157 EFFECT OF FSH STARVATION (COASTING) FOLLOWING SUPEROVULATION ON OOCYTE COMPETENCE AND CLONING EFFICIENCY IN GOATS

Abstract

Oocyte competence plays a key role in the overall efficiency of reproductive biotechnologies. In cattle, FSH starvation following superovulation (coasting) improves oocyte competence, blastocyst yield and pregnancy outcome when used in ovum pickup-in vitro production programs. The aim of this study was to compare the effect of coasting after exogenous FSH stimulation on goat oocyte quality and competence to support in vitro maturation and in vivo embryo development following cloning procedures in goats. Donor and recipient preparation, cumulus-oocyte complex (COC) retrieval and selection, IVM, cloning by somatic cell nuclear transfer, embryo transfer, and pregnancy diagnosis (Days 23–26) were performed according to our established procedures [Martins et al. 2016 doi: 10.1089/cell.2015.0082]. Cumulus-oocyte complexes were obtained in vivo from 71 cycling FSH-stimulated mature Nubian-crossed goats, combined or not with FSH starvation (coasting period). Donor females were oestrous synchronized with a progesterone intravaginal insert (Day 0). On Day 10, a 0.75-mg D-cloprostenol dose was given IM, with the onset of the superovulation treatment, composed of five 20-mg FSH doses (Folltropin®, Bioniche Animal Health, Pullman, WA, USA), via IM at 12-h intervals. Donors were subjected to laparoscopic ovum pickup either 9 h (control group, n = 36) or 21 h (coasting group, n = 35) after the last FSH dose, respectively. Skin fibroblast cell cultures from a male neonate were co-transfected with a mammary gland expression vector with the human lactoferrin (hLF) coding sequence and with CRISPR/Cas9 system either for the PRNP prion gene or the Rosa26 locus. A bi-allelic hLF-PRNP and a mono-allelic hLF-Rosa26 cell colony were used for cloning. Data were compared by ANOVA or the χ2 test (P < 0.05). No differences were observed between control and coasting for number of follicles (18.7 ± 1.4 v. 21.2 ± 1.7), and retrieved (17.3 ± 1.2 v. 20.7 ± 1.9), viable (15.9 ± 1.1 v. 19.6 ± 1.8), Grade I (1.5 ± 0.3 v. 2.5 ± 0.5), and Grades III+IV (6.0 ± 0.6 v. 5.7 ± 0.7) COC, as well as for COC retrieval (92.4%, 574/621 v. 94.5%, 685/725) and fusion (62.8%, 273/435 v. 61.3%, 311/507) rates, respectively, irrespective of the cell lines. However, the coasting group rendered higher number of Grade II COC (11.3 ± 1.2 v. 8.4 ± 0.7), number and proportion of Grades I+II COC (13.9 ± 1.5 v. 9.9 ± 0.9, 70.8% v. 62.4%), and maturation rate (70.9% v. 65.4%) than the control group, respectively, for a lower proportion of Grades III+IV (29.2% v. 37.6%, respectively). A total of 213 and 233 Day-1 cloned embryos from the control and the coasting groups were transferred to 18 (96/9 hLF-PRNP and 117/9 hLF-Rosa26 cells) and 19 (128/11 hLF-PRNP and 105/8 hLF-Rosa26 cells) female recipients, respectively, resulting in 1/9 (11.1%) and 4/11 (36.4%) pregnancies from the hLF-PRNP cells, and 3/9 (33.3%) and 3/8 (37.5%) from the hLF-Rosa26 cells, for the control (4/18, 22.2%) and coasting (7/19, 36.8%) groups, respectively, for an overall pregnancy rate of 29.7% (11/37). In conclusion, the use of coasting improved oocyte quality and in vitro maturation rate, also appearing to increase pregnancy outcome after goat cloning.