A SPERM SELECTION TECHNIQUE TO IMPROVE EMBRYO PLOIDY

Abstract

To assess the role of an enhanced sperm selection method in mitigating paternal contributions to embryo aneuploidy. Over the last 4 years, 57 couples underwent ICSI with sperm selected by density gradient centrifugation (DGC), resulting in few frozen embryo transfers (FETs) due to consistent embryo aneuploidy following preimplantation genetic testing for aneuploidy (PGT-A). These men consented to sperm chromatin fragmentation (SCF) assessment, inclusive of double-stranded DNA breaks (dsDNA) in their raw semen, as well as post-DGC and post-microfluidic sperm selection (MFSS). These couples underwent subsequent ICSI cycles with MFSS. Outcomes of cycles processed by DGC and MFSS were analyzed and compared. SCF was assessed by terminal deoxynucleotidyl dUTP transferase nick-end labeling (TUNEL) on ≥500 spermatozoa per patient, with a normal threshold of ≤15%. A neutral Comet assay was used to assess dsDNA on ≥200 spermatozoa, utilizing a modified in-house protocol and a normal threshold of ≤3%. A total of 57 men had the following semen parameters: concentration of 40.0±32x106/mL, 37.1±11% motility, and 2.2±1% normal morphology. After selection by DGC or MFSS, the concentrations were 3.3±3.4 and 8.0±13x106/mL, with 58.0±29% and 96.9±9% motility, respectively (P<0.0001). The SCF decreased from 21±14% in raw specimens to 18±6% following DGC and to 1.9±1% following MFSS (P<0.001). The dsDNA fell from 3.6±2% in raw specimens to 3.1±1% after DGC and to 0.3±0.2% after MFSS (P<0.001). These men (40.9±6 years) underwent DGC selection for 71 ICSI cycles with their female partners (36.5±5 years), achieving a fertilization rate of 58.4% (403/690) and a blastocyst euploidy rate of 28.5% (47/165). Only 19 FET cycles were performed, with a 6.7% implantation rate (2/30) and two clinical pregnancies resulting in miscarriage. Subsequently, these men had their specimens selected by MFSS in 71 ICSI cycles, resulting in a higher fertilization rate of 75.9% (647/852; P<0.0001) and a much improved (P<0.0001) blastocyst euploidy rate of 48.9% by PGT-A (192/389). In 48 FET cycles, 51 embryos were replaced with an increased implantation rate of 60.8% (31/51; P<0.0001), a CPR of 64.6% (31/48; P<0.001), and an ongoing/delivery rate of 62.5% (30/48; P<0.0001). With its dsDNA component, SCF tangibly contributes to embryo structural chromosomal abnormalities. An enhanced spermatozoa selection method for ICSI appears to remarkably increase the proportion of euploid blastocysts with consequent successful clinical outcomes.