Conducting an in vivo Study? Pass Peer Review with the ARRIVE Guidelines

Scientific breakthroughs are often made through incremental discoveries using a variety of experimental methods and models. With a few notable exceptions, the use of live animals in preclinical research has played an essential role in all the Nobel Prizes in Physiology and Medicine. Considering the importance of animal-based in vivo research, the accurate reporting of experimental procedures and animal usage plays a critical role in the research process and facilitates reproducibility during follow-up experiments and the translation of findings into humans. The Animal Research: Reporting of in vivo Experiments (ARRIVE) guidelines, when followed, ensure that enough detail is provided in scientific publications to depict the experiments carried out accurately. These guidelines were initially published in 2010 and, following a survey of the animal research literature, has recently been revised with input from the global scientific community.

Key areas where the ARRIVE guidelines are of use

1. During the experimental design phase

Focus is placed on using the correct sample size and statistical analyses to help investigators design reliable and repeatable experiments. For example, the use of an a priori statistical test with the anticipated differences in mean values and standard deviations can help identify the number of animals needed per group to satisfy a research question. This test also helps the investigator know when to call it quits when they do not see statistical significance between groups. You can find a free software download that includes this type of analysis here. Additional study design suggestions from the ARRIVE guidelines include:

• Description of inclusion and exclusion criteria
• The use of blinding and randomization to allocate experimental controls and treatment groups
• Clearly defining essential outcome measures required to test the original hypothesis of the investigation

2. During data collection

Accurate recording of the number of animals used, as well as the age, weight, sex, and strain of animals, is essential information that allows other investigators, readers, and reviewers to accurately scrutinize the methods utilized and, when necessary, to reproduce your findings. Accurate recordings of the experimental procedures utilized (e.g., what was done, how it was used) is also an essential part of the data collection process and should help during the manuscript preparation phase.

3. During the drafting and submission of a manuscript for publication in a peer-reviewed journal

This is where all the above-mentioned information is presented to the readers and reviewers. The ARRIVE guidelines suggest reporting items like the number of animals in each group, statistical comparisons made, and the number of male vs. female animals used. These suggestions are often in line with journal guidelines where this type of information is requested for each figure and should be mentioned in the figure legends. For example, the ,i>Journal of Applied Physiology, which is a sister journal of the American Journal of Physiology, requests that all figure legends include the number of animals (including the number of males and females) and the statistical test used to scrutinize the data presented. You can find more information about the Journal of Applied Physiology’s guidelines and recommendations to follow the ARRIVE guidelines here.

The ARRIVE guidelines are available for free via the following link:

https://journals.sagepub.com/doi/pdf/10.1177/0271678X20943823

The ARRIVE guidelines also go beyond general recommendations by identifying essential vs. recommended information in peer-reviewed publications. While the above-mentioned information falls within the essential category, here are a few examples of recommended items for inclusion but may not be necessary in every case:

• Details for housing and husbandry conditions, including any environmental augmentations or enrichments
• Animal care and monitoring specifics, such as describing interventions taken to reduce pain, suffering, and distress or the reporting of any adverse events
• Discussions on whether and how the findings of your investigation are likely to translate to other species or experimental conditions, including humans

Despite the clear usefulness of these guidelines to improve the rigor and reproducibility of in vivo experiments, adherence to the guidelines has been inconsistent over the years. The introduction of the ARRIVE guidelines version 2.0 in 2020 (link here and above) does an excellent job of providing an easy-to-read table of both essential and recommended criteria to improve your animal-based work. The inclusion of these critical points will not only improve the quality of your work but will also make your manuscripts easier to review by the expert referees of top-tier international journals.