Postthaw survival of in vitro-produced bovine blastocysts loaded onto the inner surface of a plastic vitrification straw

Effect of Different Vitrification Techniques on Viability and Apoptotic Index of Domestic Cat Testicular Tissue Cells

Vitrification is essential for successful tissue cryopreservation and biobanking in wild cats. This study aimed to compare different methods of vitrification (Ovarian Tissue Cryosystem-OTC, Straws-STW, and Solid Surface vitrification-SSV) for testicular fragment vitrification in tom cats. Testicular fragments were recovered from five adult tom cats and subjected to equilibrium vitrification using different cryovials and methods under the same conditions of vitrification solutions and cryoprotectants. The efficiencies of the methods were evaluated using histological analysis of spermatogonia and Sertoli cell nuclei, seminiferous tubular basement membrane detachment, and the gonadal epithelium shrinkage score scale. Cell viability was assessed using Hoechst PI and Terminal deoxynucleotidyl transferase nick end labeling (TUNEL) assay. The results showed that OTC is an effective vitrification method for maintaining the distinction between spermatogonia and Sertoli cells. OTC was similar to the control for basal membrane detachment parameters (p = 0.05). Epithelial shrinkage was low in the SSV group, which showed the highest percentage of viable cells among the vitrified groups (p = 0.0023). The OTC and SSV vitrification methods were statistically similar in terms of the percentage of TUNEL-positive cells (p = 0.05). Therefore, OTC and SSV provide favorable conditions for maintaining viable cat testicular tissue cells after vitrification.

Generation of large pig and bovine blastocysts by culturing in human induced pluripotent stem cell medium

We investigated the effect of human induced pluripotent stem cell (hiPS) medium on porcine somatic cell nuclear transfer and bovine in vitro fertilized early blastocysts, in comparison with North Carolina State University (NCSU)-37 medium and in vitro culture (IVC)-II medium. After 2 days of culture, the diameter of the portion of the blastocyst that was extruded from the zona pellucid dramatically differed between porcine blastocysts cultured in hiPS medium and those cultured in NCSU-37 medium (221.47 ± 38.94 μm versus 481.87 ± 40.61 μm, P < 0.01). Moreover, the diameter of the portion of the blastocyst significantly differed between bovine blastocysts cultured in hiPS medium and those cultured in IVC-II medium (150.30 ± 29.49 μm versus 195.58 ± 41.59 μm, P < 0.01). Furthermore, the total number of cells per porcine and bovine blastocyst was more than two-fold higher in blastocysts cultured in hiPS medium than in those cultured in NCSU-37 medium (44.33 ± 5.28 and 143.33 ± 16.05, P < 0.01) or IVC-II medium (172.12 ± 45.08 and 604.83 ± 242.64, P < 0.01), respectively. These results indicate that hiPS medium markedly improves the quality of porcine and bovine blastocysts.

Survival of vitrified in vitro-produced bovine embryos after a one-step warming in-straw cryoprotectant dilution procedure

Vitrification is an alternative to slow-rate freezing for cryopreserving bovine embryos. However, this technology requires simplification if it is to be used under field conditions. The main objective of this work was to develop a new system for the direct transfer of vitrified embryos to be used under farm conditions. For this, three objectives were set: (1) to compare the effect of vitrification, using the cryologic vitrification method (CVM), and slow-rate freezing on bovine embryo development and quality; (2) to develop a one-step warming procedure for bovine in vitro-produced (IVP) vitrified (by CVM) embryos; and (3) to assess the effects on embryo survival of a new method for the direct transfer of vitrified IVP bovine blastocysts. In vitro-produced blastocysts were initially either vitrified by CVM or subjected to slow freezing to compare embryo survival and quality (experiment 1). No differences were detected between these cryopreservation techniques in terms of the survival and quality variables at 24 hours or in terms of the proteins expressed. However, at 48 hours the vitrified embryos showed higher hatching rates, greater total cell numbers, and lower apoptotic indices (P < 0.05). In experiment 2, CVM-vitrified IVP blastocysts were warmed by the conventional two-step or one-step warming procedure by incubating them at 41 °C in 0.25 M sucrose for 10 minutes, 0.15 M sucrose for 10 minutes, or 0.25 M sucrose for 5 minutes. In addition, embryo transfer (ET) was performed using vitrified embryos warmed by the one-step procedure in 0.25 M sucrose solution for 5 minutes. As a control group, IVP fresh embryos were transferred to recipient females. No differences were observed in embryo survival or total cell number between any of the warming procedures. Moreover, no significant differences for pregnancy at 60 days were found between the ET groups. In experiment 3, expanded IVP blastocysts were then either vitrified using a conventional or a modified fiber plug designed to allow direct ET after in-straw cryoprotectant (CP) dilution. They were warmed using the one-step process (0.25 M sucrose, 5 minutes) in a 0.25 mL French straw. Embryo recovery associated with the modified fibreplug system was less reliable than with the conventional system. However, no differences were seen between the systems in terms of in vitro embryo survival among those finally recovered. Finally, IVP blastocysts were vitrified using conventional fibreplugs to maintain a high embryo recovery rate, and then warmed using the one-step warming in-straw CP dilution procedure, but using an adapter with a wider opening coupled to the French straw and a heated metal chamber to protect and keep the straw at 41 °C (experiment 4). No differences were seen in embryo survival rates between the two groups. The CVM combined with this new one-step warming in-straw CP dilution procedure could be used for direct ET under field conditions.