The Efficiency of In vitro Ovine Embryo Production Using an Undefined or a Defined Maturation Medium is Determined by the Source of the Oocyte

Abstract

In vitro oocyte maturation can be influenced by oocyte source and maturation media composition. The aim of the present study was to compare the efficiency of a defined in vitro maturation medium (TCM199 supplemented with cysteamine and epidermal growth factor; Cys + EGF) with an undefined medium (TCM199 supplemented with follicle-stimulating hormone and follicular fluid; FSH + FF) for in vitro production (IVP) of ovine embryos, using oocytes obtained by laparoscopic ovum pick-up from FSH-stimulated [n=11; 158 cumulus-oocyte complexes (COCs)] and non-stimulated (n=16; 120 COCs) live ewes, as well as abattoir-derived oocytes (170 COCs). The produced blastocysts were vitrified and some of them were transferred to synchronized recipients. The best and the worst final yields of embryo IVP observed in this study were obtained using oocytes from FSH-stimulated ewes matured in FSH + FF (41.3%; 33/80) and in Cys + EGF (19.2%; 15/78) medium, respectively (p<0.01). No significant differences between both media were attained in the blastocyst development rate or in the final yield of embryo IVP using oocytes from non-stimulated ewes or abattoir-derived oocytes. The overall in vivo survival rate of the transferred vitrified blastocysts was 13.1% (8/61), without significant differences between oocyte sources or maturation media. In conclusion, under the experimental conditions of the present study, TCM199 supplemented with cysteamine and EGF is a convenient defined maturation medium for IVP of embryos from oocytes of live non-stimulated ewes or from oocytes of abattoir-derived ovaries. However, the best final yield of embryo IVP observed in this study was attained when oocytes came from FSH-stimulated donors and TCM199 was supplemented with FSH and follicular fluid.

Influence of the FecXR Allele in Heterozygous Ewes on Follicular Population and Outcomes of IVP and ET using LOPU‐Derived Oocytes

“…Follicular fluid was prepared as described previously (Cocero et al. ). Plates were incubated at 38.5°C in 5% CO 2 in humidified air for 24 h.…”

Cryopreservation of Sheep Produced Embryos – Current and Future Perspectives

“…As stated also in other species, in vitro techniques reduce the rate of produced embryos and, as previously discussed, lead to inferior embryo survival after transfer compared to in vivo-derived embryos [23,35,99,100]. Concerning sheep embryo production from abattoir-derived oocytes, Cocero et al [101] obtained 34.6% and 40.4% blastocyst yield at days 7 and 8, respectively, Romão et al…”

“…Also, Guler et al [125] obtained better results adding follicular fluid to maturation medium or using epidermal growth factor (EGF) conjugated with FSH and E 2 [50]. The positive effect of EGF or other EGF-like ligands in COCs has been shown during IVM [126,127], whereas other researchers [101,128] preferred EGF and cysteamine. Cumulus cells are important to IVM success and subsequent fertilization.…”

“…Tissue Culture Medium (TCM199) supplemented with bicarbonate, pyruvate, LH, FSH, and estradiol (E 2 ) and with 10% fetal calf serum [10,101] or 10% estrous sheep serum [50,122] is the widest used medium for IVM. Nevertheless, other media and supplementation can be also used.…”

“…Sheep ovum pick-up systems are applied in living animals using minimal invasive procedures such as laparoscopic ovum pick-up (LOPU) technique guided by laparoscopy [113][114][115]. As referred before, these procedures when used in vivo are usually associated with follicular stimulation treatments [116] to raise the number of collected COCs [117], allowing better maturation, fertilization, and in vitro development capacities [101,118]. Moreover, the development of these in vivo techniques of oocyte collection is important, as abattoir-derived oocytes usually cannot be used in genetic programs because of their unknown sanitary and even genetic status, being applied mainly for research proposes [115].…”