title: Oocyte-secreted factors enhance oocyte developmental competence.
abstract: The capacity of fully grown oocytes to regulate their own microenvironment by paracrine factors secreted by the oocyte (oocyte-secreted factors, OSFs) may in turn contribute to oocyte developmental competence. Here, we investigated if OSFs have a direct influence on oocyte developmental competence during in vitro maturation (IVM). Bovine cumulus-oocyte complexes (COCs) were aspirated from abattoir-derived ovaries and matured in serum-free medium. COCs were either co-cultured with denuded oocytes (DOs) or treated with specific OSFs: recombinant bone morphogenetic protein 15 (BMP15) and/or growth differentiation factor 9 (GDF9). Following maturation, embryos were fertilized and cultured in vitro and blastocyst development and cell number were assessed on day 8. Co-culturing intact COCs with DOs did not affect cleavage rate, but increased (P<0.001) the proportion of cleaved embryos that reached the blastocyst stage post-insemination from 39% to 51%. OSFs also altered blastocyst cell allocation as co-culture of COCs with DOs significantly increased total and trophectoderm cell numbers, compared to control COCs. BMP15 alone, GDF9 alone or the two combined all (P<0.05) increased the proportion of oocytes that reached the blastocyst stage post-insemination from 41% (controls) to 58%, 50% and 55%, respectively. These results were further verified in neutralization experiments of the exogenous growth factors and of the native OSFs. Follistatin and the kinase inhibitor SB-431542, which antagonize BMP15 and GDF9, respectively, neutralized the stimulatory effects of the exogenous growth factors and impaired the developmental competence of control COCs. These results demonstrate that OSFs, and particularly BMP15 and GDF9, enhance oocyte developmental competence and provide evidence that OSF regulation of the COC microenvironment is an important determinant of oocyte developmental programming.
authors.affiliation: Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, The University of Adelaide, The Queen Elizabeth Hospital, South Australia 5011, Australia.
authors.forename: Tamer S
authors.initials: TS
authors.lastname: Hussein
authors.forename: Jeremy G
authors.initials: JG
authors.lastname: Thompson
authors.forename: Robert B
authors.initials: RB
authors.lastname: Gilchrist
mesh_terms: D000818:Animals; D002417:Cattle; D002450:Cell Communication / Q000502:physiology*; D002460:Cell Line; D018920:Coculture Techniques; D005260:Female; D018507:Gene Expression Regulation, Developmental; D055429:Growth Differentiation Factor 9; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology; D009865:Oocytes / Q000378:metabolism*
chemical_list: D055429:Growth Differentiation Factor 9; D036341:Intercellular Signaling Peptides and Proteins