Experimental liver fibrosis research: update on animal models, legal issues and translational aspects

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Patients with end‐stage liver disease develop acute decompensation (AD) episodes, which become more frequent and might develop into acute‐on‐chronic liver failure (ACLF). However, it remains unknown how AD induces acceleration of liver disease. We hypothesized that remodeling of collagen type III plays a role in the acceleration of liver cirrhosis after AD and analyzed its formation (Pro‐C3) and degradation (matrix metalloproteinase‐degraded type III collagen [C3M]) markers in animal models and human disease. Bile duct ligation induced different stages of liver fibrosis in rats. Fibrosis development (hydroxyprolin content, sirius red staining, α‐smooth muscle actin immunohistochemistry, messenger RNA of profibrotic cytokines), necroinflammation (aminotransferases levels), fibrolysis (matrix metalloproteinase 2 expression and activity, C1M, C4M), and Pro‐C3 and C3M were analyzed 2, 3, 4, 5, and 6 weeks after bile duct ligation (n = 5 each group). In 110 patients with decompensated liver cirrhosis who underwent a transjugular intrahepatic portosystemic shunt procedure for AD, clinical and laboratory parameters as well as Pro‐C3 and C3M were measured in blood samples from portal and hepatic veins and were collected just before the transjugular intrahepatic portosystemic shunt placement and 1‐3 weeks later. Animal studies showed increased markers of collagen type III deposition with fibrosis, necroinflammation, and decompensation of liver cirrhosis, defined as ascites development. Higher Pro‐C3 levels were associated with injury, disease severity scores (Model for End‐Stage Liver Disease, Child‐Pugh, chronic liver failure‐C AD), ACLF development, and mortality. C3M decreased with AD and the chronic liver failure‐C AD score. Collagen type III deposition ratio increased with the risk of ACLF development and mortality. Conclusion: We show for the first time that AD boosts collagen type III deposition in experimental and human cirrhosis, possibly contributing to the worsened outcome in patients with decompensated cirrhosis. (Hepatology Communications 2018;2:211–222)

Section: Discussionmentioning

confidence: 99%

Acute decompensation boosts hepatic collagen type III deposition and deteriorates experimental and human cirrhosis

Praktiknjo

Lehmann

Nielsen

et al. 2018

Self Cite

“…While myofibroblasts play a critical role in the development of hepatic fibrosis, they are believed to originate from different cellular sources, depending on the etiologies. In mouse experimental models, chronic toxic liver injuries caused by CCl 4 or TAA administration result in hepatocellular necrosis around the central vein, whereas cholestatic liver injuries caused by a DDC diet or BDL surgery result in injury of cholangiocytes in the portal region 29. Using these experimental liver injury models, it has been implied that fibrogenic myofibroblasts originate from HSCs in chronic toxic liver injuries but originate from PFs in cholestatic liver injuries 14, 30.…”

Section: Discussionmentioning

confidence: 99%

Portal fibroblasts marked by the surface antigen Thy1 contribute to fibrosis in mouse models of cholestatic liver injury

Katsumata

Miyajima

Itoh

2017

Liver fibrosis, a condition that is characterized by excessive production and accumulation of extracellular matrix, including collagen, is the most common outcome of chronic liver injuries of different etiologies. Vitamin A‐storing hepatic stellate cells (HSCs) are considered to be the main source of this collagen production, with activation in response to liver injury. In contrast, the contribution of other cell types to this fibrogenic response remains largely elusive due to the lack of specific surface markers to identify and isolate these cells for detailed analysis. Here, we identify a mesenchymal population of thymus cell antigen 1 (Thy1)+ CD45− cells (Thy1 MCs) in the mouse liver; these cells reside near the portal vein in vivo and indicate profibrogenic characteristics in vitro, shown by their expression of collagen and α‐smooth muscle actin. Flow cytometric analysis of mouse liver nonparenchymal cells revealed that vitamin A storage and Thy1 expression were mutually exclusive, indicating that Thy1 MCs are distinct from HSCs. Importantly, Thy1 MCs reacted and contributed to the development of liver fibrosis specifically in mouse models of cholestatic liver injury. With the occurrence of cholestatic liver injury, collagen‐producing Thy1 MCs expanded in cell number and inhibited collagen degradation through up‐regulation of matrix metalloproteinase inhibitor Timp1 expression, thereby promoting the accumulation of extracellular matrix in the periportal area. Conclusion: This study establishes Thy1 as a useful cell surface marker to prospectively identify and isolate periportal fibroblasts and further highlights a significant contribution of these cells to the pathogenesis of liver fibrosis caused by cholestatic liver injuries. We suggest that Thy1 MCs may be an interesting therapeutic target for treating liver fibrosis in addition to the well‐characterized HSCs. (Hepatology Communications 2017;1:198‐214)

“…CCl 4 ‐induced liver injury has been extensively used as a model of acute and chronic liver injury 13. A single injection of CCl 4 induces centrilobular necrosis by a reactive free radical metabolite, which is generated by cytochrome P450 2E1 (Cyp2e1) in centrilobular hepatocytes, and causes transient activation of HSCs as a wound healing response.…”

mentioning

confidence: 99%

Neutrophils alleviate fibrosis in the CCl4‐induced mouse chronic liver injury model

Saijou

Enomoto

Matsuda

et al. 2018

Tribbles pseudokinase 1 (Trib1) is a negative regulator of CCAAT/enhancer binding protein α (C/EBPα) and is known to induce granulopoiesis while suppressing monocyte differentiation. Loss of Trib1 was previously shown to increase the neutrophil population in the spleen but lead to M2‐like macrophage reduction. Because M2 macrophages are anti‐inflammatory and promote tissue repair by producing fibrogenic factors, we investigated liver fibrosis in Trib1‐deficient mice. Interestingly, loss of Trib1 suppressed fibrosis in the CCl4‐induced chronic liver injury model. Trib1 knockout increased neutrophils but had a minimal effect on the macrophage population in the liver. Hepatic expressions of neutrophil matrix metalloproteinases (Mmp)8 and Mmp9 were increased, but the production of fibrogenic factors, including transforming growth factor β1, was not affected by loss of Trib1. These results suggest that neutrophils are responsible for the suppression of fibrosis in Trib1‐deficient liver. Consistently, transplantation of Trib1‐deficient bone marrow cells into wild‐type mice alleviated CCl4‐induced fibrosis. Furthermore, expression of chemokine (C‐X‐C motif) ligand 1 (Cxcl1) by adeno‐associated viral vector in the normal liver recruited neutrophils and suppressed CCl4‐induced fibrosis; infusion of wild‐type neutrophils in CCl4‐treated mice also ameliorated fibrosis. Using recombinant adeno‐associated virus‐mediated expression of Mmp8 and Mmp9 alleviated liver fibrosis. Finally, neutrophil depletion by infusion of Ly6G antibody significantly enhanced CCl4‐induced fibrosis. Conclusion: While neutrophils are well known to exacerbate acute liver injury, our results demonstrate a beneficial role of neutrophils in chronic liver injury by promoting fibrolysis. (Hepatology Communications 2018;2:703‐717)