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30 May 2017 Stem cell activity of type A spermatogonia is seasonally regulated in rainbow trout
Mana Sato, Makoto Hayashi, Goro Yoshizaki
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Spermatogonial stem cells (SSCs) support continuous production of sperm throughout the male's life. However, the biological characteristics of SSCs are poorly understood in animals exhibiting seasonal reproduction, even though most wild animals are seasonal breeders. During the spermiation season in rainbow trout, the lumen of the testes contains only spermatozoa and scattered type A spermatogonia (ASG) along the walls of the testicular lobules. These few remaining ASG, designated “residual ASG,” are the only germ cells capable of supporting the next spermatogenesis, suggesting that the residual ASG are true SSCs. However, whether residual ASG can behave as SSCs in any teleost species is unknown. In this study, we attempted to clarify the biological characteristics of SSCs associated with seasonal reproduction in rainbow trout using spermatogonial transplantation. We found that the stem cell activity was clearly regulated seasonally during the annual reproductive cycle. Although the residual ASG exhibited moderate transplantability and colony-forming ability at the beginning of the spermiation season, these parameters decreased dramatically later and remained low until the next spermatogenesis was initiated. Furthermore, no clear correlations were observed between these qualitative changes and previously described morphologic characteristics of ASG or plasma sex steroid levels. Our results suggest that the biological properties of SSC populations in rainbow trout are seasonally regulated by a novel mechanism.

Summary Sentence

Stem cell activity of type A spermatogonia drastically changes during the annual reproductive cycle in adult rainbow trout.

© The Authors 2017. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail:
Mana Sato, Makoto Hayashi, and Goro Yoshizaki "Stem cell activity of type A spermatogonia is seasonally regulated in rainbow trout," Biology of Reproduction 96(6), 1303-1316, (30 May 2017).
Received: 20 February 2017; Accepted: 27 May 2017; Published: 30 May 2017

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