Cumulus cells accelerate aging of mouse oocytes.
The role of cumulus cells (CCs) that surround oocytes in maturation, ovulation, and fertilization has been extensively studied, yet little is known about their role in oocyte aging. Although early studies have shown that when ovulated oocytes are aged in vitro displayed similar morphological alterations as those aged in vivo, a recent study found that vitro culture of mouse oocytes retarded oocyte aging. The objective of this study was to test the hypothesis that CCs would accelerate oocyte aging. During in vitro aging with CCs of both in vivo-matured and in vitro-matured mouse oocytes, activation rates increased, whereas the maturation-promoting factor (MPF) activity decreased significantly as during in vivo aging of the ovulated oocytes. During aging after denudation of CCs, however, activation rates of both in vivo-matured and in vitro-matured oocytes remained low and the MPF activity decreased much more slowly compared to that of oocytes aged with CCs. Although many oocytes aged in vivo and in vitro with CCs showed a partial cortical granule (CG) release, very few cumulus-free oocytes released their CGs during in vitro aging. When denuded oocytes were cultured with cumulus-oocyte-complexes at a 1:2 ratio or on a CC monolayer, activation rates increased, while MPF activity decreased significantly. The results strongly suggested that CCs accelerated the aging progression of both in vivo-matured and in vitro-matured mouse oocytes.
Miao
Yi-Liang
YL
College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City 271018, People's Republic of China.
Liu
Xin-Yong
XY
Qiao
Tian-Wu
TW
Miao
De-Qiang
DQ
Luo
Ming-Jiu
MJ
Tan
Jing-He
JH
D000705:Anaphase / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology*; D002875:Chromosomes; D005089:Exocytosis; D005260:Female; D016200:Maturation-Promoting Factor / Q000378:metabolism; D000090204:Mesothelin; D051379:Mice; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology*; D010060:Ovulation
C000715528:Msln protein, mouse; D016200:Maturation-Promoting Factor; D000090204:Mesothelin