Human sperm chemotaxis: is progesterone a chemoattractant?

Area of Science:

• Reproductive Biology
• Sperm Motility
• Human Fertilization

Background:

• Follicular fluid (FF) is known to induce sperm chemotaxis.
• Progesterone is also known to cause sperm accumulation.
• The exact mechanism of sperm accumulation, whether chemotaxis or chemokinesis, requires clarification.

Purpose of the Study:

• To determine if progesterone induces chemotaxis in human spermatozoa.
• To ascertain if progesterone in FF is the primary chemoattractant.
• To differentiate between chemotaxis, chemokinesis, and trapping in sperm accumulation.

Main Methods:

• Assessing directional changes in sperm swimming towards pure progesterone.
• Analyzing sperm behavior in response to FF before and after progesterone removal.
• Observing sperm motility and hyperactivation-like changes.

Main Results:

• Progesterone induced sperm accumulation and hyperactivation-like motility.
• Progesterone showed minimal directional changes characteristic of chemotaxis.
• Removal of progesterone from FF abolished hyperactivation-like motility but not chemotaxis.

Conclusions:

• Progesterone is not the major chemoattractant in human FF.
• Progesterone may act as a weak chemoattractant.
• Progesterone likely causes sperm accumulation primarily through inducing hyperactivation-like motility and subsequent trapping.