Bovine oocyte vitrification before or after meiotic arrest: effects on ultrastructure and developmental ability.
The nuclear stage at which oocytes are cryopreserved influences further development ability and cryopreservation affects ultrastructure of both cumulus cells and the oocyte. In this work, we analyze the effects of vitrification at different nuclear and cytoplasmic maturation stages on the oocyte ultrastructure and developmental ability. Culture in TCM199 + PVA with roscovitine 25 M during 24h led to meiotic arrest (MA) in cumulus-oocyte complexes (COCs), while permissive in vitro maturation (IVM) was performed in TCM199, 10% FCS, FSH-LH and 17beta-estradiol for 24 h. Oocytes were vitrified using the open pulled straw method (OPS) with minor modifications. Fresh and vitrified/warmed COCs were fixed as immature, after IVM, after meiotic arrest (MA) and after MA + IVM. Vitrification combined with MA followed by IVM produced the highest rates of degeneration, regardless of the vitrification time. As a consequence, lower proportions of embryos cleaved in these groups, although differences were eliminated at the five-eight cell stage. Development rates up to day 8 were similar in all experimental groups, being significantly lower than those in fresh controls. Only oocytes vitrified after IVM were able to give blastociysts. The morphological alterations observed can be responsible for compromised development. More research is needed to explain the low survival rates of the bovine oocyte after vitrification and warming.
Diez
Carmen
C
Servicio Regional de Investigación y Desarrollo Agroalimentario, Camino de los Claveles 604, Somio, 33203 Gijón, Asturias, Spain. mcdiez@serida.org
Duque
Paloma
P
Gómez
Enrique
E
Hidalgo
Carlos O
CO
Tamargo
Carolina
C
Rodríguez
Aida
A
Fernández
Lina
L
de la Varga
Santiago
S
Fernández
Alba
A
Facal
Nieves
N
Carbajo
Maite
M
D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D003470:Culture Media; D003593:Cytoplasm / Q000502:physiology / Q000648:ultrastructure; D046149:Embryo Culture Techniques / Q000662:veterinary; D004958:Estradiol / Q000008:administration & dosage; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D005640:Follicle Stimulating Hormone / Q000008:administration & dosage; D007986:Luteinizing Hormone / Q000008:administration & dosage; D008540:Meiosis; D008854:Microscopy, Electron; D009865:Oocytes / Q000502:physiology* / Q000648:ultrastructure*; D006080:Ovarian Follicle / Q000166:cytology
D003470:Culture Media; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone