Ultrastructural markers of aging in human oocytes

Introduction: The delay of childbearing contributes to the increasing proportion of subfertile couples necessitating assisted reproduction technology (ART) procedures. Subfertility relates with decay in oocyte quality due to reproductive aging, indeed maternal aging impairs reproductive potential. Prolonged culture, also called “in vitro aging” may also impair oocyte competence. Ultra structural oocyte quality greatly affects ART outcome that also depends on to specific morphological parameters. In this report, we account for the ultrastructural markers of aging, in oocytes from over-35 years old women underwent to ART procedures, enrolled in this study after informed consent. Materials and Methods: We studied MII oocytes from women under 35 and over 35 years old, fixed at pick up or after 24 hr culture. Ultrastructural and morphometric evaluations were performed. Results: Significant increasing of vacuoles, decreasing of mitochondria-smooth endoplasmic reticulum aggregates, increasing of mitochondria-vesicle complexes density, decreasing of cortical granules and microvilli, increasing of zona pellucida density and thickness, characterized oocytes from aged women. These changes were more evident in the oocytes submitted to prolonged culture. Conclusion: These changes may be assumed as ultrastructural markers of oocyte aging. It was also demonstrated that oocytes from younger women are less sensitive to prolonged culture (in vitro aging) than the oocytes from aged women.