Fertilization and early embryology: Influence of maternal age on meiotic spindle assembly oocytes from naturally cycling women

Abstract

To examine the effects of maternal ageing on the meiotic apparatus, we obtained oocytes from naturally cycling women in two age groups, including younger (aged 20-25 years) and older (aged 40-45 years) women. Using high-resolution confocal microscopy we obtained a detailed picture of the meiotic spindle and chromosome placement during various phases of meiosis. Our data revealed that the meiotic spindle in older women is frequently abnormal, both with regard to chromosome alignment and the microtubule matrix that comprise the meiotic spindle. The spindle in 79% of the oocytes from the older group exhibited abnormal tubulin placement and one or more chromosomes were displaced from the metaphase plate during the second meiotic division. In contrast, only 17% of the oocytes from the younger age group exhibited aneuploid conditions. The majority of eggs from this group possessed a well ordered, meiotic spindle containing chromosomes that were fully aligned within a distinct metaphase plate in the spindle. Chromosome management during meiosis is directed by microtubule assembly within the spindle. These data suggest that the regulatory mechanisms responsible for assembly of the meiotic spindle are significantly altered in older women, leading to the high prevalence of aneuploidy.

Visualization and Examination of the Meiotic Spindle in Human Oocytes with Polscope

“…Battaglia et al, using oocytes of normal volunteers, reported that the proportion of oocytes with abnormal spindles was significantly higher in older than in younger woman and abnormal spindles were associated with abnormal chromosome distribution (21). Our data support their results, since comparing the age of different groups of patients involved in this study we found correlation between age of patients and number of oocytes obtained and percentage of oocytes with detected spindles (spindle positive oocytes).…”

“…Our results support the observations of others that the presence of a birefringent spindle in human oocytes could predict a higher fertilization rate and a greater probability of embryo development (11,12). Thus, spindle visualization (spindle-based selection of oocytes) can help differentiate oocytes, and the presence of spindle can serve as an early indicator of oocyte viability (11,16,21). However, the relative position of the spindle within the oocytes does not appear to influence the developmental potential of embryos (12).…”

Cryo-survival, fertilization and early embryonic development of vitrified oocytes derived from mice of different reproductive age

“…Although several previous studies reported that the quality of oocytes is associated with maternal age [10,[28][29][30][31][32], prior to the present study there has not been any report indicating whether cryo-survival of oocytes is related to maternal age of the oocyte. Ultrastructural abnormalities have been found in correlation with increase in maternal reproductive age of mouse oocytes [24].…”

Retrieval and in vitro maturation of human oocytes from ovaries removed during surgery for endometrial carcinoma: a novel strategy for human oocyte research

“…Oocyte quality begins to decrease after age 30, and drops rapidly after age 35 [6,7]. In older women, the meiotic spindle is frequently abnormal [1], and aging-associated oocyte aneuploidy and meiotic spindle defects have been described in mice [12]. However, to date, there are few studies investigating the association between aging and oocyte function.…”