Supplementation of 17β-estradiol and progesterone in the co-culture medium of bovine oviductal epithelial cells and ovine spermatozoa reduces the sperm kinematics and capacitation

Abstract

This study investigated the effect that bovine oviductal epithelial cell (BOEC) and ovine spermatozoa co-culture exposed to different hormonal environments had on ram sperm function over the course of a 24-h incubation period. Ram cooled-stored spermatozoa were selected by swim-up and then co-cultured separately for 24 h at 38.5 °C under 5% CO₂ with either: (1) Fert-TALP medium (positive control [POSControl]), (2) Fert-TALP medium supplemented with 17β-estradiol (E2) and progesterone (P4) at concentrations similar to follicular phase (Follicular NEGControl), (3) Fert-TALP medium supplemented with E2 and P4 concentrations similar to luteal phase (Luteal NEGControl), (4) BOEC cultured in the same medium as that of the Follicular NEGControl group (Follicular BOEC group), or (5) BOEC cultured in the same medium as that of the Luteal NEGControl group (Luteal BOEC group). The sperm kinematics, capacitation status, and plasma membrane (PM) integrity were evaluated at different intervals. Sperm PM integrity was not affected (P ˃ 0.05) by BOEC co-culture, regardless of the phase of the estrous cycle. After 4 h of incubation, the Luteal BOEC group presented lower (P < 0.05) progressive motility and total motility than the Luteal NEGControl group while the Follicular BOEC group showed lower (P < 0.05) velocimetric parameters and progressive motility than the Follicular NEGControl group. Throughout the incubation period, both BOEC co-culture groups showed a decrease (P < 0.05) in their capacitation rate in comparison to the POSControl group. Conversely, the Luteal BOEC group presented a higher (P < 0.05) non-capacitated rate than both the POSControl and Luteal NEGControl groups. In conclusion, BOEC co-culture with ovine spermatozoa at either the follicular or luteal phase decreases sperm kinematics and delays sperm capacitation.

Keywords: CASA system; Estrous cycle; Heterologous co-culture system; Oviduct; Ram cooled-stored spermatozoa.