Free centrifuge sorting method for high-count sperm preparation improves biological characteristics of human spermatozoa and clinical outcome: A sibling oocytes study

Sperm processing for assisted reproductive technologies (ART) aims to separate immotile and debris from the motile spermatozoa in the semen. The purpose of this study was to assess the effect of free centrifuge sorting (FCS) approach based on a combination of rheotaxis and swim-up on sperm biological characteristics and ICSI clinical outcomes. Each semen sample was splitted into two equal parts for 67 ICSI cycles with donation oocytes. Parts were processed with the Direct Swim Up (DSU) (control) and with the FCS method (experimental). Sperm quality was assessed in terms of motility, fine morphology, mitochondrial membrane potential, lipid peroxidation and sperm DNA fragmentation. Also Following ICSI, the clinical outcomes were compared between the groups. Sperm progressive motility (93.5 ± 4.1% vs. 78.6 ± 8.2%; p < 0.001), the fraction of Class I (good) morphology (30.2 ± 9.4% vs. 23.7 ± 8.5%; p < 0.0001) and the rate of mitochondrial membrane potential (77.4 ± 7.2% vs. 66.9 ± 5.7%; p < 0.0001) were significantly higher in the FCS compared to DSU groups. The level of lipid peroxidation (0.5 ± 0.05% vs. 0.6 ± 0.06%; p < 0.0001) and concentration of DNA fragmentation (DF) (7.4 ± 1.6% vs. 15.4 ± 2.6%; p < 0.0001) were lower in sperm from the FCS group compared to DSU group. There were higher rates of high-quality embryo formation (p < 0.001), implantation and clinical pregnancy rates (p = 0.03) in the FCS group compared to the control group. The processing of seminal samples using FCS collected spermatozoa with better biological quality and resulted in higher reproductive outcomes in ICSI cycles.