murine-precision-cut-liver-slices-as-an-ex-vivo-model-of-liver-biology

Murine Precision-Cut Liver Slices as an Ex Vivo Model of Liver Biology

Understanding the mechanisms of liver injury, hepatic fibrosis, and cirrhosis that underlie chronic liver diseases (i.e., viral hepatitis, non-alcoholic ...

QIMR Berghofer Medical Research Institute

Skeletal muscle remodels metabolic capacity, contractile and exercise phenotype in response to physiological demands. This adaptive remodeling response to physical activity can ameliorate/prevent diseases associated with poor diet and lifestyle. Our previous work demonstrated that skeletal muscle-specific transgenic expression of the neuron-derived orphan nuclear receptor, Nor-1 drives muscle reprogramming, improves exercise endurance, and oxidative metabolism. The current manuscript investigates the association between exercise, Nor-1 expression and the role of Nor-1 in adaptive remodeling. We demonstrate that Nor-1 expression is induced by exercise and is dependent on calcium/calcineurin signaling (in vitro and in vivo). Analysis of fatigue-resistant transgenic mice that express Nor-1 in skeletal muscle revealed increased hypertrophy and vascularization of muscle tissue. Moreover, we demonstrate that transgenic Nor-1 expression is associated with increased intracellular recycling, ie, autophagy, involving 1) increased expression of light chain 3A or LC3A-II, autophagy protein 5, and autophagy protein 12 in quadriceps femoris muscle extracts from Tg-Nor-1 (relative to Wild-type (WT) littermates); 2) decreased p62 expression indicative of increased autophagolysosome assembly; and 3) decreased mammalian target of rapamycin complex 1 activity. Transfection of LC3A-GFP-RFP chimeric plasmid demonstrated that autophagolysosome formation was significantly increased by Nor-1 expression. Furthermore, we demonstrated a single bout of exercise induced LC3A-II expression in skeletal muscle from C57BL/6 WT mice. This study, when combined with our previous studies, demonstrates that Nor-1 expression drives multiple physiological changes/pathways that are critical to the beneficial responses of muscle to exercise and provides insights into potential pharmacological manipulation of muscle reprogramming for the treatment of lifestyle induced chronic diseases. 

The Nuclear Receptor, Nor-1, Induces the Physiological Responses Associated With Exercise.

Cystic fibrosis liver disease (CFLD) in children causes progressive fibrosis leading to biliary cirrhosis, however its cause(s) and early pathogenesis are unclear. We hypothesised that a bile acid-induced Ductular Reaction (DR) drives fibrogenesis. We evaluated the DR by cytokeratin-7 immunohistochemistry in liver biopsies, staged for fibrosis, from 60 children with CFLD and demonstrated that the DR was significantly correlated with hepatic fibrosis stage and biliary taurocholate levels. To examine the mechanisms involved in DR induction liver progenitor cells (LPCs) were treated with taurocholate and key events in DR evolution were assessed: LPC proliferation, LPC biliary differentiation and hepatic stellate cell (HSC) chemotaxis. Taurocholate induced a time-dependent increase in LPC proliferation and expression of genes associated with cholangiocyte differentiation (cytokeratin-19, connexin-43, integrin-β4 and γ-glutamyltranspeptidase [GGT]), while the hepatocyte specification marker HNF4α was suppressed. Functional cholangiocyte differentiation was demonstrated via increased acetylated α-tubulin and SOX9 proteins, the number of primary cilia(+) LPCs and increased active GGT enzyme secretion. Taurocholate induced LPCs to release MCP-1, MIP1α and RANTES into conditioned medium causing HSC chemotaxis, which was inhibited by anti-MIP1α. Immunofluorescence confirmed chemokine expression localized to CK7(+) DR and LPCs in CFLD liver biopsies. This study suggests that taurocholate is involved in initiating functional LPC biliary differentiation and the development of the DR, with subsequent induction of chemokines that drive HSC recruitment in CFLD.

Taurocholate induces biliary differentiation of liver progenitor cells causing hepatic stellate cell chemotaxis in the Ductular Reaction: Role in pediatric cystic fibrosis liver disease.

Abnormal retinoic acid (RA) signalling is considered a major cause of congenital diaphragmatic hernia (CDH). Pulmonary hypoplasia and pulmonary hypertension are the major causes of morbidity and mortality in infants born with CDH. Experimental studies in animals have found that RA signalling is involved in lung and liver development, but animal models of CDH do not directly correlate with CDH in human fetuses. This study investigated if RA status is also linked to lung and liver growth in human fetuses with CDH.

Lung and liver growth and retinoic acid status in human fetuses with congenital diaphragmatic hernia.

Exercise induces various physical and metabolic changes in skeletal muscle that adaptively reprograms this tissue to current physiological and environmental demands. Underlying these changes are broad modifications to gene expression. We postulate that the nuclear hormone receptor, Nor-1, is activated after exercise, and this transcription factor modifies gene expression to drive the molecular and cellular adaptations associated with contractile reorganization.

Article	Year
The Nuclear Receptor, Nor-1, Induces the Physiological Responses Associated With Exercise. Molecular endocrinology (Baltimore, Md.)\| PubMed ID: 27144290	2016
Taurocholate induces biliary differentiation of liver progenitor cells causing hepatic stellate cell chemotaxis in the Ductular Reaction: Role in pediatric cystic fibrosis liver disease. The American journal of pathology\| PubMed ID: 28935574	2017
Lung and liver growth and retinoic acid status in human fetuses with congenital diaphragmatic hernia. Early human development\| PubMed ID: 29096166	2018
The Nuclear Receptor Nor-1 Is a Pleiotropic Regulator of Exercise-Induced Adaptations. Exercise and sport sciences reviews\| PubMed ID: 29346164	2018

Michael A. Pearen

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