Rapid warming increases survival of slow-frozen sibling oocytes: a step towards a single warming procedure irrespective of the freezing protocol?

Abstract

Nowadays, human oocytes/embryos are cryopreserved via slow freezing or vitrification. The aim of this study was to evaluate a rapid warming protocol for slow-frozen human oocytes based on the standard warming procedure for vitrification. This was a prospective study on 216 sibling oocytes randomized for either conventional rapid thawing or rapid warming with vitrification warming solution. The primary endpoint was morphological assessment of survival at 2h. Surviving oocytes were divided into two subgroups: (i) parthenogenetically activated; and (ii) fixed and observed for spindle/chromosome configuration. Secondary endpoints were parthenogenetic development and spindle/metaphase configuration. Survival rate with rapid warming was higher (92/102, 90.2%) than with rapid thawing (85/114, 74.6%; P=0.005), and after 3d of culture the rapidly warmed parthenotes had more blastomeres compared with those rapidly thawed (P=0.042). Meiotic spindle and chromosomal configuration were not significantly influenced by rapid warming or rapid thawing. The finding of this study allows IVF centres to increase the efficiency of oocyte slow freezing, enabling survival rates comparable to vitrification protocols, and potentially to optimize costs by using the same warming protocol for both slow-frozen and vitrified reproductive cells.

Freeze/thaw stress induces organelle remodeling and membrane recycling in cryopreserved human mature oocytes

“…In this regard, while vitrification seems to have a clear role in ART, continued research to establish optimal slow freezing methods for human MII oocytes seems required, which may assist in alleviating concerns over safety issues related to vitrification, such as storage, transport and the use of very high cryoprotectant concentrations [60]. Slow freezing of oocytes can thus be a still valid tool in IVF practice when performed with a suitable protocol [61,62].…”

“…Finally, a similar ultrastructural approach could be applied in the future to the study of the rehydration process in slow-frozen oocytes undergoing rapid warming [62] and in vitrified-warmed oocytes belonging to both conventional and low-cryoprotectant vitrification protocols [83].…”

Modified MicroSecure Vitrification: A Safe, Simple and Highly Effective Cryopreservation Procedure for Human Blastocysts

“…Placing a 60-mm Petri dish off to one side ( i.e., depending on the left-hand or right-hand preference of the technician), add the warmed sucrose (1.0 M) and H-HTF solutions to create a 0.5 M sucrose warming bath (uncovered). Note: VTF tips are only warmed in 0.5 M sucrose solutions as a QC safeguard, to insure the retention of embryo viability in the rare event that an embryo is expelled upon rapid warming22.Hold the upper straw seal above liquid level to confirm the identity, and then grasp and secure the straw below the internal plug using Mayo scissors (the VTF tip should still be submerged in LN 2 ).

Firmly tap the scissors on the Dewar flask (a couple times) to remove the VTF tip from the inner straw sidewall as a QC precaution; if the VTF tip is adherent, the tapping ensures that the tip base drops to the sealed end opposite the labeled end, thus providing an air space near the plug end.

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The Gametotoxic Effects of the Endometrioma Content: Insights From a Parthenogenetic Human Model

“…Given the difficulties in obtaining clear embryological data in the clinical settings and the debatable reliability of animal models, we designed a randomized, controlled, in vitro study with the objective of evaluating the effect of exposure of human cryopreserved oocytes to endometriotic fluid. To this aim, we used a validated experimental model of human parthenogenesis [21][22][23][24][25][26] .…”