In vitro handling of oocyte for fertility preservation. Recent ultrastructural acquisitions

Assisted reproduction technology (ART) success depends on the oocyte quality. In vitro handling of female gamete, and ART procedure itself, may alter the morphodynamics of oocyte organelles during maturation and thus may prejudice oocyte competence for fertilization. Electron microscopy significantly supports phase contrast microscopy, clinical, epidemiological and bimolecular data, for validation of ART procedures, such as in vitro fertilization, cryopreservation and in vitro maturation (Nottola et al 2007; Bianchi et al 2014; Coticchio et al 2016). In this study, we analyzed the ultrastructural features of the oocyte subjected to ART procedures, in order to understand whether in vitro handling of human oocytes might impair morphological integrity. The ultimate goal is providing a contribution to the realization of less aggressive protocols that may improve ART viability. We analyzed donated human oocytes, obtained during ART cycles after the informed consent of the patients. Our study demonstrated the presence of significant changes, occurring as the consequence of the application of certain ART protocols such as in vitro maturation and cryopreservation. In particular, ART derived oocytes showed vacuoles, alteration in the distribution of cortical granules, hardening of the zona pellucida and changes of mitochondria-vesicle complexes. These changes deserves of special consideration because may be related to ART failures and impairment of early embryo development, as well.