The role of spermatozoa-zona pellucida interaction in selecting fertilization-competent spermatozoa in humans

Sperm selection by zona adhesion improves assisted reproductive treatment outcomes

BACKGROUND

Zona pellucida is one of the main selective barriers for the spermatozoa before reaching the oocyte. Using native zona in the sperm selection prior to Intracytoplasmic Sperm Injection (ICSI) has been proven effective but inconvenient approach in In Vitro Fertilisation (IVF) laboratory. The application of autologous solubilised zonae pellucidae in the sperm selection prior to ICSI has not been studied yet.

OBJECTIVES

To compare the assisted reproductive treatment (ART) outcomes (implantation, pregnancy, live birth, and miscarriage rates) after ICSI performed with spermatozoa selected on their ability to adhere to immobilised solubilised zonae pellucidae and conventionally selected spermatozoa.

MATERIALS AND METHODS

In total, 500 couples fulfilled the inclusion criteria and 368 of them were included in the study. After random allocation, 192 couples had spermatozoa selected by sperm-zona adhesion for ICSI (study group) and 176 patients underwent standard ICSI (control group). In the study group, patients' own zonae were acid solubilised and immobilised on petri dishes. The partner's motile spermatozoa were placed in the dishes and the adhered spermatozoa were used for ICSI. For the control group, the conventional sperm selection by morphological criteria was applied prior ICSI. All women underwent frozen ET with euploid embryos. Chi square test was used to compare the data.

RESULTS

The sperm selection by zona adhesion resulted in significantly higher implantation rate (50.4% vs. 37.0%, p = 0.003), clinical pregnancy rate (43.8% vs. 33.3%, p = 0.018) and live birth rate (38.0% vs. 25.9%, p = 0.004) and significantly lower incidence of miscarriage (11.3% vs. 22.2%, p = 0.044) in comparison to the conventional method of the sperm selection.

DISCUSSION AND CONCLUSION

The application of solubilised zonae pellucidae in the sperm selection for ICSI benefits ART outcomes in couples with unexplained infertility. Moreover, sperm-zona selection significantly reduces the risk of miscarriages.

Differential Sperm Proteomics Reveals the Significance of Fatty Acid Synthase and Clusterin in Idiopathic Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) is a pervasive health issue affecting a large number of couples globally, which leads to increased emotional and financial strain on the affected families. While female factors have been extensively studied and are well known, the contribution of male factors to RPL remains largely unknown. As high as 40% of RPL cases are unexplained, which are termed as idiopathic RPL (iRPL), necessitating the investigation of male factors. The role of spermatozoa in early embryonic development is now well established, and recent research studies have shown that oxidative stress and DNA fragmentation in sperm cells are linked to RPL. The aim of this study was to identify proteomic markers of iRPL in human spermatozoa using tandem mass spectrometry. A label-free method quantified a total of 1820 proteins, and statistical analysis identified 359 differentially expressed proteins, the majority of which were downregulated in iRPL samples (344). Bioinformatics analysis revealed that proteomic alterations were mainly associated with biological processes such as response to stress, protein folding, chromatin organization, DNA conformation change, oxidative phosphorylation, and electron transport chain. In coherence with past studies, we determined fatty acid synthase (FASN) and clusterin (CLU) to be the most potential sperm markers for iRPL and confirmed their expression changes in iRPL by western blotting. Conclusively, we believe that FASN and CLU might serve as potential markers of iRPL and suggest exploratory functional studies to identify their specific role in pregnancy loss.