title: Differences in the Kinetic of the First Meiotic Division and in Active Mitochondrial Distribution between Prepubertal and Adult Oocytes Mirror Differences in their Developmental Competence in a Sheep Model.
abstract: Our aim is to verify if oocyte developmental potential is related to the timing of meiotic progression and to mitochondrial distribution and activity using prepubertal and adult oocytes as models of low and high developmental capacity respectively. Prepubertal and adult oocytes were incorporated in an in vitro maturation system to determine meiotic and developmental competence and to assess at different time points kinetic of meiotic maturation, 2D protein electrophoresis patterns, ATP content and mitochondria distribution. Maturation and fertilization rates did not differ between prepubertal and adult oocytes (95.1% vs 96.7% and 66.73% vs 70.62% respectively for prepubertal and adult oocytes). Compared to adults, prepubertal oocytes showed higher parthenogenesis (17.38% vs 2.08% respectively in prepubertals and adults; P<0.01) and polispermy (14.30% vs 2.21% respectively in prepubertals and adults; P<0.01), lower cleavage rates (60.00% vs 67.08% respectively in prepubertals and adults; P<0.05) and blastocyst output (11.94% vs 34.% respectively in prepubertals and adults; P<0.01). Prepubertal oocytes reached MI stage 1 hr later than adults and this delay grows as the first meiotic division proceeds. Simultaneously, the protein pattern was altered since in prepubertal oocytes it fluctuates, dropping and rising to levels similar to adults only at 24 hrs. In prepubertal oocytes ATP rise is delayed and did not reach levels comparable to adult ones. CLSM observations revealed that at MII, in the majority of prepubertal oocytes, the active mitochondria are homogenously distributed, while in adults they are aggregated in big clusters. Our work demonstrates that mitochondria and their functional aggregation during maturation play an active role to provide energy in terms of ATP. The oocyte ATP content determines the timing of the meiotic cycle and the acquisition of developmental competence. Taken together our data suggest that oocytes with low developmental competence have a slowed down energetic metabolism which delays later development.
authors.affiliation: Department of Veterinary Medicine, Sassari University, Sassari, Italy; Sardinian Animal Biodiversity Center (Centro di Competenza per la Biodiversità Animale-CCBA), Sassari, Italy.
authors.forename: Giovanni Giuseppe
authors.initials: GG
authors.lastname: Leoni
authors.affiliation: Department of Life, Health and Environmental Sciences, L'Aquila University, L'Aquila, Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Palmerini
authors.affiliation: Department of Veterinary Medicine, Sassari University, Sassari, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Satta
authors.affiliation: Department of Veterinary Medicine, Sassari University, Sassari, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Succu
authors.affiliation: Department of Veterinary Medicine, Sassari University, Sassari, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Pasciu
authors.affiliation: Department of Biomedical Sciences, Sassari University, Sassari, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Zinellu
authors.affiliation: Department of Biomedical Sciences, Sassari University, Sassari, Italy.
authors.forename: Ciriaco
authors.initials: C
authors.lastname: Carru
authors.affiliation: Department of Life, Health and Environmental Sciences, L'Aquila University, L'Aquila, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Macchiarelli
authors.affiliation: Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, La Sapienza University, Rome, Italy.
authors.forename: Stefania Annarita
authors.initials: SA
authors.lastname: Nottola
authors.affiliation: Department of Veterinary Medicine, Sassari University, Sassari, Italy; Sardinian Animal Biodiversity Center (Centro di Competenza per la Biodiversità Animale-CCBA), Sassari, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Naitana
authors.affiliation: Department of Veterinary Medicine, Sassari University, Sassari, Italy; Sardinian Animal Biodiversity Center (Centro di Competenza per la Biodiversità Animale-CCBA), Sassari, Italy.
authors.forename: Fiammetta
authors.initials: F
authors.lastname: Berlinguer
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000375:Aging; D000818:Animals; D001755:Blastocyst; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D008540:Meiosis / Q000502:physiology*; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology* / Q000254:growth & development; D010053:Ovary / Q000378:metabolism; D010312:Parthenogenesis / Q000502:physiology; D012741:Sexual Maturation; D012756:Sheep; D034561:Sheep, Domestic
chemical_list: D000255:Adenosine Triphosphate