Abstract
Simple SummaryThe domestic cat is commonly used as a model for the development of assisted reproductive technologies, including in vitro embryo production (IVEP) in felid species. Seasonal reproduction is a feature of domestic cats as well as of several species of wild feline. Likewise, the number and the quality of blastocysts produced in in vitro systems is linked to season. Maintaining stable in vitro embryo production throughout the year is crucial not only for research purposes but also for programs aimed at protecting endangered felines. We assess whether using Brilliant Cresyl Blue (BCB) selection in addition to the classical morphological selection could improve the IVEP outcomes during non-breeding season. Blastocyst yield and quality of the embryos (hatching rate and blastocyst cell numbers) were higher after IVM/IVF in oocytes defined as BCB+ (colored cytoplasm) based on the BCB test than in oocytes only morphologically selected. Furthermore, no adverse effects on bioenergetic/oxidative status were observed in oocytes subjected to BCB staining. In conclusion, BCB test implementation in IVEP programs might ensure a steady output of domestic cat blastocysts throughout the year.In domestic cats, the maturation, fertilization, and development potential in vitro decreases during the non-breeding season. This study aims at evaluating the efficacy of Brilliant Cresyl Blue (BCB) staining in selecting developmentally competent oocytes to be used in in vitro embryo production (IVEP) programs in order to overcome the season variability in blastocyst yield. Cumulus-oocytes complexes (COCs) collected from antral follicles of domestic cat ovaries during the anestrus phase (July to November) were selected by BCB staining and classified as BCB+ (colored cytoplasm) and BCB− (colorless cytoplasm). COCs not exposed to BCB staining were used as control. Before and after in vitro maturation mitochondrial activity and reactive oxygen species (ROS) were measured. Following in vitro fertilization, blastocyst rate, hatching rate, and blastocyst cell numbers were recorded. The results show that BCB staining did not alter the mitochondrial function and ROS production in cat oocytes. BCB+ oocytes presented a higher (p < 0.05) blastocyst rate, hatching rate, and blastocyst cell number than BCB− and control oocytes. In conclusion, BCB staining does not affect the bioenergetic/oxidative status of the oocyte while being a useful tool for selecting good quality oocytes to increase IVEP in domestic cats during non-breeding season.
Highlights
Over the last decades, appreciable advances have been made in the development of assisted reproductive technology (ART) for feline embryos in vitro production
Eight hundred twenty-seven Cumulus-oocytes complexes (COCs) were selected, of which 241 COCs were used as the control group and 591 COCs were exposed to Brilliant Cresyl Blue (BCB) test
It is generally demonstrated that BCB+ oocytes are more competent than BCB− ones, the lack of significant difference between blastocysts developed from BCB+ and unstained control oocytes observed in some studies [19,25,40], has led to doubts as to the real utility of the BCB test in in vitro embryo production (IVEP) technology [16,39]
Summary
Appreciable advances have been made in the development of assisted reproductive technology (ART) for feline embryos in vitro production. The possibility of using domestic cat gametes as a valuable model has allowed the improvement of in vitro embryo production (IVEP) technology that might be helpful for preserving endangered wild felids [1]. Living offspring have been produced after the transfer of in vitro produced embryos both in domestic [2,3]. Non-domestic cats [4], the efficiency of IVEP is still low compared to the level achieved in farm animals [5]. The free-ranging domestic cat is a seasonally polyestrous long-day species. The breeding season begins in January or February, with the highest incidence of estrus in February and March, and ends between
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