Chemotaxis of Capacitated Rabbit Spermatozoa to Follicular Fluid Revealed by a Novel Directionality-Based Assay1

Abstract

Precontact communication between gametes is established by chemotaxis. Sperm chemotaxis toward factor(s) in follicular fluid (FF) has been demonstrated in humans and mice. In humans, the chemotactic responsiveness is restricted to capacitated spermatozoa. Here, we investigated whether sperm chemotaxis to factor(s) present in FF also occurs in rabbits and, if so, whether only capacitated spermatozoa are chemotactically responsive. Chemotaxis assays were performed by videomicroscopy in a Zigmond chamber. We measured chemotactic responsiveness as a function of FF dilution by means of a novel directionality-based method that considers the ratio between the distances traveled by the spermatozoa both parallel to the chemoattractant gradient and perpendicular to it. A peak of maximal response was observed at 10(-4) dilution of FF, resulting in a typical chemotactic concentration-dependent curve in which 23% of the spermatozoa were chemotactically responsive. In contrast, the percentage of cells exhibiting FF-dependent enhanced speed of swimming increased with the FF concentration, whereas the percentage of cells maintaining linear motility decreased with the FF concentration. The percentages of chemotactically responsive cells were very similar to those of capacitated spermatozoa. Depletion of the latter by stimulation of the acrosome reaction resulted in a total loss of the chemotactic response, whereas the reappearance of capacitated cells resulted in a recovery of chemotactic responsiveness. We conclude that rabbit spermatozoa, like human spermatozoa, are chemotactically responsive to FF factor(s) and acquire this responsiveness as part of the capacitation process.

Possible ability of bovine follicular fluid to attract migrating bull spermatozoa

“…The sperm showed the strongest chemotaxis toward 10 3 ‐ or 10 4 ‐fold‐diluted (0.1% or 0.01%) follicular fluid 10, 11. In this study, the responsiveness of bull sperm to the BFF at the different concentrations of between 0.01% and 100% was compared and it was found that 0.1% BFF elicited the strongest response.…”

“…In the human,16, 21, 22, 23 rabbit,10 and mouse,15 sperm chemotaxis to the follicular fluid and egg‐related material has been observed, but the mechanism of sperm chemotaxis is not sufficiently understood. In this study, it was investigated whether bull sperm can be attracted to the BFF.…”

“…A couple of studies have reported that chemotaxis is valid for the selection of the sperm that can reach the oocytes and that only the capacitated sperm can exhibit chemotaxis 10, 11. It also has been suggested that hyperactivation is involved in the changes of motility direction of the chemotaxis‐exhibiting human sperm 16.…”

“…Based on a detailed kinetic analysis of migrated sperm in the female genital tract, it was found that chemotaxis,1 thermotaxis,6, 7 and rheotaxis8 are involved in sperm migration. In mammals, swine sperm chemotaxis toward the leukocytes9 and rabbit and human sperm chemotaxis toward the follicular fluid have been reported 10, 11. The follicular fluid includes the fluid that is secreted from the ovary and follicular cells and affects the physiological function and motility of the sperm.…”

Human sperm pattern of movement during chemotactic re-orientation towards a progesterone source

“…[2][3][4] Follicular fluid, oviductal fluid and the conditioned medium of the egg-cumulus complex are biological sources of chemoattractants. [3][4][5][6][7][8][9][10][11] Follicular fluid that has been obtained from one species may attract spermatozoa of other species, suggesting that chemotaxis may not be a species-specific phenomenon. 12 A small quantity of progesterone, which is secreted by the cells surrounding the egg, is able to attract spermatozoa.…”