Clinical evaluation of the efficiency of oocyte donation program using egg cryo-banking

Abstract

matured MII or IVM-MII oocytes were collected and processed rapidly. RNA was extracted and amplified using a 2-round in vitro transcription procedure, then labeled and hybridized to Applied Biosystems Human Genome Survey Microarrays. This array interrogates 29,098 genes. Up-or down-regulated genes were classified according to the molecular function, biological process, or pathway in which they participate. Statistical analysis was employed to compare each class of genes between samples.RESULTS: The in vitro transcription protocol generated an average of 12 mg of RNA per sample. GV, in vivo matured-MII and IVM-MII oocytes expressed 14,188, 16,402 and 18,299 genes, respectively. There was extensive overlap in the genes expressed by each group, but also some significant differences. Samples showing the least similarity in expression profile were GV and in vivo MII oocytes. IVM-MIIs also displayed significant differences in expression when compared to in vivo MII oocytes, indicating that the process of in vitro maturation does not perfectly mimic that achieved in vivo. A disproportionate number of genes for storage proteins displayed down-regulation in IVM-MII oocytes (relative to in vivo MII). A reduction in expression was also seen for genes involved in processes of homeostasis. Significant up-regulation of gene expression for the ubiquitin proteasome pathway was observed in both IVM-MII and GV samples.CONCLUSIONS: This study provided a detailed insight into gene expression of human oocytes, assessing virtually every gene in the genome. GV oocytes were highly active for processes related to transcription, RNA processing and early stages of protein synthesis, whereas MII oocytes were active for pathways involved in processing of mature proteins. The results suggest that although IVM-MII oocytes closely resemble in vivo-MII oocytes for pathways related to nuclear maturity, a number of those associated with cytoplasmic functions continue to be expressed in a GV-like manner. Additionally, IVM-MII oocytes have significant differences in the expression of genes related to cellular storage and homeostasis. The pathways abnormally expressed during IVM highlight specific deficiencies in culture media and point the way to further optimization of IVM protocols.

Oocyte cryopreservation: is it time to remove its experimental label?

“…Nagy et al [35] performed a study in which oocytes from ten donors were cryopreserved by vitrification and subsequently thawed for transfer to a total of 20 recipients. They achieved an 87.5% survival, 87% fertilization and 68% blastocyst formation rate.…”

“…Results from series of frozen oocytes (reviewed in ref [32]) compare favorably to these data, especially when one takes into account that in many oocyte thaw studies (those performed by the Italian groups) the number of oocytes that could be thawed and inseminated was limited to three, due to federal statute. If one looks at studies using frozen donor oocytes, the data are even more favorable, with ongoing pregnancy and delivery rates exceeding 50% in some reports [29,[33][34][35]. Thus, although the source of oocytes in the latter studies is from women age <39 years, existing age-appropriate data suggests that there may be no benefit in offering embryo cryopreservation vs. OC, at least from a subsequent thaw success perspective.…”

“…Viewing success in this way is unique to OC. Currently available data suggests that the efficiency of fresh IVF, when calculated as live born infant per oocyte is about 5-6% overall [40,41], whereas some studies with frozen oocytes report similar per oocyte efficiencies [15,35]. Efficiency defined in this manner is dependent on a number of variables such as patient age, quality of stimulation, whether there are restrictions on the number of oocytes that can be used, efficiency of embryo transfer, and the like.…”

Fifteen year follow-up of embryos cryopreserved in cancer patients for fertility preservation

“…However, advances in oocyte vitrification techniques have resulted in higher oocyte survival rates from the cryopreservation process. Recent studies have demonstrated equivalent clinical pregnancy rates in IVF cycles using cryopreserved oocytes and embryos [8,23]. The success of oocyte cryopreservation provides a new dimension to the fertility preservation options available for female oncology patients.…”

Oncofertility in Canada: cryopreservation and alternative options for future parenthood

“…Those results have been replicated in multiple other retrospective studies [23][24][25] . Other authors have also commented on the lack of differences noted in embryo quality between fresh and frozen oocytes from the same donor 26,27 . Finally, as with embryo cryopreservation, the younger age of this patient population at oocyte retrieval would favour even better success rates.…”