Effect of different cryopreservation protocols on the metaphase II spindle in human oocytes

Purpose To ascertain possible cell damage from cryopreservation, the ultrastructure of human oocytes cryopreserved by slow cooling was assessed. Materials and methods Cryopreservation was performed through two protocols with one-step or two-step propanediol. Fresh control oocytes were examined for comparison. Samples were processed for transmission electron microscopy analysis. Results By light microscopy, both fresh and frozen-thawed oocytes appeared regularly rounded, with intact zona pellucida, and homogeneous cytoplasm. By electron microscopy observation, organelles were abundant and uniformly dispersed. Mitochondria-smooth endoplasmic reticulum associations appeared regular. However, both the amount and density of cortical granules appeared abnormally reduced in frozen-thawed samples. Slight to moderate vacuolization was also found in the ooplasm of oocytes of both frozen groups. Conclusions Slow cooling ensures a good overall preservation of human oocytes. However, cytoplasmic vacuolization and cortical granule loss appears associated with cryopreservation, irrespective of the protocol used.

Section: Introductionmentioning

confidence: 99%

Qualitative and morphometric analysis of the ultrastructure of human oocytes cryopreserved by two alternative slow cooling protocols

Coticchio¹,

Borini²,

Distratis³

et al. 2010

“…In addition, although depolymerization of the oocyte's meiotic spindle is known to occur, a number of studies have now shown that the spindle reforms in the majority of oocytes after thawing [24][25][26][27][28][29]. The advent of ICSI for insemination has overcome any concern regarding potential premature cortical granule reaction [11].…”

Section: Introductionmentioning

confidence: 99%

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

Noyes

Boldt

Nagy

2010

As more reproductive-age women survive cancer at the expense of gonadotoxic therapy, the need for viable fertility preservation options has become paramount. Embryo cryopreservation, often using donor sperm, has been the standard offered these women over the past 20 years. Preservation of unfertilized oocytes now represents an acceptable and often equally viable alternative, particularly for single women, due to technologic advances made in the past decade. Given such, oocyte cryopreservation's experimental designation and need for IRB approval should thus be revisited.

“…We assume that the slight lag described for VODE at day 3 might be due to delayed intra-cytoplasmic ultrastructure reorganization of the egg after warming. If so, selecting only optimal quality of eggs before vitrification can be discussed or more than a 2-h post-warming incubation may be applied before egg microinjection [18]. Although VODE displayed lower percentage of B3 blastocysts at embryo culture day 5, percentage of blastocysts available at embryo culture day 5 is equal in VODE and FODE.…”

Section: Discussionmentioning

confidence: 99%

Morphokinetics analysis of embryos derived from vitrified/warmed oocytes

Montjean

Geoffroy-Siraudin

Boyer

et al. 2015

Purpose Oocyte vitrification is a worldwide used technique that has proved its worth. Although it was shown not to alter oocyte integrity, a recent study concluded that it may affect oocyte embryo development. As the morphology and kinetics of embryos derived from sibling fresh and vitrified oocytes have not been described previously, the present study evaluates cleavage rate, blastomeres size, fragmentation rate, and blastocyst formation in vitrified/warmed oocyte derived embryos (VODE) as compared with sibling fresh oocytes derived embryos (FODE). Methods This investigation included 90 infertility cases displaying large cohort of mature oocytes at pick up, divided into 2 groups after denudation. A part of oocytes underwent ICSI while others were vitrified. Oocyte warming cycles were performed when no pregnancy was achieved using fresh eggs. Zygote to blastocyst development was recorded prospectively in an image database up to day 5. Results VODE did not show major difference as compared with FODE in terms of cleavage rate, number of blastomeres, fragmentation rate, and blastomeres size. Furthermore, percentage of morulae at day 4 and blastocysts at day 5 are not affected by oocyte vitrification. Conclusion Although our results show that embryo development is not altered by oocyte vitrification, offspring follow-up is essential to exclude any adverse developmental effect of the technique.