Follicular fluid supplementation during in vitro maturation promotes sperm penetration in bovine oocytes by enhancing cumulus expansion and increasing mitochondrial activity in oocytes.
The aim of this study was to examine the effects of bovine follicular fluid (bFF) on mitochondrial activity in in vitro-matured (IVM) oocytes and to assess its importance for fertilisation and embryo development. Bovine follicular oocytes were subjected to IVM in medium supplemented either with polyvinylpyrrolidone, bovine serum albumin, calf serum or bFF. Nuclear maturation, cumulus expansion, mitochondrial distribution and ATP content in oocytes were compared between groups along with subsequent in vitro fertilisation (IVF) and embryo development. Compared with other supplements, bFF generated significantly enhanced re-distribution of active mitochondria in oocytes and this effect was associated with elevated intracellular ATP content. Furthermore, bFF significantly improved cumulus expansion, which was associated with improved fertilisation rates when cumulus-enclosed oocytes were subjected to IVF; however, its promoting effect was neutralised when denuded oocytes were inseminated. Elevating ATP content in oocytes by bFF did not affect maturation or embryo development but promoted fertilisation when mitochondrial electron transport was blocked in oocytes before IVF by Rotenone. In conclusion, supplementation of IVM medium with bFF promotes sperm penetration both by the improvement of cumulus expansion and by enhancing ATP levels in oocytes, which maintains their ability to be fertilised after mitochondrial stress.
NARO Institute of Livestock and Grassland Science, National Agriculture and Food Research Organisation, Tsukuba, Ibaraki 305-0901, Japan.
Tamás
T
Somfai
Yasushi
Y
Inaba
Shinya
S
Watanabe
Masaya
M
Geshi
Takashi
T
Nagai
D000818:Animals; D002417:Cattle; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003470:Culture Media / Q000494:pharmacology; D054885:Cumulus Cells / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D015571:Follicular Fluid / Q000502:physiology*; D059471:In Vitro Oocyte Maturation Techniques / Q000379:methods* / Q000662:veterinary; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D013084:Sperm-Ovum Interactions / Q000187:drug effects / Q000502:physiology
D003470:Culture Media