Between 3rs: Refining Animal Transplantation Models
Research Models
Regina Kelder

Between 3rs: Refining Animal Transplantation Models

Improving animal well-being, and advancing Type 1 diabetes research in the process. The first in a Q&A series on the 3Rs.   

For University of Minnesota scientist Melanie Graham, creating a safe and less stressful environment for research animals has led to better translation of therapeutic strategies to the clinic. Dr. Graham, who holds a PhD in animal modeling, welfare and refinement from the University of Utrecht in the Netherlands, and an MPH is epidemiology form the University of Minnesota, has been refining the use of animal transplantation models for the study of Type 1 diabetes mellitus. People with Type 1 diabetes are dependent on insulin, but a process whereby islet cells from the pancreas are transplanted can help people stabilize their glucose levels without insulin injections. Dr. Graham’s lab, which has been using nude mice to study transplantation, uses animal-centric approaches such as devising ways of avoiding repeat IV starts. Not only have these strategies improved the well-being of the animal, they have also made the science more robust.

Do you think many researchers are actively incorporating 3Rs methods into their study designs? 

MG: Absolutely, the 3Rs principles are deeply embedded into national and international legislation and regulations regarding use of animals for scientific purposes and beyond this, researchers are readily moving towards higher standards. The emphasis on the 3Rs in accreditation processes (like AAALAC), corporate social responsibility initiatives, increased prominence in mainstream scientific practice and technological innovation together reflect this forward progress. Researchers recognize the scientific imperative for developing new, robust approaches to research and development and appreciate that the 3Rs provide opportunities in supporting rigorous science, improving research efficiency.

Please describe briefly how your lab is refining the use of animal models of diabetes? 

MG: My lab focuses on developing therapies to treat metabolic disease, including cell-based therapies, devices, and novel immunotherapy approaches in transplantation. Animal models of disease remain invaluable in translation owing to the singular ability to fully model biological complexity of disease present in the patient situation. A valid model closely reflects the condition and management of disease in patients and adds the burden of serial monitoring necessary in safety and efficacy trials. This presents unique challenges in addressing animal well-being over extended periods of follow up ranging from several months to years.

One way that we addressed this was by designing animal-centric approaches in our surgical models and implementing positive reinforcement training for complicated behaviors.  One simple example of this is our use of indwelling vascular access ports so that our animals can avoid repeat IV starts necessary with intensive medical monitoring and treatment and cooperate with their own care in a familiar environment as well as exercise a degree of choice and control. From the welfare perspective, this has improved animal well-being in limiting aversive experiences, enhancing the caregiver bond, and avoids disruption of social groups. From the scientific perspective, this allows us to maximize information from each individual animal and consistently perform metabolic testing, a primary efficacy parameter, similar to the clinic without the influence of neuroendocrine responses to stress. We demonstrated objective pathological differences related to stress commonly observed in untrained animals were almost absent in trained animals, making it possible to avoid confounding that impairs accurate interpretation of safety data. 

What impact are these refinements having on translation of the diabetes models? 

MG: These refinements fundamentally supported the achievement of long-term prolonged diabetes reversal after porcine islet xenotransplant in [large animals] and induction of immune tolerance, both strategies that have broadened the scope of patients who stand to benefit from transplant therapies. Refinement has also introduced a new level of sophistication in our experimental designs, model characterizations and detailed understanding of model limitations supporting closer agreement with the human situation which has increased our ability to accelerate decision-making to either reject or move a therapy forward.

There is an exciting pipeline of in vitro tools emerging from academic labs (organ-on-chips, imaging modalities, 3D tissue constructs). How far away are we from translating these in vitro findings in the kind of research you do?

MG: We have already substantially reduced the amount of early phase preclinical studies in animals thanks to remarkable in vitro advancements. Many of our mechanistic evaluations of cell-derived products are now performed using perfusion culture and hydrogel constructs. Likewise, optimizing dosing or delivery strategies in the in vitro or in silico environment allows us to reduce the overall number of animals that are subsequently required to evaluate more complex biological interactions, engraftment, or immunologic consequences that cannot be currently assessed in these alternative models.

Along those lines, what sort of 3R innovations do you hope to see in the next 50 years?

MG: I hope we will see increased attention, funding, and serious commitment to infrastructure for the development, validation and commercialization of new 3Rs methods. In order to achieve major reductions in animal use and continued improvement in animal welfare, new and refined research models and tools need to be published, disseminated and fully adopted.

How do you think the 3Rs has changed animal research in the last 50 years?

MG: When the 3Rs are applied in their most progressive interpretation, the interests of the animal are addressed while at the same time enhancing scientific outcomes by accelerating alternative technologies and improving reproducibility with more robust approaches.  This avoids that animals are simply used as a means to an end and instead inherently respects the intrinsic value of each of our animals contributing to life changing medical interventions for other animals and humans.

Between 3Rs is a Q&A series created by Charles River Laboratories’ Eureka blog and ALN Magazine to highlight the importance of the 3Rs—replacement, reduction, and refinement—as guidelines for ethical animal use in biomedical research. If you are interested in being part of the series, contact [email protected] and [email protected].