ECG stimulation in domestic cats increases the expression of gonadotrophin-induced genes improving oocyte competence during the non-breeding season.

Abstract

The objective of this study was to evaluate the eCG stimulation on domestic cat oocyte competence during the non-breeding season. Four experimental groups were made: (a) untreated cycling cats (Breeding season group; BS), (b) untreated anestrous cats (Non-breeding group; NB), (c) anestrous cats treated with 200IU of eCG (eCG group) and (d) anestrous cats treated with 200IU of eCG and 100IU of hCG four days later (hCG group). In the BS, NB and eCG groups, grade I and II immature cumulus-oocyte complexes (COCs) were subjected to in vitro maturation or used for the gene expression analysis of FSHR, LHCGR, EGFR, EGR1, ESR2, PTGS2, GDF9, BMP15 and GATM. The in vitro matured oocytes from the BS, NB and eCG groups and the in vivo matured oocytes from the hCG group were subjected to parthenogenetic activation. The grade I and II COCs from the eCG group had an increased expression of FSHR, LHCGR, EGFR, EGR1 and ESR2 and a higher maturation rate than the BS and NB groups (p<0.05). After parthenogenetic activation, the blastocyst rate from the hCG, eCG and BS groups was higher than the NB group (p<0.05). However, no significant improvement was observed in the blastocyst rate in the hCG group compared to the eCG group (p>0.05). In conclusion, the eCG treatment increases the expression of specific genes improving the oocyte competence during the cat non-breeding season, which is reflected in an enhanced in vitro maturation and in vitro embryo development after parthenogenetic activation.