Oestrous cycle in female mice is ‘immune’ to variability

Biological sex is being increasingly recognized as a significant variable in biomedical research. Numerous animal and human studies demonstrate that males females can differ significantly their genetics, anatomy, physiology behaviour through various stages of development ageing. Moreover, these inherent differences male female biology directly contribute to disease incidence, severity, onset treatment response (Miller et al. 2017). Despite striking health disease, have been traditionally underrepresented In response, guidelines implemented by funding agencies such the National Institutes Health led improvement recruitment women clinical However, traditional biases still influence how scientists approach basic preclinical Male animals predominate neglect widespread varying disciplines research, including physiology, pharmacology, neuroscience, endocrinology immunology (Beery & Zucker, 2011). The underrepresentation research based on assumptions data from predict results or are mainly associated with reproductive function. particular, commonly excluded belief they intrinsically more than due fluctuation hormones across oestrus cycle Surprisingly, there few support this widely held belief. article Breznik colleagues issue Journal Physiology tests assessing whether oestrous biological peripheral blood immune cell population variability used C57BL/6J mice. authors utilized method known flow cytometry precisely identify quantify types cells blood, otherwise immunophenotyping. Using vaginal cytology stages, found prevalence was not altered four They did find prevalence, greater number monocytes, neutrophils natural killer mice, whilst mice had higher proportion lymphocytes. Interestingly, exhibit immunophenotype counterparts, which influenced body weight. summary, study contradicts popular during affects physiological traits animals. Rather, it male, female, showed immunophenotype. Indeed, previous meta-analyses behavioural, physiological, anatomical molecular mouse (Prendergast 2014) rat (Dayton 2016) revealed may be just variable, even so, females. Whilst levels oestrogen animals, fluctuations testosterone – hormone affect weight consequently males. Given between sexes certain traits, immunophenotype, note common using equal sample numbers for both suitable all designs. Hence, future better understand broad range will critical guiding optimal design statistical analysis each sex. Overall, (Breznik 2021) provides compelling experimental proof hormonal no longer justifies studies. Considering undeniable incidence autoimmune disorders (e.g. multiple sclerosis) susceptibility viral infections COVID-19), current findings hopefully renew enthusiasm considering field ranks one lowest reporting subjects published papers On other hand, increased cost time major obstacle community. cannot ignore fact overreliance has, part, contributed unforeseen sex-biased adverse effects Thus, analysing has potential save much minimizing risks costly failures trials. support, prominent Canadian Research taken steps ensure gender an integral component whole process, project rationale, design, methods, translation (Duchesne Taken together, basic, only produce precise reproducible applicable females, but also optimize outcomes men who account half world's population. author does any conflicts interest. Sole author. No received preparation manuscript.