Impact of a mild scrotal heat stress on DNA integrity in murine spermatozoa

Abstract

An increase in scrotal temperature can lead to the production of poor quality spermatozoa and infertility. In the present study we have used mice to examine the impact of mild, scrotal heat stress (42 8C for 30 min) on numbers of spermatozoa as well as on the integrity of their DNA. Spermatozoa recovered from the epididymides hours (1 to 24) or days (7 to 32) after treatment were analysed using COMET and sperm chromatin structure (SCSA) assays. The treatment induced a stress response in both the testis and the epididymis that was associated with reduced expression of the cold inducible RNA binding protein (Cirp) and an increase in germ cell apoptosis (Apotag positive cells). Although spermatozoa present in the epididymis at the time of heating contained correctly packaged DNA, its integrity was compromised by heat stress. In addition, although some germ cells, which were present within the testis at the time of heat stress, were removed by apoptosis, many germ cells completed their development and were recovered as motile spermatozoa with damaged DNA. In conclusion, these data demonstrate that scrotal heat stress can compromise the DNA integrity of spermatozoa and this may have clinical implications for patients undergoing IVF and intra-cytoplasmic sperm injection (ICSI).

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

“…Studies in mice have used a variety of techniques to determine the effects of heat stress on fertility and it is notable that similar disturbances in testicular function and reduced fertility have been recorded in animals housed at 36 8C for 12 or 24 h and those subjected to a transient scrotal heat stress at 42-43 8C for 20-60 min (Lue et al 1999, 2000, Rockett et al 2001, Setchell et al 2001, Banks et al 2005, Zhang et al 2005. Our study includes novel data on the origin of DNA damage found in sperm i.e.…”

“…35-36 8C) for several hours , Cammack et al 2006. In these studies, the common features of disturbances in testicular function that have been recorded include decreased testicular weights, germ cell loss and increased rates of apoptosis (McLaren et al 1994, Setchell et al 1996, 1998, Lue et al 1999, Banks et al 2005, Perez-Crespo et al 2008. Some studies have reported that pachytene spermatocytes and early spermatids are the cell types most susceptible to testicular heat stress (Setchell 1998).…”

“…Localised scrotal heating of mice is also associated with detection of DNA damage in sperm and reduced sperm counts. When DNA damage was detected in sperm recovered from the epididymes within hours of heating this was taken as evidence that epididymal sperm are still susceptible to heat-induced DNA damage even though the DNA is tightly packaged with protamines (Sailer et al 1997, Banks et al 2005.…”

Which isolated sperm abnormality is most related to sperm DNA damage in men presenting for infertility evaluation

“…genetic or developmental abnormalities) or due to secondary or extrinsic factors causing testicular or posttesticular injury (e.g. gonadotoxins, hyperthermia, oxidants, endocrine abnormalities) [2][3][4][5][6][7][8][9][10]. Investigators have suggested that protamine deficiency (with aberrant chromatin remodeling), reactive oxygen species (ROS) and abortive apoptosis may cause sperm DNA damage [11][12][13][14][15][16][17][18].…”

Downregulation of cold-inducible RNA-binding protein activates mitogen-activated protein kinases and impairs spermatogenic function in mouse testes

“…It is well known that spermatogenic function is impaired after heat stress in the testes as a result of numerous pathological processes. In earlier studies, testes were subjected to heat stress to evaluate the functions of CIRP, 18,19,27 but there is no direct evidence to indicate which pathological processes are caused by the downregulation of CIRP in heat-stressed testes. We employed the RNAi method to downregulate the expression of CIRP in the testes and found that CIRP was necessary for spermatogenesis.…”