Does a brief exposure to the uterus milieu contribute to prepare human sperm for fertilizing the oocyte?

CUBILLA M. A; FRANCHI N. A.; GIOJALAS LC

Conferencia; Gordon Research Conferences 2013; 2013

Background. In order to fertilize the oocyte, mammalian spermatozoa must undergo a series of biochemical and physical changes collectively called capacitation. It is well known that sperm capacitation takes place upon interaction with the oviduct epithelium. However, during the transit along the uterus spermatozoa are in contact with the secretions from different cell types, where some proteins secreted by endometrial cells have been reported to stimulate sperm preparation for fertilization. Objective. To evaluate whether conditioned media (CM) from endometrial epithelial cells affects human sperm physiology. Methodology. After seminal plasma removal, spermatozoa were incubated with conditioned media (CM) obtained from endometrial epithelial cells (Ishikawa cell line). Sperm viability, motility parameters, Ca2-ionophore-induced acrosome reaction and protein tyrosine phosphorylation (PY) were evaluated at different time points. Results. The percentage of induced acrosome reacted sperm significantly increased with the incubation time in the cells treated with CM, without affecting sperm viability and motility, results that were in agreement with protein PY determination. Interestingly, when spermatozoa were shortly incubated for 15 min in the presence of CM, then washed and further incubated for 0, 2 or 4 h in HAM medium, the level of induced acrosome reacted sperm was similar to that observed after 4 h continuous incubation with CM. We further investigated a candidate endometrial protein that might be responsible for priming spermatozoa for the acrosome reaction. Spermatozoa incubated in CM pre-treated with anti-MFGE8 antibody showed a significant decrease in the level of induced acrosome reaction. Conclusions. These preliminary results suggest that: (1) CM from endometrial epithelial cells prime spermatozoa for the induced acrosome reaction without affecting sperm viability and motility; (2) a similar effect is even caused by a short exposition to CM; (3) the priming effect of CM is suppressed when CM is pre-incubated with a specific antibody against MFGE8. As a whole, these results suggest that the sperm transit along the uterus may contribute to the sperm preparation for fertilizing the oocyte.