Microsuction of blastocoelic fluid before vitrification increased survival and pregnancy of mouse expanded blastocysts, but pretreatment with the cytoskeletal stabilizer did not increase blastocyst survival

Abstract

To ascertain effects of thermal change, size of blastocoele, artificial shrinkage, and cytoskeletal stabilizer on survival of blastocysts from vitrification. In vitro and in vivo study. University infertility clinic and academic research laboratory. Female mice of outbred ICR strain, aged 6 to 8 weeks. In experiment 1, various stages of mouse blastocysts were vitrified by using conventional straws or closed pulled straws (CPS). In experiment 2, microsuction was performed of blastocoelic fluid for blastocysts and expanded blastocysts before vitrification. In experiment 3, cytochalasin B (CCB) was used to treat embryos during vitrification. In experiment 4, vitrified expanded blastocysts were transferred to pseudopregnant mice. Survival and pregnancy. The survival rates of early blastocysts were high and not different between the conventional straws and the CPS. The survival rates decreased for blastocysts and expanded blastocysts in both of the two methods. But the use of CPS achieved higher survival rates for blastocysts (83% vs. 70%) and expanded blastocysts (60% vs. 39%) than did the conventional straws. Microsuction before vitrification increased the survival rates for blastocysts (92% vs. 80%) and expanded blastocysts (89% vs. 59%). Survival of vitrified embryos was not distinct between CCB treatment and non-CCB treatment. The percentage of live young from vitrified expanded blastocysts using microsuction was greater than that from vitrified expanded blastocysts without microsuction (34% vs. 9%). The size of the blastocoeles influenced survival of blastocysts from vitrification. A rapid thermal change of CPS and effective reduction of blastocoelic fluid by microsuction may facilitate vitrification and reduce ice crystal damage for blastocysts and expanded blastocysts. The microfilament inhibitor of CCB treatment did not increase their survival rates.