Optimization of a limited bedding and nesting protocol to model sex-specific effects of early-life stress in mice

Early-life stress (ELS) may constitute a risk factor for negative, physical and mental health problems. Notably, these effects are influenced by sex, with marked sex differences reported on behavior, physiology and molecular processes. Among the animal models to study ELS, the limited bedding and nesting (LBN) is a robust, reproducible, and translationally relevant protocol that disrupts maternal care and induces pup stress. As an initial stage of this work, we are currently optimizing the LBN protocol in mice. The goal is to study the interaction of ELS with the critical period of sexual differentiation of the brain, to be able to study sex-specific risk factors associated with developmental exposure to stress. During this process, different intervals of LBN exposure were tested, with the window between postnatal days 2 and 9 identified as optimal for protocol reproducibility. In addition, the enrichment parameters of the protocol were adjusted. Preliminary results on developmental landmarks showed a significant effect of ELS on weight and anogenital distance (AGD), with ELS-exposed pups exhibiting lower body weight (p < 0,0001) and greater AGD (p < 0,001). This model will allow us to evaluate the effects of ELS on the oxytocinergic system, which regulates social behavior and is susceptible to ELS-induced alterations, as well as its effects on the DNA methylation and demethylation machinery regulating the expression of its components.