Nuclear and cytoplasmic maturation of mouse oocytes after treatment with synthetic meiosis-activating sterol in vitro.
Synthetically produced meiosis-activating sterol, a sterol originally derived from follicular fluid (FF-MAS), induces meiotic maturation of mouse oocytes in vitro. We therefore compared FF-MAS-induced maturation of naked mouse oocytes arrested in prophase I by either hypoxanthine (Hx) or forskolin (Fo) with spontaneous maturation of naked oocytes. FF-MAS-treated oocytes overcame the meiotic block by Hx or Fo, although germinal vesicle breakdown was delayed by 11 h and 7 h, respectively. We also investigated the influence of FF-MAS on chromosome, microtubule, and ultrastructural dynamics in Hx-cultured oocytes by immunocytochemistry and electron microscopy. Similarly to spontaneously matured oocytes, chromosomes became aligned, a barrel-shaped spindle formed, and overall organelle distribution was normal in FF-MAS-matured oocytes. The number of small cytoplasmic asters was elevated in FF-MAS-treated oocytes. Although the number of cortical granules (CGs) was similar to that in spontaneously matured oocytes, the overall distance between CGs and oolemma was increased in the FF-MAS group. These observations suggest that the initiation of meiotic maturation in FF-MAS-treated oocytes in the presence of high cAMP levels leads to a delayed but otherwise normal nuclear maturation. FF-MAS appears to improve oocyte quality by supporting microtubule assembly and by delaying CG release, which is known to contribute to reduced fertilization.
Hegele-Hartung
C
C
Research Laboratories of Schering AG, Berlin, Germany. christa.hegelehartung@schering.de
Kuhnke
J
J
Lessl
M
M
Grøndahl
C
C
Ottesen
J
J
Beier
H M
HM
Eisner
S
S
Eichenlaub-Ritter
U
U
D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects* / Q000648:ultrastructure; D002775:Cholestadienols / Q000494:pharmacology*; D002875:Chromosomes / Q000187:drug effects / Q000648:ultrastructure; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D003593:Cytoplasm / Q000187:drug effects* / Q000648:ultrastructure; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure; D005260:Female; D019271:Hypoxanthine / Q000494:pharmacology; D066298:In Vitro Techniques; D008540:Meiosis / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects / Q000648:ultrastructure; D009865:Oocytes / Q000187:drug effects* / Q000254:growth & development / Q000648:ultrastructure
C114832:4,4-dimethyl-5alpha-cholest-8,14,24-trien-3-ol; D002775:Cholestadienols; D005576:Colforsin; D019271:Hypoxanthine; D000242:Cyclic AMP