One of the fundamental variables in preclinical biomedical research is sex:  whether one uses cells, tissues, animals or humans.   Animals are used in research when it is necessary to study the whole, living body, which is more complex than individual parts. Currently, it is not yet possible to replace the use of living animals in research with alternative methods.  The study of animals has led to a great deal of knowledge of the the body's anatomy and functions.  Even simple animals can be used to study complex biological systems that can then be applied to higher animals and humans. Many of the diseases that occur in humans can be found in animals.  This allows researchers to test potential therapies before giving them to humans.  Studying disease mechanisms in aminal models leads directly to the development of new drugs and technologies that can benefit humans.   Animals can also be altered to create models of disease that can help discover new therapies.  Testing new technologies like pacemakers and artificial organs cannot be used in humans until safety concerns are addressed in animals.  New drugs require animal testing to provide critical efficacy and safely data.  Animal testing  serves to protect consumers, workers and the environment from the harmful effect of chemicals. Some of the reasons given for not including female animals include complications of breeding, pregnancy, variability of the estrous cycle, and concerns that some species are not effective models for sex differences in humans.  As new guidelines are released by the NIH, they will be addressing these concerns.

Rationale for including both sexes in animals research:

• Methods and Techniques for Integrating the Biological Variable Sex into Preclinical Research- Proceedings from the October 20, 2014 meeting of the Office of Research on Women's Health.

• Video Broadcast of October 2014 NIH Workshop on Biological Variable Sex in Preclinical Research

• The Organization for the Study of Sex Differences (OSSD) 

• NIH Office of Research on Women's Health (ORWH)

• Draft Guidance for Industry and Food and Drug Administration Staff - Evaluation of Sex Differences in Medical Device Clinical Studies

• Of Mice and Women:  The Bias in Animal Models

 Tools for Animal Studies

Animal Cycling and Breeding Instructions

• Vaginal Cytology (Smearing) Protocol - Courtesy of the Woodruff Laboratory

• Reproductive Biology of Breeding Mice - Courtesy of The Jackson Laboratory

Shared & Core Facilities at Northwestern University

• Transgenic and Targeted Mutagenesis Lab   

• Behavioral Phenotyping

• Genomics Core Facilities 

• Mouse Histology and Phenotyping Lab 

Other Resources

• Animal Research: Designing Health and Biomedical Research - Courtesy of Stanford's Gendered Innovations
• First steps for integrating sex and gender considerations into basic experimental biomedical research
• Videos from Stanford Gender Innovations

Animal Research Tools by Disease

• Strategies and Methods to study sex differences in cardiovascular structure and function:  A guide for basic scientist

• Sex Differences in Animal Models for Cardiovascular Diseases and the Role of Estrogen

• Strategies and Methods for Research on sex differences in Brain and Behavior

• Sex bias in neuroscience and biomedical research

• Studying sex and gender differences in pain and analgesia:  A consensus report