The Wistar Hannover rat, also known as RccHan®:WIST and HsdHan®:WIST, is considered a strain of choice for toxicology and carcinogenicity studies, helping advance research for many multinational pharmaceutical, chemical, and contract research organizations (CROs), as well as further academic investigations. This blog shares a few advantages of the Wistar Han rat as compared to a similar rat model and discusses how the model can help enable consistent research outcomes.
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Using a well-studied model with a deep history

While all current global colonies of the Wistar Han are derived from the original colony, the derivation of commercial strains of Wistar Hannover and Wistar rats has led to several established colonies. However, only Inotiv provides the original Wistar Han stock, which is maintained by a Poiley rotational breeding system to reduce inbreeding and maximize heterogeneity. With this rich commercial lineage, Inotiv has amassed more than 20 years of historical control data (HCD) to help researchers select the optimal model for their studies.

Improving study efficiency

Rat strains have many anatomical, physiological, and metabolic pathway similarities to humans, making them ideal to support nonclinical safety studies. For carcinogenicity testing, the Wistar Han strain offers several advantages due to its smaller body size, longer survival, and low overall tumor incidence.

Based on HCD data generated from 50 carcinogenicity studies with Inotiv’s Wistar Hannover rats followed by a two-year analysis to establish baselines, researchers can expect:

  • Smaller body weight: At 104 weeks, male Wistar Han rats average 700 ± 100 g while females measure 441 ± 59 g. These weights are 20% lower than CRL:CD®(Sprague Dawley) male rats and 30% lower than CRL:CD®(SD) female rats

  • Increased survival: At 104 weeks, Wistar Han rats have a mean survival rate of 72% (males) and 65% (females). This exceeds the survival rate for the CRL:CD®(SD) rat where only 31% (males) and 38% (females) reached 104 weeks of age.

  • Low spontaneous mass incidence: Low background lesion incidence helps provide more sensitivity when testing compounds for their carcinogenic potential. Spontaneous tumor incidence, neoplasms, and other proliferative microscopic findings have also been tracked and documented for this model to better understand background effects that are inherent to the model.

    Promoting the 3Rs

    Considering these advantageous features together, the Wistar Han can help promote the principles of the 3Rs. Increased survival and reduced spontaneous tumor incidence allow for a reduction in the number of animals required initiate a study. The model’s smaller body weight, as compared to CRL:CD®(SD) rats, means that it may require less compound use, and its size allows for pair housing in standard size caging, which reduces associated costs of animal care.

    Following regulatory precedent

    While regulatory guidelines do not mandate a specific rat strain for carcinogenicity studies, the Wistar Hannover rat has been widely used in nonclinical toxicology studies in Europe, Japan, and the US—and supported numerous safety assessments that have led to successful regulatory approvals.

    Evaluating additional applications

    Beyond toxicology and carcinogenicity, Wistar Han has shown value in a diet-induced obesity study where a high-fat diet induces non-diabetic obesity in female rats. In this 33-week study, obese female rats were observed to have intact leptin and estrogen as well as normal liver and kidney function values. This suggests that they would make an excellent model for testing theories about the interplay between leptin and estrogen on energy regulating pathways. This model may also be useful for testing new anti-obesity compounds to assure that they can prevent or reduce obesity without making a previously healthy model develop unhealthy side effects.

    Choosing the best strain for your studies

    When choosing a rat model for toxicity and carcinogenicity testing, it’s important to understand the complete technical and scientific criteria. Our experts at Inotiv are available to share additional data and help you determine how to enhance study outcomes, save time, cost, and resources. Please contact our specialists at Inotiv to learn how you can advance your nonclinical safety studies with the most appropriate rat model.

    *CD is a registered trademark of Charles River Laboratories

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