Ultrastructure of preimplantation genetic diagnosis-derived human blastocysts grown in a coculture system after vitrification

Abstract

OBJECTIVE: To evaluate ultrastructural features of preimplantation genetic diagnosis (PGD) blastocysts before and after vitrification. DESIGN: Descriptive study of both vitrified and fresh hatching blastocysts. SETTING: PGD program at the Instituto Universitario, Instituto Valenciano de Infertilidad. PATIENT(S): Patients undergoing PGD donated their abnormal embryos for research (n = 26). INTERVENTION(S): Biopsied embryos were cultured in the presence of human endometrial cells until day 6. Sixteen blastocysts were vitrified. A total of 11 high-scored hatching blastocysts, 6 warmed and 5 fresh, were fixed for ultrastructure. MAIN OUTCOME MEASURE(S): The cytoskeleton structure, type of intercellular junctions, and basic intracellular organelles in trophoectoderm cells and the inner cell mass were analyzed. RESULT(S): Ten of 16 blastocysts (62%) survived the warming process. Six of these showed no signs of cell degeneration and light microscopy revealed similar ultrastructural characteristics to those of controls. However, in trophoectoderm cells from both fresh and cryopreserved blastocysts, a reduced number of tight junctions and the presence of degradation bodies were detected. CONCLUSION(S): The particular ultrastructural features observed in PGD-derived blastocysts could be related to embryo manipulation and culture conditions. Vitrification does not seem to alter blastocysts, as those that survive hatching do not display detectable cellular alterations when observed through electron microscopy.