Many IVF programs have reintroduced the concept of utilizing a co-culture medium to improve the quality and implantation of embryos. Co-culture is a procedure whereby “helper” cells are grown along with the developing embryo. Today, the most popular cell lines include endometrial cells (from the endometrium, or uterine lining) and cumulus cells from women’s ovaries. Both cell lines are derived from the patient, thereby eliminating any concerns regarding transmission of viruses. Endometrial cells are much more difficult to obtain and process, while cumulus cells are routinely removed along with the oocytes during IVF retrieval.
Cumulus cells play an important role in the maturation and development of oocytes. After ovulation cumulus cells normally produce a chemical called Hyaluronan. Hyaluronan is secreted by many cells of the body and is involved in regulating cell adhesion, growth and development. Recent evidence has shown that Hyaluronan is found normally in the uterus at the time of implantation..
Co-culture of cumulus cells provides an opportunity to detoxify the embryo’s culture medium that the embryos are growing in and produce growth factors important for cell development 1,2. This may explain why some human embryos can experience improved development with the use of co-culture.
Preparation of co-culture cells starts with separation of the cumulus cells from the oocytes after aspiration of the follicles. These sheets of cells are washed thoroughly and then placed in a solution that permits the sheets to separate into individual cells. The cells are then washed again and transferred to a culture dish with medium and incubated overnight. During this time individual cells will attach to the culture dish and create junctions between adjoining cells. This communication is important for normal development. The following morning, cells are washed again and all normally fertilized oocytes (embryos) are added to the dish. Embryos are grown with the cumulus cells for a period of three days to achieve maximum benefit.
Performing co-culture of embryos has improved implantation and pregnancy rates above and beyond those seen with the IVF advances previously described. More importantly, It promises to offer advantages for those patients whose previous IVF cycles were unsuccessful.
1. Barmat LI, Worrilow KC, Paynton BV. Growth factor expression by
human oviduct and buffalo rat liver coculture cells. Fertil Steril 1997;
2. Fukui Y, McGowan LT, James RW, Pugh PA, Tervit HR. Factors
affecting the in vitro development of blastocysts of bovine oocytes
matured and fertilized in vitro. J Reprod Fertil 1991;92:125–31.