Artificial activation of clinically failed human oocytes enables euploid blastocyst formation

Clinically failed human oocytes can be repurposed via in vitro maturation and artificial oocyte activation to generate euploid blastocysts, establishing an ethically unrestricted embryo resource, despite persistent challenges in deriving stem cell lines under feeder-free conditions.

Can clinically failed oocytes, usually discarded during ICSI, be utilized to generate blastocysts suitable for the derivation of human embryonic stem cells (hESCs) and parthenogenetic embryonic stem cells (phESCs) through in vitro maturation (IVM) and artificial oocyte activation (AOA)?

This prospective study included 716 immature or failed-to-fertilize (FF) oocytes donated by 185 patients undergoing 199 ICSI cycles. A total of 475 oocytes underwent IVM followed by AOA using calcium ionophore and 6-DMAP. Embryonic/parthenogenetic development was monitored through day 7. Blastocysts were graded morphologically, vitrified and assessed for chromosomal content via PGT-A. Inner cell masses (ICMs) were isolated and cultured under feeder-free, GMP-compliant conditions for hESC/phESC derivation.

AOA led to a 65.9% activation rate and 4.8% blastocyst formation rate, with higher efficiency in FF oocytes (activation: 77.9%, blastocyst: 7.2%) compared to IVM oocytes (GV, activation: 63.9%, blastocyst: 1.2%; MI, activation: 58.5%, blastocyst: 4.2%). Nearly half of the 15 blastocysts (47%) formed were euploid (four from FF and three from IVM oocytes), confirming the viability of using clinically discarded oocytes. Despite obtaining euploid blastocysts, no stem cell lines were derived successfully. Nevertheless, the process established a cryopreserved embryo bank using ethically sourced and legally unrestricted biological material.

AOA of clinically failed oocytes enables the formation of euploid blastocysts that may be suitable for hESC and phESC derivation. While derivation efficiency under feeder-free conditions remains a challenge, this strategy potentially offers an ethically sound and logistically feasible approach for expanding stem cell resources, particularly valuable in regions with legal constraints on embryo research.