Bovine oviductal epithelial cell protein secretion, and its effect on embryo development in vitr

Oviductal cell co-cultures have improved embryo survival in culture, possibly due to secretion of proteins which may interact with early embryos. Embryo development might be further improved through co-culture procedures if oviductal epithelial or uterine epithelial cell protein secretion could be altered to parallel in vivo conditions. These studies were conducted to determine if protein secretions can be altered by epithelial cells through serum supplementation, and if altered protein secretion would benefit bovine embryo in vitro development. Blood was collected from cows at 0, 2, 4, 6 and 8 d after estrus. Oviductal or uterine suspensions were conditioned for 24 h in M-199 with 20% fetal calf serum (FCS) or 20% serum representing each estrous cycle stage. Then cells were incubated in serum-free M-199 with 50$mu$ Ci/ml $sp{35}$S-methionine to detect newly synthesized proteins. Proteins in supernatants were separated by one-dimensional SDS PAGE and/or visualized by autoradiography. Over 20 different oviductal and uterine proteins were detected. Secretion of 10 oviductal and 7 uterine proteins were altered by serum supplementation.;An additional study was conducted to evaluate the effects of oviductal altered secretion on in vitro bovine embryonic development. Ovaries and oviducts were obtained from cows at slaughter, and oocytes were in vitro matured and fertilized. Three to 4-cell stage embryos were assigned to culture treatments containing different serum supplementation and oviductal epithelial cell suspensions. Treatments consisted of M-199 with, (1) 20% fetal calf serum, (2) 20% Day 0 serum, (3) 20% Day 0, then Day 4, (4) 20% Day 0 then Day 8, or (5) 20% Day 0, Day 4 then Day 8 serum. Media was changed at 48 h intervals during the 6 day culture period. More embryos developed to the blastocyst stage in media supplemented with Day 8 serum (Treatments 4 and 5) than in other treatments (P = 0.097). Blastocyst cell number was higher in media containing Day 8 serum (Treatments 4 and 5) than in other treatments (P = 0.089). These results indicate that bovine oviductal epithelial cell protein secretion can be altered in vitro, and embryo development with oviductal cells may be improved by medium supplementation with serum that parallels the natural environment of the cow.