Greater numbers of human spermatozoa associate with endosalpingeal cells derived from the isthmus compared with those from the ampulla

A simple co-culture bioassay system was used to investigate whether or notthe anatomical origin affected the ability of epithelial cells from thehuman uterine (Fallopian) tube to 'bind' spermatozoa. This study was alsoused to identify some of the factors which may be involved in theregulation of sperm-epithelial interactions in vitro by comparing differenttissue culture models and assessing the effect of oestradiol concentration.Epithelial explants harvested from different regions of human uterine tubeswere co-incubated with a known concentration of motile donor spermatozoa.All results were adjusted to reflect a standard sperm concentration of 5 x10(6)/ml. More spermatozoa associated per field of isthmic compared toampullary epithelium [isthmus 9.5 +/- 0.9, ampulla 7.1 +/- 0.7 (mean +/-SEM); n = 36, P < 0.05, ANOVA] and cells from post-menopausal patientshad an apparently reduced ability to bind spermatozoa [isthmus 5.5 +/- 2.0,ampulla 4.3 +/- 1.4 (mean +/- SEM); n = 4]. Neither menstrual cycle stagenor addition of mid-cycle concentrations of 17beta-oestradiol (750 pmol/l)affected the number of spermatozoa which bound to epithelium from eithertubal region. In addition, the number of spermatozoa which bound per fieldof polarized explants was greater (P < 0.05) than that bound todissociated primary and passaged epithelial cell monolayers. This report isthe first to provide evidence suggestive of a role for sperm- epithelialbinding in the formation of an isthmic sperm reservoir in the human uterinetube. Results also indicate that oestrogen is not involved in theregulation of these interactions, and that cell polarity is an importantfactor for such associations in vitro.