Developmental Competence of Domestic Cat Vitrified Oocytes in 3D Enriched Culture Conditions

SIMPLE SUMMARY: Oocyte vitrification is a cryopreservation method that guarantees the long-term conservation of genetic material and fertility potential in humans and wild or domestic animals. However, in the domestic cat the in vitro embryo development of immature vitrified oocytes is not yet satisfactory. In this study, a three-dimensional (3D) culture system was used for the in vitro embryo production of vitrified oocytes to provide conditions more similar to those of the in vivo microenvironment, and for comparison, control vitrified oocytes were cultured in two-dimensional (2D) conditions. Embryos were cultured for seven days and their development was assessed. The results showed that the 3D enriched culture system was able to sustain the in vitro maturation and the subsequent embryo development of vitrified oocytes, but no differences were found with the 2D system and improvements to enhance the development of vitrified oocytes are still needed. ABSTRACT: Cryoinjuries severely affect the competence of vitrified oocytes (VOs) to develop into embryos after warming. The use of culture conditions that provide physical and chemical support and resemble the in vivo microenvironment in which oocytes develop, such as 3D scaffolds and coculture systems, might be useful to improve VOs outcomes. In this study, an enriched culture system of 3D barium alginate microcapsules was employed for the in vitro embryo production of domestic cat VOs. Cryotop vitrified-warmed oocytes were in vitro matured for 24 h in the 3D system with or without fresh cumulus-oocyte complexes (COCs) in coculture, whereas a control group of VOs was cultured in traditional 2D microdrops of medium. After in vitro fertilization, presumptive embryos were cultured in 3D or 2D systems according to the maturation conditions. Vitrified oocytes were able to mature and develop into embryos in 3D microcapsules (17.42 ± 11.83%) as well as in 2D microdrops (14.96 ± 8.80%), but the coculture with companion COCs in 3D resulted in similar proportions of VOs embryo development (18.39 ± 16.67%; p = 1.00), although COCs presence allowed for blastocyst formation (0.95 ± 2.52%). In conclusion, embryos until late developmental stages were obtained from cat VOs, and 3D microcapsules were comparable to 2D microdrops, but improvements in post-warming conditions are still needed.