Oral Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

The efficacy and functional consequences of interactions between human spermatozoa and seminal fluid extracellular vesicles (#36)

Cottrell T Tamessar 1 2 , Amanda A Anderson 1 2 , Elizabeth G Bromfield 1 2 3 , Natalie A Trigg 1 2 , Shanu Parameswaran 1 2 , Simone J Stanger 1 2 , Judith Weidenhofer 4 5 , Hui-Ming Zhang 6 , Sarah A Robertson 7 , David J Sharkey 7 , Brett Nixon 1 2 , John E Schjenken 1 2
  1. School of Environmental and Life Sciences, College of Engineering, Science and Environment, The University of Newcastle, Callaghan, New South Wales, Australia
  2. Hunter Medical Research Institute, Infertility and Reproduction Research Program, New Lambton Heights, New South Wales, Australia
  3. School of Biosciences, Faculty of Science, Bio21 Institute, The University of Melbourne, Parkville, Victoria, Australia
  4. School of Biomedical Sciences and Pharmacy, College of Health, Medicine and Wellbeing, University of Newcastle, Ourimbah, New South Wales, Australia
  5. Hunter Medical Research Institute, Precision Medicine Research Program, New Lambton Heights, New South Wales, Australia
  6. Central Analytical Facility, Research and Innovation division, University of Newcastle, Callaghan, NSW, Australia
  7. The Robinson Research Institute and School of Biomedicine, University of Adelaide, Adelaide, South Australia, Australia

Seminal fluid extracellular vesicles (SFEVs) have previously been shown to interact with spermatozoa and influence their fertilisation capacity. Here, we sought to extend these studies by exploring the functional consequences of SFEV interactions with human spermatozoa.  SFEVs were isolated from seminal fluid of normozoospermic donors prior to assessing the kinetics of sperm-SFEV binding in vitro, as well as the effects of these interactions on sperm capacitation, acrosomal exocytosis and motility profile. In these experiments, media at both pH 5 and 7 were used, corresponding to the pH of the environment sperm encounter within the vagina vs the uterus. Biotin-labelled SFEV proteins were transferred primarily to the flagellum of spermatozoa within minutes of co-incubation, although additional foci of SFEV biotinylated proteins were also detected in the mid-piece and head domain. Functional analyses of high-quality spermatozoa collected following liquification revealed that SFEVs did not influence sperm motility during incubation at pH 5, yet SFEVs induced subtle increases in total and progressive motility in sperm incubated with SFEVs at pH 7. Additional investigation of sperm motility kinematic parameters revealed that SFEVs significantly decreased beat cross frequency and increased distance straight line, linearity, straightness, straight line velocity, and wobble. SFEVs did not influence capacitation status, or the ability of sperm to undergo acrosomal exocytosis. Functional assessment of both high- and low-quality spermatozoa collected prior to liquification showed limited SFEV influence, with these vesicles inducing only subtle decreases in beat cross frequency in spermatozoa of both groups. These findings raise the prospect that, aside from subtle effects on sperm motility, the encapsulated SFEV cargo may be destined for physiological targets other than the male germline, notably the female reproductive tract.