Functional assessment of donated human embryos for the generation of pluripotent embryonic stem cell lines

Research question: Can discarded embryos at blastocyst stage, donated to research because of genetic abnormalities and poor morphological quality, become a reliable source of human embryonic stem cell (HESC) lines? Design: This study was consecutively conducted with 23 discarded embryos that were donated to research between February 2020 and April 2021. All embryos, except one, were morphologically evaluated and underwent trophectoderm biopsy for preimplantation genetic testing using next-generation sequencing (NGS), and then vitrified. After warming, the embryos were placed in appropriate culture conditions for the generation of HESCs, which was functionally assessed with immunofluorescence and flow cytometry for pluripotency capacity and spontaneous in-vitro differentiation. Cytogenetic assessment of the HESC was conducted with multiplex ligation-dependent probe amplification, and micro array comparative genomic hybridization. Results: From the 23 embryos initially included, 17 survived warming, and 16 of them presented viability. Overall, the embryos presented poor morphological quality after warming. Only the previously untested embryo was capable of generating a new HESC line. Further characterization of this line revealed fully functional, euploid HESCs with preserved pluripotency, becoming a useful resource for research into human development and therapeutic investigation. Conclusions: None of the donated blastocysts with poor morphological quality in association with genetic abnormalities detected by NGS had the capacity for further in-vitro expansion to originate pluripotent HESC lines. This finding seems to provide extra support to genetic counselling on the suitability of this type of embryo for clinical use.