SPERM-OVIDUCT EPITHELIAL-CELL MONOLAYER COCULTURE - AN IN-VITRO MODELOF SPERM-FEMALE TRACT INTERACTIONS IN A MARSUPIAL, THE TAMMAR WALLABY(MACROPUS-EUGENII)

Oviduct epithelial cell (OEC) monolayers were prepared from the isthmi c and ampullary parts of the oviducts of FSH-primed tammar wallabies. Go-culture experiments found that 50-60% of wallaby spermatozoa attach ed immediately to OEC monolayers, tracheal cell monolayer controls, an d the surface of culture dishes with and without Matrigel coating. Spe rmatozoa were considered to be attached if they remained on the cultur e surface after rapidly pipetting the co-culture medium five times. Th e percentages of attached and unattached spermatozoa were calculated f rom the number of spermatozoa recovered in the agitated supernatant. A fter 2 h co-culture the percentage of attached spermatozoa rose to 60- 80%. After 6 h co-culture the number of spermatozoa attached to OEC mo nolayers derived from the oviductal isthmus remained high and only a s mall percentage were recovered in the agitated supernatant (unattached spermatozoa 3.85 +/- 0.76%, P = 0.67). However, after 6 h co-culture of spermatozoa with OEC monolayers derived from the ampulla and with t he controls the percentage of attached spermatozoa declined significan tly (unattached spermatozoa: ampullary monolayer 23.08 +/- 4.80%, P < 0.01; tracheal monolayer 23.23 +/- 5.18%, P < 0.01; Matrigel 27.23 +/- 7.76%, P < 0.01; plastic surface 28.19 +/- 5.30%, P < 0.01). After 6 h co-culture with ampullary and isthmic OEC monolayers, the percentage motility of both attached and unattached spermatozoa was maintained a t 64.00 +/- 1.90% and 56.66 +/- 3.18% and 62.00 +/- 3.11% and 52.00 +/ - 2.43%, respectively, and was then maintained at greater than or equa l to 35% after 24h incubation. In the controls, that is, tracheal mono layer and Matrigel, the motility of attached spermatozoa declined rapi dly to 48.66 +/- 2.15% and 33.63 +/- 8.66%, respectively, at 6 h, and all spermatozoa were immotile after 24 h incubation. However, the moti lity of unattached spermatozoa in the controls (tracheal monolayer and Matrigel) was maintained at 57.33 +/- 3.00% and 34.54 +/- 9.27%, resp ectively, until 6 h and then declined rapidly, and all spermatozoa wer e immotile after 24h incubation. Go-culture of wallaby spermatozoa wit h OEC monolayers also induced acrosomal modifications that were follow ed by acrosomal loss. At 6 h incubation 38.92 +/- 3.98% of spermatozoa on ampullary OEC monolayers and 36.50 +/- 3.81% spermatozoa on isthmi c OEC monolayers had shed their acrosome. Acrosomal loss during co-cul ture with both isthmic and ampullary OEC monolayers was significantly (P < 0.01) greater than that observed on tracheal epithelial monolayer (24.42 +/- 1.90%, P < 0.01), Matrigel (20.70 +/- 2.71%, P < 0.01) and plastic (15.54 +/- 2.49%, P < 0.01). Go-culturing spermatozoa with OE C monolayers also induced a transformation from streamlined orientatio n of sperm head and tail to T-shaped (thumbtack) orientation in a smal l number (10-15%) of motile spermatozoa after 6 h incubation (data not shown). The significance of these results in relation to the role of the oviduct in sperm capacitation is discussed.