Abstract
In the last two years the European Parliament and the Council of the European Union (EU) have implemented the EU Directive 2010/63 in their Member States. 1 This legislation regulates the protection of animals used for scientific or educational purposes. The Directive was adopted on 22 September 2010 and is based mainly on the execution of the 3 R principle first proposed in 1959 by William Russell and Rex L Burch as an ethical framework for conducting scientific experiments with animals that encourages the replacement, reduction and refinement of animals used for scientific purposes and testing. 2 In the 66 Articles of Directive 2010/63, strict rules for breeding, marking, and care including the accommodation and killing of animals as well as the evaluation and authorization of projects involving the use of animals in so-called ‘procedures’ are laid down. The term ‘procedure’ in this revised regulation is defined as any intervention that may cause pain, suffering, distress or lasting harm to an animal.
A report published at the end of 2007 covering statistical data that was collected in the former 25 EU Members States in 2005 revealed that about 12.1 million animals were used for experimental and other scientific purposes in the EU, of which mice (53%) and rats (19%) were by far the most used species. 3 In addition, this report further emphasized that 57.5% of the total animals used for experimental purposes in the EU were used for studies analysing both animal and human diseases. 3 On the basis of these facts, it is surprising that in many research fields that conduct ‘translational medicine’ there is no comprehensive consensus on how to execute, evaluate, or characterize potential animal models and ‘procedures’. Unfortunately, this makes the direct comparison of experimental results and the effective exchange of data between different research groups difficult or even impossible. Of course this precludes the realization of the 3 R principle and further generates conflicting data that needs to be verified by additional animal experimentation. Therefore, considerable effort is presently being expended in developing novel alternative replacement strategies and also to provide detailed and standardized operating procedures (SOPs) for the conducting of the different ‘procedures’ in biomedical research that employ animals.
In hepatological research, animal models are still the gold standard for analysing complex disease-associated cellular reactions, signalling pathways and networks, or testing the efficacy of candidate drugs. Most of these studies are carried out in laboratory mice. However, a recent literature review that highlights the reporting of details related to mouse welfare in 119 studies which involved, for example, bile duct ligation in mice as a model for hepatic fibrosis and cholestasis, has shown that there is a fundamental failure to report details that may be sources of considerable experimental variability. 4 This example indicates that the specific SOPs (including information starting from the animal’s caging, housing, care, feeding and bedding up to anaesthetic regimen, surgical procedure, and post-operative monitoring, also specifying details about nursing care and humane endpoints) are still necessary.
It is the scope of Laboratory Animals to publish papers dealing with all aspects of the use of animals in biomedical research, which also includes new animal models and guidance on improving research techniques or reducing variability of results. Therefore, this supplement is an essential contribution to improving animal welfare and well-being as well as increasing the quality of biomedical animal research.
In the present issue, leading scientists and clinicians have set up a framework for several disease models in mice that are commonly used in experimental and molecular hepatology. These models are commonly used to induce hepatic inflammation, fibrosis, cirrhosis or hepatocellular carcinoma. The framework details protocols for the performance of surgical procedures (bile duct ligation and partial hepatectomy), application of diverse hepatotoxins (concanavalin A, thioacetamide, carbon tetrachloride, acetaminophen and lipopolysaccharides), the use of dietary models, and the induction of hepatocellular carcinoma by chemical carcinogen (diethylnitrosamine) (Figure 1).
Disease models in experimental and molecular hepatology. In this Special Issue of Laboratory Animals, standardized operating procedures for experimental models of acute or chronic hepatic injury in mice are given. The protocols include guidelines for the application of various hepatotoxins or the conducting of surgeries suitable for analysing different pathobiochemical aspects in the initiation, progression or regression of hepatic inflammation, steatosis, fibrosis, cirrhosis, hepatocellular carcinogenesis or hepatic regeneration. TAA: thioacetamide; D-Gal: D-galactosamine; LPS: lipopolysaccharide; APAP: acetaminophen; BDL: bile duct ligation; C2H5OH: ethanol; ASH: alcoholic steatohepatitis; HCC: hepatocellular carcinoma; CCl4: carbon tetrachloride; ConA: concanavalin A; MCD: methionine choline deficient diet; HFD: high-fat diet; DDC: 3,5-diethoxycarbonyl-1,4-dihydrocollidine; CD: choline deficient; DEN: diethylnitrosamine; NASH: non-alcoholic steatohepatitis; PH: partial hepatectomy.
The respective guidelines have a uniform structure and include a short abstract, a brief introductory chapter summarizing the historic background of the respective model and the underlying pathobiochemical mechanisms that are involved in the induction of liver damage. These remarks are followed by experimental details describing the exact performance of individual steps of each ‘procedure’ (such as handling, concentrations, post-operative animal treatment, duration of treatment, animal burden, biometric aspects, readout systems, etc.). Moreover, in each SOP details about the classification of severity of the expected harm to be experienced by the animal during the course of the procedure are specifically defined, and range from non-recovery, mild, moderate to severe. Finally, a short concluding statement on the applicability of the respective procedure is given. The different procedures are each accompanied by 3–6 informative figures or tables.
We hope that this Special Issue ‘Experimental models of liver injury in mice’ will initiate an engaging scientific discussion on how each model can be best implemented in hepatological research and comply with the new animal welfare standards that are based on the 3 R principle. In our view, these experimental guidelines offer one beneficial step forward to improving animal welfare and general scientific quality in experimental hepatology.
We cordially thank the experts for their time in producing such practical and visually gratifying contributions and express our thanks to Martin McDonald for his kind support in realizing this protocol series in Laboratory Animals.