138 Ovarian factors associated with bovine in vitro embryo development and quality in an individual culture system
N. Azari-Dolatabad A , C. Benedetti A , A. Fernandez Montoro A , D. Angel Velez A B , G. Residwaiti A , H. Sadeghi A C , A. Van Soom A and O. Bogado Pascottini A DA Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
B Research Group in Animal Sciences - INCA-CES, School of Veterinary Medicine and Animal Production, Universidad CES, Medellin, Colombia
C Department of Theriogenology, University of Tehran, Tehran, Iran
D Department of Veterinary Sciences, Gamete Research Center, Veterinary Physiology and Biochemistry, University of Antwerp, Wilrijk, Belgium
Reproduction, Fertility and Development 34(2) 307-307 https://doi.org/10.1071/RDv34n2Ab138
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Individual embryo culture is used to study blastocyst metabolism, time-lapse imaging, and quality markers upon a given treatment. However, intrinsic ovarian factors may also influence embryo development and quality. We aimed to determine the effect of intrinsic ovarian factors such as the presence of corpus luteum (CL), CL stage, follicle (FL) size, and FL counts on in vitro embryo development and quality in a serum-free individual culture system. Slaughterhouse-derived genital tracts from Belgian Blue cows were collected, and only nonpregnant uteri without signs of gross pathology were selected (n = 50). Ovarian pair selection criteria included a ≥1.5 cm CL and the absence of a ≥2.5 cm FL in either ovary. The CL was classified in the early or late luteal phase when it was red/red-yellow or yellow/pale-yellow, respectively. The presence of a dominant FL was recorded when it was ≥12 mm in diameter. In 12 replicates, cumulus-oocyte complexes (COCs; n = 1579) were aspirated from follicles between 4 and 8 mm in diameter, and only oocytes with uniformly granulated cytoplasm and surrounded by more than three compact layers of cumulus cells were selected for in vitro maturation-fertilisation-culture in individual 20-µL droplets under paraffin oil. After collection of COCs, a 1-cm2 area of ovarian cortex was cut with a scalpel blade, placed in 4% formaldehyde, and processed for histopathological examination (hematoxylin and eosin-stained). The number of preantral FL counts (primordial and primary) was assessed in three high-power fields (magnification 200×) and divided into high or low FL counts (above or below the median, respectively). The effect of intrinsic ovarian factors on cleavage and Day 8 blastocyst rates were fitted in mixed-effects models, and blastocyst quality parameters (assessed via differential apoptotic staining) were evaluated in mixed linear regression models using the cow nested with the ovary side as random. The cleavage and blastocyst rates in ovaries bearing a CL (53.7 ± 2.5 and 12.2 ± 1.1%, respectively) were lower (P < 0.003) compared with that in ovaries without a CL (61.4 ± 2.6 and 23.1 ± 1.5%, respectively). Ovaries with low preantral FL counts (≤9) had a greater (P = 0.01) cleavage rate (60.8 ± 3.2%) than those with high counts (54.0 ± 3.4%). Remarkably, blastocysts derived from ovaries without CL presented greater numbers of cells (inner mass and trophectoderm cells) with a lower proportion of apoptosis than blastocysts derived from ovaries with a CL (P < 0.04). Interestingly, blastocysts derived from ovaries without a dominant FL had lower numbers of apoptotic cells than ovaries with a dominant FL. No differences (P > 0.1) were found for all other ovarian parameters in terms of development and quality. Oocytes derived from ovaries bearing a CL had lower developmental capacity, and resultant blastocysts were of lesser quality than those derived from ovaries without CL. Ovarian intrinsic factors should be considered when evaluating molecular aspects associated with embryo development and quality in individual culture systems.
