Effects of whole-body heat on male germ cell development and sperm motility in the laboratory mouse

Abstract

This study investigated the effects of high temperatures on male germ cell development and epididymal sperm motility of laboratory mice. In Experiment 1, adult males (n=16) were exposed to whole-body heat of 37-38°C for 8h day(-1) for 3 consecutive days, whereas controls (n=4) were left at 23-24°C. In Experiment 2, adult mice (n=6) were exposed to 37-38°C for a single 8-h period with controls (n=6) left at 23-24°C. Experiment 2 was conducted as a continuation of previous study that showed changes in spermatozoa 16h after exposure to heat of 37-38°C for 8h day(-1) for 3 consecutive days. In the present study, in Experiment 1, high temperature reduced testes weights 16h and 14 days after exposure, whereas by Day 21 testes weights were similar to those in the control group (P=0.18). At 16h, 7 and 14 days after exposure, an increase in germ cell apoptosis was noticeable in early and late stages (I-VI and XI-XII) of the cycle of the seminiferous epithelium. However, apoptosis in intermediate stages (VII-X) was evident 16h after heat exposure (P<0.05), without any change at other time periods. By 21 days, there were no significant differences between heat-treated groups and controls. Considerably more caspase-3-positive germ cells occurred in heat-treated mice 16h after heat exposure compared with the control group (P<0.0001), whereas 8h after heat in Experiment 2, sperm motility was reduced with a higher percentage of spermatozoa showing membrane damage. In conclusion, the present study shows that whole-body heat of 37-38°C induces stage-specific germ cell apoptosis and membrane changes in spermatozoa; this may result in reduced fertility at particular times of exposure after heating.

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“…The harmful effects of heat on spermatogenesis are well documented [ 49 ]. When testicles do not descend to the scrotal sac and remain within the abdomen—a condition termed cryptorchidism, the animal is sterile, although testosterone production is not affected [ 50 ].…”

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“…Furthermore, other studies have suggested that also relatively moderate heat stress can induce DNA fragmentation within the testis (Gao et al 2012;Li et Capítulo 2: Heat stress effects on bovine sperm cells: a chronological approach to early findings 48 al. 2013; Wechalekar et al 2016). During the spermatogenesis process the most heat sensitive stages of germ cell development correspond to the spermatids and the pachytene spermatocytes Zhu et al 2004).…”