8 Effects of magnetic-activated cell sorting on human sperm motility and DNA fragmentation index

Abstract

Selection of spermatozoa before their use for assisted reproductive techniques is an important step in therapy of human infertility. The DNA fragmentation index of sperm plays a major role in pregnancy rates following IVF and intracytoplasmic sperm injection (ICSI). Sperm analyses and standard sperm selection methods in many cases do not eliminate a sufficient proportion of sperm with apoptosis and DNA fragmentation. Magnetic-activated cell sorting (MACS) is a selection method that eliminates apoptotic spermatozoa based on the presence of externalized phosphatidylserine residues. The aim of our study was to evaluate the effect of MACS on human sperm motility and DNA fragmentation index (DFI) in a patient population. The participants were 63 male patients of an IVF clinic, 34 to 45 years old, with 3 years of primary infertility due to male factor. Semen analysis was performed according to the World Health Organization guidelines (2010) and revealed oligoasthenoteratozoospermia in 63 patients. The DFI of fresh semen samples was evaluated using the sperm chromatin structure assay (SCSA) test and revealed DFI 32.4 ± 5.9%. The SCSA test was done on a flow cytometer CyFlow Space (Sysmex-Partec; Evenson 2016 Anim. Reprod. Sci. 169, 56-75; https://doi.org/10.1016/j.anireprosci.2016.01.017). Sperm motility was studied on Hamilton Thorne IVOS. For MACS, we used the MACS® ART Annexin V system (Miltenyi Biotec). The semen sample was diluted to a concentration 10 × 10⁶ spermatozoa mL⁻¹. After double-density gradient centrifugation, the pellet was resuspended in 100 µL of MACS Art Annexin V reagent and added MACS Art Binding Buffer (BB) to 500 µL. The sample was gently mixed and incubated for 15 min at room temperature. After rinsing the column with BB, the sperm-bead suspension was added on top with BB and, immediately after that, the annexin V-negative and annexin V-positive fractions were obtained (MiniMACS; Miltenyi Biotec). Data were evaluated by ANOVA Student’s t-test. Fresh semen samples collected from the patients had an average sperm concentration of 29.7 ± 5.7 × 10⁶ mL⁻¹, motility of 32.7 ± 5.9%, and DFI of 32.4 ± 5.9%. Motility of spermatozoa after MACS for the annexin-negative fraction was 47.2 ± 6.3% and for the annexin-positive fraction was 3.5 ± 2.3% (P < 0.003). Similarly, the annexin-negative spermatozoa had a lower DFI (10.5 ± 3.8%) rate than did the annexin-positive fraction (67.8 ± 5.9%; P < 0.003). The MACS technique allowed a significant reduction of DNA fragmentation levels (from 32.4% for the original sample to 10.5% for the annexin-negative; P < 0.01). The separation of a distinct population of nonapoptotic spermatozoa with intact membranes may optimize outcomes from IVF and ICSI procedures. Magnetic-activated cell sorting of human sperm using annexin-V microbeads results in selection of a population with enhanced motility and reduced DFI rates.