Background: The aim of this study was to investigate the influence of the solid phase of the mucus hydrogel in facilitating the upward movement of spermatozoa during the menstrual cycle.
Methods: A total of 171 sperm migration experiments using 47 selected ovulatory mucus samples were performed in vitro in tubes of various shape and diameter. Physical constraints applied to cervical mucus combined with scanning electron microscopy (SEM) techniques permitted analysis of the mechanism of sperm orientation within cervical mucus submitted to capillary constraints simulating the various conditions of sperm orientation in vivo.
Results: The results support the theory according to which spermatozoa entering the cervical canal are constrained to follow the oriented micellar lines of strain. Stretched ovulatory mucus exhibits noticeable prevalent orientation of most filaments aligned in a manner roughly parallel to the traction axis. By contrast, even after strong stretching applied to luteal-type mucus and longer contact periods, the alignment of glycoproteic meshes was not sufficiently marked to allow spermatozoa to orient themselves and to move rapidly. The results are discussed as a function of the variations occurring in the three-dimensional macromolecular arrangement of the glycoproteic framework subjected to flow constraints.
Conclusions: The study confirms that there is a close relationship between the three-dimensional arrangement of the mucus framework and the ability of spermatozoa to move rapidly in a given direction. The high resolution and three-dimensional aspect of SEM micrographs support the correlation of sperm orientation with current data on rheologic properties of biologic hydrogels.