title: Similar patterns of embryo development in canine oocytes cultured in vitro at oxygen tensions of 5 and 20%.
abstract: The influence of two oxygen tensions (5 and 20%) on fertilization, cleavage, development, and morphological quality of canine embryos produced in vitro was investigated. To assess embryo production, canine oocytes (N = 608) were matured in vitro at 20% oxygen tension in TCM 199 supplemented with glucose (11 mM) and 0.1% polyvinyl alcohol. Oocytes and sperm were coincubated at 37 °C for 24 hours in serum-free medium. Subsequently, presumptive zygotes were cultured in vitro in synthetic oviductal fluid in either 5% CO2 in air (20% oxygen; N = 298) or 5% O2, 5% CO2 and 90% N2 (5% oxygen; N = 310) for 7 days. Regardless of the oxygen concentration (5 vs. 20%), rates of pronucleus formation, cleavage, and embryo development up to the eight-cell stage did not differ (46/310 [14.8%] vs. 35/298 [11.7%], respectively; P > 0.05). Moreover, similar proportions of embryos developed in 20 and 5% oxygen tensions (18/298 vs. 27/310). The oocyte nuclear maturation (metaphase II), in terms of decondensed sperm heads, pronucleus formation, cleavage, and embryo development, was similar (P = 0.299) between the atmospheric (20% O2; 12.4% [37/298]) and reduced oxygen tensions (5% O2; 15.8% [49/310]) at all steps of the in vitro culture (IVC) after in vitro fertilization (IVF). To our knowledge, this was the first study that demonstrated that canine embryos can be produced using a low-oxygen in vitro culture system. Both oxygen tensions (5 and 20%) resulted in similar embryonic development and therefore were feasible for IVC of canine oocytes.
authors.affiliation: Laboratory of Embryology and Biotechniques of Reproduction, Faculty of Veterinary Medicine, UFRGS, Porto Alegre, Rio Grande do Sul, Brazil. berenice@portoweb.com.br
authors.forename: B A
authors.initials: BA
authors.lastname: Rodrigues
authors.forename: C A
authors.initials: CA
authors.lastname: Rodrigues
authors.forename: M B
authors.initials: MB
authors.lastname: Salviano
authors.forename: B R
authors.initials: BR
authors.lastname: Willhelm
authors.forename: F J F
authors.initials: FJ
authors.lastname: Collares
authors.forename: J L
authors.initials: JL
authors.lastname: Rodrigues
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004285:Dogs / Q000196:embryology / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D046149:Embryo Culture Techniques; D047108:Embryonic Development / Q000187:drug effects*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods / Q000662:veterinary; D059471:In Vitro Oocyte Maturation Techniques / Q000379:methods* / Q000662:veterinary; D008297:Male; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D009866:Oogenesis / Q000187:drug effects / Q000502:physiology; D009994:Osmolar Concentration; D010100:Oxygen / Q000494:pharmacology*
chemical_list: D010100:Oxygen