Sperm navigation mechanisms

Abstract

Objective: Mechanisms of sperm navigation are important for understanding the principles of sperm selection prior to fertilization. The aim of this work is to provide an overview of current knowledge about the physiological process of sperm navigation from ejaculation to fertilization of the ovulated oocyte. Methods: Literature search of the PubMed database published up to June 2025 with terms focusing on “sperm navigation,” “fertilization,” and “chemoattractants”. Results: The principles of sperm navigation in the in vivo environment are still unclear in humans. Currently, there are simple in vivo studies performed on model animals, as well as a number of in vitro studies on human sperm. Based on these results, three main navigation systems are described: rheotaxis, thermotaxis, and chemotaxis. Rheotaxis acts over the longest distances and stimulates sperm movement against the flow of fluid. Thermotaxis acts over a shorter distance and guides sperm to places with higher temperatures. Chemotaxis acts over the shortest distance, attracting capacitated sperm to places where the ovulated oocyte is located. Conclusion: Given how massively the sperm microinjection technique is used in the treatment of human infertility, it is important to carefully select sperm prior to fertilization. Knowledge of the principles of human sperm selection in in vivo conditions is crucial for effective sperm selection in the laboratory.