Sperm display surprising reorientation and velocity recovery when encountering an obstacle

In vitro fertilization, a common process for helping otherwise infertile couples to conceive, is only successful in about one-third of cases. In order to design more efficient sperm selection and fertilization devices, it is essential to develop a stronger understanding of sperm behavior and interactions in ultra-confined cases. Bettera Marcat et al. sought to better predict sperm behavior in micro-confined environments by experimentally characterizing and simulating sperm dynamics during sperm-wall interactions.

The group found when a sperm reaches a rigid wall, its velocity suddenly decreases, sometimes even coming to a full stop. However, since the sperm is committed to moving forward, it reorients itself parallel to the wall and quickly accelerates back to a partial restoration of its previous velocity.

“We knew that sperm are stubborn, since in previous studies we had observed a tendency to move forward with determination,” said author Héctor Guidobaldi.

Under in vivo conditions, the sperm navigates between folds in spaces down to tens of micrometers wide to find an egg inside a female reproductive tract, interacting very frequently with the uterine walls.

“The interaction of the sperm with the walls in vivo may not be the same as we are observing in this in vitro condition,” Guidobaldi said. “Nevertheless, this knowledge is useful for the development of artificial sperm selection systems.”

Including this behavior in a model significantly improves the accuracy of its prediction of the system’s average behavior. This can help speed up the development of sperm selection and in vitro fertilization devices, as more realistic simulations can point toward the most promising designs worth further experimental exploration.

Source: “Hitting the wall: Human sperm velocity recovery under ultra-confined conditions,” by Matías A. Bettera Marcat, María N. Gallea, Gastón L. Miño, Marisa A. Cubilla, Adolfo J. Banchio, Laura C. Giojalas, Verónica I. Marconi, and Héctor A. Guidobaldi, Biomicrofluidics (2020). The article can be accessed at https://doi.org/10.1063/1.5143194 .