title: Evaluation of equine oocyte developmental competence using polarized light microscopy.
abstract: The purpose of this study was to observein vitro-matured equine oocytes with an objective computerized technique that involves the use of a polarized light microscope (PLM) in addition to the subjective morphological evaluation obtained using a classic light microscope (LM). Equine cumulus-oocyte complexes (COCs,n= 922) were subjected to differentin vitromaturation times (24, 36 or 45 h), however, only 36-h matured oocytes were analyzed using CLM. The 36-h matured oocytes that reached maturity were parthenogenetically activated to evaluate the quality and meiotic competence. Average maturation percentages per session in groups 1, 2 and 3 (24-, 36- and 45-h matured oocytes respectively) were 29.31 ± 13.85, 47.01 ± 9.90 and 36.62 ± 5.28%, whereas the average percentages of immature oocytes per session were 28.78 ± 20.17, 7.83 ± 5.51 and 22.36 ± 8.39% respectively. The zona pellucida (ZP) birefringent properties were estimated and correlated with activation outcome. ZP thickness and retardance of the inner layer of the zona pellucida (IL-ZP) were significantly increased in immature oocytes compared with mature oocytes (P< 0.001 andP< 0.01 respectively). The comparison between parthenogenetically activated and non-activated oocytes showed a significant increase in the area and thickness of the IL-ZP in parthenogenetically activated oocytes (P< 0.01). These results show that the 36-hin vitromaturation (IVM) protocol allowed equine oocytes to reach maturity, and PLM observation of ZP can be used to distinguish mature and immature oocytes as well as activated and non-activated oocytes.
authors.affiliation: Department of Veterinary ScienceUniversity of Torino, Grugliasco, Italy alessia.bertero@unito.it.
authors.forename: A
authors.initials: A
authors.lastname: Bertero
authors.affiliation: Department of Surgical SciencesUniversity of Torino, S. Anna Hospital, Torino, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Ritrovato
authors.affiliation: Department of Surgical SciencesUniversity of Torino, S. Anna Hospital, Torino, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Evangelista
authors.affiliation: Department of Surgical SciencesUniversity of Torino, S. Anna Hospital, Torino, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Stabile
authors.affiliation: Department of AgriculturalForestry and Food Sciences, University of Torino, Grugliasco, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Fortina
authors.affiliation: Department of Veterinary ScienceUniversity of Torino, Grugliasco, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Ricci
authors.affiliation: Department of Surgical SciencesUniversity of Torino, S. Anna Hospital, Torino, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Revelli
authors.affiliation: Department of Veterinary ScienceUniversity of Torino, Grugliasco, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Vincenti
authors.affiliation: Department of Veterinary ScienceUniversity of Torino, Grugliasco, Italy.
authors.forename: T
authors.initials: T
authors.lastname: Nervo
mesh_terms: D000818:Animals; D054885:Cumulus Cells / Q000166:cytology / Q000648:ultrastructure*; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary*; D006736:Horses; D059471:In Vitro Oocyte Maturation Techniques / Q000379:methods*; D008859:Microscopy, Polarization / Q000379:methods*; D009865:Oocytes / Q000166:cytology* / Q000648:ultrastructure*; D009866:Oogenesis / Q000502:physiology*