Protein sources used as supplements of IVF culture media are known to have several implications for the function and stability of embryo culture environment. In fact, they i) transport biologically active molecules ii) chelate heavy metals, iii) regulate media pH, iii) scavenge reactive oxygen species (ROS) and iv) attenuate osmotic stress to which cells are exposed in sub-optimal culture conditions. Instead, their specific relevance to the formulation of cryopreservation solutions used for gamete and embryo cryopreservation remains uncertain. In the present work, we tested the hypothesis that different protein supplements present in cryopreservation solutions, serum or plasma protein solution (PPS), or different concentrations of the same supplement (serum), are associated with different types and/or magnitude of cryopreservation-derived cell damage. To this end, using cryopreservation solutions containing serum or PPS, donated supernumerary human mature oocytes were frozen-thawed by slow freezing and compared with fresh controls. Ultrastructural markers of oocyte quality were adopted as objective measure to assess possible damage from cryopreservation. The study results indicate that the adoption of serum minimises cell damage induced by cryopreservation. Indeed, typical hallmarks of cryodamage in human oocytes, i.e. loss of cortical granules, zona pellucida hardening and above all vacuolization, were largely reduced in oocytes cryopreserved with solutions containing serum, especially if used a higher concentration. This suggest that oocyte cryopreservation still has significant margins of improvement that may derive also from composition of cryopreservation media.

中文翻译：

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冷冻保存溶液中蛋白质补充剂的类型对冻融人卵母细胞超微结构损伤程度的影响

已知用作 IVF 培养基补充剂的蛋白质来源对胚胎培养环境的功能和稳定性有多种影响。事实上，它们 i) 运输生物活性分子 ii) 螯合重金属，iii) 调节培养基 pH，iii) 清除活性氧 (ROS) 和 iv) 减弱细胞在次优培养条件下暴露的渗透压力。相反，它们与用于配子和胚胎冷冻保存的冷冻保存解决方案的具体相关性仍然不确定。在目前的工作中，我们检验了以下假设：冷冻保存液、血清或血浆蛋白溶液 (PPS) 或不同浓度的相同补充剂（血清）中存在不同的蛋白质补充剂，与不同类型和/或程度的冻存衍生细胞损伤有关。为此，使用含有血清或 PPS 的冷冻保存液，捐赠的多余人类成熟卵母细胞通过缓慢冷冻进行冻融，并与新鲜对照进行比较。卵母细胞质量的超微结构标志物被用作评估冷冻保存可能造成的损害的客观指标。研究结果表明，采用血清可以最大限度地减少冷冻保存引起的细胞损伤。事实上，人类卵母细胞冷冻损伤的典型特征，即皮质颗粒丢失、透明带硬化和最重要的空泡形成，在用含有血清的溶液冷冻保存的卵母细胞中大大减少，特别是如果使用更高浓度的溶液。