P-390 Can sperm DNA be affected by different cooling curves in the cryopreservation process?

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Abstract Study question Is sperm DNA fragmentation affected differently when using cryopreservation techniques with different cooling curves? Summary answer The seminal cryopreservation method that uses only the stage of exposure to Liquid Nitrogen vapor in the freezing process causes less damage to sperm DNA. What is known already Cryopreservation can be performed by different methods. The difference between them is the concentration of cryoprotectants, type of packaging and cooling curve that can be slower or faster, before being exposed to Liquid Nitrogen. These variables in these different methodologies can alter the integrity of sperm DNA. Since high sperm DNA fragmentation rates are directly linked to decreased blastulation rates and increased implantation failure and risk of miscarriage, it is important to establish a freezing protocol that affects this sperm parameter as little as possible, since it is directly related to clinical pregnancy success. Study design, size, duration A case-control study was conducted in which each case was its own control. Twenty-one samples were analyzed after seminal collection (Fresh Group) and were divided into two groups with different protocols and cooling curves before immersion in liquid nitrogen (Steam Group and Refrigerated Group). This study was carried out from February to November 2024. Participants/materials, setting, methods The seminal samples were evaluated fresh and then divided into two groups: Steam Group, which were subjected directly to N2L vapor with a temperature decrease of -20.5 °C/minute and the Refrigerated Group, which were subjected to refrigeration with a temperature decrease of approximately -0.9 °C/min before the steam stage. Subsequently, the samples from both groups were immersed in N2L. Afterwards, the samples were thawed and the seminal evaluations were repeated. Main results and the role of chance The results indicated that comparing the Fresh Group versus the freezing protocols, Steam Group and Refrigerated Group, both caused a significant reduction in vitality (85.1% versus 64.1% and 63.7%, respectively, P < 0.001), in progressive motility (47.9% versus 29.7% and 31.3%, respectively, P < 0.001) and an increase in the DNA fragmentation rate that in the Fresh Group was 27.4%, increasing to 39.6% in the Steam Group and to 35.9% in the Refrigerated Group, P < 0.001. Comparing the post-thawing results of the Steam Group versus the Refrigerated Group, no significant difference was identified in the rate of recovery of vitality (76.7% versus 76.1%, P = 0.790, respectively) and in the rate of recovery of progressive motility (64.9% versus 65.3%, P = 0.925). On the other hand, comparing the data of the sperm DNA fragmentation index, the Steam Group presented a lower sperm DNA fragmentation rate of 39.5% versus 35.9% of the Refrigerated Group, P = 0.001). Limitations, reasons for caution The results of this study need to be replicated in other studies to confirm this finding, which is so important for clinical practice. However, it is very important to control the cooling curves that were used in this research for the correct replication of the study and results. Wider implications of the findings Our findings are of great importance for clinical practice, since the discovery of a seminal cryopreservation method that causes less damage to sperm DNA may result in better embryo implantation rates with fewer miscarriages and more live births. Trial registration number No

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