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Cellular and Molecular Nature of Fragmentation of Human Embryos (2022 International Journal of Molecular Sciences Italy)

fragmentation can affect none, some, or all embryos, demonstrating that this phenomenon is both embryo- and patient-specific
A consistent body of literature linked the rate of fragmentation with a lower embryo developmental potential and implantation rate - This observation could be explained by the theory supporting an association between fragment-like entities and chromosomal abnormalities. Aberrant or exceeded chromosomes may result in the formation of DNA-containing micronuclei that ultimately may lead to the inactivation of the embryonic genome and the subsequent block of embryo development
On the other hand, a reduced embryo developmental potential may be explained also by those theories sup- porting the anucleate cytoplasmic nature of embryo cellular fragments. The loss of a large volume of cytoplasm may be detrimental to embryo potential by depleting blastocyst of essential organelles (e.g., mitochondria), mRNAs, and proteins, resulting in an early block during embryo development.
In addition, the presence of large cytoplasmic cellular fragments may also have an impact in the spatial arrangement of the blastomere in the context of ICM and trophectoderm of the blastocyst. Indeed, they can cause apoptosis or the loss of a significant volume of cytoplasm, limiting the rate of blastomere cleavage because of the distortion of the blastomere division planes, leading to abnormal compaction, cavitation and blastocyst formation.
cosmetic embryo microsurgery in terms of removal of fragments and coarse granulation from the embryo before embryo transfer has been suggested to improve cell division and implantation potential
cellular fragments could be indicative of chromosomal problems, and therefore their removal might not improve the potential of many severely fragmented embryos.