Effects of cryoprotectant and plunging temperature in liquid nitrogen on the in vitro and in vivo development of murine morulae

The effects of plunging temperature in liquid nitrogen and cryoprotectant dilution methods were evaluated for compacted mouse morulae frozen in 1.5 M ethylene-glycol (E), 1.5M propylene-glycol (P) or 1.4M glycerol (G). Morulae were equilibrated for 10 minutes in cryoprotectant solution and loaded into 0.25 ml straws with cryoprotectant solution in 3 columns (groups E1, P1, G1) or cryoprotectant in the center and PBS in the lateral columns (E2, P2). Straws were cooled at 0.5§C/min to -25 or -30§C and plunged into liquid nitrogen. Straws were thawed in water at 22§C for 20 seconds. Cryoprotectant was diluted in 3 steps for group G1 and in one step for groups E1 and P1 (direct transfer to PBS + 10 por cento FCS) and E2 and P2 (shaken to mix the 3 columns before transferring to PBS+ 10 por cento FCS). Plunging temperature had no significant effect on the proportion of morulae developed to blastocysts in vitro; this proportion was higher (p < 0.0001) in E1 (69.2 por cento) than in E2 (60.3 por cento), G1 (51.9 por cento) and combined for P1 and P2 (46.9 por cento). In second experiment, the proportion of transferred morulae that developed to viable fetuses was lower (p < 0.07) for E1-25 than for E1-30, G1-30, E2-25 or unfrozen (control) embryos (8.7, 20.0, 20.0, 17.4 and 19.8 por cento, respectively). In conclusion, the ethylene glycol diluted directly in PBS (E1) exhibit the highest rate of in vitro embryos development, but based on in vivo embryos development was more efficacious in plunging temperature at -30§C (E1-30)

Cryopresevation of mouse morulae in glycerol, sucrose and honeybee royal jelly

Compacted mouse morulae were frozen at 0.3§C/min. or 0.5§C/min. from -6§C to -24§C or -32§C in 10 por cento of glycerol plus different sucrose concentrations with or without 0.1 por cento of honeybee royal jelly. Embryos were thawed in water bath at 22§C for 20 seconds and cryoprotectant dilution was done in three steps. Embryos were cultured in Whitten's medium for 24, 48 and 72 hours at 37§C, 5 por cento of CO2 and 100por cento of humidity. The in vitro development ranged from 56.6 por cento to 100 por cento after 72 hours. Expanded blastocysts were transferred to pseudopregnant recipients on the third day of the estrous cycle. Viable fetuses rates for embryos frozen to -24 or -32§C at 0.3§C/minute in 10 por cento glycerol + 10 por cento sucrose, 10 por cento glycerol + 10 por cento sucrose + 0.1 por cento honeybee royal jelly, 10 por cento glycerol + 0.1 por cento honeybee royal jelly or 10 por cento glycerol were respectively: 28.1 por cento and 13.6 por cento, 48.7 por cento and 31.9 por cento, 28.6 por cento and 13.2 por cento, 20.0 por cento and 42.4 por cento. Viable fetuses for embryos frozen to -24§C or -32§C at 0.5§C/minute in 10 por cento glycerol + 10 por cento sucrose or 10 por cento glycerol + 10 por cento sucrose + 0.1 por cento honeybee royal jelly were respectively 29.0 por cento and 15.3 por cento, 48.8 por cento and 32.0 por cento. We can conclude that addition of 10 por cento sucrose to 10 por cento glycerol was efficient for embryo freezing at 0.3 or 0.5§C/minute and plunged in liquid nitrogen at -24§C. The honeybee royal jelly addition provided higher viable fetuses rates when embryos were cooled at 0.3 or 0.5§C/minute and plunged in liquid nitrogen at -24§C