Effect of aging on follicular function may be relieved by exogenous gonadotropin treatment in a sheep model.
The current study investigated hormonal and ovarian changes during physiological reproductive aging in Sarda ewes. In a first experiment, follicular and corpus luteum dynamics were compared during an induced oestrus cycle in aged (12-14 years) and young adult ewes (4-5 years). Oestrus cycle characteristics did not differ between the two experimental groups. However, follicular function during the follicular phase showed significant alterations in aged ewes, as determined by a lack of dominance effect and by lower mean values of circulating oestradiol (E(2)) and inhibin levels, compared with young adult ewes. In a second experiment, differences in follicle growth, hormonal milieu and oocyte quality in response to exogenous FSH administration were assessed in aged and adult ewes. No differences were recorded in ovarian response to FSH treatment between young adult and aged ewes, as evaluated by ultrasonographic data and circulating concentrations of LH, E(2) and inhibin-A. Although the total number of recovered oocytes was similar in the two age groups, the number of good quality oocytes selected for IVM was significantly lower in aged ewes compared with adult ones. Thereafter, no differences were recorded in cleavage rates, total blastocyst output, embryo developmental kinetic and quality between aged and adult groups. In conclusion, this study demonstrated that reproductive aging in sheep is associated with impaired follicle functionality and an increase in the proportion of oocytes showing morphological abnormalities. However interestingly, oocyte developmental competence in vitro and embryo cryotolerance were not affected by the aging process, when only good quality oocytes were chosen.
Department of Animal Biology, University of Sassari, Via Vienna 2, 07100 Sassari, Italy. berling@uniss.it
Fiammetta
F
Berlinguer
Antonio
A
Gonzalez-Bulnes
Antonio
A
Spezzigu
Ignacio
I
Contreras-Solis
Sara
S
Succu
Alan S
AS
McNeilly
Salvatore
S
Naitana
Giovanni G
GG
Leoni
D000367:Age Factors; D000375:Aging / Q000097:blood / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D015925:Cryopreservation; D004622:Embryo, Mammalian; D004958:Estradiol / Q000097:blood; D005260:Female; D005307:Fertilization in Vitro; D005640:Follicle Stimulating Hormone / Q000008:administration & dosage / Q000494:pharmacology; D006062:Gonadotropins / Q000494:pharmacology*; D059471:In Vitro Oocyte Maturation Techniques; D007265:Inhibins / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood; D023421:Models, Animal; D006080:Ovarian Follicle / Q000187:drug effects* / Q000502:physiology; D017697:Premenopause / Q000097:blood / Q000502:physiology; D012756:Sheep
D006062:Gonadotropins; C422362:inhibin A; D004958:Estradiol; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone