Effect of the presence of corpus luteum on the ovary and the new oocyte recovery method on the oocyte recovery rate and meiotic competence of ovine oocytes
This study was designed to identify the effects of the presence of corpus luteum (CL) on the meiotic competence of the ewe oocytes. In addition, due to the pivotal roles of oocyte recovery methods on efficiency of in vitro maturation and in vitro fertilization, this study considered the new oocyte recovery method “Oocyte Recovery with Centrifuge” (ORC); Ovine ovaries were obtained from local abattoir at Karaj, Iran. The ovaries were placed in 0.9% saline which was supplemented with penicillin/streptomycin in thermo flask at 37°C and transported to the laboratory within 1 to 2 h of slaughter. The ovaries were assigned to two groups; group-1 with functional CL and group-2 without CL. The oocytes were recovered by means of aspiration pump or ORC. After oocyte recovery, they were cultured in TCM-199 for 24 h. The mean number of oocyte recovery per ovary in group 1 ovaries (1.8 ± 0.01 via aspiration and 3.84 ± 0.05 via ORC) was lower (P<0.05) than group 2 ovaries (2.2 ± 0.00 via aspiration and 5.43 ± 0.01 via ORC). There were no significant differences (P>0.05) between percentage of nuclear maturation in oocytes which were recovered from group 2 ovaries via aspiration and ORC (75.20 ± 0.00 vs. 74.95 ± 0.00, metaphase II; M-II) method. The nuclear maturation in oocytes which were obtained via ORC from group 2 ovaries was higher (P<0.05) than group 1 ovaries (74.95 ± 0.00 vs. 60.07 ± 0.00b). Nuclear maturation for oocytes obtained via ORC from group 1 ovaries was (P<0.05) lower than oocytes obtained via aspiration (60.07 ± 0.00 vs. 74.70 ± 0.00). Result of the present study showed that the presence of CL on ovaries lead to decrease in the quality and the quantity of oocytes. ORC method increased the quantity and quality of recovered oocytes.
Key words: Aspiration, corpus luteum, in vitro maturation (IVM), oocyte recovery.