Quantification of Hair Corticosterone, DHEA and Testosterone as a Potential Tool for Welfare Assessment in Male Laboratory Mice

SIMPLE SUMMARY: Mice is the most used species in the biomedical research laboratory setting. Scientists are constantly striving to find new tools to assess their welfare, in order to ameliorate husbandry conditions, leading to a better life and scientific data. Steroid hormones can provide information regarding different behavioral tracts of laboratory animals but their quantification often require stressful sampling procedures. Hair represents a good, less invasive, alternative in such scenario and is also indicative of longer timespan due to hormones’ accumulation. The aim of the work was to quantify steroid hormones in the hair of male laboratory mice and to look for differences imputable to age and housing conditions (pairs VS groups). Age influenced all analysed hormones by increasing testosterone and dehydroepiandrosterone (DHEA) levels and decreasing corticosterone. When comparing animals housed in pairs VS groups, the only difference found was a higher level of DHEA in mice housed in groups. Due to the nature of DHEA, this finding may suggest that group housing may be beneficial for social interaction. In conclusion, it seems that hair hormones quantification may be a good tool for welfare assessment in laboratory mice and may help in refining husbandry. ABSTRACT: Steroids, providing information regarding several biological patterns including stress and sexual behavior, have been investigated in different matrices in laboratory mice. Data regarding hair quantification, indicative of longer timespans when compared to blood and saliva, are lacking. The aim of the work was to analyze the hormonal hair profile of laboratory male mice and to investigate potential relationships with age and housing, as a potential tool for welfare assessment. Fifty-six adult male C57BL/6J and C57BL/6OlaHsd substrain mice were included in the study, housed in pairs or groups. Testosterone (T) and dehydroepiandrosterone (DHEA) were quantified by radioimmunoassay, corticosterone (CORT) by ELISA. Mean hormone levels were 6.42 pg/mg for T, 23.16 pg/mg for DHEA and 502.1 pg/mg for CORT. Age influenced all hormones by significantly increasing T and DHEA levels and decreasing CORT; only DHEA, significantly higher in grouped mice, was influenced by housing conditions. The influence of age indicates the need for accurate age-related reference intervals, while the higher levels of DHEA in grouped animals suggests that such housing practice may be beneficial for social interactions. In conclusion, it seems that hair hormones quantification may be a good tool for welfare assessment in laboratory mice and may help in refining husbandry.