20 February 2017 Extragonadal oocytes residing in the mouse ovarian hilum contribute to fertility
Xiaofei Sun, Junya Ito, Sarah J. Potter, Sudhansu K. Dey, Tony DeFalco
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The observation of pups born from recipient and donor mice after ovariectomy followed by ovarian transplant poses the interesting possibility of an extraovarian source of oocytes. However, whether mammalian adult oocytes reside in extragonadal tissues remains elusive. Using transgenic fluorescent reporter mice and transplantation surgeries, we demonstrate the presence of both donorand recipient-derived corpora lutea and recovery of both donor- and recipient-derived offspring from ovariectomized mice after transplantation of donor ovaries. A potential region for extraovarian oocytes is the hilum, a ligament-like structure between the ovary and the reproductive tract. Immunofluorescent confocal microscopy of mouse ovaries and reproductive tracts revealed that a population of primordial follicles resides outside the ovary within the hilum. Ovariectomy-only controls confirmed that oocytes remain in the recipient hilum after surgery. These results provide evidence that the hilum is a reserve source of follicles, which likely return to the ovary for maturation and ovulation. By identifying a new follicle reservoir, our study addresses a long-standing question in reproductive biology and contributes to new conceptual knowledge about ovarian function and fertility.

Summary Sentence

An extraovarian source of oocytes exists within the mouse ovarian hilum, amuscular structure that connects the ovary to the reproductive tract; these oocytes reside within primordial and primary follicles and may contribute to female fertility.

© The Authors 2017. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please journals.permissions@oup.com
Xiaofei Sun, Junya Ito, Sarah J. Potter, Sudhansu K. Dey, and Tony DeFalco "Extragonadal oocytes residing in the mouse ovarian hilum contribute to fertility," Biology of Reproduction 96(5), 1060-1070, (20 February 2017). https://doi.org/10.1095/biolreprod.116.145631
Received: 12 October 2016; Accepted: 13 February 2017; Published: 20 February 2017
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