Abstract
The vitrification of human embryos is more and more frequently being utilized as a method of assisted reproduction. For this technique, gentle treatment of the embryos after thawing is crucial. In this study, the balance of amino acids released to/consumed from the cultivation media surrounding the warmed embryos was observed in the context of a cultivation environment, which was with the atmospheric oxygen concentration ≈20% or with a regulated oxygen level—hysiological (5%). It is the first time that total amino acid turnover in human embryos after their freezing at post compaction stages has been evaluated. During this study, progressive embryos (developed to blastocyst stage) and stagnant embryos (without developmental progression) were analyzed. It was observed that the embryos cultivated in conditions of physiological oxygen levels (5% oxygen) showed a significantly lower consumption of amino acids from the cultivation media. Progressively developing embryos also had significantly lower total amino acid turnovers (consumption and production of amino acids) when cultured in conditions with physiological oxygen levels. Based on these results it seems that a cultivation environment with a reduced oxygen concentration decreases the risk of degenerative changes in the embryos after thawing. Therefore, the cultivation of thawed embryos in an environment with physiological oxygen levels may preclude embryonal stagnation, and can support the further development of human embryos after their thawing.
Highlights
The cryopreservation of human gametes, and mainly embryos, is a very important method in embryological laboratories worldwide
Of the 61 embryos cultured in the environment with an atmospheric oxygen level, 41 (67.2%) showed progressive development after thawing
The results of the present study revealed that the progressively developing embryos cultured in the environment with low oxygen concentration had a statistically (p < 0.05) lower amino acid turnover than the embryos that were cultured in the environment with the atmospheric oxygen concentration (Figure 2A)
Summary
The cryopreservation of human gametes, and mainly embryos, is a very important method in embryological laboratories worldwide. One of the most important factors limiting the success of cryopreservation is post-thaw embryo survival, affected by the formation of ice crystals during the freezing and thawing processes [1]. Such crystals may damage cell membranes and lead to blastomeric lysis [2]. The cryopreservation imposes athe extra stress of the freeze–thaw process, which may affect cell homeostasis, metabolism, cell integrity and developmental potential It has been documented in the literature that the warmed embryos are more sensitive and can be damaged by oxidative stress [3]. An experiment on model animals indicated the positive effect of antioxidants present in the cultivation medium after the thawing of embryos [5]
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