Sequential Acquisition of Chemotactic Responsiveness by Human Spermatozoa1

Abstract

Recent studies have indicated that human spermatozoa respond to follicular fluid by attraction to chemotactic factor(s) in the fluid, accompanied by enhancement of motility and ultimately hyperactivation. In this study, we quantified the sperm response. We exposed spermatozoa to a gradient of a chemotactically active fraction of follicular fluid (denoted as "the attractant") and separated the spermatozoa that accumulated in the attractant and those that did not. We thus obtained two subpopulations: one enriched with chemotactically responsive spermatozoa, and one deficient in such spermatozoa. The fraction of the responsive spermatozoa out of the total sperm population was 2-12% at any measured time point. With time, the responsive spermatozoa lost their ability to be attracted, while such activity was gradually acquired by the subpopulation originally deficient in responsive spermatozoa. These results indicate that the identity of responsive spermatozoa is continuously changing. If the in vitro results are representative of the physiological conditions in vivo, they imply that the role of sperm chemotaxis combined with enhanced motility may be to select capacitated spermatozoa and bring them to the egg. Such a mechanism may, over an extended period of time, increase the prospect that an egg will meet capacitated spermatozoa as soon as it ovulates.

Aggregation of Human Sperm at Higher Temperature Is Due to Hyperactivation

“…aggregation, chemotaxis, computer-aided sperm analysis, heat, hyperactivation motility A variety of chemicals and hormones, such as progesterone or atrial natriuretic peptide, cause chemotaxis of sperm [6,13,15,23]. It is important to understand the concept of sperm attraction and why infertility occurs in dysfunctional sperm.…”

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

“…24,25 Conversely, in internal-fertilizing species, such as humans, only ,10% of cells are capable of a chemotactic response while swimming towards the source of an attractant (positive gradient), whereas there is no evidence of a visible change in the pattern of movement. [2][3][4]6,16,26 In fact, in our system, the cells that chemotactically swam from W1 (containing spermatozoa) to W2 (containing progesterone) could not be distinguished from the nonchemotactic cells according to the patterns of movement. These features of mammalian sperm chemotaxis make it technically difficult to identify an individual chemotactic cell.…”

“…[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.…”

Progesterone significantly enhances the mobility of boar spermatozoa

“…Progesterone was added to the working Accudenz solution to a final concentration of 1, 10 or 100nM and used to monitor sperm penetration rate in response to progesterone concentration. Absorbance readings were recorded at time intervals over 50 minutes (1,5,10,15,20,30,40 and 50 minutes) and cuvettes were incubated at 37°C for the duration of this time period.…”

“…This chemoattractant property is thought to be necessary in order to guide the sperm to the oocyte, although appears to only occur in capacitated cells [5,6]. The pattern of response of human sperm cells to progesterone has been suggested to involve a change in motility parameters with both positive and negative effects on hyperactivation depending on the temporal and spatial exposure [4,7,8].…”