The application of co-culture in assisted reproduction: 10 years of experience with human embryos

Go-culture techniques using fetal bovine uterine fibroblasts or bovine ovid uctal epithelial cells have improved embryonic development prior to replace ment in humans. In initial co-culture trials, embryo development and implan tation rates increased after just 1 day in culture. The most overt characte ristics noted following co-culture were improved blastomere development and characteristics, reduced fragmentation, and the appearance of swollen blas tomeres. In addition, an increase in the incidence of zona thickness variat ion was detected. Improved development of polyspermic and supernumerary emb ryos to the blastocyst stage was noted in initial trials. Retrospective ana lysis indicated that certain patient subgroups benefit the most from co-cul ture. As a result, co-culture is now applied routinely to patients that hav e previously failed attempts at in-vitro fertilization (IVF) and/or have en docrine imbalances such as polycystic ovarian syndrome and elevated day 3 c oncentrations of follicle stimulating hormone (FSH). The use of co-culture prior to or following cryopreservation has also proven to be beneficial to human embryos. The proposed beneficial mechanisms thought to improve embryo nic development include a secretary and/or a scavenging role. Evidence desc ribing the postulated benefits is discussed.