Chromosomal abnormalities in vitro produced 4-days-old cattle embryos:

SEBASTIÁN DEMYDA PEYRÁS; MIGUEL MORENO MILLÁN

Versailles

Conferencia; 41th International Embryo Transfer Society Conference; 2015

International Embryo Transfer Society

Chromosomal abnormalities were related to embryo developmental failures in cattle, being highly increased in IVFproducedcompared with multipleovulationembryo transferproducedembryos. The origin of this difference remainsunclear, but they were related to the suboptimal environmental culture laboratory conditions. We studied the influence of3 different maturation media in the appearance of chromosomal abnormalities in early in vitroproducedembryos. A totalof 562 oocytes classified as Class A were collected by follicular aspiration in slaughterhouse ovaries and matured by20 h in 3 different culture media supplemented with 10% FCS and antibiotics as follows: TCM199(T, 193 oocytes);DME (D, 178 oocytes); and RPMI1640(R, 191 oocytes). Matured oocytes were fertilized by 16 h with 1 × 10 spz mLin IVFTALPmedia and cultured by 72 h in SOF media. Later, 48 h after fertilization, 562 presumptive embryos wereevaluated showing a normal cleavage rate of 64.7, 55.2, and 54.9% in T, D, and R groups, respectively. After culture,only 181 early embryos (90 hpi) showing normal development were correctly karyotyped following our standardlaboratory techniques. Individual blastomeres were stained with Giemsa and assessed by direct observation at ×1250magnification in a brightfield microscope. The percentage of normal diploid embryos (D) and abnormal haploid (H),polyploid (P), or aneuploid (A) embryos were determined. Only embryos showing almost 2 different blastomerescorrectly karyotyped were included in this study. Cleavage rates were statistically higher (P < 0.05) in the oocytesmatured in T media in comparison with the oocytes matured in D or R media. The percentage of diploid embryos werealmost equals in the 3 groups evaluated (Table 1). There was some variation when each kind of chromosomalabnormality was assessed individually, but no statistical differences were observed. These results are in consonancewith our previous studies in which we demonstrated the maturation time and morphological quality are the 2 mainoocytederivedfactors influencing the ploidy of early embryos. It was also demonstrated that chromosomal complementswere affected, in a much lesser extent, by the maturation media supplementation. However, in the present study, thematuration media did not statistically affected embryo ploidy. However, the higher percentage of cleaved embryos usingTCM199observed agree with fact that this maturation media is one of the most widely used in IVF procedures in cattle.Based on our data, we suggest that oocyte maturation, a well established technique in cattle, could be performed usingdifferent maturation media without expecting major differences in the embryo ploidy, and therefore, the differencesobserved in cleavage rate must be originated in other physiological factors.