Pre-Treatment of Swine Oviductal Epithelial Cells with Progesterone Increases the Sperm Fertilizing Ability in an IVF Model

Simple Summary The involvement of the oviductal epithelial cells and progesterone hormone on the sperm fertilizing ability was investigated here by using an in vitro fertilization (IVF) swine model. By using different techniques, we demonstrated that oviductal epithelial cells (OECs) pre-treated with progesterone (P4) at 100 ng/mL represent the ideal environment for sperm capacitation, inducing a positive effect on the sperm acquisition of the fertilizing ability. Moreover, treatment of OECs with P4 modifies OVGP1, SPP1 and DMBT1 gene transcription but does not interfere with important cytoskeleton structures or cell doubling time, thereby allowing the correct development and progression of important biochemical pathways and signal transduction processes. Mammalian spermatozoa are infertile immediately after ejaculation and need to undergo a functional modification, called capacitation, in order to acquire their fertilizing ability. Since oviductal epithelial cells (SOECs) and progesterone (P4) are two major modulators of capacitation, here we investigated their impact on sperm functionality by using an IVF swine model. To that, we treated SOECs with P4 at 10, 100, and 1000 ng/mL before the coincubation with spermatozoa, thus finding that P4 at 100 ng/mL does not interfere with the cytoskeleton dynamics nor the cells' doubling time, but it promotes the sperm capacitation by increasing the number of spermatozoa per polyspermic oocyte (p < 0.05). Moreover, we found that SOECs pre-treatment with P4 100 ng/mL is able to promote an increase in the sperm fertilizing ability, without needing the hormone addition at the time of fertilization. Our results are probably due to the downregulation in the expression of OVGP1, SPP1 and DMBT1 genes, confirming an increase in the dynamism of our system compared to the classic IVF protocols. The results obtained are intended to contribute to the development of more physiological and efficient IVF systems.