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

Formation of a prefertilization sperm reservoir in mammals is thought to oc cur 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 sper m-OEC coculture system utilizing bovine OEC monolayers to study postejacula tory human sperm physiology. This study was done to evaluate aspects of hum an 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 monolay ers at dilutions ranging from 2 x 10(5) to 15 x 10(6) sperm per well. Numbe rs of each type of sperm attaching to OEC at each concentration were determ ined. In experiment 2, fresh and cryopreserved sperm from the same donors ( n = 4) were put into OEC coculture to observe numbers attaching and subsequ ent survival time for each sperm type. Sperm attachment to OEC occurred in a linear, dose-dependent manner for fresh and cryopreserved sperm in experi ment 1, both as a function of total sperm numbers and as a function of numb ers of motile sperm applied (R-2 greater than or equal to 0.79). However, c ryopreserved sperm attached to the OEC at a slower rate than fresh (as a fu nction of the average increase in the number of sperm attaching per unit in crease in the number of sperm applied; P < 0.05), with an overall lower per centage of the total and motile sperm applied attaching to OEC (P < 0.01) f or cryopreserved versus fresh sperm. Fewer cryopreserved sperm also attache d to the OEC, as compared with fresh sperm, in experiment 2 (P < 0.05), eve n after correcting for motility differences between the sperm types. Sperm survival time in coculture was also decreased for cryopreserved sperm as co mpared with fresh sperm (P = 0.005). Understanding the kinetics of sperm an d OEC interactions may be useful for developing improved cryopreservation p rotocols or bioassays of sperm function.