Development of screening systems for evaluation of materials used in mammalian embryo transfer

Embryo transfer units use a wide variety of materials that come in contact with embryos. Studies were conducted to evaluate procedures that could be utilized to determine the toxicity of some commonly used materials in embryo collection, culture and transfer. Forty-five female mice were sacrificed on Day 3 or 4 of gestation (Day 1 = vaginal plug), and the uterus and oviducts were removed and minced. A total of 522 embryos was collected (4-cell to blastocyst stages). Four to 16 cell embryos were cultured in Phosphate Buffered Saline (PBS) plus 20% fetal bovine serum. Morula to blastocyst stage embryos were cultured in Nutrient Mixture F10 (HAM) plus 20% fetal bovine serum gassed with 5% CO(2), 5% O(2) and 90% N(2). In Experiment I, embryos and culture media were placed in a covered embryological watch glass (EWG, control) or sealed in the lumen of a siliconized Foley catheter or a section of 1) latex tubing, 2) tygon tubing or 3) silastic tubing. In Experiment II, embryos were placed in EWG and cultured alone (control) or cocultured with sections of 1) tygon tubing, 2) silastic tubing or 3) latex tubing. In Experiment III, embryos were cultured in covered plastic petri dishes containing 15 ml of media, alone (control) or co-cultured with two new plunger tips from sterile Monoject syringes. All embryos were cultured at 32 to 34 degrees C for 24 h. The Criterion used for development was two or more cellular divisions within the 24-h period. Embryo development in Experiment I was lower (P<0.05) in latex (0%) and tygon (24%) tubing and in the siliconized Foley catheter (2%) than in silastic tubing (51%) and the EWG (46%), which did not differ. Experiment II embryos that were co-cultured with latex tubing (5%) showed very little development as compared with those co-cultured with tygon tubing (76%), silastic tubing (76%) and EWG (93%), the last of which were not significantly different. Embryos co-cultured with Monoject syringe plunger tips had a reduced embryo development rate compared to embryos in the control group (0% vs 52%). Although the embryos did not remain in contact with these seemingly toxic materials for prolonged periods, our results indicate that a significant reduction in embryo viability may occur due to this exposure.