Is the spermatozoon swimming force essential for fertilization?
Digital FluidFM Conference 2021
Is the spermatozoon swimming force essential for fertilization?Proposed by Alice Battistella
In mammalian fertilization process, one, and only one, spermatozoon must cross the glycoprotein thick protective shell, the zona pellucida (ZP) and enter the oocyte to initiate the meiotic division. We recently demonstrated that the mechanics of this layer plays an important role in the process and show that during ageing the ZP nearly double its stiffness thus reducing the probability of fertilization (Battistella 2021). This suggests that, beside the enzymatic mechanism, also the mechanical interaction may play a role, and in particular the pressure that healthy spermatozoon can produce against the ZP when trying to penetrate the egg (Baibakov 2007) . Indeed, it is well known that spermatozoa with impaired motility are not able to fertilize, even in vitro, where swimming is not essential for reaching the egg (Nascimento 2006) (Nosrati 2017).
We measured the forces developed by spermatozoa while swimming. We used optical tweezer to trap a single spermatozoon and we were able to bring it in contact with the ZP to evaluate force interaction. However, the trapping force resulted too low to measure the detachment energy (Fig. 1A).
Using FluidFM, and in particular Micropipettes with 2-4 μm holes, we successfully captured spermatozoa, and we measured the swimming thrust, which resulted in the range of 3-15nN (Fig. 1B). This number will be in future used to simulate the swimming thrust in fertilization experiments. Moreover, we observed a modulation in the swimming force that relates with the tail motion, with frequencies in the range of 1-15Hz. These values are in accordance with the literature values obtained by digital image analysis (Ishijima 2002) (Ooi 2014).
In conclusion FluidFM revealed to be a precious instrument to investigate the mechanics of fertilization and to capture and manipulate high mobility cellular systems.
Figure 1: (A) sperm cell trapped by optical tweezer is brought to the surface of the ZP, (B) sperm cell is trapped by FluidFM Micropipette (2ηm hole size).
Battistella, A., Andolfi, L., Zanetti, M., Dal Zilio, S., Stebel, M., Lazzarino, M. «Atomic force spectroscopy-based essay to evaluate oocyte post-ovulatory ageing.» 2021 (Submitted).
Baibakov, B., Gauthier, L., Talbot, P., Rankin, T. L., Dean, J. «Sperm binding to the zona pellucida is not sufficient to induce acrosome exocytosis.» Development, 2007: 933-943.
Ishijima, S., Baba, S. A., Mohri, H., Surarez, S. S. «Quantitative Analysis of Flagellar Movement in Hyperactivated and Acrosome-Reacted Golden Hamster Spermatozoa.» Molecular Reproduction and Development, 2002: 376-384.
Nascimento, J., Botvinick, E. L., Shi, L. Z., Durrant, B., Berns, M. W. «Analysis of sperm motility using optical tweezers.» Journal of Biomedical Optics, 2006.
Nosrati, R., Graham, P. J., Zhang, B., Riordon, J., Lagunov, A., Hannam, T. J., Escobedo, C., Jarvi, K., Sinton, D. «Microfluidics for sperm analysis and selection.» Nature Reviews Urology, 2017: 707-730.
Ooi, E. H., Smith, D. J., Gadelha, H., Gaffney, E. A., Kirkman-Brown, J. «The mechanics of hyperactivation in adhered human sperm.» Royal society open science, 2014.
Alice Battistella, Laura Andolfi, Dan Cojoc and Marco Lazzarino
CNR-IOM, c/o Area Science Park Basovizza 34149 Trieste Italy
Post-doc, CNR-IOM, Trieste, Italy
Alice Battistella got her Master degree in Biotechnology in 2017 from the University of Padua. During her master thesis, she spent one year in Paris at UPMC studying the catalytic role of mineral surfaces in oligopeptide formation. She got her PhD in Nanotechnology in 2021 from the University of Trieste, studying the mechanical properties of cells by AFM force spectroscopy and imaging modes for biomedical applications. She is currently a post-doc at CNR-IOM in Trieste where her research focuses on the investigation of cell mechanobiology in the field of reproductive medicine.
Dec 01, 2021 11:35 AM (Europe/Zurich)