The effect of sucrose in the thawing solution on the morphology and mobility of frozen equine embryos.

The research article discusses an experiment challenging the effects of sucrose and glycerol on the morphology and mobility of frozen equine embryos after they have been thawed. The results revealed that thawing with sucrose significantly reduced the ratio of dead cells, though the study didn’t find a significant difference in pregnancy rates from embryos thawed with or without sucrose.

Experiment Design and Procedures

• Seventy-five embryos were used, collected 6 days post-ovulation; 60 of these were frozen in straws with glycerol as the cryoprotectant via an automatic freezer.
• The experiments were oriented in two formats: Experiment 1 and Experiment 2.
• In Experiment 1, the freezing and thawing media were supplemented with 1.3 g/l Polyvinylpyrrolidone (PVP), and in Experiment 2, this was replaced with 5% Fetal Calf Serum (FCS).
• The thawing process took 30 seconds at +37 degrees Celsius in a water bath.
• The removal of glycerol from the embryos in Experiment 1 was conducted in 6 steps. For another group of embryos, both glycerol and sucrose were removed in 6 steps.
• Post removal, those embryos were stained with a chemical (4′,6′-diamidino-2-phenylindole (DAPI)) to determine the proportion of dead cells.
• Fluorescence rate was computed as a ratio of the fluorescent area to the total area to indicate the percentage of dead cells.

Results and Analysis

• The mean Fluorescent Rate (FR) from Experiment 1 was significantly lower in embryos thawed with sucrose than those without.
• In Experiment 2, similar procedures were followed. The mean FR was also noticeably lower in embryos that were thawed with sucrose in comparison to those without.
• The embryos were then transferred nonsurgically to recipient mares.
• Separately, 14 fresh embryos were also transferred as control, seven of which were pre-stained with DAPI before transfer.
• No difference in pregnancy rates was observed between DAPI-stained and non-stained embryos, indicating that the staining process did not affect embryonic survival.
• The study suffered from an insufficient number of embryos to conclusively determine any difference in pregnancy rates between embryos thawed with or without sucrose.

Conclusions

• The results imply that sucrose in the thawing solution might protect the embryo cells from damage unto death, seeing as the FR was significantly lower when sucrose was incorporated.
• However, the experiment couldn’t substantiate any notable effect of sucrose on pregnancy rates due to limitations in sample size.