Open Access

ARTICLE

Immature oocyte quality and maturational competence of porcine cumulus-oocyte complexes subpopulations

by GABRIEL MARTIN ALVAREZ, GABRIEL CARLOS DALVIT, MARÍA VERÓNICA ACHI, MARCELO SERGIO MIGUEZ, PABLO DANIEL CETICA

1. Area of Biochemistry, Institute of Research and Technology in Animal Reproduction (INITRA), School of Veterinary Sciences, University of Buenos Aires, Argentina.
2. Area of Porcine Production, School of Veterinary Sciences, University of Buenos Aires, Argentina.
* Address correspondence to: Gabriel Martin Alvarez. E-mail: galvarez@fvet.uba.ar

BIOCELL 2009, 33(3), 167-177. https://doi.org/10.32604/biocell.2009.33.167

Abstract

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 A₁ 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.

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