A single, mild, transient scrotal heat stress causes DNA damage, subfertility and impairs formation of blastocysts in mice

Abstract

Infertility represents a major clinical problem and 50% of cases are attributable to the male partner. Testicular function is temperature dependent, and in both man and mouse the position of the testes in the scrotum ensures that they are kept at between 2 and 8 8C below core body temperature. We used a mouse model to investigate the impact of a single, transient, mild, scrotal heat stress (38, 40 or 42 8C for 30 min) on testicular function, sperm DNA integrity and embryo survival. We detected temperature-dependent changes in testicular architecture, number of apoptotic cells and a significant reduction in testis weight 7 and 14 days after heat stress at 42 8C. We report for the first time that DNA strand breaks (g-H2AX-positive foci) were present in spermatocytes recovered from testes subjected to 40 or 42 8C. Fertility of heat-stressed males was tested 23-28 d after treatment (sperm at this time would have been spermatocytes at time of heating). Paternal heat stress at 42 8C resulted in reduced pregnancy rate, placental weight and litter size; pregnancies from the 40 8C group had increased resorptions at e14.5. Abnormalities in embryonic development were detected at e3.5 and in vitro fertilisation with sperm recovered 16 h or 23 d after scrotal stress at 42 8C revealed a block in development between the 4-cell and blastocyst stages. This study has provided evidence of temperature-dependent effects on germ cell DNA integrity and highlighted the importance of an intact paternal genome for normal embryo development. Reproduction (2008) 136 73-84

Effect of beta-carotene on titanium oxide nanoparticles-induced testicular toxicity in mice

“…In general, the major deleterious effects of the TNP in affected tubules were the occurrence of intraepithelial vacuoles of varying size, slouging and seminiferous tubule atrophy. The vacuoles we observed within the seminiferous epithelium resembled those described following a variety of testicular insults including exposure to toxicants, hypophysectomy, transient scrotal heat stress and acute withdrawal of androgens following destruction of Leydig cells with ethane dimethane sulphonate [39][40][41][42][43]. Sloughing is caused by the effects of the chemical on microtubules and intermediate filaments of the Sertoli cell.…”

Bovine spermatozoa react to in vitro heat stress by activating the mitogen-activated protein kinase 14 signalling pathway

“…Incubation of spermatozoa at 398C for 24 h before fertilisation has been reported to decrease blastocyst developmental competence (Lechniak et al 2003), which we confirmed in the present study using spermatozoa incubated at 418C for 4 h. It is conceivable that the quality of blastocysts produced after fertilisation of oocytes with heatstressed spermatozoa is compromised because of the increased level of sperm DNA damage. Similarly, several studies have reported that mice exposed to scrotal heat stress have an increased percentage of spermatozoa with high levels of DNA damage and, as such, insemination using these spermatozoa ultimately resulted in impaired blastocyst formation (Jannes et al 1998;Paul et al 2008;2009). Further in vitro studies in cattle have confirmed these findings: Walters et al (2005aWalters et al ( , 2005b observed less blastocyst development with higher ACR after fertilisation of oocytes with semen collected from scrotalinsulated bulls.…”

“…Studies indicate that the contribution of a spermatozoon to the oocyte is more than delivering the paternal genome, and that the centriole (for a review, see Sutovsky and Schatten 1999), RNA (Ostermeier et al 2004) and proper epigenetic marks in the form of DNA methylation (for a review, see Miller et al 2010;Steger et al 2011) are almost equally important for successful fertilisation and embryo development. Hence, in addition to causing sperm DNA damage (Paul et al 2008(Paul et al , 2009, it is also possible that heat stress damages the sperm centriole and/or causes aberrant DNA methylation in the male pronucleus that subsequently leads to a delay in fertilisation or fertilisation failure; this would be an interesting area for future research. Incubation of spermatozoa at 398C for 24 h before fertilisation has been reported to decrease blastocyst developmental competence (Lechniak et al 2003), which we confirmed in the present study using spermatozoa incubated at 418C for 4 h. It is conceivable that the quality of blastocysts produced after fertilisation of oocytes with heatstressed spermatozoa is compromised because of the increased level of sperm DNA damage.…”

Unexpected requirement for a binding partner of the syntaxin family in phagocytosis by murine testicular Sertoli cells

“…To study the effects of TXLNA ablation on testicular phagocytic activity, we treated mice with a single, mild, transient scrotal heat stress (HS). 16 At post-HS 24 h or 14 d, testes were harvested and subjected to apoptotic analyses. These two time points were chosen because HS-induced apoptosis increases to the maximum level at about 24 h, and then disappears by 14 d. 17 Histological examinations revealed a significant increase in the apoptotic GCs at post-treatment 24 h (black arrows in Supplementary Figure 1).…”