Abstract

The objective of this research was to evaluate the effect of eCG on morphological quality and gene expression profile of cumulus-oocyte complexes (COC) recovered from anestrous cats. For this purpose, 3 experimental groups were made. Group 1 consisted of 11 oestrous cats (oestrous); Group 2 had 13 anestrous cats (anestrous); and Group 3 was made up of 11 anestrous cats treated with a single subcutaneous dose of 200 IU of eCG. In oestrous and anestrous groups the ovaries were obtained directly by ovariohysterectomy, whereas in the eCG group this was achieved 4 days after the dose injection. In all groups, each cat corresponded to an individual biological replicate, whereby the COC recovered from each cat were classified and processed separately for the experiments of gene expression analysis and in vitro maturation (IVM). The COC were collected by slicing of the ovaries and classified morphologically as grade I (excellent), grade II (good), grade III (fair), and grade IV (poor) quality. For gene expression analysis, pools of 8 to 10 grade I and II immature COC were made, resulting in 7 pools for each group. Quantitative RT-PCR was performed for gonadotrophin receptor genes (FSHR and LHCGR), FSH-induced genes (EGFR, EGR1, ESR2, and PTGS2), and genes related to oocyte competence (GDF9, BMP15, and GATM). The gene SDHA was used as the internal control. The total remaining proportion of grade I and II COC were used for IVM, and maturation rate was measured by visualisation of the first polar body. Statistical analysis was performed using the Kruskal–Wallis test. No differences were found in the total number of COC (mean ± standard deviation) recovered per cat among the oestrous (56.8 ± 20.5), anestrous (80.2 ± 35.2), and eCG groups (96.5 ± 62.0; P > 0.05). With respect to morphological quality of COC, the eCG group had a higher proportion of grade I COC (33.6 ± 11.0%) than the oestrous and anestrous groups (16.5 ± 8.7 and 8.9 ± 6.0%, respectively; P < 0.05). However, the anestrous group had a higher proportion of grade II COC (26.8 ± 6.4%) than the eCG group (21.1 ± 6.6%; P < 0.05). On the other hand, the eCG group had a lower proportion of grade III and IV COC (45.3 ± 12.8%) than the anestrous group (64.3 ± 9.1%; P < 0.05), without differences from the oestrous group (57.1 ± 12.0%; P > 0.05). Concerning to gene expression analysis, COC from the eCG group had a higher relative expression of FSHR, LHCGR, and EGFR than COC from the oestrous and anestrous group (P < 0.05). Furthermore, the COC from the eCG group had a higher relative expression of EGR1 than COC from the anestrous group and a higher expression of ESR2 than COC from the oestrous group (P < 0.05). However, COC from the eCG group had a lower relative expression of GATM and PTGS2 than COC from the oestrous group and a lower expression of GDF9 and BMP15 than COC from the anestrous group (P < 0.05). Although a higher number of oocytes with a first polar body could be seen in the eCG group after IVM, no significant differences in the maturation rate were found among the eCG (55.3 ± 13.2), oestrous (43.7 ± 11.1), and anestrous groups (47.9 ± 13.6; P > 0.05). In conclusion, the treatment with eCG improved the morphological quality of COC recovered from anestrous cats, which agrees with an increased relative expression of FSHR, LHCGR, EGFR, EGR1, and ESR2 and might be related to an enhanced competence of COC.