Comparison of fresh and cryopreserved human sperm attachment to bovine oviduct (uterine tube) epithelial cells in vitro

Abstract

Formation of a prefertilization sperm reservoir in mammals is thought to occur via sperm cell attachment to fallopian tube or oviduct epithelial cells (OEC). Recent data suggests that such an interaction also occurs for human sperm in the fallopian tube. We have previously validated an in vitro sperm- OEC coculture system utilizing bovine OEC monolayers to study postejaculatory human sperm physiology. This study was done to evaluate aspects of human sperm attachment to OEC in coculture and to determine if such attachment and subsequent sperm survival differ between fresh and cryopreserved human sperm. In experiment 1, aliquots of fresh (n = 4) or cryopreserved sperm (n = 3) from normospermic donors were placed into coculture with OEC monolayers at dilutions ranging from 2 x 105 to 15 x 106 sperm per well. Numbers of each type of sperm attaching to OEC at each concentration were determined. In experiment 2, fresh and cryopreserved sperm from the same donors (n = 4) were put into OEC coculture to observe numbers attaching and subsequent survival time for each sperm type. Sperm attachment to OEC occurred in a linear, dose- dependent manner for fresh and cryopreserved sperm in experiment 1, both as a function of total sperm numbers and as a function of numbers of motile sperm applied (R2 ≥ 0.79). However, cryopreserved sperm attached to the OEC at a slower rate than fresh (as a function of the average increase in the number of sperm attaching per unit increase in the number of sperm applied; P < 0.05), with an overall lower percentage of the total and motile sperm applied attaching to OEC (P < 0.01) for cryopreserved versus fresh sperm. Fewer cryopreserved sperm also attached to the OEC, as compared with fresh sperm, in experiment 2 (P < 0.05), even after correcting for motility differences between the sperm types. Sperm survival time in coculture was also decreased for cryopreserved sperm as compared with fresh sperm (P = 0.005). Understanding the kinetics of sperm and OEC interactions may be useful for developing improved cryopreservation protocols or bioassays of sperm function.