage markers, Emr1, Ccl2, IL1β and TNFα were increasedduringfeedingofWD,indicatinginfiltrationofmacrophagesintotheliver,eventhoughthis increase was statistically not significant for the EGF module-containing mucin-like receptor (Emr1) mRNA expression levels. Of note, portal pressure increased with the duration of WD compared to animals that received a normal chow. Besides obesity, WD feeding increased systemic vascular resistance reflecting systemic endothelial and splanchnic vascular dysfunction. We conclude that transgenic TGR(mREN2)27 rats are a suitable model to investigate NAFLD development with liver fibrosis and portal hypertension. Tendency towards elevated expression of Emr1 is associated with macrophage activity point to a significant role of macrophages in NAFLD pathogenesis, probably due to a shift of the renin–angiotensin system towards a higher activation of the classical pathway. The hepatic injury induced by WD in TGR(mREN2)27 rats is suitable to evaluate different stages of fibrosis and portal hypertension in NAFLD with obesity.
Prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing. Resulting fibrosis and portal hypertension, as a possible secondary event, may necessitate treatment. Overexpression of mouse renin in the transgenic rat model, TGR(mREN2)27, leads to spontaneous development of NAFLD. Therefore, we used TGR(mREN2)27 rats as a model of NAFLD where we hypothesized increased susceptibility and investigated fibrosis and portal hypertension and associated pathways. 12-week old TGR(mREN2)27 rats received either cholestatic (BDL) or toxic injury (CCl4 inhalation). Portal and systemic hemodynamic assessments were performed using microsphere technique with and without injection of the Janus-Kinase 2 (JAK2) inhibitor AG490 or the non-peptidic Ang(1-7) agonist, AVE0991. The extent of liver fibrosis was assessed in TGR(mREN2)27 and wild-type rats using standard techniques. Protein and mRNA levels of profibrotic, renin-angiotensin system components were assessed in liver and primary hepatic stellate cells (HSC) and hepatocytes. TGR(mREN2)27 rats developed spontaneous, but mild fibrosis and portal hypertension due to the activation of the JAK2/Arhgef1/ROCK pathway. AG490 decreased migration of HSC and portal pressure in isolated liver perfusions and in vivo. Fibrosis or portal hypertension after cholestatic (BDL) or toxic injury (CCl4) was not aggravated in TGR(mREN2)27 rats, probably due to decreased mouse renin expression in hepatocytes. Interestingly, portal hypertension was even blunted in TGR(mREN2)27 rats (with or without additional injury) by AVE0991. TGR(mREN2)27 rats are a suitable model of spontaneous liver fibrosis and portal hypertension but not with increased susceptibility to liver damage. After additional injury, the animals can be used to evaluate novel therapeutic strategies targeting Mas.
Molecular and cellular research modalities for the study of liver pathologies have been tremendously improved over the recent decades. Advanced technologies offer novel opportunities to establish cell isolation techniques with excellent purity, paving the path for 2D and 3D microscopy and high-throughput assays (e.g., bulk or single-cell RNA sequencing). The use of stem cell and organoid research will help to decipher the pathophysiology of liver diseases and the interaction between various parenchymal and non-parenchymal liver cells. Furthermore, sophisticated animal models of liver disease allow for the in vivo assessment of fibrogenesis, portal hypertension and hepatocellular carcinoma (HCC) and for the preclinical testing of therapeutic strategies. The purpose of this review is to portray in detail novel in vitro and in vivo methods for the study of liver cell biology that had been presented at the workshop of the 8th meeting of the European Club for Liver Cell Biology (ECLCB-8) in October of 2018 in Bonn, Germany.
Background & Aims: Phosphodiesterase‐5 inhibitors (PDE‐5‐I) are used for treatment of erectile dysfunction (ED), which is common in patients with cirrhosis. They may improve portal hypertension (PH), but contradictory data on efficacy and side‐effects have been reported. Non‐selective beta blockers (NSBB) reduce portal pressure, but might aggravate ED. Thus, we evaluated the combination of PDE‐5‐I with NSBB and its impact on PH and ED in experimental cirrhosis.
Methods: ED was assessed in cirrhotic patients (n = 86) using standardized questionnaire. Experimental cirrhosis was induced by bile‐duct‐ligation or carbon‐tetrachloride intoxication in rats. Corpus cavernosum pressure – a surrogate of ED ‐, as well as systemic and portal haemodynamics, were measured in vivo and in situ after acute administration of udenafil alone or in combination with propranolol. mRNA and protein levels of PDE‐5 signalling were analysed using PCR and western Blot.
Results: ED in humans was related to severity of liver disease and to NSBB treatment. PDE‐5 was mainly expressed in hepatic stellate cells and upregulated in human and experimental cirrhosis. Propranolol reduced corpus cavernosum pressure in cirrhotic rats and it was restored by udenafil. Even though udenafil treatment improved PH, it led to a reduction of mean arterial pressure. The combination of udenafil and propranolol reduced portal pressure and hepatic resistance without systemic side‐effects.
Conclusions: ED is common with advanced cirrhosis and concomitant NSBB treatment. The combination of PDE‐5‐I and NSBB improves ED and PH in experimental cirrhosis.