Click here to sign in with or

by National Institutes of Natural Sciences

Testicles of most mammals are cooled in the scrota, and elevated testicular temperatures lead to spermatogenesis failure and male infertility. A research team led by Shosei Yoshida at the National Institute for Basic Biology in Japan detailed this process using organ culture and revealed that spermatogenesis is impaired at multiple steps in a delicate temperature-dependent fashion.

In particular, although spermatogenesis is completed at 34 degrees Celsius (the scrotal temperature), warming to 37–38 degrees Celsius (temperatures in the abdomen) severely affects meiosis—the process of segregating homologous chromosomes into haploid sperms—and the damaged cells undergo cell death. Demonstrating the utility of organ culture, this study will boost the study of heat vulnerability in spermatogenesis.

Many studies have been conducted on the heat impairment of spermatogenesis by raising the testis temperature using animal models, for example, surgical relocation of the testis to the abdomen. However, actual testicular temperature could not be controlled in these experiments. Furthermore, the effects of extra-testicular factors such as the endocrine and nervous systems cannot be excluded. To overcome these limitations, the research group took advantage of the testis organ culture setting that supports complete spermatogenesis in incubators, which was developed by Takehiko Ogawa and colleagues at Yokohama City University.

By culturing mouse testes at different temperatures, spermatogenesis was found to fail at multiple steps (e.g., progression of meiosis, and generation and transformation of haploid cells), showing sharp temperature dependencies between 30 degrees Celsius and 40 degrees Celsius. Yoshida says they "did not expect such a delicate ensemble of multiple temperature-dependent events to underpin this well-known phenomenon. This discovery could only have been achieved using an organ culture system."

The group further revealed that meiosis, through which homologous chromosomes segregate into haploid sperms, was severely affected at 37–38 degrees Celsius. Specifically, the repair of DNA double-strand breaks and homologous chromosome pairing, which are requisites for proper chromosome segregation, were impaired. Damaged cells undergo cell death through a surveillance mechanism or a checkpoint.

Kodai Hirano, the primary contributor to this study, says that "it was surprising that essential processes, such as meiosis, can be easily damaged at normal body core temperatures. Through the combined functions of the scrotum and checkpoint, only sperm developed at low temperatures fertilizes eggs to generate the next generation. Key questions for future studies include the molecular mechanism of heat sensitivity and the biological significance of low temperatures in sperm production."

This study has been published in Communications Biology.

More from Physics Forums | Science Articles, Homework Help, Discussion

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form. For general feedback, use the public comments section below (please adhere to guidelines).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Phys.org in any form.

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

Medical research advances and health news

The latest engineering, electronics and technology advances

The most comprehensive sci-tech news coverage on the web

This site uses cookies to assist with navigation, analyse your use of our services, collect data for ads personalisation and provide content from third parties. By using our site, you acknowledge that you have read and understand our Privacy Policy and Terms of Use.