Coculture with cumulus cells improves maturation of mouse oocytes denuded of the cumulus oophorus: observations of nuclear and cytoplasmic events.
OBJECTIVE
To study the mechanisms by which cumulus cells (CCs) promote oocyte maturation by observing the effect of removing the cumulus oophorus on nuclear and cytoplasmic events during in vitro maturation.


METHODS
Experimental animal study.


METHODS
Academic institution.


METHODS
Mice of the Kun-ming breed.


METHODS
Cumulus-free oocytes were cultured alone (DOs) or with a CC monolayer (coDOs), and the nuclear and cytoplasmic events were compared with those of oocytes matured in vivo or in vitro with the cumulus intact (COCs).


METHODS
Nuclear progression, spindle assembly, behavior of cortical granules (CGs) and mitochondria, levels of glutathione (GSH), and dynamics of maturation-promoting factor (MPF) activity during oocyte maturation under different conditions.


RESULTS
Cumulus removal increased MPF activity and accelerated the transition from the G2 to the M phase and the redistribution of CGs. Spindle assembly and mitochondrial congregation were impaired. In addition, removal of the cumulus caused a precocious exocytosis of CGs, leading to zona hardening and reduced penetrability of oocytes by sperm. After DOs were matured on the CC monolayer, however, these parameters were much improved, and the DOs acquired characteristics closer to those of cumulus-invested oocytes matured in vivo or in vitro. The level of intracellular GSH of DOs, on the other hand, did not differ from that of oocytes matured as COCs, suggesting that the mouse DOs can synthesize GSH on their own.


CONCLUSIONS
While denuding mouse oocytes of CCs impaired in vitro cytoplasmic maturation, coculture with CCs promoted maturation, possibly through the regulation of MPF activity and meiotic progression.
Ge
Li
L
College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, China.
Sui
Hong-Shu
HS
Lan
Guo-Cheng
GC
Liu
Na
N
Wang
Jun-Zuo
JZ
Tan
Jing-He
JH
D000818:Animals; D002450:Cell Communication; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism*; D048430:Cell Shape; D018920:Coculture Techniques; D054885:Cumulus Cells / Q000201:enzymology / Q000378:metabolism*; D003593:Cytoplasm / Q000201:enzymology / Q000378:metabolism*; D046149:Embryo Culture Techniques; D005260:Female; D005307:Fertilization in Vitro; D005978:Glutathione / Q000378:metabolism; D016200:Maturation-Promoting Factor / Q000378:metabolism; D008540:Meiosis; D000090204:Mesothelin; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009865:Oocytes / Q000201:enzymology / Q000378:metabolism*; D013084:Sperm-Ovum Interactions; D008941:Spindle Apparatus / Q000378:metabolism; D013997:Time Factors
C000715528:Msln protein, mouse; D016200:Maturation-Promoting Factor; D005978:Glutathione; D000090204:Mesothelin