Heparin and Ca2+-free medium can enhance release of bull sperm attached tooviductal epithelial cell monolayers

The success of assisted reproductive techniques, such as IVF, could be enha nced by being able to select the most competent spermatozoa in a sample. At tachment and subsequent release of spermatozoa from oviductal epithelial ce lls (OEC) could provide populations of functionally superior spermatozoa fo r use in these protocols. The objective of the present study was to investi gate the ability of heparin and Ca2+-free medium to induce spermatozoa rele ase from bovine OEC. Epithelial cells were grown to confluence in 24-well p lates and pooled frozen bull semen was added to a final concentration of 1x 10(6) spermatozoa/well. Spermatozoa were allowed to bind to OEC for 2 h. Me dium with unbound spermatozoa was removed and replaced by Sperm-TALP, only (control), with heparin (5, 10, or 15 IU/mL), or Ca2+-free with 2 mM EGTA. Treatments were left on sperm-OEC co-cultures for 0.5, 1, 2, 3, or 5 h. At each lime, the media were recovered and spermatozoa from each treatment wer e counted and evaluated for acrosome integrity and motility. The total numb er of spermatozoa attached to OEC after 2 h of co-culture was considered 10 0%. Spermatozoa release is expressed as percentage of the total number of s perm cells bound to OEC after 2 h of co-culture. Data were analyzed by ANOV A and results are expressed as mean +/- SEM from three independent replicat es. Beginning at 0.5 h, more sperm cells (P < 0.05) were released from OEC in the heparin groups (10 and 15 IU/mL, 77.3 +/- 6.2% and 84.0 +/- 6.2%, re spectively) as compared to the control (46.4 +/- 6.2%). The Ca2+-free mediu m also induced spermatozoa release when compared with the control, but the effect was not significant until 3 h (38.2 +/- 1.9% vs 59.5 +/- 6.9%; P < 0 .05). The percentage of acrosome reacted spermatozoa was not affected by he parin treatment. Heparin at 10 IU/mL increased (P < 0.05) the percentage of motile spermatozoa, whereas Ca2+-free medium caused the opposite effect at 0.5 h after addition of treatments. We conclude that both heparin and Ca2-free medium are able to promote spermatozoa displacement from OEC attachme nt. Based on motility and acrosome status data, we predict that released sp erm cells may be used for IVF and other assisted reproductive techniques. ( C) 2001 by Elsevier Science Inc.