Effect of maternal heat stress during pregnancy on reproductive functions of offspring in Balb/c mice

Background: In mammals, exposure to extreme temperature during pregnancy exert dramatic effects on adult offspring, especially reproductive functions. However, the studies on the long-term effect of maternal heat stress during pregnancy on the reproductive function of offspring remains very scarce. The objective of this study was, therefore, to elucidate the effect of maternal heat stress during pregnancy on reproductive performance, reproductive hormones and morphometric parameters of reproductive organs in offspring. Thirty pregnant female mice were divided into three equal groups: Control group (C), Moderate heat stress group (MS) and Heat stress group (HS), which were respectively exposed for 2 hours at a temperature of 22°C, 30°C and 39°C daily until delivered. The food intake, body weights, pregnancy outcomes of dams, and the relative weight of reproductive organs, reproductive hormones, morphometric parameters of testis and ovaries of offspring were measured. Results: : We found that maternal heat stress did not affect food intake, body weights of dams and pregnancy outcomes, including litter size and birth weight. No differences ( p > 0.05) in relative weights of reproductive organs of offspring were found. Then the results in maternal heat stressed males showed lower ( p < 0.05) reproductive hormones levels and lower ( p < 0.05) number of Leydig cells and sperm count. In maternal heat stressed females, lower ( p < 0.05) reproductive hormones levels, as well as a tendency of decreased number of secondary follicles were observed. Aside from these effects, corticosterone levels in maternal heat stressed males and females increased ( p < 0.05), which was significantly negativelyassociated with level of reproductive hormones. Conclusions: : Our results highlight the direct effects of maternal heat stress during pregnancy on reproductive hormones and histology of reproductive organs of offspring. These findings have implications for understanding the effects of HS on animal reproductive functions. In the context of continued warming and deteriorating of the global climate, it will provide a foundation for future studies to investigate heat exposure.