Immature oocyte quality and maturational competence of porcine cumulus-oocyte complexes subpopulations.
Porcine immature oocyte quality (i.e., that of live oocytes at the germinal vesicle stage) was evaluated according to features of the surrounding cumulus, aiming to establish maturational competence of different subpopulations of such cumulus-oocyte complexes. Six subpopulations were identified: A1 (with a dense cumulus), A2 (with a translucent cumulus), B1 (with the corona radiata), B2 (partly naked oocytes), C (naked oocytes), D (with a dark cumulus). The percent incidence of live oocyte in these subpopulations changed significantly as related to cumulus features, however the occurrence of oocytes in the germinal vesicle stage was lower in class D only. Similar metaphase II rates achieved in A1, A2, B1 and B2 classes after in vitro maturation suggest that the nucleus may in fact mature in vitro, in spite of the different accompanying cumulus features which are typical of these classes. In contrast, a higher cytoplasmic maturation rate obtained in class A may indicate a stronger dependence of this variable upon cumulus features than that shown by nuclear maturation. When different types of cumulus expansion after in vitro maturation were considered (i.e., fully expanded cumulus, partly expanded cumulus, and partly naked oocyte), no differences were found in the percent of oocytes reaching metaphase II or cytoplasmic maturation. It is concluded that morphological features of the collected porcine cumulus-oocyte complexes (rather than cumulus behavior during culture) may be useful for selection of potentially competent oocytes for in vitro fertilization and embryo production.
Alvarez
Gabriel Martin
GM
Area of Biochemistry, Institute of Research and Technology in Animal Reproduction (INITRA), School of Veterinary Sciences, University of Buenos Aires, Argentina. galvarez@fvet.uba.ar
Dalvit
Gabriel Carlos
GC
Achi
María Verónica
MV
Miguez
Marcelo Sergio
MS
Cetica
Pablo Daniel
PD
D000818:Animals; D054885:Cumulus Cells / Q000166:cytology*; D005260:Female; D005307:Fertilization in Vitro; D008677:Metaphase / Q000502:physiology; D009865:Oocytes / Q000166:cytology*; D006080:Ovarian Follicle / Q000166:cytology*; D013552:Swine / Q000502:physiology*