Effect of aging on follicular function may be relieved by exogenous gonadotropin treatment in a sheep model

Abstract

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.

Factors affecting in vitro maturation of alpaca (Lama paco) oocytes

“…There was a trend for a greater proportion of MNO to be recovered from aspiration in young than from old alpacas. This is likely due to the fact that females undergoing physiological reproductive aging experience a decrease in oocyte quality and developmental competence (Berlinguer et al 2012, Malhi et al 2007. In horses, sheep and cattle, it has been demonstrated that oocytes recovered from aged animals and deemed suitable for incubation were less likely to achieve maturation than those collected from young animals (Berlinguer et al 2012, Brinsko et al 1995.…”

“…This is likely due to the fact that females undergoing physiological reproductive aging experience a decrease in oocyte quality and developmental competence (Berlinguer et al 2012, Malhi et al 2007. In horses, sheep and cattle, it has been demonstrated that oocytes recovered from aged animals and deemed suitable for incubation were less likely to achieve maturation than those collected from young animals (Berlinguer et al 2012, Brinsko et al 1995. In sheep, the proportion of morphologically abnormal oocytes was significantly higher in aged animals (Berlinguer et al 2012).…”

“…In horses, sheep and cattle, it has been demonstrated that oocytes recovered from aged animals and deemed suitable for incubation were less likely to achieve maturation than those collected from young animals (Berlinguer et al 2012, Brinsko et al 1995. In sheep, the proportion of morphologically abnormal oocytes was significantly higher in aged animals (Berlinguer et al 2012). Aged oocytes undergo several morphological changes that are deleterious to developmental competence.…”

Glycerol-based formulations increases ovulation rate in sheep similarly to eCG but red blood cell indices may be affected

“…Phase 1 aimed at determining the lowest doses of glycerol as a titration feeding trial able to modify ewe's metabolic status, as previously described using a high dose (20), without impacting on RBC indices. Glycerol was administered both alone and in combination with propylene glycol, as previously described (10,19,20).…”

“…Ultrasonographic examinations were carried out using a Mylab-alpha (Esaote, Italia) fitted to an endocavitary transducer (8)(9)(10)(11). Each ovarian follicular population was scanned using both Thereafter, on day 14 ovulation rates were determined by counting the corpora lutea present in each ovary by transrectal ultrasonography with a real-time B-mode scanner (Aloka102 SSD 500; Aloka Co., Tokyo, Japan) fitted with a 7.5MHz linear-array probe.…”