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The survival of human blastocysts to vitrification with two different carriers is compared. Both vitrification carriers used in this study are in the category of closed carriers, as they completely isolate the samples from direct contact with liquid nitrogen or its vapours during cooling and storage, until warming. This characteristic is appealing because it reduces or eliminates the theoretical risk of cross-contamination during that period of time. The two closed vitrification systems used present very different design and features: in the High Security Vitrification device, the carrier straw containing the embryos is encapsulated inside an external straw before plunging in liquid nitrogen, resulting in thermal insulation during cooling. On the other hand, in the SafeSpeed carrier embryos are loaded in a thin-walled, narrow capillary designed to maximize the thermal transference. Both closed carriers achieved comparable outcomes in terms of survival of blastocysts to the vitrification process, with 97.5% vs. 96.1% survival with HSV and SafeSpeed, respectively. In conclusion, the cooling and warming rates at which these carriers operate, in combination with the cytosolic solute concentration in the cells of the cryopreserved blastocysts attained after a cryoprotectant-loading protocol, result in successful vitrification of human blastocysts for human assisted reproduction.

Ovarian tissue cryopreservation is, in most cases, the only fertility preservation option available for female patients soon to undergo gonadotoxic treatment. To date, cryopreservation of ovarian tissue has been carried out by both traditional slow freezing method and vitrification, but even with the best techniques, there is still a considerable loss of follicle viability. In this report, we investigated a stepped cryopreservation procedure which combines features of slow cooling and vitrification (hereafter called stepped vitrification). Bovine ovarian tissue was used as a tissue model. Stepwise increments of the Me2SO concentration coupled with stepwise drops-in temperature in a device specifically designed for this purpose and X-ray computed tomography were combined to investigate loading times at each step, by monitoring the attenuation of the radiation proportional to Me2SO permeation. Viability analysis was performed in warmed tissues by immunohistochemistry. Although further viability tests should be conducted after transplantation, preliminary results are very promising. Four protocols were explored. Two of them showed a poor permeation of the vitrification solution (P1 and P2). The other two (P3 and P4), with higher permeation, were studied in deeper detail. Out of these two protocols, P4, with a longer permeation time at −40 °C, showed the same histological integrity after warming as fresh controls., This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (FNRS) to C. A. Amorim as a research associate at FRS-FNRS and M.M. Dolmans (grant 5/4/150/5), Fonds Spéciaux de Recherche, Fondation St Luc, Foundation Against Cancer, Coordenação de Aperfeiçoamento de Pessoal de Nível 66 Superior (CAPES –Brazil) (grant #013/14 CAPES/WBI awarded to C.M. Lucci, with F. Paulini receiving a postdoctoral fellowship), and Wallonie-Bruxelles International, and donations from the Ferrero family. Also, it has been partially supported by Siemens Healthcare S.L.U. and Retos-Colaboración RTC-2016-4733-1 (MINECO, Spain).

Although it was qualitatively pointed out by Fahy et al. (1984), the key role of the warming rates in non-equillibrium vitrification has only recently been quantitatively established for murine oocytes by Mazur and Seki (2011). In this work we study the performance of a closed vitrification device designed under the new paradigm, for the vitrification of human oocytes. The vitrification carrier consists of a main straw in which a specifically designed capillary is mounted and where the oocytes are loaded by aspiration. It can be hermetically sealed before immersion in liquid nitrogen for vitrification, and it is warmed in a sterile water bath at 37 °C. Measured warming rates achieved with this design were of 600.000 ºC/min for a standard DMEM solution and 200.000 ºC/min with the vitrification solution for human oocytes. A cohort of 143 donor MII sibling human oocytes was split into two groups: control (fresh) and vitrified with SafeSpeed device. Similar results were found in both groups: survival (97.1%), fertilization after ICSI (74.7% in control vs. 77.3% in vitrified) and good quality embryos at day three (54.3% in control vs. 58.1% in vitrified) were settled as performance indicators. The pregnancy rate was 3/6 (50%) for the control, 2/3 (66%) for vitrified and 4/5 (80%) for mixed transfers., The study received financial support from Fundación Ginemed, Junta de Andalucia (Excellence Project, 2008) and I.N.I.A. (RTA-2012).