There won’t be blood

The welfare of laboratory animals is always foremost in the mind of in-vivo researchers – and it turns out this is incredibly important when it comes to animal experimentation being a reliable analogy to human physiology. Here Scott Tiesma tells us why telemetry is helping provide animal welfare and reliable results

Want a lab animal to serve as an accurate guide to human physiology? The key to success is for researchers to focus on the animal’s welfare, according to the National Centre for the Replacement Refinement & Reduction of Animals in Research.[i]

The more comfortable an animal feels in its environment while “on study,” the more closely its body processes will operate as if the creature were living in its natural habitat. This, in turn, can increase confidence when translating these observations of the animal’s physiologic responses to a stimulus or experimental compound.

For a vivid example of why the focus on animal welfare is important – and how ensuring animal welfare can benefit animals and humans alike – consider preclinical glucose monitoring. This is an activity common among a segment of life science researchers in the lab. As it turns out, monitoring the level of glucose in an animal’s bloodstream has a wide number of potential applications in areas of medicine such as diabetes research. Yet while it is very useful, traditional glucose monitoring has some inherent disadvantages; perhaps the single greatest challenge to these methods is that intermittent blood sampling only allows a small number of samples to be collected within a given period of time due to concerns related to loss of blood volume. Further, animal subjects need to be restrained physically or chemically to take readings.

These concerns, as well as labor requirements, can limit the number and frequency of assays that may be performed on a lab animal. These downsides can now be overcome or reduced with new technology.

A hands-on problem for lab animals

Specific guidelines to minimise the stress and maximise the welfare of lab animals have been published by the National Institutes of Health (NIH).[ii] There are limits on the amount of blood that can be drawn from a single animal at any given time and also a practical restriction on how frequently blood can be drawn from each animal in the study per day.

The NIH recommends that approximately 10 percent of the total volume can be safely removed every two to four weeks, 7.5 percent every seven days and one percent every 24 hours. However, the effects of extracting blood from the animal can potentially skew the readings obtained by blood glucose measurements – so that they no longer represent the animal in its natural state; combining this issue with the impact of animal stress further confounds the accuracy of glucose measurements.

The NIH has stipulated that it is the responsibility of researchers to ensure the use of techniques and procedures that result in the least pain and distress to the animal. As such, researchers are typically evaluating average daily glucose levels based on readings from once or twice per day at a maximum. Therefore, even if researchers are fortunate enough to estimate these average levels accurately, they may completely miss out on any information related to glycemic variability because this wasn’t sampled frequently enough.

A hands-off solution

In the face of these challenges comes a significant new advance: wireless continuous glucose monitoring. Wireless monitoring provides preclinical metabolic researchers with a method for collecting more information while at the same time serving to improve animal welfare.

This method involves implanting a telemetry device capable of recording glucose levels into the body of a laboratory animal. Although calibration is required, only one to three blood samples need to be obtained from each animal weekly to ensure accurate measurements. The device operates by continuously sensing and simultaneously transmitting these data from the animal to a receiver situated in close proximity to the animal’s living quarters. Since the animal is able to move around freely in its lab habitat, these data are collected completely absent of any artifact associated with human interaction.

The practical result of this implementation of telemetry is higher-quality data collected around the clock and the ability to obtain more precise data free from non-physiologic artifact, including the stress that results from human interaction. It has been estimated that greater than 90 percent of telemetry data sets are free from stress, meaning the data collected are superior from the standpoint of researchers.[iii]^,[iv] In fact, within nonclinical drug safety assessment, continuous telemetry data are considered high quality and are an official recommendation of the American Heart Association for many studies involving blood pressure for similar reasons that can be applied to glucose.[v]

Continuous glucose telemetry can show researchers, for example, how glucose levels vary within a lab animal on a second-to-second basis. The frequency of data collected is great enough for these researchers to be able to analyse how deviations vary over time. These kinds of observations aren’t possible when blood readings are taken infrequently. Researchers who want to study glucose response in connection with an investigational drug with a novel mechanism of action can investigate a number of questions – such as how quickly the glucose level climbs or falls following dosing of a particular food or drug, and how long or short that peak or trough lasts.

New biomarkers and study designs

With these types of data, researchers can ask and answer questions they otherwise could not. New biomarkers specific to these questions are feasible both for acute tests and chronic evaluations. In fact, some novel biomarkers can be studied for the quantification of glucose homeostasis and glycemic variability, such as the use of daily statistics, histograms and evaluation of light/dark periods. Other new biomarkers can be established in tandem with acute metabolic tests, including the ability to determine the slope of glucose uptake or disposal, precise peaks and nadirs, assessment of stress impact and more. In addition, calculations involving existing biomarkers can be made more robust with the new technology.

Wireless continuous glucose monitoring also provides the opportunity to use alternate study designs that require fewer animals to be used overall. For example, each animal can be used as its own control in dose response studies, which are performed to establish a physiologic profile of an animal’s response to administration of a specific drug. This means it becomes possible to compare how a particular animal responds to a specific drug dose on a given day versus the absence of any dosing, as well as how that specific dose compares with other levels of dosing on different days. This enables better statistics related to the dosing, which can in turn play a role in assessing a therapeutic candidate’s potential safety and efficacy.

A dose response study involving insulin, for example, can be used to detail the action of one or more insulin products to determine how quickly it reduces blood glucose levels, whether hypoglycemia is avoided and how long the lowering effect lasts.

A further application of continuous preclinical glucose monitoring involves glucose tolerance tests, which are designed to assess the body’s ability to metabolize glucose. In animal research, these tests are used to assess the efficacy of treatments or therapies or to phenotype the animal under different conditions. Similar benefits arise from the use of continuous preclinical glucose monitoring to study specific mechanisms involved in type 1 and type 2 diabetes in lab animals, including variations in glucose levels over time. In addition, animals can be used more efficiently, so that more assays can be performed within a specific animal over the course of the implant’s life.

For these types of reasons, continuous preclinical glucose monitoring represents a valuable advance – both for the animals involved and for the quality of scientific research that results from its use. As more scientists focus on designing studies that can enable a higher quality of research, look for advances such as continuous glucose monitoring to play an increasing role in studies of diabetes and other conditions in the years to come, while also contributing to improving lab animal welfare.

References:

[i] National Centre for the Replacement Refinement & Reduction of Animals in Research. The 3Rs. Available at: https://nc3rs.org.uk/the-3rs

[ii] NIH Office of Animal Care and Use. Guidelines for survival bleeding of mice and rats. 12 Aug 2015. Retrieved from: https://oacu.oir.nih.gov/sites/default/files/uploads/arac-guidelines/rodent_bleeding.pdf

[iii] Kramer K, Kinter LB. Evaluation and applications of radiotelemetry in small laboratory animals. Physiol Genomics. 2003;13(3):197-205. doi: 10.1152/physiolgenomics.00164.2002

[iv] Morton DB, Hawkins P, Beven R, et al. Refinements in telemetry procedures: Seventh report of BVAAWF/FRAME/RSPCA/UFAW Joint Working Group on Refinement, Part A, Laboratory Animals. 2003;37(4):261-299. doi: 10.1258/002367703322389861

[v] Kurtz TW, Griffin KA, Bidani AK, Davisson RL, Hall JE. AHA scientific statement: Recommendations for blood pressure measurement in humans and experimental animals. Part 2: Blood pressure measurement in experimental animals. Hypertension. 2005;45:299-310. doi: 10.1161/01.HYP.0000150857.39919.cb

Author

 Scott Tiesma is Technology Marketing Manager at Data Sciences International - a division of Harvard Bioscience.