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A model research animal: The Wistar Hannover rat

The Wistar Hannover rat (e.g., RccHan®:WIST and HsdHan®:WIST) is widely used in toxicology and carcinogenicity studies, which are necessary for regulatory approval of new drugs and chemicals. The advantages of these models are numerous, leading to beneficial economic impacts, enhanced research outcomes, and closer adherence to the 3Rs. Envigo has a long history with the Wistar Hannover rat, and is uniquely placed to help researchers capitalize on its advantages. Below, we discuss the history of the model and our role in its maintenance, and explore some of the benefits the model offers in more detail.

The Wistar Hannover rat was developed at the Wistar Institute in 1906 as a model organism for use in medical research. More than half of all laboratory rat strains are descended from the original colony, including the well-known Sprague Dawley and Long Evans rats. Envigo has maintained the original RccHan®:WIST rat, developed from the Wistar Institute colony, for nearly two decades. As such, unlike competitive models, the Envigo RccHan®:WIST rat has been maintained from the original nucleus of 156 breeding pairs from the Hannover Institute, where the model was transferred in 1960.

Envigo’s global breeding and genetic integrity assurance program employed in the RccHan®:WIST stock reduces inbreeding and maintains maximum heterogeneity between animals within the colony. All RccHan®:WIST colonies are genetically tested on an annual basis using a custom 96 single nucleotide polymorphism (SNP) marker panel to assess allelic frequencies within and between colonies worldwide.

What are the benefits of using the model in a research program?

Specific attributes of the Wistar Hannover rat make it a uniquely advantageous strain for carcinogenicity testing. For instance, relative to Sprague Dawley (and Fischer F344) animals, Wistar Hannover rats have longer survival, lower overall occurrence of spontaneous neoplastic and non-neoplastic lesions (Weber, 2017; Weber, 2011), and a lower body weight.

The superior survival rate of the Wistar Hannover rat maximizes a study’s chance of success, and can even reduce the use of animals given attrition is less of a concern at the study outset. Indeed, in Envigo’s experience, the increased survival rate of the Envigo RccHan®:WIST compared to the CRL:CD® rat translates to a 22-27% reduction in the number of animals required for a typical long-term study. In addition, lower overall tumor incidence improves research consistency by limiting the impact from uncontrolled variables not relevant to the research question. Importantly, these benefits to animal welfare help researchers align their research programs with the principles of the 3Rs.

Finally, lower body weight offers important economic benefits via less compound use per animal, lower overall food consumption, and lack of need for technicians to enforce diet restrictions. A more detailed analysis of how these advantages translate into cost savings can be accessed here.

Historical control data

Envigo’s long history with the model has enabled us to amass extensive historical control data points. In addition to acting as an important resource for researchers, this data enables continued evaluation of the growth, survival rate, and tumor incidence of the model (as described here). Envigo has also made our rich historical control dataset available, so that researchers can access and explore a range of variables related to the model, illustrated below.

The benefits discussed above justify the Wistar Hannover rat (RccHan®:WIST) as the model of choice for toxicology and carcinogenicity studies, and for gathering nonclinical safety data. More information on the model itself, and on Envigo’s role in its maintenance, can be found here. If you are interested in using the model in your research, our specialists are available to discuss your needs.