Characterisation of the cellular and molecular responses of ovine oocytes and their supporting somatic cells to pre-ovulatory levels of LH and FSH during in vitro maturation.
The response of Graafian follicles to pre-ovulatory surge levels of FSH and LH in vivo triggers the terminal differentiation of granulosa cells and oocyte maturation. In polyovular species, the LH-driven signalling uses the epidermal growth factor (EGF)-like ligands AREG, EREG and BTC to promote oocyte maturation and cumulus expansion. This experimental series used a physiologically relevant ovine in vitro maturation (IVM) system to evaluate the impact of exposure to pre-ovulatory levels (100  ng/ml) of LH and FSH on ovine cumulus cell expression of EGF-like ligands in vitro. The serum-free sheep IVM system supported high levels (91.4%) of gonadotrophin-induced maturation of cumulus-enclosed oocytes and embryo development to the blastocyst stage (34.5%). Results were equivalent to a serum-based IVM system (85.1% IVM, 25.8% blastocyst rate; P>0.05) but were significantly different (P<0.05) to serum-free medium without gonadotrophins (69.5% IVM; 8.0% blastocyst rate). Ovine BTC was cloned and sequenced. Gonadotrophin-induced AREG, EREG, BTC and EGFR expressions were quantified in cumulus and mural granulosa cells during IVM. A rapid induction of AREG expression was apparent in both cell types within 30  min of gonadotrophin exposure in vitro. LHCGR (LHR) was detected in mural cells and FSHR in both cumulus and mural granulosa cells. The data confirm the involvement of AREG and EGFR during gonadotrophin-induced cumulus expansion, oocyte maturation and the acquisition of developmental competence by sheep oocytes matured in vitro.
Division of Reproduction and Early Development Research Group, Leeds Institute for Genetics, Health and Therapeutics, University of Leeds, Clarendon Way, Leeds LS2 9JT, UK. medmcot@leeds.ac.uk
Matthew
M
Cotterill
Sally L
SL
Catt
Helen M
HM
Picton
D000818:Animals; D001483:Base Sequence; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D054885:Cumulus Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism / Q000494:pharmacology*; D005498:Follicular Phase / Q000378:metabolism; D006062:Gonadotropins / Q000494:pharmacology; D006107:Granulosa Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D059471:In Vitro Oocyte Maturation Techniques / Q000379:methods / Q000662:veterinary; D007986:Luteinizing Hormone / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D011962:Receptors, FSH / Q000235:genetics / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D012756:Sheep / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D054928:Validation Studies as Topic
D016895:Culture Media, Serum-Free; D006062:Gonadotropins; D011962:Receptors, FSH; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone