185 OVIDUCTAL CO-CULTURE CELL DID NOT REDUCE THE RATE OF CHROMOSOMAL ABNORMALITIES IN IN VITRO-PRODUCED BOVINE EMBRYOS

Abstract

One of the major causes of embryo failure on in vitro-produced cattle embryos is their increased rate of chromosomal abnormalities. It was demonstrated that they can be increased by the pre- and post-environmental conditions of culture, such as the culture media and supplementation and culture atmosphere among others. Furthermore, it was suggested that the percentage of chromosomal abnormalities detected could be used as an indirect methodology to evaluate the embryo stress during culture. The use of oviduct cells in co-culture was employed as a technique that improves the embryo quality in different culture systems in cattle, probably by modulating the variations in the embryo environment or detoxifying the culture media. For that reason, we aimed to determine if the use of an oviducal co-culture system could reduce the percentage of chromosomal abnormalities in in vitro-produced cattle embryos. Oviducal cells were obtained from abattoir oviducts, and plated and cultured in TCM-199 media following standard procedures. Cumulus-oocyte complexes were also obtained from the abattoir and matured in a standard media (TCM199, with glutamine, pyruvate, FSH, LH, and antibiotics) for 20 h (38.5°C, 5% CO₂). Matured oocytes were fertilized in IVF-TALP with 1 × 10⁶ spermatozoa/mL (previously selected through a 45–90% Percoll™ gradient) for 18 h using the same conditions. Presumptive zygotes (n = 653) were divided into 2 groups and cultured in the mSof medium for 72 h, with (SOV) or without (SOF) the addition of oviducal cells. In total, 108 embryos were successfully karyotyped following our standard laboratory techniques. Chromosomal numerical abnormalities were evaluated by direct observation at 1250× magnification in a bright-field microscope using a simple Giemsa staining. The percentage of diploid embryos (54/58 in SOV and 47/53 in SOF) and abnormal embryos (4/58 in SOV and 6/53 in SOF) were nonsignificant (P > 0.05; Z-score test for 2 population proportions). Our results suggest that the use of oviducal cells as a co-culture supplementation in in vitro-produced cattle embryos do not improve the percentage of chromosomal abnormalities detected.