Direct contact between boar spermatozoa and porcine oviductal epithelial cell (OEC) cultures is needed for optimal sperm survival in vitro

Oviductal epithelial cell (OEC) co-culture prolongs sperm viability and motility in vitro in a number of species including humans and horses. This study has sought to determine the effects of homologous OEC co-culture on boar sperm function. To determine whether the effects on spermatozoa were specifically caused by co-culture with or by OEC secretions, or by both factors together, a number of co-culture and cell-conditioned medium (CM) experiments were conducted. Firstly, Percoll-washed spermatozoa were co-cultured with OECs and pig kidney epithelial (LLC-PK1) cells, and in medium without cells. Secondly, Percoll-washed spermatozoa were incubated with CM derived from both OECs and LLC-PK1 cells and in unconditioned medium. A number of sperm function parameters were assessed after 5, 30, 60, 90, 120, and 180 min, and 24 h of co-culturing or incubation with CM. Of all the sperm function parameters investigated, the percentage (%) viability data yielded the most interesting results. OECs (mean ± S.E.M.; 31.2 ± 1.10) were better than LLC-PK1 cells (24.3 ± 0.93) at prolonging the viability of unbound spermatozoa after 24 h of co-culturing (P < 0.05). Also after 24 h, the viability of spermatozoa bound to the OECs (77.6 ± 1.83) was significantly higher than in the case of the LLC-PK1 cells (53.5 ± 1.43; P < 0.001). Other sperm function parameters, e.g., capacitation and motility, were also influenced by OEC co-culturing and incubation with CM, although to a lesser degree. In conclusion, porcine homologous OEC co-culture and CM incubation specifically affect sperm function. However, we propose that it is OEC co-culturing, rather than OEC-CM, that has the greater influence.