Transportation stress suppress reproductive performance in female mice and relevant genes detection

Animals in transport are exposed to both psychological and physical stressors, which affect performance and health. The objectives of this study were to investigate whether and how the transportation stress effect on female reproduction in mice, and detect differentially expressed genes association with stress response and reproductive capacity utilizing gene expression profiles. After transported mice by car to and from laboratory for a total period of 10 h, nearly 1000 km distance, measurements were carried out to explore effects of transportation stress on reproductive traits including puberty, estrous cycle, follicular number within ovaries, fertility and superovulation quality. Early life stress suffered mice before puberty promoted puberty onset, altered estrous cycle length and reduced large antral follicle number. Pubertal and adult mice exposure to transportation stress induced their pregnancy rate decline. Furthermore, adult stressed mice showed an obvious reduction in fertility with less litter size and litter weight in birth, which may cause reduced ovulation oocytes identified by superovulation. Assuming ovulated oocytes number as reproductive parameter, genes differently expressed between mice with extremely high and extremely low oocytes were compared within control and stress group separately. Affymetrix GeneChip® Mouse Gene 2.0 ST Arrays (PN: 902118) were used for transcriptome analysis to investigate gene expression difference between control and stressed mice for superovulation potential. Ten pairs of 6 weeks old female BABL/c mice with same parents were chosen in this experiment. Each pair of littermates were distributed into control and stress groups randomly and fed until 9 weeks old before performing superovulation. Mice were killed to number the oocytes in oviduct and separated hypothalamus (H), pituitary gland (P) and ovary (O) from each animal. The tissues were placed in a micro-centrifuge tube, flash-frozen in liquid nitrogen and stored at - 80℃ until further experiment. Each kind of tissue in both control and stress groups were divided into three sets according to mice ovulated oocytes number. The highest (h) stood for tissue from mouse with highest oocytes, the lowest (l) meant tissue from mouse with lowest oocytes and the pool (m) set were mixed samples from another 8 mice in each group.