OBJECTIVE: To evaluate the viability of vitrified mouse pronuclear embryos after polar body biopsy by cooling directly in liquid nitrogen in comparison with cooling in closed 0.5 mL straw (aseptic system). DESIGN: In vitro culture after vitrification. SETTING: Department of Gynecological Endocrinology and Reproductive Medicine, University of Bonn, Germany. PATIENT(S): Superovulated mice. INTERVENTION(S): Biopsied embryos were vitrified, warmed, and cultured in vitro. MAIN OUTCOME MEASURE(S): Development after warming. RESULT(S): Development rates up to expanded blastocyst stage after in vitro culture were 25% in group with "direct" vitrification and 23% in group with "straw in straw" vitrification. CONCLUSION(S): Cryopreservation of biopsied mouse pronuclear embryos in open-pulled straws, which are placed inside a hermetically closed container, guarantees a complete isolation of embryos from liquid nitrogen and avoids potential contamination by pathogenic microorganisms. The combination of plunging this container into liquid nitrogen and rapid warming makes this process as efficient as conventional vitrification.
OBJECTIVE: To evaluate the viability of vitrified mouse pronuclear embryos after polar body biopsy by cooling directly in liquid nitrogen in comparison with cooling in closed 0.5 mL straw (aseptic system). DESIGN: In vitro culture after vitrification. SETTING: Department of Gynecological Endocrinology and Reproductive Medicine, University of Bonn, Germany. PATIENT(S): Superovulated mice. INTERVENTION(S): Biopsied embryos were vitrified, warmed, and cultured in vitro. MAIN OUTCOME MEASURE(S): Development after warming. RESULT(S): Development rates up to expanded blastocyst stage after in vitro culture were 25% in group with "direct" vitrification and 23% in group with "straw in straw" vitrification. CONCLUSION(S): Cryopreservation of biopsied mouse pronuclear embryos in open-pulled straws, which are placed inside a hermetically closed container, guarantees a complete isolation of embryos from liquid nitrogen and avoids potential contamination by pathogenic microorganisms. The combination of plunging this container into liquid nitrogen and rapid warming makes this process as efficient as conventional vitrification.