243 EFFECT OF OOCYTE RECOVERY TECHNIQUES ON IN VITRO MATURATION OF SWINE OOCYTES

Abstract

The aim of this study was to compare 2 different techniques to obtain swine oocytes from abattoir ovaries. Ovaries were washed in saline at 35°C and submitted to slashing or aspiration, simultaneously. For the slashing group, ovaries were held with a hemostat inside a beaker containing 35 mL of HEPES-buffered Tyrode’s media (HbT) and follicles (2–6 mm) were incised with a scalpel. For every 5 slashed ovaries, HbT-containing follicular fluid was transferred to 50-mL centrifuge tubes. For the aspiration group, follicles (2–6 mm) were aspirated using an 18-gauge needle and a 5-mL syringe. The follicular fluid of each ovary was transferred to a 50-mL centrifuge tube. Tubes from both techniques were placed in a water bath at 35°C for 15 min to allow settling of the cumulus–oocyte complexes (COC). The supernatant was removed and the sediment was resuspended in HbT and placed in water bath at 35°C for an additional 15 min. The sediment was resuspended in 15 mL of HbT and COC were recovered under stereomicroscopy. Oocytes were in vitro matured for 44 h in TCM-199 added with 10% porcine follicular fluid (PFF) and hormones (LH and FSH) at 38.5°C, 5% CO₂ and high humidity. The oocyte recovery rate of each technique was determined by the ratio between the number of COC and ovaries used. To verify nuclear maturation by epifluorescence microscopy (Zeiss), oocytes were fixed, permeabilized, and incubated in 10 μg mL^–1 of RNAse for 30 min and in 10 μg mL^–1 of propidium iodide for 10 min. Heat shock protein 70 (HSP70) content was assessed as described in Kawarsky and King (2001 Zygote 9(3), 39–50) to verify the metabolic stress. Data were analyzed by ANOVA and Tukey’s test using the software Statistica for Windows. A level of 5% was considered significant in all assessments. The oocyte recovery rate (COC/ovary) was higher for the slashing group (2.665 ± 0.38) compared with the aspiration group (1.762 ± 0.15). The percentage of oocytes that reached the germinative vesicle (GV) stage (h 0 of maturation) did not differ between groups (100 ± 0 and 86.66 ± 13.36, slashing and aspiration group, respectively). The same was observed for the percentage of oocytes that reached the metaphase II stage (MII, after 44 of maturation; 79.99 ± 9.74 and 96.00 ± 4.00, slashing and aspiration group, respectively). Moreover, no difference at pixel quantification of HSP70 was observed between groups (256.50 ± 42.42 and 238.61 ± 71.18, slashing and aspiration group, respectively). In conclusion, the slashing procedure provided a better oocyte recovery rate compared with the aspiration of ovaries. This technique does not affect nuclear maturation, because no differences were observed regarding the percentage of oocytes that reached the GV and MII stages. In addition, it does not affect HSP70 content, suggesting that the slashing of ovaries does not increase the basal stress of oocytes in an in vitro-maturation system.