Pursuit of an Optimal Murine Model for Early Life Stress: Does Diet Matter?

Early life stress (ELS) is known to have negative effects on long-term human health. Neglect is a significant source of ELS during childhood and accounts for 80% of reported abuse and over 30% of maltreatment-related deaths in the United States. A major challenge of studying the impact of stress on immune competency has been difficulty developing a reliable mouse model with reproducible stress effects. Animal models of ELS emulate the nature of childhood neglect through scheduled separation. Although variations of maternal separation in rodents have been published, the reported results are inconsistent. This may in part be attributed to variations in animal housing conditions between research institutions, such as diet. In the present study, we describe a modified version of the maternal separation with early weaning (MSEW) paradigm using C57BL/6 mice and compare the effects of two commercially available diets (ClearH2O® DietGel® and PicoLab® 5058) on peripheral stress hormones and cytokine profiles of select primary and secondary lymphoid tissues. Pups were produced via in-house breeding procedures and subjected to our modified MSEW protocol. Euthanasia occurred at postnatal day (PD) 21 for tissue harvest and blood collection via cardiac puncture. Cytokines and serum catecholamine and corticosterone levels were detected using commercially available ELISA. This pilot study sheds light on the impact dietary variations have on immune outcomes in the context of stress. We describe an updated MSEW protocol in C57BL/6 mice and demonstrate diet is a critical component of our stress model. Preliminary data suggests diet affects cytokine production within select lymphoid tissues at PD21. This work provides insight into the need for MSEW diet standardization to improve the reliability and reproducibility of murine models designed to study ELS.