Ultrastructural markers of quality are impaired in human metaphase II aged oocytes: a comparison between reproductive and in vitro aging.
OBJECTIVE
Childbearing delay contributes to the increase of subfertile couples that require assisted reproductive technology (ART). Subfertility relates with reproductive aging (RA). In vitro aging (IvA) (due to extended culture) may also impair oocyte competence. Aims of this study were to evaluate and compare the oocyte ultrastructure after RA and IvA.


METHODS
Cumulus-oocyte complexes (COCs) (n = 68), with metaphase II oocyte and expanded cumulus, from consenting patients (<35 years old and ≥35 years old, n = 36), were selected by phase contrast microscopy and fixed at pick up, or after 24 h culture. COCs (n = 44) were studied by light and qualitative/morphometric transmission electron microscopy. Two-way ANOVA, with age and culture as grouping factors, was applied for statistical analysis (p < 0.05). Metaphase II cumulus-free oocytes (n = 24) were selected for confocal microscopy observations.


RESULTS
Significant decrease of mitochondria-smooth endoplasmic reticulum aggregates, increase of mitochondria-vesicle complexes size and amount, decrease of cortical granules and microvilli, and alterations of the spindle structure characterized both RA and IvA oocytes. These changes were significantly more evident in the RA oocytes submitted to IvA. RA oocytes also showed changes of the zona pellucida and occurrence of vacuoles after culture. Cumuli appeared re-compacted after culture, irrespective of the age of the patients.


CONCLUSIONS
These data demonstrated that aging is related to decay of oocyte ultrastructural quality, and that oocytes from elder women are more sensitive to prolonged culture (IvA) than the oocytes from younger women. These morphological results should be considered when applying ART in aged patients, rescue ICSI, or artificial oocyte activation.
Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
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Bianchi
Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
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Macchiarelli
Department of Gynaecology-Obstetrics & Urology, "Sapienza" University, Rome, Italy.
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Micara
Department of Gynaecology-Obstetrics & Urology, "Sapienza" University, Rome, Italy.
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Linari
Department of Gynaecology-Obstetrics & Urology, "Sapienza" University, Rome, Italy.
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Boninsegna
Department of Gynaecology-Obstetrics & Urology, "Sapienza" University, Rome, Italy.
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Aragona
Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
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Rossi
Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
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Cecconi
Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, "Sapienza" University, Rome, Italy. stefania.nottola@uniroma1.it.
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Nottola
D000328:Adult; D000375:Aging / Q000502:physiology; D015415:Biomarkers / Q000032:analysis*; D054885:Cumulus Cells / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D008540:Meiosis / Q000502:physiology; D008677:Metaphase / Q000502:physiology*; D018613:Microscopy, Confocal / Q000379:methods*; D008854:Microscopy, Electron / Q000379:methods; D009865:Oocytes / Q000166:cytology / Q000648:ultrastructure*; D012098:Reproduction / Q000502:physiology; D027724:Reproductive Techniques, Assisted; D008941:Spindle Apparatus / Q000648:ultrastructure*; D015044:Zona Pellucida / Q000648:ultrastructure*
D015415:Biomarkers
Aging; Assisted reproduction; Human; Oocyte; Quality; Ultrastructure